package peachy

import (
	"errors"
	"fmt"
	"os"

	"zombiezen.com/go/sqlite"
	"zombiezen.com/go/sqlite/sqlitex"
)

const AppID = '🍑'

var ErrInvalidDB = errors.New("invalid database file")
var ErrFileExists = errors.New("database file already exists")
var ErrFileNotExist = errors.New("database file does not exist")

type DBError struct{ error }

func (dbe DBError) Error() string {
	return "database error: " + dbe.error.Error()
}

type DB struct {
	conn *sqlite.Conn
}

func (db *DB) Close() {
	db.conn.Close()
}

func setupConn(conn *sqlite.Conn) error {
	return nil
}

func Open(path string) (db *DB, err error) {
	var conn *sqlite.Conn
	defer func() {
		if err != nil {
			conn.Close()
		}
	}()

	conn, err = sqlite.OpenConn(path, sqlite.OpenReadWrite|sqlite.OpenWAL)
	switch sqlite.ErrCode(err) {
	case sqlite.ResultOK:
	case sqlite.ResultCantOpen:
		return nil, ErrFileNotExist
	case sqlite.ResultNotADB:
		return nil, ErrInvalidDB
	default:
		return nil, DBError{err}
	}

	var goodAppID bool
	sqlitex.ExecuteTransient(conn, "PRAGMA application_id", &sqlitex.ExecOptions{
		ResultFunc: func(stmt *sqlite.Stmt) error {
			goodAppID = stmt.ColumnInt32(0) == AppID
			return nil
		}})
	if !goodAppID {
		return nil, ErrInvalidDB
	}
	err = setupConn(conn)
	if err != nil {
		return nil, err
	}
	return &DB{conn: conn}, nil
}

func Create(path string) (db *DB, err error) {
	var conn *sqlite.Conn
	defer func() {
		if err != nil {
			conn.Close()
		}
	}()

	finfo, _ := os.Stat(path)
	if finfo != nil {
		return nil, ErrFileExists
	}

	conn, err = sqlite.OpenConn(path, sqlite.OpenCreate|sqlite.OpenReadWrite|sqlite.OpenWAL)
	if err != nil {
		return nil, fmt.Errorf("could not create database: %w", err)
	}
	query := fmt.Sprintf("PRAGMA application_id=%d", AppID)
	err = sqlitex.ExecuteTransient(conn, query, nil)
	if err != nil {
		return nil, DBError{err}
	}
	err = setupConn(conn)
	if err != nil {
		return nil, err
	}
	return &DB{conn: conn}, nil
}