mpd.py: adding support for asynchronous commands

send_<cmd>/fetch_<cmd> may now be used to send/fetch the command <cmd>.
fetch_<cmd> may be called multiple times to queue up various commands, but
they must be fetched in the same order they were sent.  This functionality
cannot be mixed with command lists.

diff --git a/mpd.py b/mpd.py
index 62df3a1c80957950c2a28449cc6b4613c56650fc..2875f95ced8c42c3511ce9d60c7868692e734755 100644 (file)
--- a/mpd.py
+++ b/mpd.py
@@ -38,6 +38,9 @@ class CommandError(MPDError):
 class CommandListError(MPDError):
     pass
 
+class PendingCommandError(MPDError):
+    pass
+
 
 class _NotConnected(object):
     def __getattr__(self, attr):
@@ -131,14 +134,46 @@ class MPDClient(object):
         }
 
     def __getattr__(self, attr):
-        try:
-            retval = self._commands[attr]
-        except KeyError:
+        if attr.startswith("send_"):
+            command = attr.replace("send_", "", 1)
+            wrapper = self._send
+        elif attr.startswith("fetch_"):
+            command = attr.replace("fetch_", "", 1)
+            wrapper = self._fetch
+        else:
+            command = attr
+            wrapper = self._execute
+        if command not in self._commands:
             raise AttributeError("'%s' object has no attribute '%s'" %
                                  (self.__class__.__name__, attr))
-        return lambda *args: self._execute(attr, args, retval)
+        return lambda *args: wrapper(command, args)
 
-    def _execute(self, command, args, retval):
+    def _send(self, command, args):
+        if self._command_list is not None:
+            raise CommandListError("Cannot use send_%s in a command list" %
+                                   command)
+        self._write_command(command, args)
+        self._pending.append(command)
+
+    def _fetch(self, command, args=None):
+        if self._command_list is not None:
+            raise CommandListError("Cannot use fetch_%s in a command list" %
+                                   command)
+        if not self._pending:
+            raise PendingCommandError("No pending commands to fetch")
+        if self._pending[0] != command:
+            raise PendingCommandError("%s is not the currently "
+                                      "pending command" % command)
+        del self._pending[0]
+        retval = self._commands[command]
+        if callable(retval):
+            return retval()
+
+    def _execute(self, command, args):
+        if self._pending:
+            raise PendingCommandError("Cannot execute %s with "
+                                      "pending commands" % command)
+        retval = self._commands[command]
         if self._command_list is not None and not callable(retval):
             raise CommandListError("%s not allowed in command list" % command)
         self._write_command(command, args)
@@ -293,6 +328,7 @@ class MPDClient(object):
 
     def _reset(self):
         self.mpd_version = None
+        self._pending = []
         self._command_list = None
         self._sock = None
         self._rfile = _NotConnected()
@@ -353,6 +389,9 @@ class MPDClient(object):
     def command_list_ok_begin(self):
         if self._command_list is not None:
             raise CommandListError("Already in command list")
+        if self._pending:
+            raise PendingCommandError("Cannot begin command list "
+                                      "with pending commands")
         self._write_command("command_list_ok_begin")
         self._command_list = []