-- GUI OS v2.0 with Text Web Browser
-- Native CC:T API only, no extra libs

local term = term
local colors = colors
local paintutils = paintutils
local screenW, screenH = term.getSize()

-- System state
local currentScreen = "menu" -- menu / browser
local browserUrl = ""
local pageLines = {}
local currentPage = 1
local totalPages = 1
local linesPerPage = screenH - 6

-- ========== UI Helper Functions ==========
local function drawButton(x, y, w, h, text, bgColor)
    paintutils.drawFilledBox(x, y, x + w - 1, y + h - 1, bgColor)
    local textX = x + math.floor((w - #text) / 2)
    local textY = y + math.floor(h / 2)
    term.setCursorPos(textX, textY)
    term.setTextColor(colors.white)
    term.write(text)
end

local function pointInBox(px, py, x, y, w, h)
    return px >= x and px <= x + w - 1 and py >= y and py <= y + h - 1
end

-- ========== Main Menu Screen ==========
local menuButtons = {
    {x=3, y=4,  w=22, h=3, text="Web Browser",   color=colors.blue,   action="browser"},
    {x=3, y=8,  w=22, h=3, text="File Manager",  color=colors.green,  action="files"},
    {x=3, y=12, w=22, h=3, text="Run Program",   color=colors.yellow, action="run"},
    {x=3, y=16, w=22, h=3, text="Native Shell",  color=colors.gray,   action="shell"},
    {x=3, y=20, w=22, h=3, text="Shutdown",      color=colors.red,    action="shutdown"},
}

local function drawMenu()
    term.clear()
    -- Title bar
    paintutils.drawFilledBox(1, 1, screenW, 1, colors.gray)
    term.setCursorPos(2, 1)
    term.setTextColor(colors.white)
    term.write("GUI OS v2.0")
    
    -- Buttons
    for i = 1, #menuButtons do
        local btn = menuButtons[i]
        drawButton(btn.x, btn.y, btn.w, btn.h, btn.text, btn.color)
    end
    
    -- Status bar
    paintutils.drawFilledBox(1, screenH, screenW, screenH, colors.gray)
    term.setCursorPos(2, screenH)
    term.setTextColor(colors.white)
    term.write("Click a button to continue")
end

-- ========== File Manager ==========
local function openFileManager()
    term.clear()
    term.setCursorPos(1, 1)
    term.setTextColor(colors.white)
    term.setBackgroundColor(colors.black)
    print("=== File List (Root) ===")
    local files = fs.list("/")
    for i = 1, #files do
        if fs.isDir(files[i]) then
            print("[DIR]  " .. files[i])
        else
            print("[FILE] " .. files[i])
        end
    end
    print("\nPress any key to return")
    os.pullEvent("key")
    currentScreen = "menu"
end

-- ========== Run Program ==========
local function openRunProgram()
    term.clear()
    term.setCursorPos(1, 1)
    term.setTextColor(colors.white)
    term.setBackgroundColor(colors.black)
    write("Enter program name: ")
    local prog = read()
    if prog ~= "" then
        shell.run(prog)
        print("\nPress any key to return")
        os.pullEvent("key")
    end
    currentScreen = "menu"
end

-- ========== Web Browser ==========
local browserButtons = {
    {x=2,  y=screenH-2, w=12, h=2, text="Enter URL",  color=colors.blue,   action="url"},
    {x=15, y=screenH-2, w=10, h=2, text="Page Up",    color=colors.green,  action="up"},
    {x=26, y=screenH-2, w=12, h=2, text="Page Down",  color=colors.green,  action="down"},
    {x=39, y=screenH-2, w=10, h=2, text="Save File",  color=colors.yellow, action="save"},
    {x=50, y=screenH-2, w=10, h=2, text="Back",       color=colors.red,    action="back"},
}

local function loadPage(url)
    browserUrl = url
    pageLines = {}
    currentPage = 1
    
    local res, err = http.get(url)
    if not res then
        table.insert(pageLines, "Error loading page:")
        table.insert(pageLines, tostring(err or "Connection failed"))
        totalPages = 1
        return
    end
    
    local content = res.readAll()
    res.close()
    
