Improve handling of unknown protocols / missing plugins

Instead of failing to load the config, a fake prpl is created to load
the account, keep its settings, and refuse to log in with a helpful
error message.

Also added a new explain_unknown_protocol() function which returns text
which attempts to explain why a protocol is missing, handling several
typical cases, including the future removal of several dead libpurple
plugins.

That message is shown when logging in to a loaded account with a missing
protocol and when adding a new one with 'account add', with the
difference that the latter doesn't leave a placeholder fake account.

3 files changed, 56 insertions, 1 deletions

diff --git a/protocols/Makefile b/protocols/Makefile
index b4565ab6..ae969bde 100644
--- a/protocols/Makefile
+++ b/protocols/Makefile
@@ -12,7 +12,7 @@ _SRCDIR_ := $(_SRCDIR_)protocols/
 endif
 
 # [SH] Program variables
-objects = account.o bee.o bee_chat.o bee_ft.o bee_user.o nogaim.o
+objects = account.o bee.o bee_chat.o bee_ft.o bee_user.o nogaim.o unknown.o 
 
 
 # [SH] The next two lines should contain the directory name (in $(subdirs))
diff --git a/protocols/nogaim.c b/protocols/nogaim.c
index d6d2e8e3..608e4d33 100644
--- a/protocols/nogaim.c
+++ b/protocols/nogaim.c
@@ -159,6 +159,7 @@ GList *get_plugins()
 
 GList *protocols = NULL;
 GList *disabled_protocols = NULL;
+static struct prpl *unknown_prpl;
 
 void register_protocol(struct prpl *p)
 {
@@ -190,11 +191,57 @@ struct prpl *find_protocol(const char *name)
 	return gl ? gl->data: NULL;
 }
 
+struct prpl *make_unknown_protocol(const char *name)
+{
+	struct prpl *ret = g_memdup(unknown_prpl, sizeof(struct prpl));
+	ret->name = g_strdup(name);
+	register_protocol(ret);
+	return ret;
+}
+
 gboolean is_protocol_disabled(const char *name)
 {
 	return g_list_find_custom(disabled_protocols, name, proto_name_cmp) != NULL;
 }
 
+/* Returns heap allocated string with text attempting to explain why a protocol is missing 
+ * Free the return value with g_free() */
+char *explain_unknown_protocol(const char *name)
+{
+	char *extramsg = NULL;
+
+	if (is_protocol_disabled(name)) {
+		return g_strdup("Protocol disabled in the global config (bitlbee.conf)");
+	}
+
+	if (strcmp(name, "yahoo") == 0) {
+		return g_strdup("The old yahoo protocol is gone, try the funyahoo++ libpurple plugin instead.");
+	}
+
+#ifdef WITH_PURPLE
+	if ((strcmp(name, "msn") == 0) ||
+	    (strcmp(name, "loubserp-mxit") == 0) ||
+	    (strcmp(name, "myspace") == 0)) {
+		return g_strdup("This protocol has been removed from your libpurple version.");
+	}
+
+	if (strcmp(name, "hipchat") == 0) {
+		return g_strdup("This account type isn't supported by libpurple's jabber.");
+	}
+
+#else
+	if (strcmp(name, "aim") == 0 || strcmp(name, "icq") == 0) {
+		return g_strdup("This account uses libpurple specific aliases for oscar. "
+		                "Re-add the account with `account add oscar ...'");
+	}
+
+	extramsg = "If this is a libpurple plugin, you might need to install bitlbee-libpurple instead.";
+#endif
+	return g_strconcat("The protocol plugin is not installed or could not be loaded. "
+	                   "Use the `plugins' command to list available protocols. ",
+	                   extramsg, NULL);
+}
+
 void nogaim_init()
 {
 	extern void msn_initmodule();
@@ -203,6 +250,9 @@ void nogaim_init()
 	extern void jabber_initmodule();
 	extern void twitter_initmodule();
 	extern void purple_initmodule();
+	extern void unknown_prpl_initmodule();
+
+	unknown_prpl_initmodule(&unknown_prpl);
 
 #ifdef WITH_MSN
 	msn_initmodule();
diff --git a/protocols/nogaim.h b/protocols/nogaim.h
index b5a46524..3aa89c3b 100644
--- a/protocols/nogaim.h
+++ b/protocols/nogaim.h
@@ -158,6 +158,9 @@ typedef enum {
 
 	/* The protocol is not suitable for OTR, see OPT_NOOTR */
 	PRPL_OPT_NOOTR = 1 << 12,
+
+	/* This prpl is a placeholder for a missing protocol */
+	PRPL_OPT_UNKNOWN_PROTOCOL = 1 << 13,
 } prpl_options_t;
 
 struct prpl {
@@ -320,6 +323,8 @@ G_MODULE_EXPORT GList *get_protocols_disabled();
 G_MODULE_EXPORT GSList *get_connections();
 G_MODULE_EXPORT struct prpl *find_protocol(const char *name);
 G_MODULE_EXPORT gboolean is_protocol_disabled(const char *name);
+G_MODULE_EXPORT struct prpl *make_unknown_protocol(const char *name);
+G_MODULE_EXPORT char *explain_unknown_protocol(const char *name);
 /* When registering a new protocol, you should allocate space for a new prpl
  * struct, initialize it (set the function pointers to point to your
  * functions), finally call this function. */