media

#!/usr/bin/env lua

-- check if a value is in a list
local function contains(list, value)
	for i, v in ipairs(list) do
		if v==value then
			return true
		end
	end
	return false
end

-- list all mpris-compatible apps
local function getapps()
	local t={}
	for l in io.popen('qdbus | grep org.mpris.MediaPlayer2'):lines() do
		table.insert(t, l:match("org%.mpris%.MediaPlayer2%.(%S+)$"))
	end
	return t
end

-- read result of DBus call
local function readvalue(name, key)
	local fd=io.popen('qdbus org.mpris.MediaPlayer2.'..name..' /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.'..key)
	local value=fd:read '*l'
	fd:close()
	return value
end

-- read app status
local function getstatus(name)
	local status={}
	do
		local st=readvalue(name, 'PlaybackStatus')
		status.status=st and st:lower()
	end
	do
		local vol=readvalue(name, 'Volume')
		status.volume=vol and tonumber(vol)
	end
	do
		local pos=readvalue(name, 'Position')
		status.position=pos and tonumber(pos)
	end
	do
		local fd=io.popen('qdbus org.mpris.MediaPlayer2.'..name..' /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Metadata')
		for line in fd:lines() do
			local k, v=line:match('^(%S+): (.+)$')
			if k then
				status[k]=v
			end
		end
		fd:close()
	end
	return status
end

-- execute DBus call
local function exec(name, fn, ...)
	local args=''
	local n=select('#', ...)
	if n~=0 then
		args=' '..table.concat({...}, 1, n)
	end
	return os.execute('qdbus org.mpris.MediaPlayer2.'..name..' /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.'..fn..args)
end

-- control playback
local function playpause(name)
	return exec(name, 'PlayPause')
end
local function play(name)
	return exec(name, 'Play')
end
local function pause(name)
	return exec(name, 'Pause')
end
local function stop(name)
	return exec(name, 'Stop')
end
local function volume(name, value)
	return exec(name, 'Volume', value)
end

-- create a global table
media={}
media.getapps=getapps
media.readvalue=readvalue
media.getstatus=getstatus
media.exec=exec
media.playpause=playpause
media.play=play
media.pause=pause
media.stop=stop
media.volume=volume

-- read arguments
local args={...}

if not args[1] then
	-- write everything we know about all apps
	for i, v in ipairs(getapps()) do
		io.write(v)
		io.write ':\n'
		for name, value in pairs(getstatus(v)) do
			io.write '\t'
			io.write(name)
			io.write '\t'
			io.write(value)
			io.write '\n'
		end
	end
elseif args[1]=='exec' then
	-- read script file
	local fd, code
	if args[2]=='-' then
		fd=io.stdin
	elseif type(args[2])=='string' then
		fd=io.open(args[2])
	end
	if not fd then
		io.stderr:write "Syntax:\n"
		io.stderr:write "\tmedia exec <script>\n"
		io.stderr:write "\t\twhere <script> is a Lua source file which will receive the media lib\n"
		io.stderr:write "\t\tif <script> is '-' then the standard input will be used instead\n"
		os.exit(1)
	end
	code=fd:read '*a'
	
	-- execute script
	local load=loadstring or load
	local block, err=load(code, args[2], 't')
	if block then
		block()
	else
		io.stderr:write "Error loading script:\n"
		io.stderr:write(err)
		io.stderr:write "\n"
		os.exit(1)
	end
elseif contains({'play', 'pause', 'stop', 'playpause'}, args[1]) then
	-- do the specific action on the player
	if type(args[2])=='string' then
		local a, b, c=media[args[1]](args[2])
		if type(a)=='boolean' then
			return c
		else
			return (a and 0 or 1)
		end
	else
		io.stderr:write "Syntax:\n"
		io.stderr:write "\tmedia play|pause|stop|playpause <player>\n"
		io.stderr:write "\t\twhere <player> is the internal name of the media player\n"
		os.exit(1)
	end
elseif args[1]=='status' then
	-- read the status of an app
	if type(args[2])=='string' then
		for k, v in pairs(getstatus(args[2])) do
			io.write(k)
			io.write '\t'
			io.write(v)
			io.write '\n'
		end
	else
		io.stderr:write "Syntax:\n"
		io.stderr:write "\tmedia status <player>\n"
		io.stderr:write "\t\twhere <player> is the internal name of the media player\n"
		os.exit(1)
	end
elseif args[1]=='list' then
	-- lists the available apps
	for i, v in ipairs(getapps()) do
		io.write(v)
		io.write '\n'
	end
elseif args[1]=='volume' then
	if not args[2] or args[3] and not tonumber(args[3]) then
		io.stderr:write "Syntax:\n"
		io.stderr:write "\tmedia volume <player> [value]\n"
		io.stderr:write "\t\twhere <player> is the internal name of the media player\n"
		io.stderr:write "\t\twhere [volume] is the optional volume to set\n"
	end
	if not args[3] then
		io.write(readvalue(args[2], 'Volume'))
		io.write '\n'
	else
		local a, b, c=volume(args[2], tonumber(args[3]))
		if type(a)=='boolean' then
			return c
		else
			return (a and 0 or 1)
		end
	end
else
	-- write syntax
	io.stderr:write "Syntax:\n"
	io.stderr:write "\tmedia\n"
	io.stderr:write "\tmedia list\n"
	io.stderr:write "\tmedia exec <script>\n"
	io.stderr:write "\tmedia status <player>\n"
	io.stderr:write "\tmedia play|pause|stop|playpause <player>\n"
	io.stderr:write "\tmedia volume <player> [value]\n"
	os.exit(1)
end