package main

import (
	"errors"
	"fmt"
	"image"
	"image/png"
	"net"
	"net/http"
	"os"
	"sync"
	"time"
)

var (
	fetchClient = &http.Client{
		Timeout: 500 * time.Millisecond,
	}

	submitClient = &http.Client{
		Timeout: 50 * time.Millisecond,
	}
)

func main() {
	f, err := os.Open("img.png")
	if err != nil {
		panic(err)
	}

	img, err := png.Decode(f)
	if err != nil {
		panic(err)
	}

	for {
		if err := draw(img); err != nil {
			fmt.Println(err)
		}

		<-time.After(100 * time.Millisecond)
	}
}

func draw(img image.Image) error {
	fmt.Println("redraw")

	req, err := http.NewRequest("GET", "https://cqql.site/chaosbtn", nil)
	if err != nil {
		return err
	}

	res, err := fetchClient.Do(req)
	if err != nil {
		return err
	}
	defer res.Body.Close()

	if res.StatusCode != 200 {
		return errors.New("could not fetch current button state")
	}

	currentState, err := png.Decode(res.Body)
	if err != nil {
		return err
	}

	wg := &sync.WaitGroup{}

	for x := 0; x < 88; x++ {
		wg.Add(1)
		go drawCol(wg, x, img, currentState)
	}
	wg.Wait()

	return nil
}

func drawCol(wg *sync.WaitGroup, x int, img image.Image, currentState image.Image) error {
	defer wg.Done()

	for y := 0; y < 31; y++ {
		r, g, b, _ := img.At(x, y).RGBA()
		curR, curG, curB, _ := currentState.At(x, y).RGBA()

		if r == curR && g == curG && b == curB {
			continue
		}

		uri := fmt.Sprintf("https://cqql.site/chaosbtn/draw?x=%d&y=%d&r=%d&g=%d&b=%d", x, y, r/257, g/257, b/257)
		fmt.Printf("send [%02d,%02d] [%03d %03d %03d]\n", x, y, r/257, g/257, b/257)

		req, err := http.NewRequest("GET", uri, nil)
		if err != nil {
			return err
		}

		_, err = submitClient.Do(req)
		if err != nil {
			var netErr net.Error
			if errors.As(err, &netErr) && netErr.Timeout() {
				continue
			}

			return err
		}
	}

	return nil
}