local initd = false;
local api = {
	meta = {
		connect = {}
	},
	commands = {},
}

function api.init (channel, protocol, side)
	api.channel = channel
	api.hostname = os.getComputerLabel() or ("computer_" .. math.random(1, 2^31-1));
	api.protocol = protocol;
	api.modem = peripheral.wrap(side);
	api.modem.open(channel);
	initd = true;
end

function api.start_listener ()
	assert(initd, "init needs to be called before starting listener")
	coroutine.resume(coroutine.create(function()
		while 1 do
			local event, modemSide, senderChannel,
				replyChannel, message, senderDistance = os.pullEvent("modem_message")

			api.proccess_message(modemSide, senderChannel,
				replyChannel, message, senderDistance);
		end
	end))
end
function api.send_message (recipient, channel, command, content)
	api.modem.transmit(channel, 1, {protocol=api.protocol, recipient=recipient,
		from=api.hostname, command=command, content=content})
end

function api.connect (remotehost, channel)
	return setmetatable({
		protocol = api.protocol,
		remotehost = recipient,
	}, {__index == api.meta.connect});
	--send_message(remotehost, channel, "API_CONNECT",
end

function api.msg_address (message, replyChannel)
	return message.from .. "@" .. message.protocol .. "#" .. replyChannel;
end
----------------------------
-- connect object methods --
function api.meta.connect:message(command, content)
	send_message(self.remotehost, self.channel, command, content)
end

function api.meta.connect:print	(msg)
	self:message("PRINT", msg);
end


function api.meta.connect:loadstring (script)
	self:message("LOADSTRING", script)
end
-----------------------
-- message processor --

function api.proccess_message (modemSide, senderChannel,
		replyChannel, message, senderDistance)

	if type(message) == "table" and message.protocol == api.protocol then
		if message.protocol == api.protocol then
			if message.recipient == api.hostname then
				if message.from ~= nil then
					local com = api.commands[message.command]
					if com then com(modemSide, senderChannel, replyChannel, message, senderDistance) end
				else
					print("ERR_MALFORMED_MSG: Missing 'from' in message from unknown host on channel #" .. replyChannel .. ".");
				end
			else
				print("INFO_NOT_RECIPIENT: message recieved, different recipient specified, ignoring message");
			end
		else
			pcall(function()
				print("INFO_UNKNOWN_PROTOCOL: " .. api.msg_address(message, replyChannel) .. " sent a message with an unrecognized protocol; ignoring message")
			end)
		end
	else
		print("ERR_MALFORMED_MSG: Unrecognized message format");
	end

end


-----------------------------
-- message commands action --

function api.commands.LOADSTRING (modemSide, senderChannel, replyChannel, message, senderDistance)
	if type(message.content) == "string" then
		local success, result = pcall(loadstring, message.content);
		if success then
			setfenv(result, getfenv())
			local call_success, call_result = pcall(result)
			assert(call_success, "ERR_LOADSTRING_CALL: error occured when calling content from " .. api.msg_address(message, replyChannel) .. " :: " .. call_result);
		else
			print("ERR_LOADSTRING: failed to perform loadstring on content from " .. api.msg_address(message, replyChannel) .. " :: " .. result);
		end
	else
		print("ERR_MALFORMED_CMD: expected content to be of type string, " .. api.msg_address(message, replyChannel) .. " sent content of type " .. type(message.content));
	end
end

function api.commands.PRINT (modemSide, senderChannel, replyChannel, message, senderDistance)
	local suc, res = pcall(tostring, message.content)
	if not suc then
		print("ERR_PRINT: could not convert content to string, from " .. api.msg_address(message, replyChannel))
	else
		print(api.msg_address(message, replyChannel) .. ": " .. res)
	end
end




return api