http_server.lua

function parse(request)
    local _, _, method, path, vars = string.find(request, "([A-Z]+) (.+)?(.+) HTTP")
    if not method then
        _, _, method, path = string.find(request, "([A-Z]+) (.+) HTTP")
    end
    
    local _GET = {}
    if vars then
        for k, v in string.gmatch(vars, "(%w+)=(%w+)&*") do
            _GET[k] = v
        end
    end
    
    local json
    if method == 'POST' then
        _, _, json = string.find(request, '\n({.*})$')
        json = json and cjson.decode(json)
    end
  
    return {
        method = method,
        path = path,
        params = _GET,
        body = json
    }
end

function readFile(name)
    file.open(name);
    local buf = file.read();
    file.close();
    return buf;
end

function startServer()
    local index = readFile("index.html")
    local app = readFile("app.js")
    local status = {
        distance = 0,
        yellow = false,
        red = false
    }
    local statusResponse = ""

    function buildResponse()
        statusResponse = "HTTP/1.1 200 OK\nContent-Type: application/json\n\n" .. cjson.encode(status) .. "\n"
    end

    buildResponse();

    function onReceive(client, request)
        local r = parse(request)
        if (r.method == "GET" and r.path == "/status") then
            client:send(statusResponse)
        elseif (r.method == "GET" and r.path == "/") then
            client:send(index)
        elseif (r.method == "GET" and r.path == "/app.js") then
            client:send(app)
        elseif (r.method == "POST" and r.path == "/io") then
            if (r.body) then
                if r.body.red then
                    status.red = r.body.red
                end
        
                if r.body.yellow then
                    status.yellow = r.body.yellow
                end
            end
      
            client:send(statusResponse)
        else
            local buf = "Oooops"
            client:send(buf)
        end
    
        client:close()
    end
  
    srv = net.createServer(net.TCP, 5)
    srv:listen(80, function(connection)
        connection:on("receive", onReceive)
    end)
end

wifi.setmode(wifi.STATION);
wifi.sta.config("********", "************");
startServer();