refactor: split mutex, add download queue, wire context cancellation

- Split single sync.Mutex into per-map mutexes (activeJobs, stepStates,
  rateLimiter, pendingInput, cancelFuncs) to reduce contention
- Add download semaphore (channel-buffered, 3 concurrent) as worker pool
- Add cancelFuncs map with context cancellation wired into download
  goroutines for clean shutdown
- Replace playlist busy-poll (500ms sleep loop) with synchronous
  runDownload + Done channel for completion tracking
- Use full UUID for job IDs instead of 8-char prefix
- Download thumbnail URL to temp file before sending (InputFileUpload)
- Change MAX_FILE_SIZE_MB default from 2000 to 50
- Clean up cancel funcs after normal download completion

.env.example

@@ -3,7 +3,7 @@ HTTP_PROXY=
 HTTPS_PROXY=
 DB_PATH=data/uptodown.db
 DOWNLOAD_DIR=/tmp/uptodown
-MAX_FILE_SIZE_MB=2000
+MAX_FILE_SIZE_MB=50
 COOKIES_FILE=
 TZ=UTC
 BOT_ALLOWED_USERS=

README.md

@@ -41,7 +41,7 @@ Copy `.env.example` to `.env` and configure:
 | `HTTPS_PROXY`       | empty              | Outbound HTTPS proxy             |
 | `DB_PATH`           | `data/uptodown.db` | SQLite database path             |
 | `DOWNLOAD_DIR`      | `/tmp/uptodown`    | Temporary download directory     |
-| `MAX_FILE_SIZE_MB`  | `2000`             | Maximum upload file size in MB   |
+| `MAX_FILE_SIZE_MB`  | `50`               | Maximum upload file size in MB   |
 | `COOKIES_FILE`      | empty              | Path to cookies.txt for auth     |
 | `TZ`                | `UTC`              | Timezone                         |
 | `BOT_ALLOWED_USERS` | empty              | Comma-separated allowed user IDs |

cmd/bot/main.go

@@ -29,7 +29,7 @@ func main() {
 	token := os.Getenv("BOT_TOKEN")
 	dbPath := getEnvDefault("DB_PATH", "data/uptodown.db")
 	downloadDir := getEnvDefault("DOWNLOAD_DIR", "/tmp/uptodown")
-	maxFileSizeMB := getEnvIntDefault("MAX_FILE_SIZE_MB", 2000)
+	maxFileSizeMB := getEnvIntDefault("MAX_FILE_SIZE_MB", 50)
 	cookiesFile := os.Getenv("COOKIES_FILE")
 
 	if token == "" {

internal/domain/constants.go

@@ -6,7 +6,7 @@ const (
 	RateLimitInterval      = 1 * time.Second
 	ProgressThreshold      = 5.0
 	MaxFileSizeEnvKey      = "MAX_FILE_SIZE_MB"
-	DefaultMaxFileSize     = 2000
+	DefaultMaxFileSize     = 50
 	DefaultDailyQuotaMB    = 100
 	DefaultWeeklyQuotaMB   = 500
 	DefaultMonthlyQuotaMB  = 2000

internal/domain/types.go

@@ -129,6 +129,7 @@ type DownloadJob struct {
 	Title          string
 	QuotaApplied   bool
 	StderrLog      string
+	Done           chan struct{}
 	CancelCh       chan struct{}
 	Cmd            *exec.Cmd
 }

internal/handler/download.go

@@ -3,8 +3,10 @@ package handler
 import (
 	"context"
 	"fmt"
+	"io"
 	"log/slog"
 	"math"
+	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
@@ -33,20 +35,20 @@ type stepState struct {
 }
 
 func (h *Handler) getUserStepState(chatID int64) *stepState {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.stepStatesMu.Lock()
+	defer h.stepStatesMu.Unlock()
 	return h.stepStates[chatID]
 }
 
 func (h *Handler) setUserStepState(chatID int64, ss *stepState) {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.stepStatesMu.Lock()
+	defer h.stepStatesMu.Unlock()
 	h.stepStates[chatID] = ss
 }
 
 func (h *Handler) clearStepState(chatID int64) {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.stepStatesMu.Lock()
+	defer h.stepStatesMu.Unlock()
 	delete(h.stepStates, chatID)
 }
 
