IIM r4

local session, nick
local running = true
local term_w, term_h = term.getSize()

local function urlencode(msg)
    local ok = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~"
    local enc = ""
    local fmt = "%%%02X"
    for k = 1, msg:len() do
        local ch = msg:sub(k, k)
        if ok:find(ch, 1, true) then
            enc = enc .. ch
        else
            enc = enc .. fmt:format(string.byte(ch))
        end
    end
    return enc
end

local function getLastIndex()
    local f = http.get("http://immibis.awardspace.biz/cc/iim/get.php")
    local last = tonumber(f.readLine())
    f.close()
    return last
end

local function sendLogout()
    http.request("http://immibis.awardspace.biz/cc/iim/leave.php?s="..urlencode(session))
end

local function startSession()
    local f = http.get("http://immibis.awardspace.biz/cc/iim/start.php?nick="..urlencode(nick))
    local response = f.readLine()
    f.close()
    if response:sub(1,2) == "OK" then
        session = response:sub(3)
    else
        print(response)
    end
end

local function sendMessage(msg)
    http.request("http://immibis.awardspace.biz/cc/iim/send.php?s="..urlencode(session).."&msg="..urlencode(msg))
end

local buffer = {}
local typing = ""
local typing_pos = 0
local typing_scroll = 0
local history_pos = 0
local history = {}
local lastChatIndex = getLastIndex()

local function addLine(line)
    if #buffer >= term_h - 1 then
        table.remove(buffer, 1)
    end
    table.insert(buffer, line)
end

local function displayChat(msg)
    while msg:len() > term_w do
        addLine(msg:sub(1,term_w))
        msg = msg:sub(term_w + 1)
    end
    addLine(msg)
end

local function updateCursor()
    term.setCursorPos(typing_pos - typing_scroll + 3, term_h)
end

local function updateInputLine()
    term.setCursorPos(1, term_h)
    term.clearLine()
    term.write("> " .. typing:sub(typing_scroll + 1))
    updateCursor()
end

local function updateScreen()
    for k = 1, term_h - 1 do
        term.setCursorPos(1, k)
        term.clearLine()
        term.write(buffer[k] or "")
    end
    updateCursor()
end

local pollURL

local function startPoll()
    pollURL = "http://immibis.awardspace.biz/cc/iim/get.php?last=" .. lastChatIndex .. "&ping=" .. session
    http.request(pollURL)
end

local function handlePollResponse(f)
    local any = false
    while true do
        local line = f.readLine()
        if line == nil then break end
        if line == "EMPTY" then break end
        if line == "END" then break end
        local index = line:find(" ")
        if index ~= nil then
            local id = tonumber(line:sub(1, index-1))
            local msg = line:sub(index+1)
            lastChatIndex = id
            displayChat(msg)
            any = true
        end
    end
    f.close()
    if any then updateScreen() end
end

repeat
    print("Enter your nickname: ")
    nick = read()
    startSession()
until session ~= nil

local function updateHScroll()
    if typing_pos < typing_scroll + 4 and typing_pos > 4 then
        typing_scroll = math.max(0, typing_pos - 4)
        return true
    elseif typing_pos > typing_scroll + term_w - 7 then
        typing_scroll = typing_pos - term_w + 7
        return true
    else
        return false
    end
end

local function onInputLine(msg)
    if msg == "/quit" then
        sendLogout()
        running = false
    else
        sendMessage(msg)
    end
end

lastChatIndex = 0
startPoll()
term.setCursorBlink(true)
updateScreen()
updateInputLine()
while running do
    local evt, p1, p2 = os.pullEvent()
    if evt == "http_failure" and p1 == pollURL then
        displayChat("Network error")
    elseif evt == "http_success" and p1 == pollURL then
        handlePollResponse(p2)
        startPoll()
    elseif evt == "http_success" then
        p2.close()
    elseif evt == "char" then
        typing = typing:sub(1, typing_pos)..p1..typing:sub(typing_pos + 1)
        typing_pos = typing_pos + 1
        updateHScroll()
        updateInputLine()
    elseif evt == "key" then
        if p1 == 28 then
            -- Enter
            onInputLine(typing)
            table.insert(history, typing)
            typing = ""
            typing_pos = 0
            typing_scroll = 0
            history_pos = #history
            updateInputLine()
        elseif p1 == 203 then
            -- Left
            if typing_pos > 0 then
                typing_pos = typing_pos - 1
                if updateHScroll() then
                    updateInputLine()
                else
                    updateCursor()
                end
            end
        elseif p1 == 205 then
            -- Right
            if typing_pos < typing:len() then
                typing_pos = typing_pos + 1
                if updateHScroll() then
                    updateInputLine()
                else
                    updateCursor()
                end
            end
        elseif p1 == 14 then
            -- Backspace
            if typing_pos > 0 then
                typing = typing:sub(1, typing_pos-1) .. typing:sub(typing_pos+1)
                typing_pos = typing_pos - 1
                updateHScroll()
                updateInputLine()
            end
        elseif p1 == 200 then
            -- Up
            if history_pos > 1 then
                history_pos = history_pos - 1
                typing = history[history_pos]
                typing_pos = typing:len()
                updateHScroll()
                updateInputLine()
            end
        elseif p1 == 208 then
            -- Down
            if history_pos < #history then
                history_pos = history_pos + 1
                typing = history[history_pos]
                typing_pos = typing:len()
                updateHScroll()
                updateInputLine()
            end
        end
    end
end