//
// WRP - Web Rendering Proxy
//
// Copyright (c) 2013-2018 Antoni Sawicki
// Copyright (c) 2019-2024 Google LLC
//

package main

import (
	"bytes"
	"context"
	"embed"
	"flag"
	"fmt"
	"html/template"
	"image"
	"image/color/palette"
	"image/gif"
	"image/jpeg"
	"image/png"
	"io"
	"io/ioutil"
	"log"
	"math"
	"math/rand"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/MaxHalford/halfgone"
	"github.com/chromedp/cdproto/css"
	"github.com/chromedp/cdproto/emulation"
	"github.com/chromedp/cdproto/page"
	"github.com/chromedp/chromedp"
	"github.com/soniakeys/quant/median"
)

const version = "4.6.0"

var (
	addr        = flag.String("l", ":8080", "Listen address:port, default :8080")
	headless    = flag.Bool("h", true, "Headless mode / hide browser window (default true)")
	noDel       = flag.Bool("n", false, "Do not free maps and images after use")
	defType     = flag.String("t", "gif", "Image type: png|gif|jpg")
	jpgQual     = flag.Int("q", 80, "Jpeg image quality, default 80%")
	fgeom       = flag.String("g", "1152x600x216", "Geometry: width x height x colors, height can be 0 for unlimited")
	htmFnam     = flag.String("ui", "wrp.html", "HTML template file for the UI")
	delay       = flag.Duration("s", 2*time.Second, "Delay/sleep after page is rendered and before screenshot is taken")
	userAgent   = flag.String("ua", "", "override chrome user agent")
	srv         http.Server
	actx, ctx   context.Context
	acncl, cncl context.CancelFunc
	img         = make(map[string]bytes.Buffer)
	ismap       = make(map[string]wrpReq)
	defGeom     geom
	htmlTmpl    *template.Template
)

//go:embed *.html
var fs embed.FS

type geom struct {
	w int64
	h int64
	c int64
}

// Data for html template
type uiData struct {
	Version    string
	URL        string
	BgColor    string
	NColors    int64
	Width      int64
	Height     int64
	Zoom       float64
	ImgType    string
	ImgURL     string
	ImgSize    string
	ImgWidth   int
	ImgHeight  int
	MapURL     string
	PageHeight string
}

// Parameters for HTML print function
type printParams struct {
	bgColor    string
	pageHeight string
	imgSize    string
	imgURL     string
	mapURL     string
	imgWidth   int
	imgHeight  int
}

// WRP Request
type wrpReq struct {
	url     string  // url
	width   int64   // width
	height  int64   // height
	zoom    float64 // zoom/scale
	colors  int64   // #colors
	mouseX  int64   // mouseX
	mouseY  int64   // mouseY
	keys    string  // keys to send
	buttons string  // Fn buttons
	imgType string  // imgtype
	w       http.ResponseWriter
	r       *http.Request
}

// Parse HTML Form, Process Input Boxes, Etc.
func (rq *wrpReq) parseForm() {
	rq.r.ParseForm()
	rq.url = rq.r.FormValue("url")
	if len(rq.url) > 1 && !strings.HasPrefix(rq.url, "http") {
		rq.url = fmt.Sprintf("http://www.google.com/search?q=%s", url.QueryEscape(rq.url))
	}
	rq.width, _ = strconv.ParseInt(rq.r.FormValue("w"), 10, 64)
	rq.height, _ = strconv.ParseInt(rq.r.FormValue("h"), 10, 64)
	if rq.width < 10 && rq.height < 10 {
		rq.width = defGeom.w
		rq.height = defGeom.h
	}
	rq.zoom, _ = strconv.ParseFloat(rq.r.FormValue("z"), 64)
	if rq.zoom < 0.1 {
		rq.zoom = 1.0
	}
	rq.colors, _ = strconv.ParseInt(rq.r.FormValue("c"), 10, 64)
	if rq.colors < 2 || rq.colors > 256 {
		rq.colors = defGeom.c
	}
	rq.keys = rq.r.FormValue("k")
	rq.buttons = rq.r.FormValue("Fn")
	rq.imgType = rq.r.FormValue("t")
	switch rq.imgType {
	case "png":
	case "gif":
	case "jpg":
	default:
		rq.imgType = *defType
	}
	log.Printf("%s WrpReq from UI Form: %+v\n", rq.r.RemoteAddr, rq)
}

