Getting this command puts the connection into a special mode where it
awaits MPD events (like the player changing state or the playlist
changing due to other clients interacting with the server.
The MPD specification states that events should queue while a client is
connected, and when it issues the `idle` command any matching events
should be sent immediately if there are any, or as soon as they happen
otherwise.
Keep track of a list of currently-connected clients.
Use `socket.getpeername()` to get an identifier for each connection and
include this in each log message. This function is documented as not
being available on all systems, but it's unclear which systems this
involves.
Also log a message on client connect and disconnect events. If the
disconnection reason is because the client sent a blank line, match MPD
by returning a protocol error then hanging up. Escape curly braces.
Improved the method to get the path of the current song. Before, the complete playlist was fetched from the server. Now, the command "currentsong" is used for this purpose. This improves performance when a huge playlist is active.
Check function signature instead of using TypeError to crudely guess
that the wrong number of arguments were provided.
Prevent bpd from crashing when trying to log a traceback. The
`traceback.format_exc` function takes an optional argument which is
supposed to be an integer restricting the length of the backtrace to
show. Instead we were passing the exception object to this function and
causing a new exception to be raised.
Previously issuing the 'previous' command when at position 0 on the
playlist would cause bpd to stop playing. MPD instead just restarts the
currently playing song instead, so we now match this behaviour.
The songs are indexed starting from zero for the play command, however
the bound check was off by one. An index matching the length of the
playlist would crash the server instead of responding with an error
message over the protocol.
The repeat flag indicates that the entire playlist should be repeated.
If both the repeat and single flags are set then this triggers the old
behaviour of looping over a single track.
This command instructs bpd to stop playing when the current song
finishes. In the MPD 0.20 protocol this flag gains a value 'oneshot' but
for now we just support its older version with a boolean value.
The real MPD offers persistent playlist manipulation, storing the
playlists in a directory set in the config file. If that directory is
not available then the feature is disabled and the relevant commands all
respond with errors. Based on this, the initial support in bpd just
returns errors matching the MPD server in the disabled mode.
For playlistadd, extend the _bpd_add helper to work with playlists other
than the queue in order to support testing the real implementations of
these commands in the future.
There's a special status command for checking the replay gain mode,
which can be set to one of a short list of possible values. For now at
least we can ignore this feature, but track the setting anyway.
MPD supports a deprecated command 'volume' which was used to change the
volume by a relative amount unlike its replacement 'setvol' which uses
an absolute amount. As far as I can tell 'volume' always responds with a system
error message "No mixer".
These are a more sophisticated version of crossfade so we're free to
ignore them, at least for now. We now track the values of the two
settings, and show them in the status output. Like MPD, we suppress the
mixrampdb value if it's set to nan, which is how it signals that the
feature should be turned off.
If an MPC client is expecting a command to take an argument that bpd
isn't expecting (e.g. because of a difference in protocol versions) then
bpd currently crashes completely. Instead, do what the real MPD does and
return an error message over the protocol.
