ast.go

// Package ast defines the abstract syntax tree for ClickHouse SQL.
package ast

import (
	"encoding/json"
	"math"

	"github.com/sqlc-dev/doubleclick/token"
)

// Node is the interface implemented by all AST nodes.
type Node interface {
	Pos() token.Position
	End() token.Position
}

// Statement is the interface implemented by all statement nodes.
type Statement interface {
	Node
	statementNode()
}

// Expression is the interface implemented by all expression nodes.
type Expression interface {
	Node
	expressionNode()
}

// -----------------------------------------------------------------------------
// Statements

// SelectWithUnionQuery represents a SELECT query possibly with UNION.
type SelectWithUnionQuery struct {
	Position             token.Position `json:"-"`
	Selects              []Statement    `json:"selects"`
	UnionAll             bool           `json:"union_all,omitempty"`
	UnionModes           []string       `json:"union_modes,omitempty"` // "ALL", "DISTINCT", or "" for each union
	Settings             []*SettingExpr `json:"settings,omitempty"`    // Union-level SETTINGS
	SettingsAfterFormat  bool           `json:"settings_after_format,omitempty"`
	SettingsBeforeFormat bool           `json:"settings_before_format,omitempty"`
}

func (s *SelectWithUnionQuery) Pos() token.Position { return s.Position }
func (s *SelectWithUnionQuery) End() token.Position { return s.Position }
func (s *SelectWithUnionQuery) statementNode()      {}

// SelectIntersectExceptQuery represents SELECT ... INTERSECT/EXCEPT ... queries.
type SelectIntersectExceptQuery struct {
	Position  token.Position `json:"-"`
	Selects   []Statement    `json:"selects"`
	Operators []string       `json:"operators,omitempty"` // "INTERSECT", "EXCEPT", etc. for each operator between selects
}

func (s *SelectIntersectExceptQuery) Pos() token.Position { return s.Position }
func (s *SelectIntersectExceptQuery) End() token.Position { return s.Position }
func (s *SelectIntersectExceptQuery) statementNode()      {}

// SelectQuery represents a SELECT statement.
type SelectQuery struct {
	Position    token.Position        `json:"-"`
	With        []Expression          `json:"with,omitempty"`
	Distinct    bool                  `json:"distinct,omitempty"`
	DistinctOn  []Expression          `json:"distinct_on,omitempty"` // DISTINCT ON (col1, col2, ...) syntax
	Top         Expression            `json:"top,omitempty"`
	Columns     []Expression          `json:"columns"`
	From        *TablesInSelectQuery  `json:"from,omitempty"`
	ArrayJoin   *ArrayJoinClause      `json:"array_join,omitempty"`
	PreWhere    Expression            `json:"prewhere,omitempty"`
	Where       Expression            `json:"where,omitempty"`
	GroupBy     []Expression          `json:"group_by,omitempty"`
	GroupByAll  bool                  `json:"group_by_all,omitempty"` // true if GROUP BY ALL was used
	GroupingSets bool                 `json:"grouping_sets,omitempty"` // true if GROUP BY uses GROUPING SETS
	WithRollup  bool                  `json:"with_rollup,omitempty"`
	WithCube    bool                  `json:"with_cube,omitempty"`
	WithTotals  bool                  `json:"with_totals,omitempty"`
	Having      Expression            `json:"having,omitempty"`
	Qualify     Expression            `json:"qualify,omitempty"`
	Window      []*WindowDefinition   `json:"window,omitempty"`
	OrderBy      []*OrderByElement      `json:"order_by,omitempty"`
	Interpolate  []*InterpolateElement  `json:"interpolate,omitempty"`
	Limit            Expression            `json:"limit,omitempty"`
	LimitBy          []Expression          `json:"limit_by,omitempty"`
	LimitByLimit     Expression            `json:"limit_by_limit,omitempty"`     // LIMIT value before BY (e.g., LIMIT 1 BY x LIMIT 3)
	LimitByOffset    Expression            `json:"limit_by_offset,omitempty"`    // Offset for LIMIT BY (e.g., LIMIT 2, 3 BY x -> offset=2)
	LimitByHasLimit  bool                  `json:"limit_by_has_limit,omitempty"` // true if LIMIT BY was followed by another LIMIT
	Offset           Expression            `json:"offset,omitempty"`
	Settings            []*SettingExpr `json:"settings,omitempty"`
	SettingsAfterFormat bool           `json:"settings_after_format,omitempty"`  // true if SETTINGS came after FORMAT (at union level)
	SettingsBeforeFormat bool          `json:"settings_before_format,omitempty"` // true if SETTINGS came before FORMAT (at union level)
	IntoOutfile *IntoOutfileClause    `json:"into_outfile,omitempty"`
	Format      *Identifier           `json:"format,omitempty"`
}

// ArrayJoinClause represents an ARRAY JOIN clause.
type ArrayJoinClause struct {
	Position token.Position `json:"-"`
	Left     bool           `json:"left,omitempty"`
	Columns  []Expression   `json:"columns"`
}

func (a *ArrayJoinClause) Pos() token.Position { return a.Position }
func (a *ArrayJoinClause) End() token.Position { return a.Position }

// WindowDefinition represents a named window definition in the WINDOW clause.
type WindowDefinition struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name"`
	Spec     *WindowSpec    `json:"spec"`
}

func (w *WindowDefinition) Pos() token.Position { return w.Position }
func (w *WindowDefinition) End() token.Position { return w.Position }

// IntoOutfileClause represents INTO OUTFILE clause.
type IntoOutfileClause struct {
	Position token.Position `json:"-"`
	Filename string         `json:"filename"`
	Truncate bool           `json:"truncate,omitempty"`
}

func (i *IntoOutfileClause) Pos() token.Position { return i.Position }
func (i *IntoOutfileClause) End() token.Position { return i.Position }

func (s *SelectQuery) Pos() token.Position { return s.Position }
func (s *SelectQuery) End() token.Position { return s.Position }
func (s *SelectQuery) statementNode()      {}

// TablesInSelectQuery represents the tables in a SELECT query.
type TablesInSelectQuery struct {
	Position token.Position              `json:"-"`
	Tables   []*TablesInSelectQueryElement `json:"tables"`
}

func (t *TablesInSelectQuery) Pos() token.Position { return t.Position }
func (t *TablesInSelectQuery) End() token.Position { return t.Position }

// TablesInSelectQueryElement represents a single table element in a SELECT.
type TablesInSelectQueryElement struct {
	Position  token.Position    `json:"-"`
	Table     *TableExpression  `json:"table,omitempty"`
	Join      *TableJoin        `json:"join,omitempty"`
	ArrayJoin *ArrayJoinClause  `json:"array_join,omitempty"` // For ARRAY JOIN as table element
}

func (t *TablesInSelectQueryElement) Pos() token.Position { return t.Position }
func (t *TablesInSelectQueryElement) End() token.Position { return t.Position }

// TableExpression represents a table reference.
type TableExpression struct {
	Position token.Position `json:"-"`
	Table    Expression     `json:"table"` // TableIdentifier, Subquery, or Function
	Alias    string         `json:"alias,omitempty"`
	Final    bool           `json:"final,omitempty"`
	Sample   *SampleClause  `json:"sample,omitempty"`
}

func (t *TableExpression) Pos() token.Position { return t.Position }
func (t *TableExpression) End() token.Position { return t.Position }

// SampleClause represents a SAMPLE clause.
type SampleClause struct {
	Position token.Position `json:"-"`
	Ratio    Expression     `json:"ratio"`
	Offset   Expression     `json:"offset,omitempty"`
}

func (s *SampleClause) Pos() token.Position { return s.Position }
func (s *SampleClause) End() token.Position { return s.Position }

// TableJoin represents a JOIN clause.
type TableJoin struct {
	Position  token.Position `json:"-"`
	Type      JoinType       `json:"type"`
	Strictness JoinStrictness `json:"strictness,omitempty"`
	Global    bool           `json:"global,omitempty"`
	On        Expression     `json:"on,omitempty"`
	Using     []Expression   `json:"using,omitempty"`
}

func (t *TableJoin) Pos() token.Position { return t.Position }
func (t *TableJoin) End() token.Position { return t.Position }

// JoinType represents the type of join.
type JoinType string

const (
	JoinInner JoinType = "INNER"
	JoinLeft  JoinType = "LEFT"
	JoinRight JoinType = "RIGHT"
	JoinFull  JoinType = "FULL"
	JoinCross JoinType = "CROSS"
	JoinPaste JoinType = "PASTE"
)

// JoinStrictness represents the join strictness.
type JoinStrictness string

const (
	JoinStrictAny  JoinStrictness = "ANY"
	JoinStrictAll  JoinStrictness = "ALL"
	JoinStrictAsof JoinStrictness = "ASOF"
	JoinStrictSemi JoinStrictness = "SEMI"
	JoinStrictAnti JoinStrictness = "ANTI"
)

// OrderByElement represents an ORDER BY element.
type OrderByElement struct {
	Position      token.Position `json:"-"`
	Expression    Expression     `json:"expression"`
	Descending    bool           `json:"descending,omitempty"`
	NullsFirst    *bool          `json:"nulls_first,omitempty"`
	Collate       string         `json:"collate,omitempty"`
	WithFill      bool           `json:"with_fill,omitempty"`
	FillFrom      Expression     `json:"fill_from,omitempty"`
	FillTo        Expression     `json:"fill_to,omitempty"`
	FillStep      Expression     `json:"fill_step,omitempty"`
	FillStaleness Expression     `json:"fill_staleness,omitempty"`
}

func (o *OrderByElement) Pos() token.Position { return o.Position }
func (o *OrderByElement) End() token.Position { return o.Position }

// InterpolateElement represents a single column interpolation in INTERPOLATE clause.
// Example: INTERPOLATE (value AS value + 1)
type InterpolateElement struct {
	Position token.Position `json:"-"`
	Column   string         `json:"column"`
	Value    Expression     `json:"value,omitempty"` // nil if just column name
}

func (i *InterpolateElement) Pos() token.Position { return i.Position }
func (i *InterpolateElement) End() token.Position { return i.Position }

// SettingExpr represents a setting expression.
type SettingExpr struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name"`
	Value    Expression     `json:"value"`
}

func (s *SettingExpr) Pos() token.Position { return s.Position }
func (s *SettingExpr) End() token.Position { return s.Position }