// Display WP UI
func (rq *wrpReq) printHTML(p printParams) {
	rq.w.Header().Set("Cache-Control", "max-age=0")
	rq.w.Header().Set("Expires", "-1")
	rq.w.Header().Set("Pragma", "no-cache")
	rq.w.Header().Set("Content-Type", "text/html")
	data := uiData{
		Version:    version,
		URL:        rq.url,
		BgColor:    p.bgColor,
		Width:      rq.width,
		Height:     rq.height,
		NColors:    rq.colors,
		Zoom:       rq.zoom,
		ImgType:    rq.imgType,
		ImgSize:    p.imgSize,
		ImgWidth:   p.imgWidth,
		ImgHeight:  p.imgHeight,
		ImgURL:     p.imgURL,
		MapURL:     p.mapURL,
		PageHeight: p.pageHeight,
	}
	err := htmlTmpl.Execute(rq.w, data)
	if err != nil {
		log.Fatal(err)
	}
}

// Determine what action to take
func (rq *wrpReq) action() chromedp.Action {
	// Mouse Click
	if rq.mouseX > 0 && rq.mouseY > 0 {
		log.Printf("%s Mouse Click %d,%d\n", rq.r.RemoteAddr, rq.mouseX, rq.mouseY)
		return chromedp.MouseClickXY(float64(rq.mouseX)/float64(rq.zoom), float64(rq.mouseY)/float64(rq.zoom))
	}
	// Buttons
	if len(rq.buttons) > 0 {
		log.Printf("%s Button %v\n", rq.r.RemoteAddr, rq.buttons)
		switch rq.buttons {
		case "Bk":
			return chromedp.NavigateBack()
		case "St":
			return chromedp.Stop()
		case "Re":
			return chromedp.Reload()
		case "Bs":
			return chromedp.KeyEvent("\b")
		case "Rt":
			return chromedp.KeyEvent("\r")
		case "<":
			return chromedp.KeyEvent("\u0302")
		case "^":
			return chromedp.KeyEvent("\u0304")
		case "v":
			return chromedp.KeyEvent("\u0301")
		case ">":
			return chromedp.KeyEvent("\u0303")
		}
	}
	// Keys
	if len(rq.keys) > 0 {
		log.Printf("%s Sending Keys: %#v\n", rq.r.RemoteAddr, rq.keys)
		return chromedp.KeyEvent(rq.keys)
	}
	// Navigate to URL
	log.Printf("%s Processing Capture Request for %s\n", rq.r.RemoteAddr, rq.url)
	return chromedp.Navigate(rq.url)
}

// Navigate to the desired URL.
func (rq *wrpReq) navigate() {
	ctxErr(chromedp.Run(ctx, rq.action()), rq.w)
}

// Handle context errors
func ctxErr(err error, w io.Writer) {
	// TODO: callers should have retry logic, perhaps create another function
	// that takes ...chromedp.Action and retries with give up
	if err == nil {
		return
	}
	log.Printf("Context error: %s", err)
	fmt.Fprintf(w, "Context error: %s<BR>\n", err)
	if err.Error() != "context canceled" {
		return
	}
	ctx, cncl = chromedp.NewContext(actx)
	log.Printf("Created new context, try again")
	fmt.Fprintln(w, "Created new context, try again")
}

// https://github.com/chromedp/chromedp/issues/979
func chromedpCaptureScreenshot(res *[]byte, h int64) chromedp.Action {
	if res == nil {
		panic("res cannot be nil")
	}
	if h == 0 {
		return chromedp.CaptureScreenshot(res)
	}

	return chromedp.ActionFunc(func(ctx context.Context) error {
		var err error
		*res, err = page.CaptureScreenshot().Do(ctx)
		return err
	})
}

