feat: now simple users can only occupy one seat at a time

client/src/components/seats-widget.js

@@ -65,7 +65,7 @@ export async function createSeatWidget($roomGrid, roomId) {
         })
 
         // Listener for takeing or leaving a seat
-        $seat.addEventListener('click', () => {
+        $seat.addEventListener('click', async () => {
             if (!user) {
                 location.href = '/login.html'
                 return
@@ -76,14 +76,38 @@ export async function createSeatWidget($roomGrid, roomId) {
             if (occupiedBy.length === 0) {
                 const confirmResponse = confirm('Occupare il posto?')
                 if (confirmResponse) {
-                    $seat.classList.remove('libero')
-                    Database.occupySeat(seatId)
+                    try {
+                        await Database.occupySeat(seatId)
+                        $seat.classList.remove('libero')
+                        $seat.classList.add('mio')
+                    } catch (e) {
+                        alert(e.toString())
+                    }
                 }
             } else if (occupiedBy.length === 1 && occupiedBy[0] === user.id) {
                 const answer = confirm('Lasciare veramente il posto?')
                 if (answer) {
-                    $seat.classList.remove('mio')
-                    Database.leaveSeat(seatId)
+                    try {
+                        await Database.leaveSeat(seatId)
+                        $seat.classList.remove('mio')
+                        $seat.classList.add('libero')
+                    } catch (e) {
+                        alert(e.toString())
+                    }
+                }
+            } else if (
+                user.permissions.includes('admin') ||
+                user.permissions.includes('moderator')
+            ) {
+                const answer = confirm(`Liberare veramente il posto di @${occupiedBy[0]}?`)
+                if (answer) {
+                    try {
+                        await Database.leaveSeat(seatId)
+                        $seat.classList.remove('occupato')
+                        $seat.classList.add('libero')
+                    } catch (e) {
+                        alert(e.toString())
+                    }
                 }
             } else {
                 alert('Posto già occupato!')

client/src/index.js

@@ -26,9 +26,21 @@ export const Database = {
         return seats
     },
     async occupySeat(seatId) {
-        await (await fetch(`/api/seat/occupy?id=${seatId}`, { method: 'POST' })).json()
+        const response = await fetch(`/api/seat/occupy?id=${seatId}`, { method: 'POST' })
+
+        if (!response.ok) {
+            throw new Error(await response.text())
+        }
+
+        await response.json()
     },
     async leaveSeat(seatId) {
-        await (await fetch(`/api/seat/leave?id=${seatId}`, { method: 'POST' })).json()
+        const response = await fetch(`/api/seat/leave?id=${seatId}`, { method: 'POST' })
+
+        if (!response.ok) {
+            throw new Error(await response.text())
+        }
+
+        await response.json()
     },
 }

server/db/database.go

@@ -6,6 +6,9 @@ package db
 import (
 	"errors"
 	"fmt"
+	"sync"
+
+	"git.phc.dm.unipi.it/aziis98/posti-dm/server/util"
 )
 
 // ErrAlreadyExists is the error thrown from Store functions when an entity already exists.
@@ -14,6 +17,11 @@ var ErrAlreadyExists = errors.New(`object already exists in database`)
 // ErrDoesntExist is the error thrown from Store functions when an entity doesn't exist.
 var ErrDoesntExist = errors.New(`object doesn't exist in database`)
 
+const (
+	PermissionAdmin     = "admin"
+	PermissionModerator = "moderator"
+)
+
 // Entities
 
 // type FrontendUser struct {
@@ -24,23 +32,12 @@ var ErrDoesntExist = errors.New(`object doesn't exist in database`)
 
 // User represents a user in the database.
 type User struct {
-	ID          string   `json:"id"`
-	Permissions []string `json:"permissions"`
+	ID          string         `json:"id"`
+	Permissions util.StringSet `json:"permissions"`
 
 	// passwordSaltHash string
 }
 
-// HasPermission checks if the user has a specific permission.
-func (user User) HasPermission(neededPerm string) bool {
-	for _, perm := range user.Permissions {
-		if perm == neededPerm {
-			return true
-		}
-	}
-
-	return false
-}
-
 // Room represents a room in the database, a room has an id, a name and a collection of seatIDs of this room.
 type Room struct {
 	ID      string   `json:"id"`
@@ -49,6 +46,26 @@ type Room struct {
 	// gridRows, gridCols int
 }
 
