package loopdb

import (
	"errors"
	"fmt"

	"github.com/jackc/pgconn"
	"github.com/jackc/pgerrcode"
	"modernc.org/sqlite"
	sqlite3 "modernc.org/sqlite/lib"
)

// MapSQLError attempts to interpret a given error as a database agnostic SQL
// error.
func MapSQLError(err error) error {
	// Attempt to interpret the error as a sqlite error.
	var sqliteErr *sqlite.Error
	if errors.As(err, &sqliteErr) {
		return parseSqliteError(sqliteErr)
	}

	// Attempt to interpret the error as a postgres error.
	var pqErr *pgconn.PgError
	if errors.As(err, &pqErr) {
		return parsePostgresError(pqErr)
	}

	// Return original error if it could not be classified as a database
	// specific error.
	return err
}

// parsePostgresError attempts to parse a sqlite error as a database agnostic
// SQL error.
func parseSqliteError(sqliteErr *sqlite.Error) error {
	switch sqliteErr.Code() {
	// Handle unique constraint violation error.
	case sqlite3.SQLITE_CONSTRAINT_UNIQUE:
		return &ErrSqlUniqueConstraintViolation{
			DbError: sqliteErr,
		}

	default:
		return fmt.Errorf("unknown sqlite error: %w", sqliteErr)
	}
}

// parsePostgresError attempts to parse a postgres error as a database agnostic
// SQL error.
func parsePostgresError(pqErr *pgconn.PgError) error {
	switch pqErr.Code {
	// Handle unique constraint violation error.
	case pgerrcode.UniqueViolation:
		return &ErrSqlUniqueConstraintViolation{
			DbError: pqErr,
		}

	default:
		return fmt.Errorf("unknown postgres error: %w", pqErr)
	}
}

// ErrSqlUniqueConstraintViolation is an error type which represents a database
// agnostic SQL unique constraint violation.
type ErrSqlUniqueConstraintViolation struct {
	DbError error
}

func (e ErrSqlUniqueConstraintViolation) Error() string {
	return fmt.Sprintf("sql unique constraint violation: %v", e.DbError)
}