Convorse

local theme = {
    background = colors.white,
    accent = colors.blue,
    text = colors.black,
    header = colors.white,
    input = colors.white,
    inputText = colors.gray,
    placeholder = colors.lightGray,
}

if not term.isColor() then
    theme = {
        background = colors.white,
        accent = colors.black,
        text = colors.black,
        header = colors.white,
        input = colors.white,
        inputText = colors.black,
        placeholder = colors.black,
    }
end

local t = {
    bg = term.setBackgroundColor,
    tc = term.setTextColor,
    p = term.setCursorPos,
    gp = term.getCursorPos,
    c = term.clear,
    cl = term.clearLine,
    w = term.write,
    nl = function(num)
        if not num then num = 1 end
        local x, y = term.getCursorPos()
        term.setCursorPos(1, y + num)
    end,
    o = function() term.setCursorPos(1, 1) end,
    db = function(height)
        local x, y = term.getCursorPos()
        for i = 1, height do
            term.setCursorPos(1, y + i - 1)
            term.clearLine()
        end
        term.setCursorPos(x, y)
    end
}

local w, h = term.getSize()

local function textField(startX, startY, length, startingText, placeholder,
        shouldHideText, eventCallback)
    local horizontalScroll = 1
    local cursorPosition = 1
    local data = startingText
    local eventCallbackResponse = nil
    local method = "enter"

    if not data then
        data = ""
    else
        cursorPosition = data:len() + 1
    end

    while true do
        term.setCursorBlink(true)
        term.setBackgroundColor(theme.background)
        term.setTextColor(theme.inputText)

        term.setCursorPos(startX, startY)
        term.write(string.rep(" ", length))
        term.setCursorPos(startX, startY)

        local text = data
        if shouldHideText then
            text = string.rep("*", #data)
        end
        term.write(text:sub(horizontalScroll, horizontalScroll + length - 1))

        if #data == 0 and placeholder then
            term.setTextColor(theme.placeholder)
            term.write(placeholder)
        end

        term.setCursorPos(startX + cursorPosition - horizontalScroll, startY)

        local event = {os.pullEvent()}
        if eventCallback then
            local shouldReturn, response = eventCallback(event)
            if shouldReturn then
                eventCallbackResponse = response
                method = "callback"
                break
            end
        end

        local isMouseEvent = event[1] == "mouse_click" or event[1] == "mouse_drag"

        if isMouseEvent then
            local inHorizontalBounds = event[3] >= startX and event[3] < startX + length
            local inVerticalBounds = event[4] == startY
            if inHorizontalBounds and inVerticalBounds then
                local previousX = term.getCursorPos()
                local position = cursorPosition - (previousX - event[3])
                cursorPosition = math.min(position, #data + 1)
            end
        elseif event[1] == "char" then
            if term.getCursorPos() >= startX + length - 1 then
                horizontalScroll = horizontalScroll + 1
            end

            cursorPosition = cursorPosition + 1
            local before = data:sub(1, cursorPosition - 1)
            local after = data:sub(cursorPosition, -1)
            data = before .. event[2] .. after
        elseif event[1] == "key" then
            if event[2] == keys.enter then
                break
            elseif event[2] == keys.left and cursorPosition > 1 then
                cursorPosition = cursorPosition - 1
                if cursorPosition <= horizontalScroll and horizontalScroll > 1 then
                    local amount = ((horizontalScroll - cursorPosition) + 1)
                    horizontalScroll = horizontalScroll - amount
                end
            elseif event[2] == keys.right and cursorPosition <= data:len() then
                cursorPosition = cursorPosition + 1
                if 1 >= length - (cursorPosition - horizontalScroll) + 1 then
                    horizontalScroll = horizontalScroll + 1
                end
            elseif event[2] == keys.backspace and cursorPosition > 1 then
                data = data:sub(1, cursorPosition - 2) .. data:sub(cursorPosition, -1)
                cursorPosition = cursorPosition - 1
                if cursorPosition <= horizontalScroll and horizontalScroll > 1 then
                    local amount = ((horizontalScroll - cursorPosition) + 1)
                    horizontalScroll = horizontalScroll - amount
                end
            end
        end
    end