+// Version 1:
+//
+// type SeatState struct {
+// 	Occupied  bool
+// 	Anonymous bool
+// 	UserID    string
+// }
+
+// Version 2:
+//
+// type SeatState interface{ isSeatState() }
+//
+// type SeatNotOccupied struct{}
+// type SeatOccupiedByUser struct{ UserID string }
+// type SeatOccupiedByAnonymous struct{}
+//
+// func (s SeatNotOccupied) isSeatState()
+// func (s SeatOccupiedByUser) isSeatState()
+// func (s SeatOccupiedByAnonymous) isSeatState()
+
 // Seat represents a seat in the database, it belongs to a single room and can be free or occupied by some user (referenced by userID).
 type Seat struct {
 	ID     string `json:"id"`
@@ -81,6 +98,9 @@ type Seat struct {
 
 // Store is the main interface for interacting with database implementations, for now the only implementation is "memDB".
 type Store interface {
+	BeginTransaction()
+	EndTransaction()
+
 	CreateUser(user *User) error
 	CreateRoom(room *Room) error
 	CreateSeat(seat *Seat) error
@@ -98,7 +118,7 @@ type Store interface {
 	GetRoomOccupiedSeats(roomID string) ([]string, error)
 	GetRoomFreeSeats(roomID string) ([]string, error)
 
-	GetUserSeat(userID string) ([]string, error)
+	GetUserSeats(userID string) (util.StringSet, error)
 
 	OccupySeat(seatID, userID string) error
 	FreeSeat(seatID string) error
@@ -109,6 +129,8 @@ type Store interface {
 // NewInMemoryStore creates an instance of memDB hidden behind the Store interface.
 func NewInMemoryStore() Store {
 	db := &memDB{
+		&sync.Mutex{},
+
 		make(map[string]*User),
 		make(map[string]*Room),
 		make(map[string]*Seat),
@@ -135,12 +157,12 @@ func NewInMemoryStore() Store {
 
 	db.users["aziis98"] = &User{
 		ID:          "aziis98",
-		Permissions: []string{"admin"},
+		Permissions: util.NewStringSet(PermissionAdmin),
 	}
 
 	db.users["bachoseven"] = &User{
 		ID:          "bachoseven",
-		Permissions: []string{"admin"},
+		Permissions: util.NewStringSet(PermissionAdmin),
 	}
 
 	return db

server/db/inmemory.go

@@ -1,17 +1,29 @@
 package db
 
-import "fmt"
+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 {
-	// FIXME: Giusto per la cronaca fare le modifiche in questo modo alle mappe non è per niente thread safe, servirebbe come minimo usare un mutex per quando si scrive su una di queste variabili
-	// mutex *sync.Mutex
+	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
@@ -134,14 +146,14 @@ func (db *memDB) GetRoomFreeSeats(roomID string) ([]string, error) {
 	return seats, nil
 }
 
-func (db *memDB) GetUserSeat(userID string) ([]string, error) {
+func (db *memDB) GetUserSeats(userID string) (util.StringSet, error) {
 	for _, seat := range db.seats {
 		if len(seat.OccupiedBy) > 0 && seat.OccupiedBy[0] == userID {
-			return []string{userID}, nil
+			return util.NewStringSet(seat.ID), nil
 		}
 	}
 
-	return []string{}, nil
+	return util.NewStringSet(), nil
 }
 
 func (db *memDB) OccupySeat(seatID, userID string) error {

server/go.mod

@@ -3,7 +3,6 @@ module git.phc.dm.unipi.it/aziis98/posti-dm/server
 go 1.17
 
 require (
-	github.com/alecthomas/repr v0.0.0-20220113201626-b1b626ac65ae
 	github.com/go-chi/chi/v5 v5.0.7
 	github.com/joho/godotenv v1.4.0
 )

server/go.sum

@@ -1,5 +1,3 @@
-github.com/alecthomas/repr v0.0.0-20220113201626-b1b626ac65ae h1:zzGwJfFlFGD94CyyYwCJeSuD32Gj9GTaSi5y9hoVzdY=
-github.com/alecthomas/repr v0.0.0-20220113201626-b1b626ac65ae/go.mod h1:2kn6fqh/zIyPLmm3ugklbEi5hg5wS435eygvNfaDQL8=
 github.com/go-chi/chi/v5 v5.0.7 h1:rDTPXLDHGATaeHvVlLcR4Qe0zftYethFucbjVQ1PxU8=
 github.com/go-chi/chi/v5 v5.0.7/go.mod h1:DslCQbL2OYiznFReuXYUmQ2hGd1aDpCnlMNITLSKoi8=
 github.com/joho/godotenv v1.4.0 h1:3l4+N6zfMWnkbPEXKng2o2/MR5mSwTrBih4ZEkkz1lg=

server/server.go

@@ -37,7 +37,7 @@ func NewServer() *Server {
 				// FIXME: al momento quando la password è giusta creiamo tutti gli account necessari
 				err := database.CreateUser(&db.User{
 					ID:          userID,
-					Permissions: []string{},
+					Permissions: make(util.StringSet),
 				})
 				if err != nil {
 					log.Printf(`got "%v" while trying to log as @%s`, err, userID)
@@ -52,7 +52,7 @@ func NewServer() *Server {
 					return nil, err
 				}
 
