// Package migrate runs database schema migrations embedded in the binary.
package migrate

import (
	"errors"
	"fmt"

	"github.com/golang-migrate/migrate/v4"
	_ "github.com/golang-migrate/migrate/v4/database/postgres"
	"github.com/golang-migrate/migrate/v4/source/iofs"

	"osdb/migrations"
)

func newMigrator(databaseURL string) (*migrate.Migrate, error) {
	src, err := iofs.New(migrations.FS, ".")
	if err != nil {
		return nil, fmt.Errorf("create iofs source: %w", err)
	}

	m, err := migrate.NewWithSourceInstance("iofs", src, databaseURL)
	if err != nil {
		return nil, fmt.Errorf("create migrator: %w", err)
	}

	return m, nil
}

// Up applies all pending migrations.
func Up(databaseURL string) error {
	m, err := newMigrator(databaseURL)
	if err != nil {
		return err
	}
	defer m.Close()

	if err := m.Up(); err != nil && !errors.Is(err, migrate.ErrNoChange) {
		return fmt.Errorf("migrate up: %w", err)
	}

	return nil
}

// Down rolls back a single migration step.
func Down(databaseURL string) error {
	m, err := newMigrator(databaseURL)
	if err != nil {
		return err
	}
	defer m.Close()

	if err := m.Steps(-1); err != nil && !errors.Is(err, migrate.ErrNoChange) {
		return fmt.Errorf("migrate down: %w", err)
	}

	return nil
}