// InsertQuery represents an INSERT statement.
type InsertQuery struct {
	Position          token.Position   `json:"-"`
	Database          string           `json:"database,omitempty"`
	Table             string           `json:"table,omitempty"`
	Function          *FunctionCall    `json:"function,omitempty"` // For INSERT INTO FUNCTION syntax
	Columns           []*Identifier    `json:"columns,omitempty"`
	ColumnExpressions []Expression     `json:"column_expressions,omitempty"` // For asterisk/COLUMNS expressions with transformers
	AllColumns        bool             `json:"all_columns,omitempty"`        // For (*) syntax meaning all columns
	PartitionBy       Expression       `json:"partition_by,omitempty"`       // For PARTITION BY clause
	Infile            string           `json:"infile,omitempty"`             // For FROM INFILE clause
	Compression       string           `json:"compression,omitempty"`        // For COMPRESSION clause
	Values            [][]Expression   `json:"-"`                            // For VALUES clause (format only, not in AST JSON)
	Select            Statement        `json:"select,omitempty"`
	With              []Expression     `json:"with,omitempty"` // For WITH ... INSERT ... SELECT syntax
	Format            *Identifier      `json:"format,omitempty"`
	HasSettings       bool             `json:"has_settings,omitempty"` // For SETTINGS clause
	Settings          []*SettingExpr   `json:"settings,omitempty"`     // For SETTINGS clause in INSERT
}

func (i *InsertQuery) Pos() token.Position { return i.Position }
func (i *InsertQuery) End() token.Position { return i.Position }
func (i *InsertQuery) statementNode()      {}

// CreateQuery represents a CREATE statement.
type CreateQuery struct {
	Position         token.Position       `json:"-"`
	OrReplace        bool                 `json:"or_replace,omitempty"`
	IfNotExists      bool                 `json:"if_not_exists,omitempty"`
	Temporary        bool                 `json:"temporary,omitempty"`
	Database         string               `json:"database,omitempty"`
	Table            string               `json:"table,omitempty"`
	View             string               `json:"view,omitempty"`
	Materialized     bool                 `json:"materialized,omitempty"`
	WindowView       bool                 `json:"window_view,omitempty"` // WINDOW VIEW type
	InnerEngine      *EngineClause        `json:"inner_engine,omitempty"` // INNER ENGINE for window views
	ToDatabase       string               `json:"to_database,omitempty"` // Target database for materialized views
	To               string               `json:"to,omitempty"`          // Target table for materialized views
	Populate         bool                 `json:"populate,omitempty"`    // POPULATE for materialized views
	HasRefresh       bool                 `json:"has_refresh,omitempty"` // Has REFRESH clause
	RefreshType      string               `json:"refresh_type,omitempty"` // AFTER or EVERY
	RefreshInterval  Expression           `json:"refresh_interval,omitempty"` // Interval value
	RefreshUnit      string               `json:"refresh_unit,omitempty"` // SECOND, MINUTE, etc.
	RefreshAppend    bool                 `json:"refresh_append,omitempty"` // APPEND TO was specified
	Empty            bool                 `json:"empty,omitempty"`       // EMPTY keyword was specified
	Columns          []*ColumnDeclaration `json:"columns,omitempty"`
	Indexes          []*IndexDefinition   `json:"indexes,omitempty"`
	Projections      []*Projection        `json:"projections,omitempty"`
	Constraints         []*Constraint        `json:"constraints,omitempty"`
	ColumnsPrimaryKey       []Expression         `json:"columns_primary_key,omitempty"`        // PRIMARY KEY in column list
	HasEmptyColumnsPrimaryKey bool               `json:"has_empty_columns_primary_key,omitempty"` // TRUE if PRIMARY KEY () was seen with empty parens
	Engine               *EngineClause        `json:"engine,omitempty"`
	OrderBy              []Expression         `json:"order_by,omitempty"`
	OrderByHasModifiers  bool                 `json:"order_by_has_modifiers,omitempty"` // True if ORDER BY has ASC/DESC modifiers
	PartitionBy          Expression           `json:"partition_by,omitempty"`
	PrimaryKey          []Expression         `json:"primary_key,omitempty"`
	SampleBy         Expression           `json:"sample_by,omitempty"`
	TTL              *TTLClause           `json:"ttl,omitempty"`
	Settings             []*SettingExpr       `json:"settings,omitempty"`
	QuerySettings        []*SettingExpr       `json:"query_settings,omitempty"`          // Query-level SETTINGS (second SETTINGS clause)
	SettingsBeforeComment bool                `json:"settings_before_comment,omitempty"` // True if SETTINGS comes before COMMENT
	AsSelect         Statement            `json:"as_select,omitempty"`
	AsTableFunction  Expression           `json:"as_table_function,omitempty"` // AS table_function(...) in CREATE TABLE
	CloneAs          string               `json:"clone_as,omitempty"`          // CLONE AS source_table in CREATE TABLE
	Comment          string               `json:"comment,omitempty"`
	OnCluster        string               `json:"on_cluster,omitempty"`
	CreateDatabase   bool                 `json:"create_database,omitempty"`
	CreateFunction   bool                 `json:"create_function,omitempty"`
	CreateUser       bool                 `json:"create_user,omitempty"`
	AlterUser        bool                 `json:"alter_user,omitempty"`
	HasAuthenticationData bool            `json:"has_authentication_data,omitempty"`
	AuthenticationValues []string         `json:"authentication_values,omitempty"` // Password/hash values from IDENTIFIED BY
	SSHKeyCount          int              `json:"ssh_key_count,omitempty"`         // Number of SSH keys for ssh_key auth
	CreateDictionary   bool                              `json:"create_dictionary,omitempty"`
	DictionaryAttrs    []*DictionaryAttributeDeclaration `json:"dictionary_attrs,omitempty"`
	DictionaryDef      *DictionaryDefinition             `json:"dictionary_def,omitempty"`
	FunctionName       string                            `json:"function_name,omitempty"`
	FunctionBody     Expression           `json:"function_body,omitempty"`
	UserName         string               `json:"user_name,omitempty"`
	Format           string               `json:"format,omitempty"` // For FORMAT clause
}

func (c *CreateQuery) Pos() token.Position { return c.Position }
func (c *CreateQuery) End() token.Position { return c.Position }
func (c *CreateQuery) statementNode()      {}

// ColumnDeclaration represents a column definition.
type ColumnDeclaration struct {
	Position      token.Position `json:"-"`
	Name          string         `json:"name"`
	Type          *DataType      `json:"type"`
	Nullable      *bool          `json:"nullable,omitempty"`
	Default       Expression     `json:"default,omitempty"`
	DefaultKind   string         `json:"default_kind,omitempty"` // DEFAULT, MATERIALIZED, ALIAS, EPHEMERAL
	Codec         *CodecExpr     `json:"codec,omitempty"`
	Statistics    []*FunctionCall `json:"statistics,omitempty"` // STATISTICS clause
	TTL           Expression     `json:"ttl,omitempty"`
	PrimaryKey    bool           `json:"primary_key,omitempty"` // PRIMARY KEY constraint
	Comment       string         `json:"comment,omitempty"`
	Settings      []*SettingExpr `json:"settings,omitempty"`    // Column-level SETTINGS
}

func (c *ColumnDeclaration) Pos() token.Position { return c.Position }
func (c *ColumnDeclaration) End() token.Position { return c.Position }

// DictionaryAttributeDeclaration represents a dictionary attribute definition.
type DictionaryAttributeDeclaration struct {
	Position    token.Position `json:"-"`
	Name        string         `json:"name"`
	Type        *DataType      `json:"type"`
	Default     Expression     `json:"default,omitempty"`
	Expression  Expression     `json:"expression,omitempty"`   // EXPRESSION clause
	Hierarchical bool          `json:"hierarchical,omitempty"` // HIERARCHICAL flag
	Injective   bool           `json:"injective,omitempty"`    // INJECTIVE flag
	IsObjectID  bool           `json:"is_object_id,omitempty"` // IS_OBJECT_ID flag
}

func (d *DictionaryAttributeDeclaration) Pos() token.Position { return d.Position }
func (d *DictionaryAttributeDeclaration) End() token.Position { return d.Position }

// DictionaryDefinition represents the definition part of a dictionary (PRIMARY KEY, SOURCE, LIFETIME, LAYOUT).
type DictionaryDefinition struct {
	Position   token.Position        `json:"-"`
	PrimaryKey []Expression          `json:"primary_key,omitempty"`
	Source     *DictionarySource     `json:"source,omitempty"`
	Lifetime   *DictionaryLifetime   `json:"lifetime,omitempty"`
	Layout     *DictionaryLayout     `json:"layout,omitempty"`
	Range      *DictionaryRange      `json:"range,omitempty"`
	Settings   []*SettingExpr        `json:"settings,omitempty"`
}

func (d *DictionaryDefinition) Pos() token.Position { return d.Position }
func (d *DictionaryDefinition) End() token.Position { return d.Position }

// DictionarySource represents the SOURCE clause of a dictionary.
type DictionarySource struct {
	Position token.Position   `json:"-"`
	Type     string           `json:"type"`      // e.g., "CLICKHOUSE", "MYSQL", "FILE"
	Args     []*KeyValuePair  `json:"args,omitempty"`
}

func (d *DictionarySource) Pos() token.Position { return d.Position }
func (d *DictionarySource) End() token.Position { return d.Position }

// KeyValuePair represents a key-value pair in dictionary source or other contexts.
type KeyValuePair struct {
	Position token.Position `json:"-"`
	Key      string         `json:"key"`
	Value    Expression     `json:"value"`
}

func (k *KeyValuePair) Pos() token.Position { return k.Position }
func (k *KeyValuePair) End() token.Position { return k.Position }

// DictionaryLifetime represents the LIFETIME clause of a dictionary.
type DictionaryLifetime struct {
	Position token.Position `json:"-"`
	Min      Expression     `json:"min,omitempty"`
	Max      Expression     `json:"max,omitempty"`
}

func (d *DictionaryLifetime) Pos() token.Position { return d.Position }
func (d *DictionaryLifetime) End() token.Position { return d.Position }

