package models

import (
	"database/sql/driver"
	"encoding/json"
	"strings"
	"time"
)

// NullTime wraps *time.Time with custom JSON and GORM handling:
//   - JSON marshal:   nil → "1970-01-01T00:00:00Z", non-nil → RFC3339
//   - JSON unmarshal: null / "" / "1970-01-01..." → nil (stored as NULL in DB)
//   - GORM Scan/Value: nil ↔ NULL column
type NullTime struct {
	Time *time.Time
}

func (nt NullTime) MarshalJSON() ([]byte, error) {
	if nt.Time == nil {
		return []byte(`"1970-01-01T00:00:00Z"`), nil
	}
	return json.Marshal(nt.Time.Format(time.RFC3339))
}

func (nt *NullTime) UnmarshalJSON(data []byte) error {
	if string(data) == "null" {
		nt.Time = nil
		return nil
	}
	var s string
	if err := json.Unmarshal(data, &s); err != nil {
		return err
	}
	if s == "" || strings.HasPrefix(s, "1970-01-01") {
		nt.Time = nil
		return nil
	}
	t, err := time.Parse(time.RFC3339, s)
	if err != nil {
		return err
	}
	nt.Time = &t
	return nil
}

// Value implements driver.Valuer so GORM writes NULL for nil.
func (nt NullTime) Value() (driver.Value, error) {
	if nt.Time == nil {
		return nil, nil
	}
	return *nt.Time, nil
}

// Scan implements sql.Scanner so GORM reads NULL as nil.
func (nt *NullTime) Scan(value interface{}) error {
	if value == nil {
		nt.Time = nil
		return nil
	}
	t, ok := value.(time.Time)
	if !ok {
		nt.Time = nil
		return nil
	}
	nt.Time = &t
	return nil
}