package postgres

import (
	"errors"

	"github.com/jackc/pgx/v5/pgconn"

	"github.com/neilotoole/sq/libsq/core/errz"
	"github.com/neilotoole/sq/libsq/driver"
)

// errw wraps any error from the db. It should be called at
// every interaction with the db. If err is nil, nil is returned.
// Certain errors will be wrapped in specific error types,
// e.g, errz.NotExistError.
func errw(err error) error {
	switch {
	case err == nil:
		return nil
	case hasErrCode(err, errCodeRelationNotExist):
		return driver.NewNotExistError(err)
	default:
		return errz.Err(err)
	}
}

const (
	errCodeRelationNotExist   = "42P01"
	errCodeTooManyConnections = "53300"
)

// isErrTooManyConnections returns true if err is a postgres error
// with code 53300 (too_many_connections).
//
// See: https://www.postgresql.org/docs/14/errcodes-appendix.html
func isErrTooManyConnections(err error) bool {
	return hasErrCode(err, errCodeTooManyConnections)
}

// isErrRelationNotExist  returns true if err is a postgres error
// with code 42P01 (undefined_table).
//
// See: https://www.postgresql.org/docs/14/errcodes-appendix.html
func isErrRelationNotExist(err error) bool {
	return hasErrCode(err, errCodeRelationNotExist)
}

// hasErrCode returns true if err (or its cause error)
// is of type *pgconn.PgError and err.Number equals code.
// See: isErrTooManyConnections.
func hasErrCode(err error, code string) bool {
	if err == nil {
		return false
	}
	var pgErr *pgconn.PgError

	if errors.As(err, &pgErr) {
		return pgErr.Code == code
	}

	return false
}