// DictionaryLayout represents the LAYOUT clause of a dictionary.
type DictionaryLayout struct {
	Position token.Position   `json:"-"`
	Type     string           `json:"type"` // e.g., "FLAT", "HASHED", "COMPLEX_KEY_HASHED"
	Args     []*KeyValuePair  `json:"args,omitempty"`
}

func (d *DictionaryLayout) Pos() token.Position { return d.Position }
func (d *DictionaryLayout) End() token.Position { return d.Position }

// DictionaryRange represents the RANGE clause of a dictionary.
type DictionaryRange struct {
	Position token.Position `json:"-"`
	Min      Expression     `json:"min,omitempty"`
	Max      Expression     `json:"max,omitempty"`
}

func (d *DictionaryRange) Pos() token.Position { return d.Position }
func (d *DictionaryRange) End() token.Position { return d.Position }

// DataType represents a data type.
type DataType struct {
	Position       token.Position `json:"-"`
	Name           string         `json:"name"`
	Parameters     []Expression   `json:"parameters,omitempty"`
	HasParentheses bool           `json:"has_parentheses,omitempty"`
}

func (d *DataType) Pos() token.Position { return d.Position }
func (d *DataType) End() token.Position { return d.Position }
func (d *DataType) expressionNode()     {}

// ObjectTypeArgument wraps an expression that is an argument to JSON/OBJECT types.
// This matches ClickHouse's ASTObjectTypeArgument node structure.
type ObjectTypeArgument struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
}

func (o *ObjectTypeArgument) Pos() token.Position { return o.Position }
func (o *ObjectTypeArgument) End() token.Position { return o.Position }
func (o *ObjectTypeArgument) expressionNode()     {}

// NameTypePair represents a named type pair, used in Nested types.
type NameTypePair struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name"`
	Type     *DataType      `json:"type"`
}

func (n *NameTypePair) Pos() token.Position { return n.Position }
func (n *NameTypePair) End() token.Position { return n.Position }
func (n *NameTypePair) expressionNode()     {}

// CodecExpr represents a CODEC expression.
type CodecExpr struct {
	Position token.Position  `json:"-"`
	Codecs   []*FunctionCall `json:"codecs"`
}

func (c *CodecExpr) Pos() token.Position { return c.Position }
func (c *CodecExpr) End() token.Position { return c.Position }

// IndexDefinition represents an INDEX definition in CREATE TABLE.
type IndexDefinition struct {
	Position    token.Position `json:"-"`
	Name        string         `json:"name"`
	Expression  Expression     `json:"expression"`
	Type        *FunctionCall  `json:"type"`
	Granularity Expression     `json:"granularity,omitempty"`
}

func (i *IndexDefinition) Pos() token.Position { return i.Position }
func (i *IndexDefinition) End() token.Position { return i.Position }
func (i *IndexDefinition) expressionNode()     {}

// Constraint represents a table constraint.
type Constraint struct {
	Position   token.Position `json:"-"`
	Name       string         `json:"name,omitempty"`
	Expression Expression     `json:"expression"`
}

func (c *Constraint) Pos() token.Position { return c.Position }
func (c *Constraint) End() token.Position { return c.Position }

// EngineClause represents an ENGINE clause.
type EngineClause struct {
	Position      token.Position `json:"-"`
	Name          string         `json:"name"`
	Parameters    []Expression   `json:"parameters,omitempty"`
	HasParentheses bool          `json:"has_parentheses,omitempty"` // true if called with ()
}

func (e *EngineClause) Pos() token.Position { return e.Position }
func (e *EngineClause) End() token.Position { return e.Position }

// TTLClause represents a TTL clause.
type TTLClause struct {
	Position    token.Position `json:"-"`
	Expression  Expression     `json:"expression"`
	Expressions []Expression   `json:"expressions,omitempty"` // Additional TTL expressions (for multiple TTL elements)
	Elements    []*TTLElement  `json:"elements,omitempty"`    // TTL elements with WHERE conditions
}

func (t *TTLClause) Pos() token.Position { return t.Position }
func (t *TTLClause) End() token.Position { return t.Position }

// TTLElement represents a single TTL element with optional WHERE condition.
type TTLElement struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
	Where    Expression     `json:"where,omitempty"` // WHERE condition for DELETE
}

func (t *TTLElement) Pos() token.Position { return t.Position }
func (t *TTLElement) End() token.Position { return t.Position }

// DropQuery represents a DROP statement.
type DropQuery struct {
	Position        token.Position     `json:"-"`
	IfExists        bool               `json:"if_exists,omitempty"`
	Database        string             `json:"database,omitempty"`
	Table           string             `json:"table,omitempty"`
	Tables          []*TableIdentifier `json:"tables,omitempty"` // For DROP TABLE t1, t2, t3
	View            string             `json:"view,omitempty"`
	User            string             `json:"user,omitempty"`
	Function        string             `json:"function,omitempty"` // For DROP FUNCTION
	Dictionary      string             `json:"-"`                  // For DROP DICTIONARY (format only, not in AST JSON)
	Role            string             `json:"role,omitempty"`     // For DROP ROLE
	Quota           string             `json:"quota,omitempty"`    // For DROP QUOTA
	Policy          string             `json:"policy,omitempty"`   // For DROP POLICY
	RowPolicy       string             `json:"row_policy,omitempty"` // For DROP ROW POLICY
	SettingsProfile string             `json:"settings_profile,omitempty"` // For DROP SETTINGS PROFILE
	Index           string             `json:"index,omitempty"`            // For DROP INDEX
	Temporary       bool               `json:"temporary,omitempty"`
	OnCluster       string             `json:"on_cluster,omitempty"`
	DropDatabase    bool               `json:"drop_database,omitempty"`
	Sync            bool               `json:"sync,omitempty"`
	Format          string             `json:"format,omitempty"`   // For FORMAT clause
	Settings        []*SettingExpr     `json:"settings,omitempty"` // For SETTINGS clause
}

func (d *DropQuery) Pos() token.Position { return d.Position }
func (d *DropQuery) End() token.Position { return d.Position }
func (d *DropQuery) statementNode()      {}

// UndropQuery represents an UNDROP TABLE statement.
type UndropQuery struct {
	Position  token.Position `json:"-"`
	Database  string         `json:"database,omitempty"`
	Table     string         `json:"table"`
	OnCluster string         `json:"on_cluster,omitempty"`
	UUID      string         `json:"uuid,omitempty"`
	Format    string         `json:"format,omitempty"`
}

func (u *UndropQuery) Pos() token.Position { return u.Position }
func (u *UndropQuery) End() token.Position { return u.Position }
func (u *UndropQuery) statementNode()      {}

// UpdateQuery represents a standalone UPDATE statement.
// In ClickHouse, UPDATE is syntactic sugar for ALTER TABLE ... UPDATE
type UpdateQuery struct {
	Position    token.Position `json:"-"`
	Database    string         `json:"database,omitempty"`
	Table       string         `json:"table"`
	Assignments []*Assignment  `json:"assignments"`
	Where       Expression     `json:"where,omitempty"`
}

func (u *UpdateQuery) Pos() token.Position { return u.Position }
func (u *UpdateQuery) End() token.Position { return u.Position }
func (u *UpdateQuery) statementNode()      {}

// AlterQuery represents an ALTER statement.
type AlterQuery struct {
	Position  token.Position  `json:"-"`
	Database  string          `json:"database,omitempty"`
	Table     string          `json:"table"`
	Commands  []*AlterCommand `json:"commands"`
	OnCluster string          `json:"on_cluster,omitempty"`
	Settings  []*SettingExpr  `json:"settings,omitempty"`
	Format    string          `json:"format,omitempty"` // For FORMAT clause
}

func (a *AlterQuery) Pos() token.Position { return a.Position }
func (a *AlterQuery) End() token.Position { return a.Position }
func (a *AlterQuery) statementNode()      {}

// AlterCommand represents an ALTER command.
type AlterCommand struct {
	Position       token.Position       `json:"-"`
	Type           AlterCommandType     `json:"type"`
	Column         *ColumnDeclaration   `json:"column,omitempty"`
	ColumnName     string               `json:"column_name,omitempty"`
	AfterColumn    string               `json:"after_column,omitempty"`
	NewName        string               `json:"new_name,omitempty"`
	IfNotExists    bool                 `json:"if_not_exists,omitempty"`
	IfExists       bool                 `json:"if_exists,omitempty"`
	Index          string               `json:"index,omitempty"`
	IndexExpr      Expression           `json:"index_expr,omitempty"`
	IndexType      string               `json:"index_type,omitempty"`
	IndexDef       *IndexDefinition     `json:"index_def,omitempty"`       // For ADD INDEX with full definition
	Granularity    int                  `json:"granularity,omitempty"`
	AfterIndex     string               `json:"after_index,omitempty"`     // For ADD INDEX ... AFTER name
	Constraint     *Constraint          `json:"constraint,omitempty"`
	ConstraintName string               `json:"constraint_name,omitempty"`
	Partition      Expression           `json:"partition,omitempty"`
	PartitionIsID  bool                 `json:"partition_is_id,omitempty"` // True when using PARTITION ID 'value' syntax
	IsPart         bool                 `json:"-"`                         // True for PART (not PARTITION) - output directly without Partition wrapper
	FromTable      string               `json:"from_table,omitempty"`
	ToDatabase     string               `json:"to_database,omitempty"` // For MOVE PARTITION TO TABLE
	ToTable        string               `json:"to_table,omitempty"`    // For MOVE PARTITION TO TABLE
	FromPath       string               `json:"from_path,omitempty"`   // For FETCH PARTITION FROM
	TTL            *TTLClause           `json:"ttl,omitempty"`
	Settings       []*SettingExpr       `json:"settings,omitempty"`
	Where          Expression           `json:"where,omitempty"`       // For DELETE WHERE
	Assignments    []*Assignment        `json:"assignments,omitempty"` // For UPDATE
	Projection     *Projection          `json:"projection,omitempty"`  // For ADD PROJECTION
	ProjectionName string               `json:"projection_name,omitempty"` // For DROP/MATERIALIZE/CLEAR PROJECTION
	StatisticsColumns []string          `json:"statistics_columns,omitempty"` // For ADD/DROP/CLEAR/MATERIALIZE STATISTICS
	StatisticsTypes   []*FunctionCall   `json:"statistics_types,omitempty"`   // For ADD/MODIFY STATISTICS TYPE
	Comment           string            `json:"comment,omitempty"`            // For COMMENT COLUMN
	OrderByExpr       []Expression      `json:"order_by_expr,omitempty"`      // For MODIFY ORDER BY
	SampleByExpr      Expression        `json:"sample_by_expr,omitempty"`     // For MODIFY SAMPLE BY
	ResetSettings     []string          `json:"reset_settings,omitempty"`     // For MODIFY COLUMN ... RESET SETTING
	Query             Statement         `json:"query,omitempty"`              // For MODIFY QUERY
}