@@ -355,6 +357,8 @@ func (h *Handler) handleContainerSelection(ctx context.Context, chatID int64, ms
 		return
 	}
 
+	dlCtx, dlCancel := context.WithCancel(context.Background())
+
 	job := &domain.DownloadJob{
 		ID:             h.generateJobID(),
 		UserID:         userID,
@@ -369,17 +373,33 @@ func (h *Handler) handleContainerSelection(ctx context.Context, chatID int64, ms
 		Status:         domain.StatusDownloading,
 		Title:          ss.MediaInfo.Title,
 		FileSize:       fileSize,
+		Done:           make(chan struct{}),
 	}
 
 	h.editText(ctx, chatID, msgID, "Processing...", nil)
 	h.setActiveJob(userID, job)
+	h.setCancelFunc(userID, dlCancel)
 	h.clearStepState(chatID)
 
-	go h.runDownload(context.Background(), job)
+	go h.runDownload(dlCtx, job)
 }
 
 // runDownload manages the download lifecycle, progress, and completion.
 func (h *Handler) runDownload(ctx context.Context, job *domain.DownloadJob) {
+	defer func() {
+		if job.Done != nil {
+			close(job.Done)
+		}
+	}()
+
+	// Acquire semaphore slot or wait for cancellation
+	select {
+	case h.downloadSem <- struct{}{}:
+	case <-ctx.Done():
+		return
+	}
+	defer func() { <-h.downloadSem }()
+
 	kb := progressKeyboard(0, "", "")
 	msg, err := h.Bot.SendMessage(ctx, &tgbot.SendMessageParams{
 		ChatID:      job.ChatID,
@@ -396,61 +416,77 @@ func (h *Handler) runDownload(ctx context.Context, job *domain.DownloadJob) {
 	if err != nil {
 		h.editText(ctx, job.ChatID, job.MessageID, fmt.Sprintf("Download failed: %s", err.Error()), nil)
 		job.Status = domain.StatusFailed
-		h.mu.Lock()
+		h.activeJobsMu.Lock()
 		delete(h.activeJobs, job.UserID)
-		h.mu.Unlock()
+		h.activeJobsMu.Unlock()
 		return
 	}
 
 	lastProgress := 0.0
-	for upd := range updates {
-		slog.Info("progress update", "pct", upd.Progress, "speed", upd.Speed, "status", upd.Status)
+loop:
+	for {
+		select {
+		case upd, ok := <-updates:
+			if !ok {
+				break loop
+			}
+			slog.Info("progress update", "pct", upd.Progress, "speed", upd.Speed, "status", upd.Status)
 
