local monitor = peripheral.find("monitor")
local programs = {}
local isRunning = false


local function addProgram(name, program)
    table.insert(programs, {name = name, program = program})
end

local function runProgram(programOrPath)
    local programModule

    if type(programOrPath) == "string" then
        if fs.exists(programOrPath) then
            -- Load the file as a chunk. In Lua 5.2+ use the env parameter instead of setfenv.
            local env = _ENV or _G
            local programChunk, err = loadfile(programOrPath, "t", env)
            if not programChunk then
                print("Error loading program: " .. err)
                return false
            end

            -- Run the chunk to get the module table
            local success, result = pcall(programChunk)

            if not success then
                print("Error executing program file: " .. tostring(result))
                return false
            end
            programModule = result
        else
            print("Program not found: " .. programOrPath)
            return false
        end
    elseif type(programOrPath) == "table" then
        programModule = programOrPath
    else
        print("Invalid program type")
        return false
    end

    if type(programModule) ~= "table" or not programModule.main then
        print("Error: Program must return a table with at least a 'main' function.")
        return false
    end

    -- Setup Monitor
    local w, h = monitor.getSize()
    monitor.setBackgroundColor(colors.black)
    monitor.clear()
    
    -- Draw X button
    monitor.setCursorPos(w, 1)
    monitor.setBackgroundColor(colors.red)
    monitor.setTextColor(colors.white)
    monitor.write("X")
    monitor.setBackgroundColor(colors.black)
    
    -- Create window for program
    local win = window.create(monitor, 1, 2, w, h - 1)
    local oldTerm = term.redirect(win)
    
    -- Lifecycle: START
    if programModule.start then
        local ok, err = pcall(programModule.start)
        if not ok then
            print("Error in start(): " .. tostring(err))
            term.redirect(oldTerm)
            return false
        end
    end

    -- Lifecycle: MAIN (Run in parallel with exit watcher)
    local function runMain()
            -- We wrap main in pcall to catch errors without crashing the driver
            local ok, err = pcall(programModule.main)
            if not ok then
                win.setTextColor(colors.red)
                win.write("Runtime Error: " .. tostring(err))
                sleep(2) -- Let user see error
            end
    end
    
    local function watchExit()
        while true do
            local _, _, x, y = os.pullEvent("monitor_touch")
            if x == w and y == 1 then
                return
            end
        end
    end
    
    parallel.waitForAny(runMain, watchExit)
    
    -- Lifecycle: STOP
    if programModule.stop then
        pcall(programModule.stop)
    end

    term.redirect(oldTerm)
    return true
end

local function exitProgram()
    isRunning = false
end

local function drawList()
    monitor.clear()
    monitor.setCursorPos(1, 1)
    monitor.write("Available Programs:")
    
    for i, program in ipairs(programs) do
        monitor.setCursorPos(1, i + 2) -- Start from line 3
        monitor.write(i .. ". " .. program.name)
    end
    
    monitor.setCursorPos(1, #programs + 4)
    monitor.write("Click to run")
end

local function listPrograms()
    isRunning = true
    while isRunning do
        drawList()
        
        local event, side, x, y = os.pullEvent("monitor_touch")
        local programIndex = y - 2
        
        if programIndex > 0 and programIndex <= #programs then
            local program = programs[programIndex]
            monitor.clear()
            monitor.setCursorPos(1,1)
            monitor.write("Running " .. program.name .. "...")
            sleep(0.5)
            runProgram(program.program)
        end
    end
end

return {
    addProgram = addProgram,
    runProgram = runProgram,
    exitProgram = exitProgram,
    listPrograms = listPrograms
}