// Package db holds the embedded golang-migrate migrations and the sqlc
// generated query code (internal/db/sqlcgen).
package db

import (
	"embed"
	"errors"
	"fmt"
	"net/url"

	"github.com/golang-migrate/migrate/v4"
	_ "github.com/golang-migrate/migrate/v4/database/pgx/v5"
	"github.com/golang-migrate/migrate/v4/source/iofs"
)

//go:embed migrations/*.sql
var migrationsFS embed.FS

// newMigrate builds a *migrate.Migrate over the embedded migration files and
// the given database connection string.
func newMigrate(databaseURL string) (*migrate.Migrate, error) {
	sourceDriver, err := iofs.New(migrationsFS, "migrations")
	if err != nil {
		return nil, fmt.Errorf("db: loading embedded migrations: %w", err)
	}

	m, err := migrate.NewWithSourceInstance("iofs", sourceDriver, wrapDatabaseURL(databaseURL))
	if err != nil {
		return nil, fmt.Errorf("db: initializing migrate: %w", err)
	}
	return m, nil
}

// wrapDatabaseURL swaps the postgres(ql):// scheme for pgx5:// as required
// by golang-migrate's pgx/v5 database driver registration.
func wrapDatabaseURL(databaseURL string) string {
	u, err := url.Parse(databaseURL)
	if err != nil {
		return databaseURL
	}
	u.Scheme = "pgx5"
	return u.String()
}

// MigrateUp applies all pending migrations. It returns nil if there is
// nothing to do.
func MigrateUp(databaseURL string) error {
	m, err := newMigrate(databaseURL)
	if err != nil {
		return err
	}
	defer func() { _, _ = m.Close() }()

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

// MigrateDown rolls back all migrations. It returns nil if there is nothing
// to do.
func MigrateDown(databaseURL string) error {
	m, err := newMigrate(databaseURL)
	if err != nil {
		return err
	}
	defer func() { _, _ = m.Close() }()

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