1package captcha
 2
 3import (
 4	"http"
 5	"os"
 6	"path"
 7	"strconv"
 8)
 9
10type captchaHandler struct {
11	imgWidth  int
12	imgHeight int
13}
14
15// Server returns a handler that serves HTTP requests with image or
16// audio representations of captchas. Image dimensions are accepted as
17// arguments. The server decides which captcha to serve based on the last URL
18// path component: file name part must contain a captcha id, file extension —
19// its format (PNG or WAV).
20//
21// For example, for file name "B9QTvDV1RXbVJ3Ac.png" it serves an image captcha
22// with id "B9QTvDV1RXbVJ3Ac", and for "B9QTvDV1RXbVJ3Ac.wav" it serves the
23// same captcha in audio format.
24//
25// To serve a captcha as a downloadable file, the URL must be constructed in
26// such a way as if the file to serve is in "download" subdirectory:
27// "/download/B9QTvDV1RXbVJ3Ac.wav".
28//
29// To reload captcha (get a different solution for the same captcha id), append
30// "?reload=x" to URL, where x may be anything (for example, current time or a
31// random number to make browsers refetch an image instead of loading it from
32// cache).
33func Server(w, h int) http.Handler { return &captchaHandler{w, h} }
34
35func (h *captchaHandler) serve(w http.ResponseWriter, id, ext string, download bool) os.Error {
36	if download {
37		w.Header().Set("Content-Type", "application/octet-stream")
38	}
39	switch ext {
40	case ".png":
41		if !download {
42			w.Header().Set("Content-Type", "image/png")
43		}
44		return WriteImage(w, id, h.imgWidth, h.imgHeight)
45	case ".wav":
46		if !download {
47			w.Header().Set("Content-Type", "audio/x-wav")
48		}
49		//return WriteAudio(w, id)
50		//XXX(dchest) Workaround for Chrome: it wants content-length,
51		//or else will start playing NOT from the beginning.
52		//Filed issue: http://code.google.com/p/chromium/issues/detail?id=80565
53		d := globalStore.Get(id, false)
54		if d == nil {
55			return ErrNotFound
56		}
57		a := NewAudio(d)
58		w.Header().Set("Content-Length", strconv.Itoa(a.EncodedLen()))
59		_, err := a.WriteTo(w)
60		return err
61	}
62	return ErrNotFound
63}
64
65func (h *captchaHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
66	dir, file := path.Split(r.URL.Path)
67	ext := path.Ext(file)
68	id := file[:len(file)-len(ext)]
69	if ext == "" || id == "" {
70		http.NotFound(w, r)
71		return
72	}
73	if r.FormValue("reload") != "" {
74		Reload(id)
75	}
76	download := path.Base(dir) == "download"
77	if err := h.serve(w, id, ext, download); err != nil {
78		if err == ErrNotFound {
79			http.NotFound(w, r)
80			return
81		}
82		http.Error(w, "error serving captcha", http.StatusInternalServerError)
83	}
84}