package main

import (
	"asink"
	"database/sql"
	"errors"
	_ "github.com/mattn/go-sqlite3"
	"sync"
)

type AsinkDB struct {
	db   *sql.DB
	lock sync.Mutex
}

var DuplicateUsernameErr = errors.New("Username already exists")
var NoUserErr = errors.New("User doesn't exist")

func GetAndInitDB() (*AsinkDB, error) {
	dbLocation := "asink-server.db" //TODO make me configurable

	db, err := sql.Open("sqlite3", "file:"+dbLocation+"?cache=shared&mode=rwc")
	if err != nil {
		return nil, err
	}

	//make sure all the tables are created
	tx, err := db.Begin()
	if err != nil {
		return nil, err
	}

	rows, err := tx.Query("SELECT name FROM sqlite_master WHERE type='table' AND name='events';")
	if err != nil {
		return nil, err
	}
	if !rows.Next() {
		//if this is false, it means no rows were returned
		tx.Exec("CREATE TABLE events (id INTEGER PRIMARY KEY ASC, userid INTEGER, type INTEGER, path TEXT, hash TEXT, predecessor TEXT, timestamp INTEGER, permissions INTEGER);")
		tx.Exec("CREATE INDEX IF NOT EXISTS pathidx on events (path);")
		tx.Exec("CREATE INDEX IF NOT EXISTS timestampidx on events (timestamp);")
	} else {
		rows.Close()
	}

	rows, err = tx.Query("SELECT name FROM sqlite_master WHERE type='table' AND name='users';")
	if err != nil {
		return nil, err
	}
	if !rows.Next() {
		//if this is false, it means no rows were returned
		tx.Exec("CREATE TABLE users (id INTEGER PRIMARY KEY ASC, username TEXT, pwhash TEXT, role INTEGER);")
	} else {
		rows.Close()
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	ret := new(AsinkDB)
	ret.db = db
	return ret, nil
}

func (adb *AsinkDB) DatabaseAddEvent(u *User, e *asink.Event) (err error) {
	adb.lock.Lock()
	tx, err := adb.db.Begin()
	if err != nil {
		return err
	}

	//make sure the transaction gets rolled back on error, and the database gets unlocked
	defer func() {
		if err != nil {
			tx.Rollback()
		}
		adb.lock.Unlock()
	}()

	result, err := tx.Exec("INSERT INTO events (userid, type, path, hash, predecessor, timestamp, permissions) VALUES (?,?,?,?,?,?,?);", u.Id, e.Type, e.Path, e.Hash, e.Predecessor, e.Timestamp, e.Permissions)
	if err != nil {
		return err
	}
	id, err := result.LastInsertId()
	if err != nil {
		return err
	}
	err = tx.Commit()
	if err != nil {
		return err
	}

	e.Id = id
	e.InDB = true
	return nil
}

func (adb *AsinkDB) DatabaseRetrieveEvents(firstId uint64, maxEvents uint, u *User) (events []*asink.Event, err error) {
	adb.lock.Lock()
	//make sure the database gets unlocked on return
	defer func() {
		adb.lock.Unlock()
	}()
	rows, err := adb.db.Query("SELECT id, type, path, hash, predecessor, timestamp, permissions FROM events WHERE userid = ? AND id >= ? ORDER BY id ASC LIMIT ?;", u.Id, firstId, maxEvents)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		var event asink.Event
		err = rows.Scan(&event.Id, &event.Type, &event.Path, &event.Hash, &event.Predecessor, &event.Timestamp, &event.Permissions)
		if err != nil {
			return nil, err
		}
		events = append(events, &event)
	}

	return events, nil
}

func (adb *AsinkDB) DatabaseAddUser(u *User) (err error) {
	adb.lock.Lock()
	tx, err := adb.db.Begin()
	if err != nil {
		return err
	}

	//make sure the transaction gets rolled back on error, and the database gets unlocked
	defer func() {
		if err != nil {
			tx.Rollback()
		}
		adb.lock.Unlock()
	}()

	//make sure the username we're switching to doesn't already exist in the database
	existingUsername := ""
	row := tx.QueryRow("SELECT username FROM users WHERE username == ?;", u.Username)
	err = row.Scan(&existingUsername)
	switch {
	case err == sql.ErrNoRows:
		//keep going
	case err != nil:
		return err
	default:
		return DuplicateUsernameErr
	}

	result, err := tx.Exec("INSERT INTO users (username, pwhash, role) VALUES (?,?,?);", u.Username, u.PWHash, u.Role)
	if err != nil {
		return err
	}
	u.Id, err = result.LastInsertId()
	if err != nil {
		return err
	}
	err = tx.Commit()
	if err != nil {
		return err
	}

	return nil
}

//set attributes for the user with the same Id as *u
func (adb *AsinkDB) DatabaseUpdateUser(u *User) (err error) {
	adb.lock.Lock()
	tx, err := adb.db.Begin()
	if err != nil {
		return err
	}

	//make sure the transaction gets rolled back on error, and the database gets unlocked
	defer func() {
		if err != nil {
			tx.Rollback()
		}
		adb.lock.Unlock()
	}()

	//make sure the username we're switching to doesn't already exist in the database
	existingUsername := ""
	row := tx.QueryRow("SELECT username FROM users WHERE username == ? AND id != ?;", u.Username, u.Id)
	err = row.Scan(&existingUsername)
	switch {
	case err == sql.ErrNoRows:
		//keep going
	case err != nil:
		return err
	default:
		return DuplicateUsernameErr
	}

	_, err = tx.Exec("UPDATE users SET username=?, pwhash=?, role=? WHERE id=?;", u.Username, u.PWHash, u.Role, u.Id)
	if err != nil {
		return err
	}
	err = tx.Commit()
	if err != nil {
		return err
	}

	return nil
}

func (adb *AsinkDB) DatabaseGetUser(username string) (user *User, err error) {
	adb.lock.Lock()
	//make sure the database gets unlocked
	defer adb.lock.Unlock()

	row := adb.db.QueryRow("SELECT id, username, pwhash, role FROM users WHERE username == ?;", username)

	user = new(User)
	err = row.Scan(&user.Id, &user.Username, &user.PWHash, &user.Role)

	switch {
	case err == sql.ErrNoRows:
		return nil, NoUserErr
	case err != nil:
		return nil, err
	default:
		return user, nil
	}
}

func (adb *AsinkDB) DatabaseDeleteUser(u *User) (err error) {
	adb.lock.Lock()
	tx, err := adb.db.Begin()
	if err != nil {
		return err
	}

	//make sure the transaction gets rolled back on error, and the database gets unlocked
	defer func() {
		if err != nil {
			tx.Rollback()
		}
		adb.lock.Unlock()
	}()

	res, err := tx.Exec("DELETE FROM users WHERE username=?;", u.Username)
	if err != nil {
		return err
	}
	rows, err := res.RowsAffected()
	if err != nil {
		return err
	}
	if rows == 0 {
		return NoUserErr
	} else if rows > 1 {
		return errors.New("Error: attempting to delete user by username, but more than row will be affected: " + u.Username)
	}
	err = tx.Commit()
	if err != nil {
		return err
	}

	return nil
}