package sqlite

import (
	"database/sql"
	"errors"

	"code.nochebuena.dev/einherjar/core/xerrors"
)

// coder is the duck-type interface for SQLite extended error codes.
// modernc.org/sqlite errors implement this interface.
type coder interface{ Code() int }

const (
	sqliteConstraintPrimaryKey = 1555
	sqliteConstraintUnique     = 2067
	sqliteConstraintForeignKey = 787
)

// HandleError maps database/sql and SQLite errors to typed [xerrors] values.
// Returns nil when err is nil. Also available as [Provider.HandleError].
//
// Mapped codes:
//   - sql.ErrNoRows                      → ErrNotFound
//   - SQLITE_CONSTRAINT_UNIQUE (2067)    → ErrAlreadyExists
//   - SQLITE_CONSTRAINT_PRIMARYKEY (1555)→ ErrAlreadyExists
//   - SQLITE_CONSTRAINT_FOREIGNKEY (787) → ErrInvalidInput
//   - all others                         → ErrInternal
func HandleError(err error) error {
	if err == nil {
		return nil
	}
	if errors.Is(err, sql.ErrNoRows) {
		return xerrors.New(xerrors.ErrNotFound, "record not found").WithError(err)
	}
	var ce coder
	if errors.As(err, &ce) {
		switch ce.Code() {
		case sqliteConstraintUnique, sqliteConstraintPrimaryKey:
			return xerrors.New(xerrors.ErrAlreadyExists, "record already exists").WithError(err)
		case sqliteConstraintForeignKey:
			return xerrors.New(xerrors.ErrInvalidInput, "data integrity violation").WithError(err)
		}
	}
	return xerrors.New(xerrors.ErrInternal, "unexpected database error").WithError(err)
}