input/lastfm: use metadata

Added a patch to flush out the last.fm input plugin slightly. It
basically turns it into a wrapper for the appropriate plugin. Most
notably metadata is now extracted.

NEWS

@@ -3,6 +3,8 @@ ver 0.16 (20??/??/??)
   - send song modification time to client
   - added "update" idle event
   - removed the deprecated "volume" command
+* input:
+  - lastfm: use metadata
 * tags:
   - added tags "ArtistSort", "AlbumArtistSort"
   - id3: revised "performer" tag support

src/input/lastfm_input_plugin.c

@@ -18,26 +18,72 @@
  */
 
 #include "input/lastfm_input_plugin.h"
-#include "input/curl_input_plugin.h"
 #include "input_plugin.h"
+#include "tag.h"
 #include "conf.h"
 
+#include <stdlib.h>
 #include <string.h>
 
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "input_lastfm"
 
-static const char *lastfm_user, *lastfm_password;
+static struct lastfm_data {
+	char *user;
+	char *md5;
+} lastfm_data;
+
+struct lastfm_input {
+	/* our very own plugin wrapper */
+	struct input_plugin wrap_plugin;
+
+	/* pointer to input stream's plugin */
+	const struct input_plugin *plugin;
+
+	/* pointer to input stream's data */
+	void *data;
+
+	/* current track's tag */
+	struct tag *tag;
+};
 
 static bool
 lastfm_input_init(const struct config_param *param)
 {
-	lastfm_user = config_get_block_string(param, "user", NULL);
-	lastfm_password = config_get_block_string(param, "password", NULL);
+	const char *passwd = config_get_block_string(param, "password", NULL);
+	const char *user = config_get_block_string(param, "user", NULL);
+	if (passwd == NULL || user == NULL)
+		return false;
 
-	return lastfm_user != NULL && lastfm_password != NULL;
+#if GLIB_CHECK_VERSION(2,16,0)
+	lastfm_data.user = g_uri_escape_string(user, NULL, false);
+#else
+	lastfm_data.user = g_strdup(user);
+#endif
+
+#if GLIB_CHECK_VERSION(2,16,0)
+	if (strlen(passwd) != 32)
+		lastfm_data.md5 = g_compute_checksum_for_string(G_CHECKSUM_MD5,
+						    passwd, strlen(passwd));
+	else
+#endif
+		lastfm_data.md5 = g_strdup(passwd);
+
+	return true;
 }
 
+static void
+lastfm_input_finish(void)
+{
+	g_free(lastfm_data.user);
+	g_free(lastfm_data.md5);
+}
+
+/**
+ * Simple data fetcher.
+ * @param url path or url of data to fetch.
+ * @return data fetched, or NULL on error. Must be freed with g_free.
+ */
 static char *
 lastfm_get(const char *url)
 {
@@ -78,6 +124,12 @@ lastfm_get(const char *url)
 	return g_strndup(buffer, length);
 }
 
+/**
+ * Ini-style value fetcher.
+ * @param response data through which to search.
+ * @param name name of value to search for.
+ * @return value for param name in param reponse or NULL on error. Free with g_free.
+ */
 static char *
 lastfm_find(const char *response, const char *name)
 {
@@ -98,10 +150,192 @@ lastfm_find(const char *response, const char *name)
 	}
 }
 