-		h.mu.Lock()
-		currentJob := h.activeJobs[job.UserID]
-		h.mu.Unlock()
-		if currentJob == nil {
-			return
+			h.activeJobsMu.Lock()
+			currentJob := h.activeJobs[job.UserID]
+			h.activeJobsMu.Unlock()
+			if currentJob == nil {
+				return
+			}
+
+			if upd.Status == domain.StatusCancelled {
+				h.editText(ctx, job.ChatID, job.MessageID, "Download cancelled.", nil)
+				h.activeJobsMu.Lock()
+				delete(h.activeJobs, job.UserID)
+				h.activeJobsMu.Unlock()
+				return
+			}
+
+			if upd.Status == domain.StatusFailed {
+				h.editText(ctx, job.ChatID, job.MessageID, "Download failed.", nil)
+				h.activeJobsMu.Lock()
+				delete(h.activeJobs, job.UserID)
+				h.activeJobsMu.Unlock()
+				return
+			}
+
+			if upd.Progress > 0 && lastProgress == 0 {
+				lastProgress = upd.Progress
+			} else if upd.Progress-lastProgress < domain.ProgressThreshold && upd.Status != domain.StatusCompleted {
+				continue
+			} else {
+				lastProgress = upd.Progress
+			}
+
+			if upd.Progress > domain.QuotaProgressThreshold && !job.QuotaApplied && job.FileSize > 0 {
+				job.QuotaApplied = true
+				h.applyQuota(job.UserID, job.FileSize)
+			}
+
+			kb := progressKeyboard(upd.Progress, upd.Speed, upd.ETA)
+			text := fmt.Sprintf("Downloading: %s", job.Title)
+			h.editText(ctx, job.ChatID, job.MessageID, text, &kb)
+
+		case <-ctx.Done():
+			dl.CancelDownload(job)
+			for range updates {
+			}
+			break loop
 		}
-
-		if upd.Status == domain.StatusCancelled {
-			h.editText(ctx, job.ChatID, job.MessageID, "Download cancelled.", nil)
-			h.mu.Lock()
-			delete(h.activeJobs, job.UserID)
-			h.mu.Unlock()
-			return
-		}
-
-		if upd.Status == domain.StatusFailed {
-			h.editText(ctx, job.ChatID, job.MessageID, "Download failed.", nil)
-			h.mu.Lock()
-			delete(h.activeJobs, job.UserID)
-			h.mu.Unlock()
-			return
-		}
-
-		// Always show the first real progress update, then throttle at 5% intervals
-		if upd.Progress > 0 && lastProgress == 0 {
-			lastProgress = upd.Progress
-		} else if upd.Progress-lastProgress < domain.ProgressThreshold && upd.Status != domain.StatusCompleted {
-			continue
-		} else {
-			lastProgress = upd.Progress
-		}
-
-		if upd.Progress > domain.QuotaProgressThreshold && !job.QuotaApplied && job.FileSize > 0 {
-			job.QuotaApplied = true
-			h.applyQuota(job.UserID, job.FileSize)
-		}
-
-		kb := progressKeyboard(upd.Progress, upd.Speed, upd.ETA)
-		text := fmt.Sprintf("Downloading: %s", job.Title)
-		h.editText(ctx, job.ChatID, job.MessageID, text, &kb)
 	}
 
-	h.mu.Lock()
+	h.activeJobsMu.Lock()
 	delete(h.activeJobs, job.UserID)
-	h.mu.Unlock()
+	h.activeJobsMu.Unlock()
+
+	h.cancelFuncsMu.Lock()
+	delete(h.cancelFuncs, job.UserID)
+	h.cancelFuncsMu.Unlock()
 
 	if job.Status == domain.StatusCompleted {
 		pattern := filepath.Join(h.downloadDir, job.ID+"_*")
@@ -518,12 +554,19 @@ func (h *Handler) sendDocument(ctx context.Context, chatID int64, filePath, titl
 func (h *Handler) handleCancelDownload(ctx context.Context, chatID int64, msgID int, cbID string, userID int64) {
 	defer h.answerCb(ctx, cbID)
 
+	h.cancelFuncsMu.Lock()
+	if cancel, ok := h.cancelFuncs[userID]; ok {
+		cancel()
+		delete(h.cancelFuncs, userID)
+	}
+	h.cancelFuncsMu.Unlock()
+
 	job := h.getActiveJob(userID)
 	if job != nil {
 		dl.CancelDownload(job)
-		h.mu.Lock()
+		h.activeJobsMu.Lock()
 		delete(h.activeJobs, userID)
-		h.mu.Unlock()
+		h.activeJobsMu.Unlock()
 		h.editText(ctx, chatID, msgID, "Download cancelled.", nil)
 		return
 	}
@@ -647,21 +690,71 @@ func (h *Handler) sendMediaPreview(ctx context.Context, chatID int64, info *doma
 	}
 
