package dbx

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

	"github.com/segmentio/ksuid"
)

// StringKSUID wraps segmentio/ksuid for text-column storage (VARCHAR, TEXT).
// SQL Scan/Value use the base62 string encoding. GraphQL transit uses a string
// scalar (base62 KSUID).
type StringKSUID struct {
	ksuid.KSUID
}

// NilStringKSUID is the zero/nil StringKSUID value.
var NilStringKSUID = StringKSUID{KSUID: ksuid.Nil}

// Equal reports whether two StringKSUID values represent the same identifier,
// treating two nil values as equal. Implements [ApplyInterface].
func (s StringKSUID) Equal(rh StringKSUID) bool {
	return equalKSUID(s.KSUID, rh.KSUID)
}

// IsZero reports whether s is nil. Implements [ApplyInterface].
func (s StringKSUID) IsZero() bool {
	return s.IsNil()
}

// NewStringKSUID generates a new StringKSUID.
func NewStringKSUID() StringKSUID {
	return StringKSUID{KSUID: ksuid.New()}
}

// ParseStringKSUID parses a StringKSUID from its base62 string form.
func ParseStringKSUID(s string) (StringKSUID, error) {
	id, err := ksuid.Parse(s)
	if err != nil {
		return StringKSUID{}, err
	}
	return StringKSUID{KSUID: id}, nil
}

// AsBinaryKSUID returns a BinaryKSUID view of the same identifier.
func (s StringKSUID) AsBinaryKSUID() BinaryKSUID {
	return BinaryKSUID{KSUID: s.KSUID}
}

// Scan implements sql.Scanner for string-backed KSUID columns.
func (s *StringKSUID) Scan(src any) error {
	switch v := src.(type) {
	case nil:
		*s = StringKSUID{}
		return nil
	case string:
		id, err := ksuid.Parse(v)
		if err != nil {
			return fmt.Errorf("StringKSUID.Scan: %w", err)
		}
		*s = StringKSUID{KSUID: id}
		return nil
	case []byte:
		if len(v) == ksuidBinaryLength {
			return fmt.Errorf("StringKSUID.Scan: binary KSUID payload (%d bytes); use BinaryKSUID", len(v))
		}
		id, err := ksuid.Parse(string(v))
		if err != nil {
			return fmt.Errorf("StringKSUID.Scan: %w", err)
		}
		*s = StringKSUID{KSUID: id}
		return nil
	default:
		return fmt.Errorf("StringKSUID.Scan: unable to scan type %T", v)
	}
}

// Value implements driver.Valuer for string-backed KSUID columns.
func (s StringKSUID) Value() (driver.Value, error) {
	if s.IsNil() {
		return nil, nil
	}
	return s.String(), nil
}

// UnmarshalGQL implements the graphql.Unmarshaler interface.
func (s *StringKSUID) UnmarshalGQL(value any) error {
	return unmarshalKSUIDFromGQL(value, s.UnmarshalText)
}

// MarshalGQL implements the graphql.Marshaler interface.
func (s StringKSUID) MarshalGQL(w io.Writer) {
	marshalKSUIDToGQL(w, s.KSUID)
}