// Projection represents a projection definition.
type Projection struct {
	Position token.Position            `json:"-"`
	Name     string                    `json:"name"`
	Select   *ProjectionSelectQuery    `json:"select"`
}

func (p *Projection) Pos() token.Position { return p.Position }
func (p *Projection) End() token.Position { return p.Position }

// ProjectionSelectQuery represents the SELECT part of a projection.
type ProjectionSelectQuery struct {
	Position token.Position   `json:"-"`
	With     []Expression     `json:"with,omitempty"` // WITH clause expressions
	Columns  []Expression     `json:"columns"`
	GroupBy  []Expression     `json:"group_by,omitempty"`
	OrderBy  []Expression     `json:"order_by,omitempty"` // ORDER BY columns
}

// Assignment represents a column assignment in UPDATE.
type Assignment struct {
	Position token.Position `json:"-"`
	Column   string         `json:"column"`
	Value    Expression     `json:"value"`
}

func (a *Assignment) Pos() token.Position { return a.Position }
func (a *Assignment) End() token.Position { return a.Position }

func (a *AlterCommand) Pos() token.Position { return a.Position }
func (a *AlterCommand) End() token.Position { return a.Position }

// AlterCommandType represents the type of ALTER command.
type AlterCommandType string

const (
	AlterAddColumn         AlterCommandType = "ADD_COLUMN"
	AlterDropColumn        AlterCommandType = "DROP_COLUMN"
	AlterModifyColumn      AlterCommandType = "MODIFY_COLUMN"
	AlterRenameColumn      AlterCommandType = "RENAME_COLUMN"
	AlterClearColumn       AlterCommandType = "CLEAR_COLUMN"
	AlterMaterializeColumn AlterCommandType = "MATERIALIZE_COLUMN"
	AlterCommentColumn     AlterCommandType = "COMMENT_COLUMN"
	AlterAddIndex          AlterCommandType = "ADD_INDEX"
	AlterDropIndex         AlterCommandType = "DROP_INDEX"
	AlterClearIndex        AlterCommandType = "CLEAR_INDEX"
	AlterMaterializeIndex  AlterCommandType = "MATERIALIZE_INDEX"
	AlterAddConstraint     AlterCommandType = "ADD_CONSTRAINT"
	AlterDropConstraint    AlterCommandType = "DROP_CONSTRAINT"
	AlterModifyTTL          AlterCommandType = "MODIFY_TTL"
	AlterMaterializeTTL     AlterCommandType = "MATERIALIZE_TTL"
	AlterRemoveTTL          AlterCommandType = "REMOVE_TTL"
	AlterModifySetting      AlterCommandType = "MODIFY_SETTING"
	AlterResetSetting       AlterCommandType = "RESET_SETTING"
	AlterDropPartition         AlterCommandType = "DROP_PARTITION"
	AlterDropDetachedPartition AlterCommandType = "DROP_DETACHED_PARTITION"
	AlterDetachPartition       AlterCommandType = "DETACH_PARTITION"
	AlterAttachPartition    AlterCommandType = "ATTACH_PARTITION"
	AlterReplacePartition   AlterCommandType = "REPLACE_PARTITION"
	AlterFetchPartition     AlterCommandType = "FETCH_PARTITION"
	AlterMovePartition      AlterCommandType = "MOVE_PARTITION"
	AlterFreezePartition    AlterCommandType = "FREEZE_PARTITION"
	AlterFreeze             AlterCommandType = "FREEZE"
	AlterApplyPatches       AlterCommandType = "APPLY_PATCHES"
	AlterDeleteWhere        AlterCommandType = "DELETE_WHERE"
	AlterUpdate             AlterCommandType = "UPDATE"
	AlterAddProjection      AlterCommandType = "ADD_PROJECTION"
	AlterDropProjection     AlterCommandType = "DROP_PROJECTION"
	AlterMaterializeProjection AlterCommandType = "MATERIALIZE_PROJECTION"
	AlterClearProjection    AlterCommandType = "CLEAR_PROJECTION"
	AlterAddStatistics      AlterCommandType = "ADD_STATISTICS"
	AlterModifyStatistics   AlterCommandType = "MODIFY_STATISTICS"
	AlterDropStatistics        AlterCommandType = "DROP_STATISTICS"
	AlterClearStatistics       AlterCommandType = "CLEAR_STATISTICS"
	AlterMaterializeStatistics AlterCommandType = "MATERIALIZE_STATISTICS"
	AlterModifyComment         AlterCommandType = "MODIFY_COMMENT"
	AlterModifyOrderBy         AlterCommandType = "MODIFY_ORDER_BY"
	AlterModifySampleBy        AlterCommandType = "MODIFY_SAMPLE_BY"
	AlterModifyQuery           AlterCommandType = "MODIFY_QUERY"
	AlterRemoveSampleBy        AlterCommandType = "REMOVE_SAMPLE_BY"
	AlterApplyDeletedMask      AlterCommandType = "APPLY_DELETED_MASK"
)

// TruncateQuery represents a TRUNCATE statement.
type TruncateQuery struct {
	Position         token.Position `json:"-"`
	Temporary        bool           `json:"temporary,omitempty"`
	IfExists         bool           `json:"if_exists,omitempty"`
	TruncateDatabase bool           `json:"truncate_database,omitempty"` // True for TRUNCATE DATABASE
	Database         string         `json:"database,omitempty"`
	Table            string         `json:"table"`
	OnCluster        string         `json:"on_cluster,omitempty"`
	Settings         []*SettingExpr `json:"settings,omitempty"`
}

func (t *TruncateQuery) Pos() token.Position { return t.Position }
func (t *TruncateQuery) End() token.Position { return t.Position }
func (t *TruncateQuery) statementNode()      {}

// DeleteQuery represents a lightweight DELETE statement.
type DeleteQuery struct {
	Position  token.Position `json:"-"`
	Database  string         `json:"database,omitempty"`
	Table     string         `json:"table"`
	OnCluster string         `json:"on_cluster,omitempty"` // ON CLUSTER clause
	Partition Expression     `json:"partition,omitempty"`  // IN PARTITION clause
	Where     Expression     `json:"where,omitempty"`
	Settings  []*SettingExpr `json:"settings,omitempty"`
}

func (d *DeleteQuery) Pos() token.Position { return d.Position }
func (d *DeleteQuery) End() token.Position { return d.Position }
func (d *DeleteQuery) statementNode()      {}

// UseQuery represents a USE statement.
type UseQuery struct {
	Position token.Position `json:"-"`
	Database string         `json:"database"`
}

func (u *UseQuery) Pos() token.Position { return u.Position }
func (u *UseQuery) End() token.Position { return u.Position }
func (u *UseQuery) statementNode()      {}

// DetachQuery represents a DETACH statement.
type DetachQuery struct {
	Position   token.Position `json:"-"`
	Database   string         `json:"database,omitempty"`
	Table      string         `json:"table,omitempty"`
	Dictionary string         `json:"dictionary,omitempty"`
}

func (d *DetachQuery) Pos() token.Position { return d.Position }
func (d *DetachQuery) End() token.Position { return d.Position }
func (d *DetachQuery) statementNode()      {}

// AttachQuery represents an ATTACH statement.
type AttachQuery struct {
	Position           token.Position       `json:"-"`
	IfNotExists        bool                 `json:"if_not_exists,omitempty"`
	Database           string               `json:"database,omitempty"`
	Table              string               `json:"table,omitempty"`
	Dictionary         string               `json:"dictionary,omitempty"`
	FromPath           string               `json:"from_path,omitempty"`     // FROM 'path' clause
	Columns            []*ColumnDeclaration `json:"columns,omitempty"`
	ColumnsPrimaryKey       []Expression         `json:"columns_primary_key,omitempty"`        // PRIMARY KEY in column list
	HasEmptyColumnsPrimaryKey bool               `json:"has_empty_columns_primary_key,omitempty"` // TRUE if PRIMARY KEY () was seen with empty parens
	Indexes            []*IndexDefinition   `json:"indexes,omitempty"`             // INDEX definitions in column list
	Engine             *EngineClause        `json:"engine,omitempty"`
	OrderBy            []Expression         `json:"order_by,omitempty"`
	PrimaryKey         []Expression         `json:"primary_key,omitempty"`
	IsMaterializedView bool                 `json:"is_materialized_view,omitempty"`
	UUID               string               `json:"uuid,omitempty"`       // UUID clause
	InnerUUID          string               `json:"inner_uuid,omitempty"` // TO INNER UUID clause
	PartitionBy        Expression           `json:"partition_by,omitempty"`
	SelectQuery        Statement            `json:"select_query,omitempty"` // AS SELECT clause
	Settings           []*SettingExpr       `json:"settings,omitempty"`     // SETTINGS clause
}

func (a *AttachQuery) Pos() token.Position { return a.Position }
func (a *AttachQuery) End() token.Position { return a.Position }
func (a *AttachQuery) statementNode()      {}

// BackupQuery represents a BACKUP statement.
type BackupQuery struct {
	Position   token.Position `json:"-"`
	Database   string         `json:"database,omitempty"`
	Table      string         `json:"table,omitempty"`
	Dictionary string         `json:"dictionary,omitempty"`
	All        bool           `json:"all,omitempty"` // BACKUP ALL
	Temporary  bool           `json:"temporary,omitempty"`
	Target     *FunctionCall  `json:"target,omitempty"` // Disk('path') or Null
	Settings   []*SettingExpr `json:"settings,omitempty"`
	Format     string         `json:"format,omitempty"`
}

func (b *BackupQuery) Pos() token.Position { return b.Position }
func (b *BackupQuery) End() token.Position { return b.Position }
func (b *BackupQuery) statementNode()      {}