-				return user.Permissions, nil
+				return user.Permissions.Elements(), nil
 			},
 			SessionTokenFromUser: func(userID string) (string, error) {
 				user, err := database.GetUser(userID)
@@ -105,6 +105,10 @@ func (server *Server) setupRoutes() {
 	database := server.Database
 	auth := server.authService
 
+	// FIXME: in realtà tutte le routes che interagiscono con il db dovrebbero essere in transazione con
+	// database.BeginTransaction()
+	// defer database.EndTransaction()
+
 	// Authenticated Routes
 
 	api.Post("/login", func(w http.ResponseWriter, r *http.Request) {
@@ -186,6 +190,9 @@ func (server *Server) setupRoutes() {
 
 	api.With(auth.LoggedMiddleware()).
 		Post("/seat/occupy", func(w http.ResponseWriter, r *http.Request) {
+			database.BeginTransaction()
+			defer database.EndTransaction()
+
 			userID, err := auth.RequestUser(r)
 			if err != nil {
 				http.Error(w, err.Error(), http.StatusUnauthorized)
@@ -210,8 +217,20 @@ func (server *Server) setupRoutes() {
 				return
 			}
 
+			// a seat can be occupied only if empty; simple users can occupy a seat only if they have occupied no other seat; admins and moderator (for now) can occupy even more than one seat (as occupied by an anonymous?) to fix the free seat count of the room
 			if len(seat.OccupiedBy) == 0 {
-				if err := database.OccupySeat(seatID[0], user.ID); err != nil {
+				userSeats, err := database.GetUserSeats(userID)
+				if err != nil {
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+
+				if !user.Permissions.HasAny(db.PermissionAdmin, db.PermissionModerator) && len(userSeats) > 0 {
+					http.Error(w, `you can occupy only one seat at a time`, http.StatusUnprocessableEntity)
+					return
+				}
+
+				if err := database.OccupySeat(seatID[0], userID); err != nil {
 					http.Error(w, err.Error(), http.StatusInternalServerError)
 					return
 				}
@@ -249,10 +268,9 @@ func (server *Server) setupRoutes() {
 				return
 			}
 
-			// Check permissions
+			// Check permissions, if the place is occupied then only its owner, a moderator or an admin can clear it
 			if len(seat.OccupiedBy) > 0 {
-				if user.ID == seat.OccupiedBy[0] || user.HasPermission("admin") || user.HasPermission("moderator") {
-
+				if user.ID == seat.OccupiedBy[0] || user.Permissions.HasAny(db.PermissionAdmin, db.PermissionModerator) {
 					if err := database.FreeSeat(seatID[0]); err != nil {
 						http.Error(w, err.Error(), http.StatusInternalServerError)
 						return

server/util/sets.go

@@ -0,0 +1,77 @@
+package util
+
+import "encoding/json"
+
+type present struct{}
+
+// Waiting for Go 18...
+// type Set[T comparable] map[T]present
+type StringSet map[string]present
+
+func NewStringSet(elements ...string) StringSet {
+	set := StringSet{}
+
+	for _, elem := range elements {
+		set.Add(elem)
+	}
+
+	return set
+}
+
+func (set StringSet) Has(value string) bool {
+	_, present := set[value]
+	return present
+}
+
+func (set StringSet) HasAny(values ...string) bool {
+	for _, value := range values {
+		if _, present := set[value]; present {
+			return true
+		}
+	}
+	return false
+}
+
+func (set StringSet) Contains(other StringSet) bool {
+	for v := range other {
+		if !set.Has(v) {
+			return false
+		}
+	}
+	return true
+}
+
+func (set StringSet) Add(value string) {
+	set[value] = present{}
+}
+
+func (set StringSet) Remove(value string) {
+	delete(set, value)
+}
+
+func (set StringSet) Elements() []string {
+	elements := []string{}
+
+	for elem := range set {
+		elements = append(elements, elem)
+	}
+
+	return elements
+}
+
+func (set StringSet) MarshalJSON() ([]byte, error) {
+	return json.Marshal(set.Elements())
+}
+
+func (set StringSet) UnmarshalJSON(data []byte) error {
+	elements := []string{}
+	if err := json.Unmarshal(data, &elements); err != nil {
+		return err
+	}
+
+	for _, v := range elements {
+		set.Add(v)
+	}
+
+	return nil
+}