 	if info.Thumbnail != "" {
-		photo := &models.InputFileString{Data: info.Thumbnail}
-		_, err := h.Bot.SendPhoto(ctx, &tgbot.SendPhotoParams{
-			ChatID:  chatID,
-			Photo:   photo,
-			Caption: caption,
+		thumbPath, err := downloadFile(info.Thumbnail, h.downloadDir)
+		if err != nil {
+			slog.Warn("download thumbnail failed, falling back to text", "url", info.Thumbnail, "error", err)
+			h.sendText(ctx, chatID, caption)
+			return
+		}
+		defer os.Remove(thumbPath)
+
+		f, err := os.Open(thumbPath)
+		if err != nil {
+			slog.Warn("open thumbnail failed, falling back to text", "error", err)
+			h.sendText(ctx, chatID, caption)
+			return
+		}
+		defer f.Close()
+
+		photo := &models.InputFileUpload{Filename: "thumb.jpg", Data: f}
+		_, err = h.Bot.SendPhoto(ctx, &tgbot.SendPhotoParams{
+			ChatID: chatID, Photo: photo, Caption: caption,
 		})
 		if err == nil {
 			return
 		}
-		slog.Warn("send thumbnail failed, falling back to text", "error", err)
+		slog.Warn("send thumbnail photo failed, falling back to text", "error", err)
 	}
 
 	h.sendText(ctx, chatID, caption)
 }
 
+// downloadFile downloads a URL to a temp file in the given directory and returns the path.
+func downloadFile(url, dir string) (string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return "", fmt.Errorf("http get: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("unexpected status: %s", resp.Status)
+	}
+
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return "", fmt.Errorf("create download dir: %w", err)
+	}
+
+	f, err := os.CreateTemp(dir, "thumb_*")
+	if err != nil {
+		return "", fmt.Errorf("create temp file: %w", err)
+	}
+
+	_, err = io.Copy(f, resp.Body)
+	if err != nil {
+		f.Close()
+		os.Remove(f.Name())
+		return "", fmt.Errorf("write temp file: %w", err)
+	}
+
+	if err := f.Close(); err != nil {
+		os.Remove(f.Name())
+		return "", fmt.Errorf("close temp file: %w", err)
+	}
+
+	return f.Name(), nil
+}
+
 func formatDuration(seconds float64) string {
 	if seconds <= 0 {
 		return "0:00"

internal/handler/handler.go

@@ -36,18 +36,29 @@ type PendingInput struct {
 	Data      map[string]string
 }
 
+const maxConcurrentDownloads = 3
+
 type Handler struct {
 	Bot          *tgbot.Bot
 	Repo         repo.Repository
 	YtDlp        *dl.Client
 	AllowedUsers map[int64]bool
+
 	activeJobs   map[int64]*domain.DownloadJob
 	stepStates   map[int64]*stepState
 	lastMsgTime  map[int64]time.Time
 	pendingInput map[int64]*PendingInput
-	mu           sync.Mutex
-	downloadDir  string
-	maxFileSize  int64
+	cancelFuncs  map[int64]context.CancelFunc
+
+	activeJobsMu   sync.Mutex
+	stepStatesMu   sync.Mutex
+	rateLimiterMu  sync.Mutex
+	pendingInputMu sync.Mutex
+	cancelFuncsMu  sync.Mutex
+
+	downloadDir string
+	maxFileSize int64
+	downloadSem chan struct{}
 }
 
 func NewHandler(bot *tgbot.Bot, store repo.Repository, ytdlp *dl.Client, allowed map[int64]bool, downloadDir string, maxFileSize int64) *Handler {
@@ -60,8 +71,10 @@ func NewHandler(bot *tgbot.Bot, store repo.Repository, ytdlp *dl.Client, allowed
 		stepStates:   make(map[int64]*stepState),
 		lastMsgTime:  make(map[int64]time.Time),
 		pendingInput: make(map[int64]*PendingInput),
+		cancelFuncs:  make(map[int64]context.CancelFunc),
 		downloadDir:  downloadDir,
 		maxFileSize:  maxFileSize,
+		downloadSem:  make(chan struct{}, maxConcurrentDownloads),
 	}
 	go h.periodicCleanup()
 	return h
@@ -70,27 +83,29 @@ func NewHandler(bot *tgbot.Bot, store repo.Repository, ytdlp *dl.Client, allowed
 func (h *Handler) periodicCleanup() {
 	for {
 		time.Sleep(domain.CleanupInterval)
-		h.mu.Lock()
 
