package repository

import (
	"database/sql"
	"embed"
	"fmt"
	"log/slog"

	"github.com/golang-migrate/migrate/v4"
	"github.com/golang-migrate/migrate/v4/database/sqlite3"
	"github.com/golang-migrate/migrate/v4/source/iofs"
)

const Version uint = 1

//go:embed migrations/*
var migrationFiles embed.FS

func checkDBVersion(db *sql.DB) error {
	var m *migrate.Migrate

	driver, err := sqlite3.WithInstance(db, &sqlite3.Config{})
	if err != nil {
		return err
	}
	d, err := iofs.New(migrationFiles, "migrations")
	if err != nil {
		return err
	}

	m, err = migrate.NewWithInstance("iofs", d, "sqlite3", driver)
	if err != nil {
		return err
	}

	v, dirty, err := m.Version()
	if err != nil {
		if err == migrate.ErrNilVersion {
			slog.Error("Legacy database without version or missing database file!")
		} else {
			return err
		}
	}

	if v < Version {
		return fmt.Errorf("unsupported database version %d, need %d.\nPlease backup your database file and run server -migrate-db", v, Version)
	} else if v > Version {
		return fmt.Errorf("unsupported database version %d, need %d.\nPlease refer to documentation how to downgrade db with external migrate tool", v, Version)
	}

	if dirty {
		return fmt.Errorf("last migration to version %d has failed, please fix the db manually and force version with -force-db flag", Version)
	}

	return nil
}

func getMigrateInstance(dsnURI string) (m *migrate.Migrate, err error) {
	d, err := iofs.New(migrationFiles, "migrations")
	if err != nil {
		slog.Error("failed to get instance", "Error", err)
	}

	m, err = migrate.NewWithSourceInstance("iofs", d, "sqlite3://"+dsnURI)
	if err != nil {
		return m, err
	}

	return m, nil
}

func MigrateDB(db string) error {
	m, err := getMigrateInstance(db)
	if err != nil {
		return err
	}

	_, dirty, err := m.Version()
	if err != nil {
		if err == migrate.ErrNilVersion {
			slog.Warn("Legacy database without version or missing database file!")
		} else {
			return err
		}
	}

	if dirty {
		return fmt.Errorf("last migration to version %d has failed, please fix the db manually and force version with -force-db flag", Version)
	}

	if err := m.Up(); err != nil {
		if err == migrate.ErrNoChange {
			slog.Info("DB already up to date!")
		} else {
			return err
		}
	}

	m.Close()
	return nil
}

func RevertDB(db string) error {
	m, err := getMigrateInstance(db)
	if err != nil {
		return err
	}

	if err := m.Migrate(Version - 1); err != nil {
		if err == migrate.ErrNoChange {
			slog.Info("DB already up to date!")
		} else {
			return err
		}
	}

	m.Close()
	return nil
}

func ForceDB(db string) error {
	m, err := getMigrateInstance(db)
	if err != nil {
		return err
	}

	if err := m.Force(int(Version)); err != nil {
		return err
	}

	m.Close()
	return nil
}