OpenResty + Fengari debug console

client.lua

local js = require 'js'.global

function js.window:onload()
    local stdin = js.document:getElementById('stdin')
    local stdout = js.document:getElementById('stdout')
    stdin:focus()
    local conn
    local indicator = js.document:getElementById('connecting')
    local connected = false
    local remote = true

    local function append(s, color)
        local item = js.document:createElement('span')
        item.innerText = s
        item.innerHTML = item.innerHTML..'<br/>'
        if color then
            item.innerHTML = '<span style="color:'..color..';">'..item.innerHTML..'</span>'
        end
        stdout:appendChild(item)
        js.window:scrollTo(0, js.document.body.scrollHeight);
    end

    _G.print = append

    local f = {}
    function f.clear()
        stdout.innerText = ''
    end
    function f.reset()
        conn:close()
    end
    function f.swap()
        remote = not remote
        append('remote = '..tostring(remote), 'lightblue')
    end

    local history = {}
    local hist_idx = nil
    local saved_text

    local function run_cmd(cmd)
        if remote then
            conn:send(cmd)
        else
            local f, err = load('return '..cmd)
            if not f then
                f, err = load(cmd)
            end
            if not f then
                append(err, 'red')
            else
                local success, result = pcall(f)
                if success then
                    _G._ = result
                    append(tostring(result), 'lightgreen')
                else
                    append(tostring(result), 'red')
                end
            end
        end
    end

    function stdin:onkeydown(e)
        if #history == 0 then return end

        if e.keyCode == 38 then -- up
            if not hist_idx then
                hist_idx = #history
                saved_text = stdin.value
            else
                hist_idx = hist_idx - 1
                if hist_idx < 1 then
                    hist_idx = 1
                end
            end
        elseif e.keyCode == 40 and hist_idx then -- down
            hist_idx = hist_idx + 1
            if hist_idx > #history then
                hist_idx = nil
            end
        else
            return
        end

        if hist_idx then
            stdin.value = history[hist_idx]
        else
            stdin.value = saved_text
            saved_text = nil
        end
    end

    function stdin:onkeypress(e)
        -- enter
        if not(e.keyCode == 13) or not connected then return end
        append('> '..stdin.value)
        if f[stdin.value] then
            f[stdin.value]()
        else
            run_cmd(stdin.value)
        end
        table.insert(history, stdin.value)
        stdin.value = ''
        hist_idx = nil
    end

    local function connect()
        conn = js:eval('new WebSocket("ws://localhost:8080/ws/console");')
        function conn:onclose(event)
            indicator.style.visibility = 'visible'
            connected = true
            js:setTimeout(connect, 1000)
        end
        function conn:onopen(event)
            indicator.style.visibility = 'hidden'
            connected = true
        end
        function conn:onmessage(event)
            local json = js.JSON:parse(event.data)
            append(json.text, json.color)
        end
    end

    function js.document.body:onclick()
        stdin:focus()
    end

    append('LOL LUA CONSOLE', 'lightblue')

    connect()
end

html.html

    #console {
        width:100%;
        min-height:100%;
        background:rgba(0,0,0,0.6);
        color:#ffffff;
    }
    #connecting {
        visibility:visible;
    }
    .console{
        font-family:courier new;
        font-size:20px;
        color:#ffffff;
    }
    #stdin{
        background-color:transparent;
        border:0;
        width:100%;
    }
    .input_container {
        width:100%;
        display:table;
    }
    .carrot {
        display:table-cell;
        width:21px;
    }
    .input {
        display:table-cell;
    }
    input:focus {
        outline:none;
        outline-width: 0;
    }
    </style>
    <div id="console" class="console">
        <span id="connecting">Connecting...</span>
        <div id="stdout"></div>
        <div class="input_container">
            <div class="carrot">&gt;</div>
            <div class="input"><input id="stdin" class="console"/></div>
        </div>
    </div>
    <script type="text/lua" src="/client.lua"></script>

server.lua

local websocket = require 'resty.websocket.server'
local cjson = require 'cjson'
return function()
    local ws, err = websocket:new{timeout = 30000, max_payload_len = 65535}
    -- recieve loop
    while true do
        local bytes, typ, err = ws:recv_frame()
        if ws.fatal then
            break
        elseif not bytes then
            ws:send_ping()
        elseif typ == 'close' then
            break
        elseif typ == 'text' then
            local f, err = load('return '..bytes)
            if not f then
                f, err = load(bytes)
            end
            if not f then
                ws:send_text(cjson.encode{text = err, color = 'red'})
            else
                local success, result = xpcall(f, debug.traceback)
                if success then
                    _G._ = result
                    ws:send_text(cjson.encode{text = tostring(result), color = 'lightgreen'})
                else
                    ws:send_text(cjson.encode{text = tostring(result), color = 'red'})
                end
            end
        end
    end
    ws:send_close()
  end