// RestoreQuery represents a RESTORE statement.
type RestoreQuery struct {
	Position   token.Position `json:"-"`
	Database   string         `json:"database,omitempty"`
	Table      string         `json:"table,omitempty"`
	Dictionary string         `json:"dictionary,omitempty"`
	All        bool           `json:"all,omitempty"` // RESTORE ALL
	Temporary  bool           `json:"temporary,omitempty"`
	Source     *FunctionCall  `json:"source,omitempty"` // Disk('path') or Null
	Settings   []*SettingExpr `json:"settings,omitempty"`
	Format     string         `json:"format,omitempty"`
}

func (r *RestoreQuery) Pos() token.Position { return r.Position }
func (r *RestoreQuery) End() token.Position { return r.Position }
func (r *RestoreQuery) statementNode()      {}

// DescribeQuery represents a DESCRIBE statement.
type DescribeQuery struct {
	Position      token.Position   `json:"-"`
	Database      string           `json:"database,omitempty"`
	Table         string           `json:"table,omitempty"`
	TableFunction *FunctionCall    `json:"table_function,omitempty"`
	TableExpr     *TableExpression `json:"table_expr,omitempty"` // For DESCRIBE (SELECT ...)
	Settings      []*SettingExpr   `json:"settings,omitempty"`
	Format        string           `json:"format,omitempty"`
}

func (d *DescribeQuery) Pos() token.Position { return d.Position }
func (d *DescribeQuery) End() token.Position { return d.Position }
func (d *DescribeQuery) statementNode()      {}

// ShowQuery represents a SHOW statement.
type ShowQuery struct {
	Position      token.Position `json:"-"`
	ShowType      ShowType       `json:"show_type"`
	Temporary     bool           `json:"temporary,omitempty"`
	Database      string         `json:"database,omitempty"`
	From          string         `json:"from,omitempty"`
	Like          string         `json:"like,omitempty"`
	Where         Expression     `json:"where,omitempty"`
	Limit         Expression     `json:"limit,omitempty"`
	Format        string         `json:"format,omitempty"`
	HasSettings   bool           `json:"has_settings,omitempty"` // Whether SETTINGS clause was specified
	MultipleUsers bool           `json:"multiple_users,omitempty"` // True when SHOW CREATE USER has multiple users
}

func (s *ShowQuery) Pos() token.Position { return s.Position }
func (s *ShowQuery) End() token.Position { return s.Position }
func (s *ShowQuery) statementNode()      {}

// ShowType represents the type of SHOW statement.
type ShowType string

const (
	ShowTables                  ShowType = "TABLES"
	ShowDatabases               ShowType = "DATABASES"
	ShowProcesses               ShowType = "PROCESSLIST"
	ShowCreate                  ShowType = "CREATE"
	ShowCreateDB                ShowType = "CREATE_DATABASE"
	ShowCreateDictionary        ShowType = "CREATE_DICTIONARY"
	ShowCreateView              ShowType = "CREATE_VIEW"
	ShowCreateUser              ShowType = "CREATE_USER"
	ShowCreateRole              ShowType = "CREATE_ROLE"
	ShowCreatePolicy            ShowType = "CREATE_POLICY"
	ShowCreateRowPolicy         ShowType = "CREATE_ROW_POLICY"
	ShowCreateQuota             ShowType = "CREATE_QUOTA"
	ShowCreateSettingsProfile   ShowType = "CREATE_SETTINGS_PROFILE"
	ShowColumns                 ShowType = "COLUMNS"
	ShowDictionaries            ShowType = "DICTIONARIES"
	ShowFunctions               ShowType = "FUNCTIONS"
	ShowSettings                ShowType = "SETTINGS"
	ShowSetting                 ShowType = "SETTING"
	ShowGrants                  ShowType = "GRANTS"
)

// ExplainQuery represents an EXPLAIN statement.
type ExplainQuery struct {
	Position       token.Position `json:"-"`
	ExplainType    ExplainType    `json:"explain_type"`
	Statement      Statement      `json:"statement"`
	HasSettings    bool           `json:"has_settings,omitempty"`
	ExplicitType   bool           `json:"explicit_type,omitempty"` // true if type was explicitly specified
	OptionsString  string         `json:"options_string,omitempty"` // Formatted options like "actions = 1"
}

func (e *ExplainQuery) Pos() token.Position { return e.Position }
func (e *ExplainQuery) End() token.Position { return e.Position }
func (e *ExplainQuery) statementNode()      {}

// ExplainType represents the type of EXPLAIN.
type ExplainType string

const (
	ExplainAST                ExplainType = "AST"
	ExplainSyntax             ExplainType = "SYNTAX"
	ExplainPlan               ExplainType = "PLAN"
	ExplainPipeline           ExplainType = "PIPELINE"
	ExplainEstimate           ExplainType = "ESTIMATE"
	ExplainQueryTree          ExplainType = "QUERY TREE"
	ExplainCurrentTransaction ExplainType = "CURRENT TRANSACTION"
)

// SetQuery represents a SET statement.
type SetQuery struct {
	Position token.Position `json:"-"`
	Settings []*SettingExpr `json:"settings"`
}

func (s *SetQuery) Pos() token.Position { return s.Position }
func (s *SetQuery) End() token.Position { return s.Position }
func (s *SetQuery) statementNode()      {}

// OptimizeQuery represents an OPTIMIZE statement.
type OptimizeQuery struct {
	Position      token.Position `json:"-"`
	Database      string         `json:"database,omitempty"`
	Table         string         `json:"table"`
	Partition     Expression     `json:"partition,omitempty"`
	PartitionByID bool           `json:"partition_by_id,omitempty"` // PARTITION ID vs PARTITION expr
	Final         bool           `json:"final,omitempty"`
	Cleanup       bool           `json:"cleanup,omitempty"`
	Dedupe        bool           `json:"dedupe,omitempty"`
	OnCluster     string         `json:"on_cluster,omitempty"`
	Settings      []*SettingExpr `json:"settings,omitempty"`
}

func (o *OptimizeQuery) Pos() token.Position { return o.Position }
func (o *OptimizeQuery) End() token.Position { return o.Position }
func (o *OptimizeQuery) statementNode()      {}

// CheckQuery represents a CHECK TABLE statement.
type CheckQuery struct {
	Position  token.Position `json:"-"`
	Database  string         `json:"database,omitempty"`
	Table     string         `json:"table"`
	Partition Expression     `json:"partition,omitempty"`
	Part      Expression     `json:"part,omitempty"`
	Format    string         `json:"format,omitempty"`
	Settings  []*SettingExpr `json:"settings,omitempty"`
}

func (c *CheckQuery) Pos() token.Position { return c.Position }
func (c *CheckQuery) End() token.Position { return c.Position }
func (c *CheckQuery) statementNode()      {}

// SystemQuery represents a SYSTEM statement.
type SystemQuery struct {
	Position             token.Position `json:"-"`
	Command              string         `json:"command"`
	Database             string         `json:"database,omitempty"`
	Table                string         `json:"table,omitempty"`
	OnCluster            string         `json:"on_cluster,omitempty"`
	DuplicateTableOutput bool           `json:"duplicate_table_output,omitempty"` // True for commands that need database/table output twice
	Settings             []*SettingExpr `json:"settings,omitempty"`
}

func (s *SystemQuery) Pos() token.Position { return s.Position }
func (s *SystemQuery) End() token.Position { return s.Position }
func (s *SystemQuery) statementNode()      {}

// TransactionControlQuery represents a transaction control statement (BEGIN, COMMIT, ROLLBACK, SET TRANSACTION SNAPSHOT).
type TransactionControlQuery struct {
	Position token.Position `json:"-"`
	Action   string         `json:"action"` // "BEGIN", "COMMIT", "ROLLBACK", "SET_SNAPSHOT"
	Snapshot int64          `json:"snapshot,omitempty"`
}

func (t *TransactionControlQuery) Pos() token.Position { return t.Position }
func (t *TransactionControlQuery) End() token.Position { return t.Position }
func (t *TransactionControlQuery) statementNode()      {}

// RenamePair represents a single rename pair in RENAME TABLE.
type RenamePair struct {
	FromDatabase string `json:"from_database,omitempty"`
	FromTable    string `json:"from_table"`
	ToDatabase   string `json:"to_database,omitempty"`
	ToTable      string `json:"to_table"`
}

// RenameQuery represents a RENAME TABLE statement.
type RenameQuery struct {
	Position       token.Position `json:"-"`
	Pairs          []*RenamePair  `json:"pairs"`                     // Multiple rename pairs
	From           string         `json:"from,omitempty"`            // Deprecated: for backward compat
	To             string         `json:"to,omitempty"`              // Deprecated: for backward compat
	OnCluster      string         `json:"on_cluster,omitempty"`
	Settings       []*SettingExpr `json:"settings,omitempty"`
	IfExists       bool           `json:"if_exists,omitempty"`       // IF EXISTS modifier
	RenameDatabase bool           `json:"rename_database,omitempty"` // True for RENAME DATABASE
}

func (r *RenameQuery) Pos() token.Position { return r.Position }
func (r *RenameQuery) End() token.Position { return r.Position }
func (r *RenameQuery) statementNode()      {}

// ExchangeQuery represents an EXCHANGE TABLES statement.
type ExchangeQuery struct {
	Position  token.Position `json:"-"`
	Database1 string         `json:"database1,omitempty"`
	Table1    string         `json:"table1"`
	Database2 string         `json:"database2,omitempty"`
	Table2    string         `json:"table2"`
	OnCluster string         `json:"on_cluster,omitempty"`
}

func (e *ExchangeQuery) Pos() token.Position { return e.Position }
func (e *ExchangeQuery) End() token.Position { return e.Position }
func (e *ExchangeQuery) statementNode()      {}

// ExistsType represents the type of EXISTS query.
type ExistsType string

const (
	ExistsTable      ExistsType = "TABLE"
	ExistsDictionary ExistsType = "DICTIONARY"
	ExistsDatabase   ExistsType = "DATABASE"
	ExistsView       ExistsType = "VIEW"
)

