turash/bugulma/backend/internal/domain/postgis.go

package domain

import (
	"database/sql/driver"
	"fmt"
	"strings"
)

// Point represents a PostGIS Point geometry with SRID 4326 (WGS84)
// Implements sql.Scanner and driver.Valuer for proper GORM integration
type Point struct {
	Longitude float64
	Latitude  float64
	Valid     bool
}

// GormDataType specifies the database column type for GORM
func (Point) GormDataType() string {
	return "geometry(Point,4326)"
}

// Scan implements sql.Scanner interface to read PostGIS geometry from database
func (p *Point) Scan(value interface{}) error {
	if value == nil {
		p.Valid = false
		return nil
	}

	var bytes []byte
	switch v := value.(type) {
	case []byte:
		bytes = v
	case string:
		bytes = []byte(v)
	default:
		return fmt.Errorf("cannot scan %T into Point", value)
	}

	// PostGIS returns geometry in EWKB format or WKT format
	// Try to parse as WKT first (common format)
	str := string(bytes)

	// Handle EWKB format (starts with specific bytes)
	if len(bytes) > 0 && bytes[0] == 0x00 {
		// This is EWKB format, we need to decode it
		// For now, we'll extract coordinates from a common pattern
		// In production, consider using a library like github.com/twpayne/go-geom
		return fmt.Errorf("EWKB format not yet supported, use WKT")
	}

	// Try to parse WKT format: POINT(lng lat) or POINT(lat lng)
	// PostGIS typically returns: "0101000020E6100000..." (EWKB hex) or WKT
	// For simplicity, we'll handle the case where we have lat/lng separately
	// and let the database handle the conversion

	// If it's a hex string (EWKB), we can't easily parse it here
	// The best approach is to use ST_AsText in queries or handle it at DB level
	if strings.HasPrefix(str, "0101") || len(str) > 50 {
		// Likely EWKB hex format - we'll need to query as text or use ST_AsText
		p.Valid = false
		return nil
	}

	// Try WKT format: POINT(lng lat)
	if strings.HasPrefix(str, "POINT") {
		var lng, lat float64
		_, err := fmt.Sscanf(str, "POINT(%f %f)", &lng, &lat)
		if err != nil {
			// Try reverse order: POINT(lat lng)
			_, err = fmt.Sscanf(str, "POINT(%f %f)", &lat, &lng)
			if err != nil {
				p.Valid = false
				return nil
			}
		}
		p.Longitude = lng
		p.Latitude = lat
		p.Valid = true
		return nil
	}

	p.Valid = false
	return nil
}

// Value implements driver.Valuer interface to write PostGIS geometry to database
func (p Point) Value() (driver.Value, error) {
	if !p.Valid {
		return nil, nil
	}
	// Return WKT format for PostGIS
	// PostGIS will convert this to the proper geometry type
	return fmt.Sprintf("SRID=4326;POINT(%f %f)", p.Longitude, p.Latitude), nil
}

// String returns the WKT representation of the point
func (p Point) String() string {
	if !p.Valid {
		return "POINT EMPTY"
	}
	return fmt.Sprintf("POINT(%f %f)", p.Longitude, p.Latitude)
}

// IsEmpty returns true if the point is not valid
func (p Point) IsEmpty() bool {
	return !p.Valid
}

// NewPoint creates a new Point from longitude and latitude
func NewPoint(longitude, latitude float64) Point {
	return Point{
		Longitude: longitude,
		Latitude:  latitude,
		Valid:     true,
	}
}

// AfterFind hook helper to populate Point from lat/lng if geometry is not set
// This can be used in GORM hooks to ensure geometry is always populated
func (p *Point) EnsureFromLatLng(lat, lng float64) {
	if !p.Valid && lat != 0 && lng != 0 {
		p.Longitude = lng
		p.Latitude = lat
		p.Valid = true
	}
}

// BeforeSave hook helper to ensure geometry is set from lat/lng
// This can be used in GORM BeforeSave hooks
func (p *Point) EnsureValid(lat, lng float64) {
	if lat != 0 && lng != 0 {
		p.Longitude = lng
		p.Latitude = lat
		p.Valid = true
	}
}