    -- Split content into lines
    for line in string.gmatch(content, "[^\n]+") do
        table.insert(pageLines, line)
    end
    
    if #pageLines == 0 then
        table.insert(pageLines, "(empty page)")
    end
    
    totalPages = math.max(1, math.ceil(#pageLines / linesPerPage))
end

local function drawBrowser()
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)
    
    -- Address bar
    paintutils.drawFilledBox(1, 1, screenW, 2, colors.lightGray)
    term.setCursorPos(2, 1)
    term.setTextColor(colors.black)
    term.write("URL: " .. (browserUrl ~= "" and browserUrl or "(not loaded)"))
    
    -- Page content
    local startLine = (currentPage - 1) * linesPerPage + 1
    local endLine = math.min(startLine + linesPerPage - 1, #pageLines)
    
    for i = startLine, endLine do
        term.setCursorPos(1, 3 + (i - startLine))
        term.write(pageLines[i]:sub(1, screenW))
    end
    
    -- Page info
    term.setCursorPos(2, screenH - 3)
    term.setTextColor(colors.lightGray)
    term.write(string.format("Page %d / %d  |  Lines: %d", currentPage, totalPages, #pageLines))
    
    -- Bottom buttons
    for i = 1, #browserButtons do
        local btn = browserButtons[i]
        drawButton(btn.x, btn.y, btn.w, btn.h, btn.text, btn.color)
    end
end

local function handleBrowserClick(x, y)
    for i = 1, #browserButtons do
        local btn = browserButtons[i]
        if pointInBox(x, y, btn.x, btn.y, btn.w, btn.h) then
            if btn.action == "url" then
                term.setCursorPos(2, screenH - 3)
                term.clearLine()
                term.setTextColor(colors.white)
                write("Enter URL: ")
                local url = read()
                if url ~= "" then
                    loadPage(url)
                end
                
            elseif btn.action == "up" then
                if currentPage > 1 then
                    currentPage = currentPage - 1
                end
                
            elseif btn.action == "down" then
                if currentPage < totalPages then
                    currentPage = currentPage + 1
                end
                
            elseif btn.action == "save" then
                term.setCursorPos(2, screenH - 3)
                term.clearLine()
                term.setTextColor(colors.white)
                write("Save as filename: ")
                local fname = read()
                if fname ~= "" then
                    local f = fs.open(fname, "w")
                    f.write(table.concat(pageLines, "\n"))
                    f.close()
                end
                
            elseif btn.action == "back" then
                currentScreen = "menu"
            end
            break
        end
    end
end

-- ========== Main Loop ==========
while true do
    if currentScreen == "menu" then
        drawMenu()
        local _, _, x, y = os.pullEvent("mouse_click")
        
        for i = 1, #menuButtons do
            local btn = menuButtons[i]
            if pointInBox(x, y, btn.x, btn.y, btn.w, btn.h) then
                if btn.action == "browser" then
                    currentScreen = "browser"
                elseif btn.action == "files" then
                    openFileManager()
                elseif btn.action == "run" then
                    openRunProgram()
                elseif btn.action == "shell" then
                    term.clear()
                    term.setCursorPos(1, 1)
                    print("Entered native shell. Type 'exit' to return.")
                    shell.run("shell")
                elseif btn.action == "shutdown" then
                    term.clear()
                    term.setCursorPos(1, 1)
                    print("Shutting down...")
                    sleep(0.5)
                    os.shutdown()
                end
                break
            end
        end
        
    elseif currentScreen == "browser" then
        drawBrowser()
        local _, _, x, y = os.pullEvent("mouse_click")
        handleBrowserClick(x, y)
    end
end