package db

import (
	"fmt"
	"sync"

	"git.phc.dm.unipi.it/aziis98/posti-dm/server/util"
)

// memDB is the first Store implementation used for testing.
type memDB struct {
	mutex *sync.Mutex

	users map[string]*User
	rooms map[string]*Room
	seats map[string]*Seat
}

func (db *memDB) BeginTransaction() {
	db.mutex.Lock()
}

func (db *memDB) EndTransaction() {
	db.mutex.Unlock()
}

func (db *memDB) CreateUser(user *User) error {
	if _, present := db.users[user.ID]; present {
		return ErrAlreadyExists
	}
	db.users[user.ID] = user
	return nil
}

func (db *memDB) CreateRoom(room *Room) error {
	if _, present := db.rooms[room.ID]; present {
		return ErrAlreadyExists
	}
	db.rooms[room.ID] = room
	return nil
}

func (db *memDB) CreateSeat(seat *Seat) error {
	if _, present := db.seats[seat.ID]; present {
		return ErrAlreadyExists
	}
	db.seats[seat.ID] = seat
	return nil
}

func (db *memDB) DeleteUser(user *User) error {
	if _, present := db.users[user.ID]; !present {
		return ErrDoesntExist
	}

	delete(db.users, user.ID)
	return nil
}

func (db *memDB) DeleteRoom(room *Room) error {
	if _, present := db.rooms[room.ID]; !present {
		return ErrDoesntExist
	}

	delete(db.rooms, room.ID)
	return nil
}

func (db *memDB) DeleteSeat(seat *Seat) error {
	if _, present := db.seats[seat.ID]; !present {
		return ErrDoesntExist
	}

	delete(db.seats, seat.ID)
	return nil
}

func (db *memDB) GetUser(userID string) (*User, error) {
	user, present := db.users[userID]
	if !present {
		return nil, fmt.Errorf(`no such user "%s"`, userID)
	}

	return user, nil
}

func (db *memDB) GetRoom(roomID string) (*Room, error) {
	room, present := db.rooms[roomID]
	if !present {
		return nil, fmt.Errorf(`no such room "%s"`, roomID)
	}

	return room, nil
}

func (db *memDB) GetSeat(seatID string) (*Seat, error) {
	seat, present := db.seats[seatID]
	if !present {
		return nil, fmt.Errorf(`no such seat "%s"`, seatID)
	}

	return seat, nil
}

func (db *memDB) GetRooms() ([]string, error) {
	roomIDs := []string{}

	for roomID := range db.rooms {
		roomIDs = append(roomIDs, roomID)
	}

	return roomIDs, nil
}

func (db *memDB) GetRoomOccupiedSeats(roomID string) ([]string, error) {
	room, err := db.GetRoom(roomID)
	if err != nil {
		return nil, err
	}

	seats := []string{}
	for _, seatID := range room.SeatIDs {
		seat := db.seats[seatID]
		if len(seat.OccupiedBy) == 1 {
			seats = append(seats, seatID)
		}
	}

	return seats, nil
}

func (db *memDB) GetRoomFreeSeats(roomID string) ([]string, error) {
	room, err := db.GetRoom(roomID)
	if err != nil {
		return nil, err
	}

	seats := []string{}
	for _, seatID := range room.SeatIDs {
		seat := db.seats[seatID]
		if len(seat.OccupiedBy) == 0 {
			seats = append(seats, seatID)
		}
	}

	return seats, nil
}

func (db *memDB) GetUserSeats(userID string) (util.StringSet, error) {
	for _, seat := range db.seats {
		if len(seat.OccupiedBy) > 0 && seat.OccupiedBy[0] == userID {
			return util.NewStringSet(seat.ID), nil
		}
	}

	return util.NewStringSet(), nil
}

func (db *memDB) OccupySeat(seatID, userID string) error {
	db.seats[seatID].OccupiedBy = []string{userID}
	return nil
}

func (db *memDB) FreeSeat(seatID string) error {
	db.seats[seatID].OccupiedBy = []string{}
	return nil
}