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		//XXX(dchest) Workaround for Chrome: it wants content-length,
47		//or else will start playing NOT from the beginning.
48		//Filed issue: http://code.google.com/p/chromium/issues/detail?id=80565
49		d := globalStore.Get(id, false)
50		if d == nil {
51			return ErrNotFound
52		}
53		a := NewAudio(d)
54		if !download {
55			w.Header().Set("Content-Type", "audio/x-wav")
56		}
57		w.Header().Set("Content-Length", strconv.Itoa(a.EncodedLen()))
58		_, err := a.WriteTo(w)
59		return err
60	}
61	return ErrNotFound
62}
63
64func (h *captchaHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
65	dir, file := path.Split(r.URL.Path)
66	ext := path.Ext(file)
67	id := file[:len(file)-len(ext)]
68	if ext == "" || id == "" {
69		http.NotFound(w, r)
70		return
71	}
72	if r.FormValue("reload") != "" {
73		Reload(id)
74	}
75	download := path.Base(dir) == "download"
76	if h.serve(w, id, ext, download) == ErrNotFound {
77		http.NotFound(w, r)
78	}
79	// Ignore other errors.
80}