[rhythmbox] podcast: remove tags and decode entities in html podcast descriptions

[Jonathan Matthew <jmatthew src gnome org>]

commit c1cc0d663f55ba6a4de371579a0e34293f39a504
Author: Jonathan Matthew <jonathan d14n org>
Date:   Sun Jun 19 17:02:58 2016 +1000

    podcast: remove tags and decode entities in html podcast descriptions

 podcast/rb-podcast-properties-dialog.c |  156 +++++++++++++++++++++++++++++++-
 1 files changed, 153 insertions(+), 3 deletions(-)
---
diff --git a/podcast/rb-podcast-properties-dialog.c b/podcast/rb-podcast-properties-dialog.c
index 8529ff1..22d3085 100644
--- a/podcast/rb-podcast-properties-dialog.c
+++ b/podcast/rb-podcast-properties-dialog.c
@@ -30,6 +30,7 @@
 
 #include <string.h>
 #include <time.h>
+#include <errno.h>
 
 #include <glib/gi18n.h>
 #include <gtk/gtk.h>
@@ -110,6 +111,142 @@ enum
 
 G_DEFINE_TYPE (RBPodcastPropertiesDialog, rb_podcast_properties_dialog, GTK_TYPE_DIALOG)
 
+/* list of HTML-ish strings that we search for to distinguish plain text from HTML podcast
+ * descriptions.  we don't really have anything else to go on - regular content type
+ * sniffing only works for proper HTML documents, but these are just tiny fragments, usually
+ * with some simple formatting tags.  if we find any of these in a podcast description,
+ * we'll strip HTML tags and attempt to decode entities.
+ */
+static const char *html_clues[] = {
+       "<p>",
+       "<a ",
+       "<b>",
+       "<i>",
+       "<ul>",
+       "<br",
+       "<img ",
+       "&lt;",
+       "&gt;",
+       "&amp;",
+       "&quot;",
+       "&apos;",
+       "&lsquo;",
+       "&rsquo;",
+       "&ldquo;",
+       "&rdquo;",
+       "&#",
+};
+
+static char *
+unhtml (const char *str)
+{
+       const char *p;
+       char *out, *o, *e;
+       enum {
+               NORMAL,
+               TAG,
+               ENTITY,
+               BAD_ENTITY
+       } state;
+       char entity[6];
+       int elen;
+
+       out = g_malloc (strlen (str) + 1);
+
+       p = str;
+       o = out;
+       state = NORMAL;
+       while (*p != '\0') {
+               switch (state) {
+               case TAG:
+                       if (*p == '>') {
+                               state = NORMAL;
+                       }
+                       break;
+
+               case BAD_ENTITY:
+                       switch (*p) {
+                       case ';':
+                       case ' ':
+                               *o++ = '?';
+                               state = NORMAL;
+                               break;
+                       default:
+                               break;
+                       }
+                       break;
+
+               case ENTITY:
+                       if (*p == ';' || *p == ' ') {
+                               *e++ = '\0';
+                               if (strncmp (entity, "amp", sizeof(entity)) == 0) {
+                                       *o++ = '&';
+                               } else if (strncmp (entity, "lt", sizeof(entity)) == 0) {
+                                       *o++ = '<';
+                               } else if (strncmp (entity, "quot", sizeof(entity)) == 0) {
+                                       *o++ = '"';
+                               } else if (strncmp (entity, "apos", sizeof(entity)) == 0) {
+                                       *o++ = '\'';
+                               } else if (strncmp (entity, "nbsp", sizeof(entity)) == 0) {
+                                       *o++ = ' ';
+                               } else if (entity[0] == '#') {
+                                       int base = 10;
+                                       char *str = entity + 1;
+                                       char *end = NULL;
+                                       gulong l;
+
+                                       if (str[0] == 'x') {
+                                               base = 16;
+                                               str++;
+                                       }
+
+                                       errno = 0;
+                                       l = strtoul (str, &end, base);
+                                       if (end == str || errno != 0 || *end != '\0') {
+                                               *o++ = '?';
+                                       } else {
+                                               o += g_unichar_to_utf8 (l, o);
+                                       }
+                               } else if (elen == 0) {
+                                       /* bare ampersand */
+                                       *o++ = '&';
+                                       *o++ = *p;
+                               } else {
+                                       /* unsupported entity */
+                                       *o++ = '?';
+                               }
+                               state = NORMAL;
+                               break;
+                       }
+                       elen++;
+                       if (elen == sizeof(entity)) {
+                               state = BAD_ENTITY;
+                               break;
+                       }
+                       *e++ = *p;
+                       break;
+
+               case NORMAL:
+                       switch (*p) {
+                       case '<':
+                               state = TAG;
+                               break;
+                       case '&':
+                               state = ENTITY;
+                               e = entity;
+                               elen = 0;
+                               break;
+                       default:
+                               *o++ = *p;
+                       }
+               }
+               p++;
+       }
+
+       *o++ = '\0';
+       return out;
+}
+
 static void
 rb_podcast_properties_dialog_class_init (RBPodcastPropertiesDialogClass *klass)
 {
@@ -538,9 +675,22 @@ rb_podcast_properties_dialog_update_date (RBPodcastPropertiesDialog *dialog)
 static void
 rb_podcast_properties_dialog_update_description (RBPodcastPropertiesDialog *dialog)
 {
-       const char *str;
-       str = rhythmdb_entry_get_string (dialog->priv->current_entry, RHYTHMDB_PROP_DESCRIPTION);
-       gtk_label_set_text (GTK_LABEL (dialog->priv->description), str);
+       int i;
+       const char *desc;
+
+       desc = rhythmdb_entry_get_string (dialog->priv->current_entry, RHYTHMDB_PROP_DESCRIPTION);
+       for (i = 0; i < G_N_ELEMENTS (html_clues); i++) {
+               if (g_strstr_len (desc, -1, html_clues[i]) != NULL) {
+                       char *text;
+
+                       text = unhtml (desc);
+                       gtk_label_set_text (GTK_LABEL (dialog->priv->description), text);
+                       g_free (text);
+                       return;
+               }
+       }
+
+       gtk_label_set_text (GTK_LABEL (dialog->priv->description), desc);
 }
 
 static char *