package db

import (
	"fmt"

	"github.com/jmoiron/sqlx"

	"git.offline-twitter.com/offline-labs/gas-stack/pkg/must"
	"git.offline-twitter.com/offline-labs/gas-stack/pkg/textutils"
)

type Migration struct {
	// ID is the version number that the schema will be at, after applying the migration.
	ID int

	// Title is an optional name for the migration.
	Title string

	// SQL is the body of the migration that will be executed.
	SQL string
}

// Apply runs the migration in a transaction.  Foreign key checking is delayed until right before committing the transaction.
func (m Migration) Apply(db *sqlx.DB) error {
	fmt.Print(textutils.ColorCyan)
	fmt.Println(m.SQL)
	fmt.Print(textutils.ColorReset)

	// Temporarily suspend foreign keys until the migration is finished
	db.MustExec("pragma foreign_keys = off")
	defer db.MustExec("pragma foreign_keys = on")

	tx := db.MustBegin()
	defer func() { _ = tx.Rollback() }()

	// Sanity: should initially be on the previous version
	var prevVersion int
	must.Do(tx.Get(&prevVersion, `select version from db_version`))
	if prevVersion != m.ID-1 {
		return fmt.Errorf("%w: tried to apply migration %d on DB version %d", ErrMigrationOrder, m.ID, prevVersion)
	}

	// Execute the migration
	tx.MustExec(m.SQL)
	tx.MustExec("update db_version set version = ?", m.ID)
	must.Do(PragmaForeignKeyCheck(tx))
	must.Do(tx.Commit())

	return nil
}