+/**
+ * Replace XML's five predefined entities with the equivalant characters.
+ * glib doesn't seem to have code to do this, even in the xml parser.
+ * We don't manage numerical character references such as &#nnnn; or &#xhhhh;.
+ * @param value XML text to decode.
+ * @return decoded string, which must be freed with g_free.
+ * @todo make sure this is ok for utf-8.
+ */
+static char *
+lastfm_xmldecode(const char *value)
+{
+	struct entity {
+		const char *text;
+		char repl;
+	} entities[] = {
+		{"&amp;",  '&'},
+		{"&quot;", '"'},
+		{"&apos;", '\''},
+		{"&gt;",   '>'},
+		{"&lt;",   '<'}
+	};
+	char *txt = g_strdup(value);
+	unsigned int i;
+
+	for (i = 0; i < sizeof(entities)/sizeof(entities[0]); ++i) {
+		int slen = strlen(entities[i].text);
+		char *p = strstr(txt, entities[i].text);
+		if (p == NULL)
+			continue;
+
+		*p = entities[i].repl;
+		g_strlcpy(p + 1, p + slen, strlen(p) - slen);
+	}
+	return txt;
+}
+
+/**
+ * Extract the text between xml start and end tags specified by param tag.
+ * Caveat: This function does not handle nested tags properly.
+ * @param response XML to extract text from.
+ * @param tag name of tag of which text should be extracted from.
+ * @return text between tags specified by param tag, NULL on error; Must be freed with g_free.
+ */
+static char *
+lastfm_xmltag(const char *response, const char *tag)
+{
+	char *tn = g_strconcat("<", tag, ">", NULL);
+	char *p, *q;
+
+	if (!(p = strstr(response, tn))) {
+		g_free(tn);
+		return NULL;
+	}
+
+	p += strlen(tn);
+	g_free(tn);
+
+	tn = g_strconcat("</", tag, ">", NULL);
+
+	if (!(q = strstr(p, tn))) {
+		g_free(tn);
+		return NULL;
+	}
+
+	g_free(tn);
+
+	return g_strndup(p, q - p);
+}
+
+/**
+ * Parses xspf track and generates mpd tag.
+ * @return tag which must be freed with tag_free.
+ */
+static struct tag *
+lastfm_read_tag(const char *response)
+{
+	struct tagalias {
+		enum tag_type type;
+		const char *xmltag;
+	} aliases[] = {
+		{TAG_ITEM_ARTIST, "creator"},
+		{TAG_ITEM_TITLE, "title"},
+		{TAG_ITEM_ALBUM, "album"}
+	};
+	struct tag *tag = tag_new();
+	unsigned int i;
+	char *track_time = lastfm_xmltag(response, "duration");
+
+	if (track_time != NULL) {
+		int mtime = strtol(track_time, 0, 0);
+		g_free(track_time);
+
+		/* make sure to round up */
+		tag->time = ((mtime + 999) / 1000);
+	}
+	else
+		tag->time = 0;
+
+	for (i = 0; i < sizeof(aliases)/sizeof(aliases[0]); ++i) {
+		char *p, *value = lastfm_xmltag(response, aliases[i].xmltag);
+		if (value == NULL)
+			continue;
+
+		p = lastfm_xmldecode(value);
+		g_free(value);
+		value = p;
+
+		tag_add_item(tag, aliases[i].type, value);
+		g_free(value);
+	}
+	return tag;
+}
+
+static size_t
+lastfm_input_read_wrap(struct input_stream *is, void *ptr, size_t size)
+{
+	size_t ret;
+	struct lastfm_input *d = is->data;
+	is->data = d->data;
+	ret = (* d->plugin->read)(is, ptr, size);
+	is->data = d;
+	return ret;
+}
+
+static bool
+lastfm_input_eof_wrap(struct input_stream *is)
+{
+	bool ret;
+	struct lastfm_input *d = is->data;
+	is->data = d->data;
+	ret = (* d->plugin->eof)(is);
+	is->data = d;
+	return ret;
+}
+
+static bool
+lastfm_input_seek_wrap(struct input_stream *is, off_t offset, int whence)
+{
+	bool ret;
+	struct lastfm_input *d = is->data;
+	is->data = d->data;
+	ret = (* d->plugin->seek)(is, offset, whence);
+	is->data = d;
+	return ret;
+}
+
+static int
+lastfm_input_buffer_wrap(struct input_stream *is)
+{
+	int ret;
+	struct lastfm_input *d = is->data;
+	is->data = d->data;
+	ret = (* d->plugin->buffer)(is);
+	is->data = d;
+	return ret;
+}
+
+static struct tag *
+lastfm_input_tag(struct input_stream *is)
+{
+	struct lastfm_input *d = is->data;
+	struct tag *tag = d->tag;
+	d->tag = NULL;
+	return tag;
+}
+
+static void
+lastfm_input_close(struct input_stream *is)
+{
+	struct lastfm_input *d = is->data;
+
+	if (is->plugin->close) {
+		is->data = d->data;
+		is->plugin = d->plugin;
+		(* is->plugin->close)(is);
+	}
+
+	if (d->tag)
+		tag_free(d->tag);
+	g_free(d);
+}
+
 static bool
 lastfm_input_open(struct input_stream *is, const char *url)
 {
-	char *md5, *p, *q, *response, *session, *stream_url;
+	char *p, *q, *response, *track, *session, *stream_url;
 	bool success;
 
 	if (strncmp(url, "lastfm://", 9) != 0)
@@ -109,27 +343,11 @@ lastfm_input_open(struct input_stream *is, const char *url)
 
