package migrations

import (
	// stdlib
	"database/sql"
	"log"
	"os"
	"strconv"

	// other
	"github.com/pressly/goose"
)

func Initialize() {
	log.Println("Initializing database migrations...")

	_ = goose.SetDialect("postgres")

	goose.AddNamedMigration("1_create_users_table.go", CreateUsersTableUp, CreateUsersTableDown)

	// Migrations should be registered here.
}

func Migrate(db *sql.DB) {
	log.Println("Starting database migration procedure...")

	// Prepare migrations configuration.
	var action = "UP"
	actionFromEnv, actionFound := os.LookupEnv("DATABASE_ACTION")
	if actionFound {
		log.Println("Migration action override: " + actionFromEnv)
		action = actionFromEnv
	} else {
		log.Println("Executing default migration action (UP)")
	}

	var count int64
	countFromEnv, countFound := os.LookupEnv("DATABASE_COUNT")
	if countFound {
		log.Println("Migration count override: " + countFromEnv)
		countAsInt, err := strconv.ParseInt(countFromEnv, 10, 64)
		if err != nil {
			log.Fatalln("Failed to convert count gathered from DATABASE_COUNT to integer")
		}
		count = countAsInt
	} else {
		log.Println("Applying or rollback this count of migrations: " + countFromEnv + ". 0 - all.")
	}

	// Execute migrations.
	var err error
	currentDBVersion, gooseerr := goose.GetDBVersion(db)
	if gooseerr != nil {
		log.Fatalln("Failed to get database version: " + gooseerr.Error())
	}
	log.Println("Current database version obtained: " + strconv.Itoa(int(currentDBVersion)))
	if action == "UP" && count == 0 {
		log.Println("Applying all unapplied migrations...")
		err = goose.Up(db, ".")
	} else if action == "UP" && count != 0 {
		newVersion := currentDBVersion + count
		log.Println("Migrating database to specific version: " + strconv.Itoa(int(newVersion)))
		err = goose.UpTo(db, ".", newVersion)
	} else if action == "DOWN" && count == 0 {
		log.Println("Downgrading database to zero state, you'll need to re-apply migrations!")
		err = goose.Down(db, ".")
		log.Fatalln("Database downgraded to zero state. You have to re-apply migrations")
	} else if action == "DOWN" && count != 0 {
		newVersion := currentDBVersion - count
		log.Println("Downgrading database to specific version: " + strconv.Itoa(int(newVersion)))
		err = goose.DownTo(db, ".", newVersion)
	} else {
		log.Fatalln("Unsupported set of migration parameters, cannot continue: " + action + "/" + countFromEnv)
	}

	if err != nil {
		log.Fatalln("Failed to execute migration sequence: " + err.Error())
	}

	log.Println("Database migrated successfully")
}