// ExistsQuery represents an EXISTS table_name statement (check if table exists).
type ExistsQuery struct {
	Position   token.Position `json:"-"`
	ExistsType ExistsType     `json:"exists_type,omitempty"`
	Temporary  bool           `json:"temporary,omitempty"`
	Database   string         `json:"database,omitempty"`
	Table      string         `json:"table"`
	Settings   []*SettingExpr `json:"settings,omitempty"`
}

func (e *ExistsQuery) Pos() token.Position { return e.Position }
func (e *ExistsQuery) End() token.Position { return e.Position }
func (e *ExistsQuery) statementNode()      {}

// GrantQuery represents a GRANT or REVOKE statement.
type GrantQuery struct {
	Position token.Position `json:"-"`
	IsRevoke bool           `json:"is_revoke,omitempty"`
}

func (g *GrantQuery) Pos() token.Position { return g.Position }
func (g *GrantQuery) End() token.Position { return g.Position }
func (g *GrantQuery) statementNode()      {}

// ShowGrantsQuery represents a SHOW GRANTS statement.
type ShowGrantsQuery struct {
	Position token.Position `json:"-"`
	Format   string         `json:"format,omitempty"`
}

func (s *ShowGrantsQuery) Pos() token.Position { return s.Position }
func (s *ShowGrantsQuery) End() token.Position { return s.Position }
func (s *ShowGrantsQuery) statementNode()      {}

// KillQuery represents a KILL QUERY/MUTATION statement.
type KillQuery struct {
	Position token.Position `json:"-"`
	Type     string         `json:"type"`              // "QUERY" or "MUTATION"
	Where    Expression     `json:"where,omitempty"`   // WHERE condition
	Sync     bool           `json:"sync,omitempty"`    // SYNC mode (default false = ASYNC)
	Test     bool           `json:"test,omitempty"`    // TEST mode
	Format   string         `json:"format,omitempty"`  // FORMAT clause
	Settings []*SettingExpr `json:"settings,omitempty"`
}

func (k *KillQuery) Pos() token.Position { return k.Position }
func (k *KillQuery) End() token.Position { return k.Position }
func (k *KillQuery) statementNode()      {}

// ShowPrivilegesQuery represents a SHOW PRIVILEGES statement.
type ShowPrivilegesQuery struct {
	Position token.Position `json:"-"`
}

func (s *ShowPrivilegesQuery) Pos() token.Position { return s.Position }
func (s *ShowPrivilegesQuery) End() token.Position { return s.Position }
func (s *ShowPrivilegesQuery) statementNode()      {}

// ShowCreateQuotaQuery represents a SHOW CREATE QUOTA statement.
type ShowCreateQuotaQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
	Format   string         `json:"format,omitempty"`
}

func (s *ShowCreateQuotaQuery) Pos() token.Position { return s.Position }
func (s *ShowCreateQuotaQuery) End() token.Position { return s.Position }
func (s *ShowCreateQuotaQuery) statementNode()      {}

// CreateQuotaQuery represents a CREATE QUOTA statement.
type CreateQuotaQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
}

func (c *CreateQuotaQuery) Pos() token.Position { return c.Position }
func (c *CreateQuotaQuery) End() token.Position { return c.Position }
func (c *CreateQuotaQuery) statementNode()      {}

// CreateSettingsProfileQuery represents a CREATE SETTINGS PROFILE statement.
type CreateSettingsProfileQuery struct {
	Position token.Position `json:"-"`
	Names    []string       `json:"names,omitempty"`
}

func (c *CreateSettingsProfileQuery) Pos() token.Position { return c.Position }
func (c *CreateSettingsProfileQuery) End() token.Position { return c.Position }
func (c *CreateSettingsProfileQuery) statementNode()      {}

// AlterSettingsProfileQuery represents an ALTER SETTINGS PROFILE statement.
type AlterSettingsProfileQuery struct {
	Position token.Position `json:"-"`
	Names    []string       `json:"names,omitempty"`
}

func (a *AlterSettingsProfileQuery) Pos() token.Position { return a.Position }
func (a *AlterSettingsProfileQuery) End() token.Position { return a.Position }
func (a *AlterSettingsProfileQuery) statementNode()      {}

// DropSettingsProfileQuery represents a DROP SETTINGS PROFILE statement.
type DropSettingsProfileQuery struct {
	Position token.Position `json:"-"`
	Names    []string       `json:"names,omitempty"`
	IfExists bool           `json:"if_exists,omitempty"`
}

func (d *DropSettingsProfileQuery) Pos() token.Position { return d.Position }
func (d *DropSettingsProfileQuery) End() token.Position { return d.Position }
func (d *DropSettingsProfileQuery) statementNode()      {}

// CreateNamedCollectionQuery represents a CREATE NAMED COLLECTION statement.
type CreateNamedCollectionQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
}

func (c *CreateNamedCollectionQuery) Pos() token.Position { return c.Position }
func (c *CreateNamedCollectionQuery) End() token.Position { return c.Position }
func (c *CreateNamedCollectionQuery) statementNode()      {}

// AlterNamedCollectionQuery represents an ALTER NAMED COLLECTION statement.
type AlterNamedCollectionQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
}

func (a *AlterNamedCollectionQuery) Pos() token.Position { return a.Position }
func (a *AlterNamedCollectionQuery) End() token.Position { return a.Position }
func (a *AlterNamedCollectionQuery) statementNode()      {}

// DropNamedCollectionQuery represents a DROP NAMED COLLECTION statement.
type DropNamedCollectionQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
	IfExists bool           `json:"if_exists,omitempty"`
}

func (d *DropNamedCollectionQuery) Pos() token.Position { return d.Position }
func (d *DropNamedCollectionQuery) End() token.Position { return d.Position }
func (d *DropNamedCollectionQuery) statementNode()      {}

// ShowCreateSettingsProfileQuery represents a SHOW CREATE SETTINGS PROFILE statement.
type ShowCreateSettingsProfileQuery struct {
	Position token.Position `json:"-"`
	Names    []string       `json:"names,omitempty"`
	Format   string         `json:"format,omitempty"`
}

func (s *ShowCreateSettingsProfileQuery) Pos() token.Position { return s.Position }
func (s *ShowCreateSettingsProfileQuery) End() token.Position { return s.Position }
func (s *ShowCreateSettingsProfileQuery) statementNode()      {}

// CreateRowPolicyQuery represents a CREATE ROW POLICY or ALTER ROW POLICY statement.
type CreateRowPolicyQuery struct {
	Position token.Position `json:"-"`
	IsAlter  bool           `json:"is_alter,omitempty"`
}

func (c *CreateRowPolicyQuery) Pos() token.Position { return c.Position }
func (c *CreateRowPolicyQuery) End() token.Position { return c.Position }
func (c *CreateRowPolicyQuery) statementNode()      {}

// DropRowPolicyQuery represents a DROP ROW POLICY statement.
type DropRowPolicyQuery struct {
	Position token.Position `json:"-"`
	IfExists bool           `json:"if_exists,omitempty"`
}

func (d *DropRowPolicyQuery) Pos() token.Position { return d.Position }
func (d *DropRowPolicyQuery) End() token.Position { return d.Position }
func (d *DropRowPolicyQuery) statementNode()      {}

// ShowCreateRowPolicyQuery represents a SHOW CREATE ROW POLICY statement.
type ShowCreateRowPolicyQuery struct {
	Position token.Position `json:"-"`
	Format   string         `json:"format,omitempty"`
}

func (s *ShowCreateRowPolicyQuery) Pos() token.Position { return s.Position }
func (s *ShowCreateRowPolicyQuery) End() token.Position { return s.Position }
func (s *ShowCreateRowPolicyQuery) statementNode()      {}

// CreateRoleQuery represents a CREATE ROLE or ALTER ROLE statement.
type CreateRoleQuery struct {
	Position token.Position `json:"-"`
	IsAlter  bool           `json:"is_alter,omitempty"`
}

func (c *CreateRoleQuery) Pos() token.Position { return c.Position }
func (c *CreateRoleQuery) End() token.Position { return c.Position }
func (c *CreateRoleQuery) statementNode()      {}

// DropRoleQuery represents a DROP ROLE statement.
type DropRoleQuery struct {
	Position token.Position `json:"-"`
	IfExists bool           `json:"if_exists,omitempty"`
}

func (d *DropRoleQuery) Pos() token.Position { return d.Position }
func (d *DropRoleQuery) End() token.Position { return d.Position }
func (d *DropRoleQuery) statementNode()      {}

// ShowCreateRoleQuery represents a SHOW CREATE ROLE statement.
type ShowCreateRoleQuery struct {
	Position  token.Position `json:"-"`
	RoleCount int            `json:"role_count,omitempty"` // Number of roles specified
	Format    string         `json:"format,omitempty"`
}

func (s *ShowCreateRoleQuery) Pos() token.Position { return s.Position }
func (s *ShowCreateRoleQuery) End() token.Position { return s.Position }
func (s *ShowCreateRoleQuery) statementNode()      {}

// SetRoleQuery represents a SET DEFAULT ROLE statement.
type SetRoleQuery struct {
	Position token.Position `json:"-"`
}

func (s *SetRoleQuery) Pos() token.Position { return s.Position }
func (s *SetRoleQuery) End() token.Position { return s.Position }
func (s *SetRoleQuery) statementNode()      {}

// CreateResourceQuery represents a CREATE RESOURCE statement.
type CreateResourceQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name"`
}

func (c *CreateResourceQuery) Pos() token.Position { return c.Position }
func (c *CreateResourceQuery) End() token.Position { return c.Position }
func (c *CreateResourceQuery) statementNode()      {}

// DropResourceQuery represents a DROP RESOURCE statement.
type DropResourceQuery struct {
	Position token.Position `json:"-"`
}

func (d *DropResourceQuery) Pos() token.Position { return d.Position }
func (d *DropResourceQuery) End() token.Position { return d.Position }
func (d *DropResourceQuery) statementNode()      {}

// CreateWorkloadQuery represents a CREATE WORKLOAD statement.
type CreateWorkloadQuery struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name"`
	Parent   string         `json:"parent,omitempty"` // Parent workload name (after IN)
}

func (c *CreateWorkloadQuery) Pos() token.Position { return c.Position }
func (c *CreateWorkloadQuery) End() token.Position { return c.Position }
func (c *CreateWorkloadQuery) statementNode()      {}

