WaitForSong

-- Loops forever, plays song on rednet requests
-- When finished, sends signal back to indicate
-- Can't terminate a song...
local function getVars(song)
	-- This expects us to be given a function name, which we tack .lua on the end of
	-- We then return an array containing each of the global var names
	local varNames = {}
	local int index = 1
	print("Opening " .. song .. ".lua")
	local reader = fs.open(song .. ".lua","r")
	while true do
		local line = reader.readLine()
		print("Reading line: " .. line)
		if string.find(line,"_G.",1,true) ~= 1 then -- No more vars, exit loop
			break
		end
		-- Otherwise we need to read the var...
		-- _G.AcousticGrandPiano0 = "Guitar"
		-- So skip to position 4
		local varName = string.sub(line,4,string.find(line," ")-1)
		-- We might need the value, but we'll see
		-- We can't guarantee it will be set before we get yielded to, can we?
		varNames[index] = varName
		index = index + 1
	end
	return varNames
end

local currentsong = nil

local function startSong(name,id)
  shell.run(name)
  rednet.send(id,"done")
end

local routine = coroutine.create(startSong)
local lastEvent = nil

local playing = false

rednet.open("back")
while true do
	event ={os.pullEvent()}
	if playing and event[1] == lastEvent then
	  code, lastEvent = coroutine.resume(routine,unpack(event))
	elseif event[1] == "rednet_message" then
		local msg = event[3]
		if msg ~= nil then
		  print(msg)
		  if msg == "stop" then
			playing = false
			lastEvent = nil
			routine = coroutine.create(startSong)
		    elseif string.find(msg,"changeinstrument") == 1 then
				-- format: changeinstrument:variableName:newValue
				local msg2 = string.sub(msg, string.find(msg,":")+1) -- variableName:newValue
				local varName = string.sub(msg2, 1, string.find(msg2,":")-1)
				local newValue = string.sub(msg2, string.find(msg2,":")+1)
				_G[varName] = newValue
		    else
				-- Before we play the song, let's parse out all the instruments...
				-- We don't need to store their value, we can send that with _G[]
				-- Once we have these, we send them in a rednet message back so it can store them for UI purposes
				varNames = getVars(msg)
				print(textutils.serialize(varNames))
				currentsong = msg
				playing = true
				code, lastEvent = coroutine.resume(routine,currentsong, event[2])
				rednet.send(event[2],textutils.serialize(varNames))
				values = {}
				for i,name in pairs(varNames) do
					values[i] = _G[name]
				end
				rednet.send(event[2],textutils.serialize(values))
		  end
	    end
	end
end