-		// Clean rate limit entries
-		cutoff := time.Now().Add(-domain.RateLimitInterval * 2)
-		for uid, t := range h.lastMsgTime {
-			if t.Before(cutoff) {
-				delete(h.lastMsgTime, uid)
+		func() {
+			h.rateLimiterMu.Lock()
+			defer h.rateLimiterMu.Unlock()
+			cutoff := time.Now().Add(-domain.RateLimitInterval * 2)
+			for uid, t := range h.lastMsgTime {
+				if t.Before(cutoff) {
+					delete(h.lastMsgTime, uid)
+				}
 			}
-		}
+		}()
 
-		// Clean stale pending inputs
-		pendingCutoff := time.Now().Add(-5 * time.Minute)
-		for chatID, pi := range h.pendingInput {
-			if pi.CreatedAt.Before(pendingCutoff) {
-				delete(h.pendingInput, chatID)
+		func() {
+			h.pendingInputMu.Lock()
+			defer h.pendingInputMu.Unlock()
+			pendingCutoff := time.Now().Add(-5 * time.Minute)
+			for chatID, pi := range h.pendingInput {
+				if pi.CreatedAt.Before(pendingCutoff) {
+					delete(h.pendingInput, chatID)
+				}
 			}
-		}
+		}()
 
-		h.mu.Unlock()
-
-		// Clean old temp files (>1h)
 		h.cleanOldTempFiles()
 	}
 }
@@ -116,8 +131,8 @@ func (h *Handler) cleanOldTempFiles() {
 }
 
 func (h *Handler) isRateLimited(userID int64) bool {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.rateLimiterMu.Lock()
+	defer h.rateLimiterMu.Unlock()
 	now := time.Now()
 	if last, ok := h.lastMsgTime[userID]; ok && now.Sub(last) < domain.RateLimitInterval {
 		return true
@@ -147,19 +162,19 @@ func (h *Handler) HandleMessage(ctx context.Context, msg *models.Message) {
 	slog.Info("message", "chat_id", msg.Chat.ID, "text", msg.Text)
 
 	if msg.Text[0] == '/' {
-		h.mu.Lock()
+		h.pendingInputMu.Lock()
 		delete(h.pendingInput, msg.Chat.ID)
-		h.mu.Unlock()
+		h.pendingInputMu.Unlock()
 		h.routeCommand(ctx, msg, userID)
 		return
 	}
 
-	h.mu.Lock()
+	h.pendingInputMu.Lock()
 	pi, hasPI := h.pendingInput[msg.Chat.ID]
 	if hasPI {
 		delete(h.pendingInput, msg.Chat.ID)
 	}
-	h.mu.Unlock()
+	h.pendingInputMu.Unlock()
 
 	if hasPI {
 		h.processPendingInput(ctx, msg, userID, pi)
@@ -212,9 +227,9 @@ func (h *Handler) HandleCallback(ctx context.Context, cb *models.CallbackQuery)
 	}
 	slog.Info("callback", "chat_id", chatID, "data", cb.Data)
 
-	h.mu.Lock()
+	h.pendingInputMu.Lock()
 	delete(h.pendingInput, chatID)
-	h.mu.Unlock()
+	h.pendingInputMu.Unlock()
 
 	msgID := cb.Message.Message.ID
 	data := cb.Data
@@ -294,7 +309,7 @@ func (h *Handler) routePrefixedCallback(ctx context.Context, chatID int64, msgID
 }
 