// DropWorkloadQuery represents a DROP WORKLOAD statement.
type DropWorkloadQuery struct {
	Position token.Position `json:"-"`
}

func (d *DropWorkloadQuery) Pos() token.Position { return d.Position }
func (d *DropWorkloadQuery) End() token.Position { return d.Position }
func (d *DropWorkloadQuery) statementNode()      {}

// CreateIndexQuery represents a CREATE INDEX statement.
type CreateIndexQuery struct {
	Position             token.Position `json:"-"`
	IndexName            string         `json:"index_name"`
	Table                string         `json:"table"`
	Columns              []Expression   `json:"columns,omitempty"`
	ColumnsParenthesized bool           `json:"columns_parenthesized,omitempty"` // True if columns in (...)
	Type                 string         `json:"type,omitempty"`                  // Index type (minmax, bloom_filter, etc.)
	Granularity          int            `json:"granularity,omitempty"`           // GRANULARITY value
}

func (c *CreateIndexQuery) Pos() token.Position { return c.Position }
func (c *CreateIndexQuery) End() token.Position { return c.Position }
func (c *CreateIndexQuery) statementNode()      {}

// -----------------------------------------------------------------------------
// Expressions

// Identifier represents an identifier.
type Identifier struct {
	Position      token.Position `json:"-"`
	Parts         []string       `json:"parts"` // e.g., ["db", "table", "column"] for db.table.column
	Alias         string         `json:"alias,omitempty"`
	Parenthesized bool           `json:"-"` // true if wrapped in parentheses, affects dot access parsing
}

func (i *Identifier) Pos() token.Position { return i.Position }
func (i *Identifier) End() token.Position { return i.Position }
func (i *Identifier) expressionNode()     {}

// Name returns the full identifier name.
func (i *Identifier) Name() string {
	if len(i.Parts) == 0 {
		return ""
	}
	if len(i.Parts) == 1 {
		return i.Parts[0]
	}
	result := i.Parts[0]
	for _, p := range i.Parts[1:] {
		result += "." + p
	}
	return result
}

// TableIdentifier represents a table identifier.
type TableIdentifier struct {
	Position token.Position `json:"-"`
	Database string         `json:"database,omitempty"`
	Table    string         `json:"table"`
	Alias    string         `json:"alias,omitempty"`
}

func (t *TableIdentifier) Pos() token.Position { return t.Position }
func (t *TableIdentifier) End() token.Position { return t.Position }
func (t *TableIdentifier) expressionNode()     {}

// Literal represents a literal value.
type Literal struct {
	Position       token.Position `json:"-"`
	Type           LiteralType    `json:"type"`
	Value          interface{}    `json:"value"`
	Source         string         `json:"source,omitempty"`          // Original source text (for preserving 0.0 vs 0)
	Negative       bool           `json:"negative,omitempty"`        // True if literal was explicitly negative (for -0)
	Parenthesized  bool           `json:"parenthesized,omitempty"`   // True if wrapped in explicit parentheses
	SpacedCommas   bool           `json:"spaced_commas,omitempty"`   // True if array/tuple had spaces after commas
	SpacedBrackets bool           `json:"spaced_brackets,omitempty"` // True if array had whitespace after [ and before ]
	IsBigInt       bool           `json:"is_big_int,omitempty"`      // True if this is a large integer stored as string
}

func (l *Literal) Pos() token.Position { return l.Position }
func (l *Literal) End() token.Position { return l.Position }
func (l *Literal) expressionNode()     {}

// MarshalJSON handles special float values (NaN, +Inf, -Inf) that JSON doesn't support.
func (l *Literal) MarshalJSON() ([]byte, error) {
	type literalAlias Literal
	// Handle special float values
	if f, ok := l.Value.(float64); ok {
		if math.IsNaN(f) {
			return json.Marshal(&struct {
				*literalAlias
				Value string `json:"value"`
			}{
				literalAlias: (*literalAlias)(l),
				Value:        "NaN",
			})
		}
		if math.IsInf(f, 1) {
			return json.Marshal(&struct {
				*literalAlias
				Value string `json:"value"`
			}{
				literalAlias: (*literalAlias)(l),
				Value:        "+Inf",
			})
		}
		if math.IsInf(f, -1) {
			return json.Marshal(&struct {
				*literalAlias
				Value string `json:"value"`
			}{
				literalAlias: (*literalAlias)(l),
				Value:        "-Inf",
			})
		}
	}
	return json.Marshal((*literalAlias)(l))
}

// LiteralType represents the type of a literal.
type LiteralType string

const (
	LiteralString  LiteralType = "String"
	LiteralInteger LiteralType = "Integer"
	LiteralFloat   LiteralType = "Float"
	LiteralBoolean LiteralType = "Boolean"
	LiteralNull    LiteralType = "Null"
	LiteralArray   LiteralType = "Array"
	LiteralTuple   LiteralType = "Tuple"
)

// Asterisk represents a *.
type Asterisk struct {
	Position     token.Position       `json:"-"`
	Table        string               `json:"table,omitempty"`        // for table.*
	Except       []string             `json:"except,omitempty"`       // for * EXCEPT (col1, col2) - deprecated, use Transformers
	Replace      []*ReplaceExpr       `json:"replace,omitempty"`      // for * REPLACE (expr AS col) - deprecated, use Transformers
	Apply        []string             `json:"apply,omitempty"`        // for * APPLY (func1) APPLY(func2) - deprecated, use Transformers
	Transformers []*ColumnTransformer `json:"transformers,omitempty"` // ordered list of transformers
}

func (a *Asterisk) Pos() token.Position { return a.Position }
func (a *Asterisk) End() token.Position { return a.Position }
func (a *Asterisk) expressionNode()     {}

// ReplaceExpr represents an expression in REPLACE clause.
type ReplaceExpr struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
	Name     string         `json:"name"`
}

func (r *ReplaceExpr) Pos() token.Position { return r.Position }
func (r *ReplaceExpr) End() token.Position { return r.Position }

// ColumnTransformer represents a single transformer (APPLY, EXCEPT, or REPLACE) in order.
type ColumnTransformer struct {
	Position    token.Position `json:"-"`
	Type        string         `json:"type"`                   // "apply", "except", "replace"
	Apply       string         `json:"apply,omitempty"`        // function name for APPLY
	ApplyParams []Expression   `json:"apply_params,omitempty"` // parameters for parameterized APPLY functions like quantiles(0.5)
	ApplyLambda Expression     `json:"apply_lambda,omitempty"` // lambda expression for APPLY x -> expr
	Except      []string       `json:"except,omitempty"`       // column names for EXCEPT
	Pattern     string         `json:"pattern,omitempty"`      // regex pattern for EXCEPT('pattern')
	Replaces    []*ReplaceExpr `json:"replaces,omitempty"`     // replacement expressions for REPLACE
}

// ColumnsMatcher represents COLUMNS('pattern') or COLUMNS(col1, col2) expression.
// When Pattern is set, it's a regex matcher (ColumnsRegexpMatcher in explain).
// When Columns is set, it's a list matcher (ColumnsListMatcher in explain).
type ColumnsMatcher struct {
	Position     token.Position       `json:"-"`
	Pattern      string               `json:"pattern,omitempty"`
	Columns      []Expression         `json:"columns,omitempty"`      // For COLUMNS(id, name) syntax
	Except       []string             `json:"except,omitempty"`       // for EXCEPT (col1, col2) - deprecated, use Transformers
	Replace      []*ReplaceExpr       `json:"replace,omitempty"`      // for REPLACE (expr AS col) - deprecated, use Transformers
	Apply        []string             `json:"apply,omitempty"`        // for APPLY (func1) APPLY(func2) - deprecated, use Transformers
	Qualifier    string               `json:"qualifier,omitempty"`    // For qualified matchers like table.COLUMNS(...)
	Transformers []*ColumnTransformer `json:"transformers,omitempty"` // ordered list of transformers
}

func (c *ColumnsMatcher) Pos() token.Position { return c.Position }
func (c *ColumnsMatcher) End() token.Position { return c.Position }
func (c *ColumnsMatcher) expressionNode()     {}

// FunctionCall represents a function call.
type FunctionCall struct {
	Position    token.Position `json:"-"`
	Name        string         `json:"name"`
	Parameters  []Expression   `json:"parameters,omitempty"` // For parametric functions like quantile(0.9)(x)
	Arguments   []Expression   `json:"arguments,omitempty"`
	Settings    []*SettingExpr `json:"settings,omitempty"` // For table functions with SETTINGS
	Distinct    bool           `json:"distinct,omitempty"`
	Filter      Expression     `json:"filter,omitempty"`       // FILTER(WHERE condition) clause
	Over        *WindowSpec    `json:"over,omitempty"`
	Alias       string         `json:"alias,omitempty"`
	SQLStandard bool           `json:"sql_standard,omitempty"` // True for SQL standard syntax like TRIM(... FROM ...)
}

func (f *FunctionCall) Pos() token.Position { return f.Position }
func (f *FunctionCall) End() token.Position { return f.Position }
func (f *FunctionCall) expressionNode()     {}

// WindowSpec represents a window specification.
type WindowSpec struct {
	Position    token.Position     `json:"-"`
	Name        string             `json:"name,omitempty"`
	PartitionBy []Expression       `json:"partition_by,omitempty"`
	OrderBy     []*OrderByElement  `json:"order_by,omitempty"`
	Frame       *WindowFrame       `json:"frame,omitempty"`
}

func (w *WindowSpec) Pos() token.Position { return w.Position }
func (w *WindowSpec) End() token.Position { return w.Position }

// WindowFrame represents a window frame.
type WindowFrame struct {
	Position   token.Position  `json:"-"`
	Type       WindowFrameType `json:"type"`
	StartBound *FrameBound     `json:"start"`
	EndBound   *FrameBound     `json:"end,omitempty"`
}

func (w *WindowFrame) Pos() token.Position { return w.Position }
func (w *WindowFrame) End() token.Position { return w.Position }

// WindowFrameType represents the type of window frame.
type WindowFrameType string

const (
	FrameRows   WindowFrameType = "ROWS"
	FrameRange  WindowFrameType = "RANGE"
	FrameGroups WindowFrameType = "GROUPS"
)

