Added custom types for un/marshaling (#92)

* Added custom types for marshaling

This adds special handling for "date" and "byte" string formats in
OpenAPI 3.  When marshaled, "date" strings should have their time
truncated, and "byte" strings should be Base64 encoded.

* Remove unnecessary byte handling

* Use struct to track import mappings

Author: jmcnevin

date.go

@@ -0,0 +1,30 @@
+package types
+
+import (
+	"encoding/json"
+	"time"
+)
+
+const dateFormat = "2006-01-02"
+
+type Date struct {
+	time.Time
+}
+
+func (d Date) MarshalJSON() ([]byte, error) {
+	return json.Marshal(d.Time.Format(dateFormat))
+}
+
+func (d *Date) UnmarshalJSON(data []byte) error {
+	var dateStr string
+	err := json.Unmarshal(data, &dateStr)
+	if err != nil {
+		return err
+	}
+	parsed, err := time.Parse(dateFormat, dateStr)
+	if err != nil {
+		return err
+	}
+	d.Time = parsed
+	return nil
+}

date_test.go

@@ -0,0 +1,32 @@
+package types
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDate_MarshalJSON(t *testing.T) {
+	testDate := time.Date(2019, 4, 1, 0, 0, 0, 0, time.UTC)
+	b := struct {
+		DateField Date	`json:"date"`
+	}{
+		DateField: Date{testDate},
+	}
+	jsonBytes, err := json.Marshal(b)
+	assert.NoError(t, err)
+	assert.JSONEq(t, `{"date":"2019-04-01"}`, string(jsonBytes))
+}
+
+func TestDate_UnmarshalJSON(t *testing.T) {
+	testDate := time.Date(2019, 4, 1, 0, 0, 0, 0, time.UTC)
+	jsonStr := `{"date":"2019-04-01"}`
+	b := struct {
+		DateField Date	`json:"date"`
+	}{}
+	err := json.Unmarshal([]byte(jsonStr), &b)
+	assert.NoError(t, err)
+	assert.Equal(t, testDate, b.DateField.Time)
+}