 func (h *Handler) setPending(ctx context.Context, chatID int64, msgID int, userID int64, kind PendingKind, data map[string]string) {
-	h.mu.Lock()
+	h.pendingInputMu.Lock()
 	h.pendingInput[chatID] = &PendingInput{
 		Kind:      kind,
 		UserID:    userID,
@@ -302,7 +317,7 @@ func (h *Handler) setPending(ctx context.Context, chatID int64, msgID int, userI
 		MsgID:     msgID,
 		Data:      data,
 	}
-	h.mu.Unlock()
+	h.pendingInputMu.Unlock()
 }
 
 func (h *Handler) processPendingInput(ctx context.Context, msg *models.Message, userID int64, pi *PendingInput) {
@@ -412,26 +427,40 @@ func (h *Handler) backToMenu(ctx context.Context, chatID int64, msgID int, cbID
 }
 
 func (h *Handler) clearActiveJob(userID int64) {
-	h.mu.Lock()
-	defer h.mu.Unlock()
-	if job, ok := h.activeJobs[userID]; ok {
+	h.activeJobsMu.Lock()
+	job, ok := h.activeJobs[userID]
+	if ok {
 		dl.CancelDownload(job)
 		delete(h.activeJobs, userID)
 	}
+	h.activeJobsMu.Unlock()
+
+	h.cancelFuncsMu.Lock()
+	if cancel, ok := h.cancelFuncs[userID]; ok {
+		cancel()
+		delete(h.cancelFuncs, userID)
+	}
+	h.cancelFuncsMu.Unlock()
 }
 
 func (h *Handler) getActiveJob(userID int64) *domain.DownloadJob {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.activeJobsMu.Lock()
+	defer h.activeJobsMu.Unlock()
 	return h.activeJobs[userID]
 }
 
 func (h *Handler) setActiveJob(userID int64, job *domain.DownloadJob) {
-	h.mu.Lock()
-	defer h.mu.Unlock()
+	h.activeJobsMu.Lock()
+	defer h.activeJobsMu.Unlock()
 	h.activeJobs[userID] = job
 }
 
+func (h *Handler) setCancelFunc(userID int64, cancel context.CancelFunc) {
+	h.cancelFuncsMu.Lock()
+	defer h.cancelFuncsMu.Unlock()
+	h.cancelFuncs[userID] = cancel
+}
+
 func formatBytes(bytes int64) string {
 	const unit = 1024
 	if bytes < unit {
@@ -455,7 +484,7 @@ func formatBytes(bytes int64) string {
 }
 
 func (h *Handler) generateJobID() string {
-	return uuid.NewString()[:8]
+	return uuid.NewString()
 }
 
 // handleStart shows the main menu and cleans up any stale state.

internal/handler/playlist.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"strconv"
-	"time"
 
 	"uptodownBot/internal/domain"
 )
@@ -164,6 +163,8 @@ func (h *Handler) handlePlaylistConfirm(ctx context.Context, chatID int64, msgID
 			}
 		}
 
+		dlCtx, dlCancel := context.WithCancel(context.Background())
+
 		job := &domain.DownloadJob{
 			ID:             h.generateJobID(),
 			UserID:         userID,
@@ -176,19 +177,17 @@ func (h *Handler) handlePlaylistConfirm(ctx context.Context, chatID int64, msgID
 			Status:         domain.StatusDownloading,
 			Title:          entry.Title,
 			FileSize:       format.Filesize,
+			Done:           make(chan struct{}),
 		}
 
 		h.setActiveJob(userID, job)
-		h.runDownload(context.Background(), job)
+		h.setCancelFunc(userID, dlCancel)
 
-		// Wait for active job to complete
-		for {
-			j := h.getActiveJob(userID)
-			if j == nil || j.Status == domain.StatusCompleted || j.Status == domain.StatusFailed || j.Status == domain.StatusCancelled {
-				break
-			}
-			time.Sleep(500 * time.Millisecond)
-		}
+		h.runDownload(dlCtx, job)
+
+		// runDownload is synchronous — it blocks until the download completes.
+		// The Done channel is closed inside runDownload when it exits.
+		// No busy-polling needed.
 	}
 
 	h.sendText(ctx, chatID, "All playlist downloads completed.")