Restructure go project (#2356)

* Move main to cmd
* Move api to internal
* Move logger and manager to internal
* Move shell hiding code to separate package
* Decouple job from desktop and utils
* Decouple session from config
* Move static into internal
* Decouple config from dlna
* Move desktop to internal
* Move dlna to internal
* Decouple remaining packages from config
* Move config into internal
* Move jsonschema and paths to models
* Make ffmpeg functions private
* Move file utility methods into fsutil package
* Move symwalk into fsutil
* Move single-use util functions into client package
* Move slice functions to separate packages
* Add env var to suppress windowsgui arg
* Move hash functions into separate package
* Move identify to internal
* Move autotag to internal
* Touch UI when generating backend

internal/manager/downloads.go

@@ -0,0 +1,113 @@
+package manager
+
+import (
+	"net/http"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/stashapp/stash/pkg/hash"
+	"github.com/stashapp/stash/pkg/logger"
+)
+
+// DownloadStore manages single-use generated files for the UI to download.
+type DownloadStore struct {
+	m     map[string]*storeFile
+	mutex sync.Mutex
+}
+
+type storeFile struct {
+	path        string
+	contentType string
+	keep        bool
+	wg          sync.WaitGroup
+	once        sync.Once
+}
+
+func NewDownloadStore() *DownloadStore {
+	return &DownloadStore{
+		m: make(map[string]*storeFile),
+	}
+}
+
+func (s *DownloadStore) RegisterFile(fp string, contentType string, keep bool) (string, error) {
+	const keyLength = 4
+	const attempts = 100
+
+	// keep generating random keys until we get a free one
+	// prevent infinite loop by only attempting a finite amount of times
+	var h string
+	generate := true
+	a := 0
+
+	s.mutex.Lock()
+	for generate && a < attempts {
+		var err error
+		h, err = hash.GenerateRandomKey(keyLength)
+		if err != nil {
+			return "", err
+		}
+		_, generate = s.m[h]
+		a++
+	}
+
+	s.m[h] = &storeFile{
+		path:        fp,
+		contentType: contentType,
+		keep:        keep,
+	}
+	s.mutex.Unlock()
+
+	return h, nil
+}
+
+func (s *DownloadStore) Serve(hash string, w http.ResponseWriter, r *http.Request) {
+	s.mutex.Lock()
+	f, ok := s.m[hash]
+
+	if !ok {
+		s.mutex.Unlock()
+		http.NotFound(w, r)
+		return
+	}
+
+	if !f.keep {
+		s.waitAndRemoveFile(hash, &w, r)
+	}
+
+	s.mutex.Unlock()
+
+	if f.contentType != "" {
+		w.Header().Add("Content-Type", f.contentType)
+	}
+	http.ServeFile(w, r, f.path)
+}
+
+func (s *DownloadStore) waitAndRemoveFile(hash string, w *http.ResponseWriter, r *http.Request) {
+	f := s.m[hash]
+	notify := r.Context().Done()
+	f.wg.Add(1)
+
+	go func() {
+		<-notify
+		s.mutex.Lock()
+		defer s.mutex.Unlock()
+
+		f.wg.Done()
+	}()
+
+	go f.once.Do(func() {
+		// leave it up for 30 seconds after the first request to allow for multiple requests
+		time.Sleep(30 * time.Second)
+
+		f.wg.Wait()
+		s.mutex.Lock()
+		defer s.mutex.Unlock()
+
+		delete(s.m, hash)
+		err := os.Remove(f.path)
+		if err != nil {
+			logger.Errorf("error removing %s after downloading: %s", f.path, err.Error())
+		}
+	})
+}