package model

import (
	"database/sql/driver"
	"encoding/base32"
	"fmt"
	"io"

	"github.com/google/uuid"
)

// Crockford's low-ambiguity base32 alphabet
var base32Encoding = base32.
	NewEncoding("0123456789abcdefghjkmnpqrstvwxyz").
	WithPadding(base32.NoPadding)

// An RID is a unique resource ID.
type RID struct {
	uuid uuid.NullUUID
}

// Creates a new resource ID.
func NewRID() RID {
	uu, err := uuid.NewV7()
	if err != nil {
		panic(err)
	}
	return RID{
		uuid: uuid.NullUUID{
			UUID:  uu,
			Valid: true,
		},
	}
}

// Returns the UUID representation of this RID.
func (rid *RID) UUID() uuid.UUID {
	if !rid.uuid.Valid {
		panic(fmt.Errorf("invalid UUID"))
	}
	return rid.uuid.UUID
}

// Returns the string representation of this RID.
func (rid *RID) String() string {
	if !rid.uuid.Valid {
		return ""
	}
	return base32Encoding.EncodeToString(rid.uuid.UUID[:])
}

func (rid RID) MarshalGQL(w io.Writer) {
	w.Write(fmt.Appendf(nil, `"%s"`, rid.String()))
}

func (rid *RID) unmarshalString(s string) error {
	if len(s) == 0 {
		rid.uuid.Valid = false
		return nil
	}
	bytes, err := base32Encoding.DecodeString(s)
	if err != nil {
		return err
	}
	rid.uuid.UUID, err = uuid.FromBytes(bytes)
	if err != nil {
		rid.uuid.Valid = false
		return err
	}
	rid.uuid.Valid = true
	return nil
}

func (rid *RID) UnmarshalGQL(v any) error {
	switch v := v.(type) {
	case string:
		return rid.unmarshalString(v)
	default:
		return fmt.Errorf("%T is not a valid RID", v)
	}
}

// database/sql.Scanner
func (rid *RID) Scan(src any) error {
	switch src := src.(type) {
	case string:
		return rid.unmarshalString(src)
	default:
		return rid.uuid.Scan(src)
	}
}

// database/sql/driver.Valuer
func (rid RID) Value() (driver.Value, error) {
	return rid.uuid.Value()
}