// FrameBound represents a window frame bound.
type FrameBound struct {
	Position     token.Position  `json:"-"`
	Type         FrameBoundType  `json:"type"`
	Offset       Expression      `json:"offset,omitempty"`
}

func (f *FrameBound) Pos() token.Position { return f.Position }
func (f *FrameBound) End() token.Position { return f.Position }

// FrameBoundType represents the type of frame bound.
type FrameBoundType string

const (
	BoundCurrentRow   FrameBoundType = "CURRENT_ROW"
	BoundUnboundedPre FrameBoundType = "UNBOUNDED_PRECEDING"
	BoundUnboundedFol FrameBoundType = "UNBOUNDED_FOLLOWING"
	BoundPreceding    FrameBoundType = "PRECEDING"
	BoundFollowing    FrameBoundType = "FOLLOWING"
)

// BinaryExpr represents a binary expression.
type BinaryExpr struct {
	Position      token.Position `json:"-"`
	Left          Expression     `json:"left"`
	Op            string         `json:"op"`
	Right         Expression     `json:"right"`
	Parenthesized bool           `json:"parenthesized,omitempty"` // True if wrapped in explicit parentheses
}

func (b *BinaryExpr) Pos() token.Position { return b.Position }
func (b *BinaryExpr) End() token.Position { return b.Position }
func (b *BinaryExpr) expressionNode()     {}

// UnaryExpr represents a unary expression.
type UnaryExpr struct {
	Position token.Position `json:"-"`
	Op       string         `json:"op"`
	Operand  Expression     `json:"operand"`
}

func (u *UnaryExpr) Pos() token.Position { return u.Position }
func (u *UnaryExpr) End() token.Position { return u.Position }
func (u *UnaryExpr) expressionNode()     {}

// TernaryExpr represents a ternary conditional expression (cond ? then : else).
type TernaryExpr struct {
	Position  token.Position `json:"-"`
	Condition Expression     `json:"condition"`
	Then      Expression     `json:"then"`
	Else      Expression     `json:"else"`
}

func (t *TernaryExpr) Pos() token.Position { return t.Position }
func (t *TernaryExpr) End() token.Position { return t.Position }
func (t *TernaryExpr) expressionNode()     {}

// Subquery represents a subquery.
type Subquery struct {
	Position token.Position `json:"-"`
	Query    Statement      `json:"query"`
	Alias    string         `json:"alias,omitempty"`
}

func (s *Subquery) Pos() token.Position { return s.Position }
func (s *Subquery) End() token.Position { return s.Position }
func (s *Subquery) expressionNode()     {}

// WithElement represents a WITH element (CTE).
type WithElement struct {
	Position   token.Position `json:"-"`
	Name       string         `json:"name"`
	Query      Expression     `json:"query"`       // Subquery or Expression
	ScalarWith bool           `json:"scalar_with"` // True for "(expr) AS name" syntax, false for "name AS (SELECT ...)"
}

func (w *WithElement) Pos() token.Position { return w.Position }
func (w *WithElement) End() token.Position { return w.Position }
func (w *WithElement) expressionNode()     {}

// CaseExpr represents a CASE expression.
type CaseExpr struct {
	Position    token.Position  `json:"-"`
	Operand     Expression      `json:"operand,omitempty"` // for CASE x WHEN ...
	Whens       []*WhenClause   `json:"whens"`
	Else        Expression      `json:"else,omitempty"`
	Alias       string          `json:"alias,omitempty"`
	QuotedAlias bool            `json:"quoted_alias,omitempty"` // true if alias was double-quoted
}

func (c *CaseExpr) Pos() token.Position { return c.Position }
func (c *CaseExpr) End() token.Position { return c.Position }
func (c *CaseExpr) expressionNode()     {}

// WhenClause represents a WHEN clause in a CASE expression.
type WhenClause struct {
	Position  token.Position `json:"-"`
	Condition Expression     `json:"condition"`
	Result    Expression     `json:"result"`
}

func (w *WhenClause) Pos() token.Position { return w.Position }
func (w *WhenClause) End() token.Position { return w.Position }

// CastExpr represents a CAST expression.
type CastExpr struct {
	Position       token.Position `json:"-"`
	Expr           Expression     `json:"expr"`
	Type           *DataType      `json:"type,omitempty"`
	TypeExpr       Expression     `json:"type_expr,omitempty"` // For dynamic type like CAST(x, if(cond, 'Type1', 'Type2'))
	Alias          string         `json:"alias,omitempty"`
	OperatorSyntax bool           `json:"operator_syntax,omitempty"` // true if using :: syntax
	UsedASSyntax   bool           `json:"-"`                         // true if CAST(x AS Type) syntax used (not CAST(x, 'Type'))
}

func (c *CastExpr) Pos() token.Position { return c.Position }
func (c *CastExpr) End() token.Position { return c.Position }
func (c *CastExpr) expressionNode()     {}

// ExtractExpr represents an EXTRACT expression.
type ExtractExpr struct {
	Position token.Position `json:"-"`
	Field    string         `json:"field"` // YEAR, MONTH, DAY, etc.
	From     Expression     `json:"from"`
	Alias    string         `json:"alias,omitempty"`
}

func (e *ExtractExpr) Pos() token.Position { return e.Position }
func (e *ExtractExpr) End() token.Position { return e.Position }
func (e *ExtractExpr) expressionNode()     {}

// IntervalExpr represents an INTERVAL expression.
type IntervalExpr struct {
	Position token.Position `json:"-"`
	Value    Expression     `json:"value"`
	Unit     string         `json:"unit"` // YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, etc.
}

func (i *IntervalExpr) Pos() token.Position { return i.Position }
func (i *IntervalExpr) End() token.Position { return i.Position }
func (i *IntervalExpr) expressionNode()     {}

// ArrayAccess represents array element access.
type ArrayAccess struct {
	Position token.Position `json:"-"`
	Array    Expression     `json:"array"`
	Index    Expression     `json:"index"`
}

func (a *ArrayAccess) Pos() token.Position { return a.Position }
func (a *ArrayAccess) End() token.Position { return a.Position }
func (a *ArrayAccess) expressionNode()     {}

// TupleAccess represents tuple element access.
type TupleAccess struct {
	Position token.Position `json:"-"`
	Tuple    Expression     `json:"tuple"`
	Index    Expression     `json:"index"`
}

func (t *TupleAccess) Pos() token.Position { return t.Position }
func (t *TupleAccess) End() token.Position { return t.Position }
func (t *TupleAccess) expressionNode()     {}

// Lambda represents a lambda expression.
type Lambda struct {
	Position      token.Position `json:"-"`
	Parameters    []string       `json:"parameters"`
	Body          Expression     `json:"body"`
	Parenthesized bool           `json:"-"` // True if wrapped in explicit parentheses
}

func (l *Lambda) Pos() token.Position { return l.Position }
func (l *Lambda) End() token.Position { return l.Position }
func (l *Lambda) expressionNode()     {}

// Parameter represents a parameter placeholder.
type Parameter struct {
	Position token.Position `json:"-"`
	Name     string         `json:"name,omitempty"`
	Type     *DataType      `json:"type,omitempty"`
}

func (p *Parameter) Pos() token.Position { return p.Position }
func (p *Parameter) End() token.Position { return p.Position }
func (p *Parameter) expressionNode()     {}

// AliasedExpr represents an expression with an alias.
type AliasedExpr struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
	Alias    string         `json:"alias"`
}

func (a *AliasedExpr) Pos() token.Position { return a.Position }
func (a *AliasedExpr) End() token.Position { return a.Position }
func (a *AliasedExpr) expressionNode()     {}

// BetweenExpr represents a BETWEEN expression.
type BetweenExpr struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
	Not      bool           `json:"not,omitempty"`
	Low      Expression     `json:"low"`
	High     Expression     `json:"high"`
}

func (b *BetweenExpr) Pos() token.Position { return b.Position }
func (b *BetweenExpr) End() token.Position { return b.Position }
func (b *BetweenExpr) expressionNode()     {}

// InExpr represents an IN expression.
type InExpr struct {
	Position      token.Position `json:"-"`
	Expr          Expression     `json:"expr"`
	Not           bool           `json:"not,omitempty"`
	Global        bool           `json:"global,omitempty"`
	List          []Expression   `json:"list,omitempty"`
	Query         Statement      `json:"query,omitempty"`
	TrailingComma bool           `json:"trailing_comma,omitempty"` // true if list had trailing comma like (2,)
}

func (i *InExpr) Pos() token.Position { return i.Position }
func (i *InExpr) End() token.Position { return i.Position }
func (i *InExpr) expressionNode()     {}

// IsNullExpr represents an IS NULL or IS NOT NULL expression.
type IsNullExpr struct {
	Position token.Position `json:"-"`
	Expr     Expression     `json:"expr"`
	Not      bool           `json:"not,omitempty"`
}

func (i *IsNullExpr) Pos() token.Position { return i.Position }
func (i *IsNullExpr) End() token.Position { return i.Position }
func (i *IsNullExpr) expressionNode()     {}

// LikeExpr represents a LIKE or ILIKE expression.
type LikeExpr struct {
	Position        token.Position `json:"-"`
	Expr            Expression     `json:"expr"`
	Not             bool           `json:"not,omitempty"`
	CaseInsensitive bool           `json:"case_insensitive,omitempty"` // true for ILIKE
	Pattern         Expression     `json:"pattern"`
	Alias           string         `json:"alias,omitempty"`
}

func (l *LikeExpr) Pos() token.Position { return l.Position }
func (l *LikeExpr) End() token.Position { return l.Position }
func (l *LikeExpr) expressionNode()     {}

// ExistsExpr represents an EXISTS expression.
type ExistsExpr struct {
	Position token.Position `json:"-"`
	Query    Statement      `json:"query"`
}

func (e *ExistsExpr) Pos() token.Position { return e.Position }
func (e *ExistsExpr) End() token.Position { return e.Position }
func (e *ExistsExpr) expressionNode()     {}

// ParallelWithQuery represents multiple statements executed in parallel with PARALLEL WITH.
type ParallelWithQuery struct {
	Position   token.Position `json:"-"`
	Statements []Statement    `json:"statements"`
}

func (p *ParallelWithQuery) Pos() token.Position { return p.Position }
func (p *ParallelWithQuery) End() token.Position { return p.Position }
func (p *ParallelWithQuery) statementNode()      {}