package main

import (
	"log"
	"os"
	"sync"

	"gioui.org/app"
	"gioui.org/op"
	"gioui.org/text"
	"gioui.org/unit"

	"pad/internal/ui"
)

func main() {
	go func() {
		w := new(app.Window)
		w.Option(app.Title("Pad"))
		w.Option(app.Size(unit.Dp(390), unit.Dp(844)))
		if err := run(w); err != nil {
			log.Fatal(err)
		}
		os.Exit(0)
	}()
	app.Main()
}

func run(w *app.Window) error {
	var ops op.Ops

	shaper := text.NewShaper()
	renderer := ui.New(ui.Theme{FontSize: 14}, shaper)

	// Channels for communication between goroutines
	configChan := make(chan ui.ConfigEvent)
	frameChan := make(chan []ui.Element)
	inputChan := make(chan []ui.InputEvent)

	// Shared state protected by mutex
	var mu sync.Mutex
	var elems []ui.Element

	// Initial screen size
	screenWidth := unit.Dp(390)
	screenHeight := unit.Dp(844)

	// Compute initial elements
	elems = ui.EditorLayout(screenWidth, screenHeight)

	// Start logic goroutine
	go logic(w, shaper, screenWidth, screenHeight, configChan, frameChan, inputChan)

	// Start frame receiver goroutine
	go frameReceiver(w, &mu, &elems, frameChan)

	// Main event loop
	for {
		switch e := w.Event().(type) {
		case app.DestroyEvent:
			return e.Err
		case app.ConfigEvent:
			// Send config event to logic goroutine
			configChan <- ui.ConfigEvent{
				Width:  unit.Dp(e.Config.Size.X),
				Height: unit.Dp(e.Config.Size.Y),
			}
		case app.FrameEvent:
			// Acquire mutex, read frame, draw, release mutex
			mu.Lock()
			currentElems := elems
			mu.Unlock()

			gtx := app.NewContext(&ops, e)
			renderer.Draw(gtx, currentElems)
			e.Frame(&ops)
		}
	}
}

// logic runs in a separate goroutine and owns all application state.
func logic(w *app.Window, shaper *text.Shaper, screenWidth, screenHeight unit.Dp,
	configChan <-chan ui.ConfigEvent, frameChan chan<- []ui.Element, inputChan <-chan []ui.InputEvent) {

	// Initial elements
	elems := ui.EditorLayout(screenWidth, screenHeight)

	for {
		select {
		case cfg := <-configChan:
			// Update screen size and recompute layout
			screenWidth = cfg.Width
			screenHeight = cfg.Height
			elems = ui.EditorLayout(screenWidth, screenHeight)
			frameChan <- elems
		case <-inputChan:
			// Process input (not implemented in mockup)
			frameChan <- elems
		}
	}
}

// frameReceiver runs in a separate goroutine and bridges frameChan to the main loop.
func frameReceiver(w *app.Window, mu *sync.Mutex, elems *[]ui.Element, frameChan <-chan []ui.Element) {
	for {
		frame := <-frameChan
		mu.Lock()
		*elems = frame
		w.Invalidate()
		mu.Unlock()
	}
}