 	/* handshake */
 
-#if GLIB_CHECK_VERSION(2,16,0)
-	q = g_uri_escape_string(lastfm_user, NULL, false);
-#else
-	q = g_strdup(lastfm_username);
-#endif
-
-#if GLIB_CHECK_VERSION(2,16,0)
-	if (strlen(lastfm_password) != 32)
-		md5 = g_compute_checksum_for_string(G_CHECKSUM_MD5,
-						    lastfm_password,
-						    strlen(lastfm_password));
-	else
-#endif
-		md5 = g_strdup(lastfm_password);
-
 	p = g_strconcat("http://ws.audioscrobbler.com/radio/handshake.php?"
 			"version=1.1.1&platform=linux&"
-			"username=", q, "&"
-			"passwordmd5=", md5, "&debug=0&partner=", NULL);
-	g_free(q);
-	g_free(md5);
+			"username=", lastfm_data.user, "&"
+			"passwordmd5=", lastfm_data.md5, "&"
+			"debug=0&partner=", NULL);
 
 	response = lastfm_get(p);
 	g_free(p);
@@ -195,35 +413,71 @@ lastfm_input_open(struct input_stream *is, const char *url)
 		return false;
 	}
 
-	p = strstr(response, "<location>");
-	if (p == NULL) {
-		g_free(response);
+	/* From here on, we only care about the first track, extract that
+	 *
+	 * Note: if you want to get information about the next track (needed
+	 *   for continuous playback) extract the other track info here too.
+	 */
+
 	g_free(stream_url);
+	track = lastfm_xmltag(response, "track");
+	g_free(response);
+
+	/* If there are no tracks in the tracklist, it's possible that the
+	 * station doesn't have enough content.
+	 */
+
+	if (track == NULL)
+		return false;
+
+	stream_url = lastfm_xmltag(track, "location");
+	if (stream_url == NULL) {
+		g_free(track);
 		return false;
 	}
 
-	p += 10;
-	q = strchr(p, '<');
-
-	if (q == NULL) {
-		g_free(response);
-		g_free(stream_url);
-		return false;
-	}
-
-	g_free(stream_url);
-	stream_url = g_strndup(p, q - p);
-	g_free(response);
-
 	/* now really open the last.fm radio stream */
 
 	success = input_stream_open(is, stream_url);
+	if (success) {
+		/* instantiate our transparent wrapper plugin
+		 * this is needed so that the backend knows what functions are
+		 * properly available.
+		 */
+
+		struct lastfm_input *d = g_new0(struct lastfm_input, 1);
+		d->wrap_plugin.name = "lastfm";
+		d->wrap_plugin.open = lastfm_input_open;
+		d->wrap_plugin.close = lastfm_input_close;
+		d->wrap_plugin.read = lastfm_input_read_wrap;
+		d->wrap_plugin.eof = lastfm_input_eof_wrap;
+		d->wrap_plugin.tag = lastfm_input_tag;
+		if (is->seekable)
+			d->wrap_plugin.seek = lastfm_input_seek_wrap;
+		if (is->plugin->buffer)
+			d->wrap_plugin.buffer = lastfm_input_buffer_wrap;
+
+		d->tag = lastfm_read_tag(track);
+		d->plugin = is->plugin;
+		d->data = is->data;
+
+		/* give the backend our wrapper plugin */
+
+		is->plugin = &d->wrap_plugin;
+		is->data = d;
+	}
+
 	g_free(stream_url);
+	g_free(track);
+
 	return success;
 }
 
 const struct input_plugin lastfm_input_plugin = {
 	.name = "lastfm",
 	.init = lastfm_input_init,
+	.finish = lastfm_input_finish,
 	.open = lastfm_input_open,
+	.close = lastfm_input_close,
+	.tag  = lastfm_input_tag,
 };