package model

import (
	"database/sql"
	"log"

	_ "github.com/mattn/go-sqlite3"

	"xengineering.eu/ceres/model/migrations"
)

var db *sql.DB

func ConnectDatabase(path string) {
	var err error

	db, err = sql.Open("sqlite3", path)
	if err != nil {
		log.Fatal(err)
	}

	err = db.Ping()
	if err != nil {
		log.Fatal(err)
	}
}

func Transaction(f func(*sql.Tx) error) error {
	tx, err := db.Begin()
	if err != nil {
		log.Printf("Failed to start database transaction: %v", err)
		return err
	}
	defer func() {
		if tx.Rollback() == nil {
			log.Println("Rolled back transaction")
		}
	}()

	err = f(tx)
	if err != nil {
		log.Printf("Failed transaction: %v", err)
		return err
	}

	return tx.Commit()
}

func isDatabaseEmpty(tx *sql.Tx) bool {
	cmd := `SELECT COUNT(*) FROM sqlite_master WHERE type='table'`
	rows, err := tx.Query(cmd)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	if !rows.Next() {
		log.Fatalf("No rows on request of database table number")
	}

	var number int
	err = rows.Scan(&number)
	if err != nil {
		log.Fatalf("Failed to scan number of database tables to integer")
	}

	return number == 0
}

func setupMinimalDatabase(tx *sql.Tx, execVersion string) error {
	cmd := `
CREATE TABLE metadata (
	key   TEXT PRIMARY KEY,
	value TEXT
);
INSERT INTO metadata
	(key, value)
VALUES
	('version', ?);
`
	_, err := tx.Exec(cmd, execVersion)
	return err
}

func getDatabaseVersion(tx *sql.Tx) string {
	rows, err := tx.Query(`SELECT value FROM metadata WHERE key='version';`)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	if !rows.Next() {
		log.Fatalf("No rows on request of database version")
	}

	var version string
	err = rows.Scan(&version)
	if err != nil {
		log.Fatalf("Failed to scan database version to string")
	}

	return version
}

func MigrateDatabase(execVersion string) {
	err := Transaction(func(tx *sql.Tx) error {
		if isDatabaseEmpty(tx) {
			log.Println("Starting with empty database")
			err := setupMinimalDatabase(tx, execVersion)
			if err != nil {
				log.Fatalf("Failed to setup minimal database schema: %v", err)
			}

			log.Println("Executing initial migration")
			err = migrations.Migration001(tx)
			if err != nil {
				return err
			}
		}

		dbVersion := getDatabaseVersion(tx)
		if dbVersion != execVersion {
			log.Fatalf(
				"Database version '%s' does not match executable version '%s'",
				dbVersion,
				execVersion,
			)
		}

		return nil
	})
	if err != nil {
		log.Fatalf("Fatal: Database migration failed")
	}
}

func InjectExampleRecipes() {
	err := Transaction(func(tx *sql.Tx) error {
		recipes := RecipeTestData()

		for _, recipe := range recipes {
			err := recipe.Create(tx)
			if err != nil {
				return err
			}
		}

		return nil
	})
	if err != nil {
		log.Fatalf("Failed to inject example recipes: %v", err)
	}
}

func DisconnectDatabase() {
	var err error = db.Close()
	if err != nil {
		log.Printf("Failed to close database: %v\n", err)
	} else {
		log.Println("Closed database")
	}
}