    term.setCursorBlink(false)
    return method, data, eventCallbackResponse
end

local centerField = function(width, placeholder)
    local x, y = t.gp()
    t.p(math.floor(w / 2 - width / 2) + 1, y)
    t.bg(theme.input)
    t.tc(theme.placeholder)
    t.w(placeholder .. string.rep(" ", width - #placeholder))
    t.p(1, y + 1)
    return {math.floor(w / 2 - width / 2) + 1, y}
end

local center = function(text)
    local x, y = t.gp()
    t.p(math.floor(w / 2 - text:len() / 2) + 1, y)
    t.w(text)
    t.p(1, y + 1)
    return {math.floor(w / 2 - text:len() / 2) + 1, y}
end

local centerButton = function(width, text)
    local x, y = t.gp()
    t.p(math.floor(w / 2 - width / 2) + 1, y)
    t.bg(theme.accent)
    t.tc(theme.header)
    t.w(string.rep(" ", width))
    center(text)
    return {math.floor(w / 2 - width / 2) + 1, y}
end

local usernameFieldStart, passwordFieldStart, buttonTopLeft, buttonBottomRight, registerStart

local function drawLogin()
    t.bg(theme.background)
    t.c()

    t.o()
    t.tc(theme.header)
    t.bg(theme.accent)
    t.db(4)

    t.nl()
    center("- Convorse -")
    center("A web chat client")
    t.nl()

    t.tc(theme.text)
    t.bg(theme.background)
    t.nl()
    center("Welcome Back")
    t.nl()
    usernameFieldStart = centerField(20, "Username")
    center("--------------------")
    passwordFieldStart = centerField(20, "Password")
    center("--------------------")
    t.nl()
    loginStart = centerButton(20, "Login")
    t.nl()
    t.tc(theme.accent)
    t.bg(theme.background)
    registerStart = center("Need an account?    ")
end

local activeField = "username"
local username = ""
local password = ""

-- local function textField(posX, posY, length, curData, placeholder, handler)

local function loginFocusManager()
    local activeField = "username"

    while true do
        local function textHandler(events)
            if events[1] == "mouse_click" then
                if events[4] == usernameFieldStart[2] and
                events[3] >= usernameFieldStart[1] and
                events[3] <= usernameFieldStart[1] + 19 then
                    if activeField ~= "username" then
                        return true, {"username", unpack(events)}
                    end
                elseif events[4] == passwordFieldStart[2] and
                events[3] >= passwordFieldStart[1] and
                events[3] <= passwordFieldStart[1] + 19 then
                    if activeField ~= "password" then
                        return true, {"password", unpack(events)}
                    end
                elseif events[4] == loginStart[2] and
                events[3] >= loginStart[1] and events[3] <= buttonBottomRight[1] + 20 then
                    return true, {"login", unpack(events)}
                elseif events[4] == registerStart[2] and events[3] >= registerStart[1] and events[3] <= registerStart[1] + 16 then
                    return true, {"register", unpack(events)}
                else
                    return true, {"nothing", unpack(events)}
                end
            end
        end

        if activeField == "nothing" then
            while true do
                local resp
                resp, callbackResponse = textHandler({os.pullEvent()})
                if resp then
                    activeField = callbackResponse[1]
                    break
                end
            end
        elseif activeField == "username" then
            local resp, data, callback = textField(usernameFieldStart[1], usernameFieldStart[2], 20, username, "Username", false, textHandler)

            if resp == "enter" then
                activeField = "password"
                username = data
            else
                activeField = callback[1]
                username = data
                os.queueEvent(callback[2], callback[3], callback[4], callback[5])
            end
        elseif activeField == "password" then
            local resp, data, callback = textField(passwordFieldStart[1], passwordFieldStart[2], 20, password, "Password", true, textHandler)

            if resp == "enter" then
                activeField = "nothing"
                password = data
                login()
            else
                activeField = callback[1]
                password = data
                os.queueEvent(callback[2], callback[3], callback[4], callback[5])
            end
        elseif activeField == "login" then
            login()
        elseif activeField == "register" then
            register()
        end
    end
end

drawLogin()
loginFocusManager()