package database

import (
	"database/sql"
	"log"
	"net/http"
	"os"

	"github.com/golang-migrate/migrate/v4"
	"github.com/golang-migrate/migrate/v4/database/postgres"
	"github.com/golang-migrate/migrate/v4/source/httpfs"
	"github.com/jmoiron/sqlx"
)

// GetMigrator returns a Database Migrator for PostgreSQL for the supplied
// http.FileSystem and path.
func getMigrator(db *sql.DB, fs http.FileSystem, path string) (*migrate.Migrate, error) {
	driver, err := postgres.WithInstance(db, &postgres.Config{})
	if err != nil {
		return nil, err
	}

	migrations, err := httpfs.New(fs, path)
	if err != nil {
		return nil, err
	}

	// the strings are only for logging purpose
	migrator, err := migrate.NewWithInstance(
		"assets", migrations,
		"database", driver,
	)
	if err != nil {
		return nil, err
	}

	return migrator, err
}

type wrappedLogger struct {
	*log.Logger
}

func (l wrappedLogger) Verbose() bool {
	return true
}

const (
	// MigrateDrop is the revision number that will cause all tables to be
	// dropped from the database.
	MigrateDrop = -3
	// MigrateUp is the revision number that will cause the database to be
	// migrated to the very latest revision.
	MigrateUp = -1
)

// GetCurrentMigration returns the currently active migration version.
// If no migration has been applied yet, it will return ErrNilVersion.
func GetCurrentMigration(db *sqlx.DB) (version uint, dirty bool, err error) {
	migrator, err := getMigrator(db.DB, http.Dir("/invalid/path/unused"), "/unused")
	if err != nil {
		return 0, false, err
	}

	return migrator.Version()
}

// Migrate Migrates the schema of the supplied Database. Supported
// methods are:
//  * database.MigrateUp – Migrate to the latest version
//  * database.MigrateDrop – empty everything
//  * `(integer)` – Migrate to specific version
func Migrate(db *sqlx.DB, fs http.FileSystem, revision int) error {
	// migrate database
	const migrationPathInFs = "/migrations"

	migrator, err := getMigrator(db.DB, fs, migrationPathInFs)
	if err != nil {
		return err
	}

	wl := wrappedLogger{log.New(os.Stdout, "[MIGRATIONS] ", log.LstdFlags)}
	migrator.Log = wl

	switch revision {
	case MigrateUp:
		err = migrator.Up()
	case MigrateDrop:
		err = migrator.Drop()
	default:
		err = migrator.Migrate(uint(revision))
	}

	if err == migrate.ErrNoChange {
		wl.Println("no change")
	} else if err != nil {
		return err
	}

	return nil
}