func gifPalette(i image.Image, n int64) image.Image {
	switch n {
	case 2:
		i = halfgone.FloydSteinbergDitherer{}.Apply(halfgone.ImageToGray(i))
	case 216:
		var FastGifLut = [256]int{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5}
		r := i.Bounds()
		// NOTE: the color index computation below works only for palette.WebSafe!
		p := image.NewPaletted(r, palette.WebSafe)
		if i64, ok := i.(image.RGBA64Image); ok {
			for y := r.Min.Y; y < r.Max.Y; y++ {
				for x := r.Min.X; x < r.Max.X; x++ {
					c := i64.RGBA64At(x, y)
					r6 := FastGifLut[c.R>>8]
					g6 := FastGifLut[c.G>>8]
					b6 := FastGifLut[c.B>>8]
					p.SetColorIndex(x, y, uint8(36*r6+6*g6+b6))
				}
			}
		} else {
			for y := r.Min.Y; y < r.Max.Y; y++ {
				for x := r.Min.X; x < r.Max.X; x++ {
					c := i.At(x, y)
					r, g, b, _ := c.RGBA()
					r6 := FastGifLut[r&0xff]
					g6 := FastGifLut[g&0xff]
					b6 := FastGifLut[b&0xff]
					p.SetColorIndex(x, y, uint8(36*r6+6*g6+b6))
				}
			}
		}
		i = p
	default:
		q := median.Quantizer(n)
		i = q.Paletted(i)
	}
	return i
}

// Capture currently rendered web page to an image and fake ISMAP
func (rq *wrpReq) capture() {
	var styles []*css.ComputedStyleProperty
	var r, g, b int
	var h int64
	var pngCap []byte
	chromedp.Run(ctx,
		emulation.SetDeviceMetricsOverride(int64(float64(rq.width)/rq.zoom), 10, rq.zoom, false),
		chromedp.Location(&rq.url),
		chromedp.ComputedStyle("body", &styles, chromedp.ByQuery),
		chromedp.ActionFunc(func(ctx context.Context) error {
			_, _, _, _, _, s, err := page.GetLayoutMetrics().Do(ctx)
			if err == nil {
				h = int64(math.Ceil(s.Height))
			}
			return nil
		}),
	)
	for _, style := range styles {
		if style.Name == "background-color" {
			fmt.Sscanf(style.Value, "rgb(%d,%d,%d)", &r, &g, &b)
		}
	}
	log.Printf("%s Landed on: %s, Height: %v\n", rq.r.RemoteAddr, rq.url, h)
	height := int64(float64(rq.height) / rq.zoom)
	if rq.height == 0 && h > 0 {
		height = h + 30
	}
	chromedp.Run(
		ctx, emulation.SetDeviceMetricsOverride(int64(float64(rq.width)/rq.zoom), height, rq.zoom, false),
		chromedp.Sleep(*delay), // TODO(tenox): find a better way to determine if page is rendered
	)
	// Capture screenshot...
	ctxErr(chromedp.Run(ctx, chromedpCaptureScreenshot(&pngCap, rq.height)), rq.w)
	seq := rand.Intn(9999)
	imgPath := fmt.Sprintf("/img/%04d.%s", seq, rq.imgType)
	mapPath := fmt.Sprintf("/map/%04d.map", seq)
	ismap[mapPath] = *rq
	var sSize string
	var iW, iH int
	switch rq.imgType {
	case "png":
		pngBuf := bytes.NewBuffer(pngCap)
		img[imgPath] = *pngBuf
		cfg, _, _ := image.DecodeConfig(pngBuf)
		sSize = fmt.Sprintf("%.0f KB", float32(len(pngBuf.Bytes()))/1024.0)
		iW = cfg.Width
		iH = cfg.Height
		log.Printf("%s Got PNG image: %s, Size: %s, Res: %dx%d\n", rq.r.RemoteAddr, imgPath, sSize, iW, iH)
	case "gif":
		i, err := png.Decode(bytes.NewReader(pngCap))
		if err != nil {
			log.Printf("%s Failed to decode PNG screenshot: %s\n", rq.r.RemoteAddr, err)
			fmt.Fprintf(rq.w, "<BR>Unable to decode page PNG screenshot:<BR>%s<BR>\n", err)
			return
		}
		st := time.Now()
		var gifBuf bytes.Buffer
		err = gif.Encode(&gifBuf, gifPalette(i, rq.colors), &gif.Options{})
		if err != nil {
			log.Printf("%s Failed to encode GIF: %s\n", rq.r.RemoteAddr, err)
			fmt.Fprintf(rq.w, "<BR>Unable to encode GIF:<BR>%s<BR>\n", err)
			return
		}
		img[imgPath] = gifBuf
		sSize = fmt.Sprintf("%.0f KB", float32(len(gifBuf.Bytes()))/1024.0)
		iW = i.Bounds().Max.X
		iH = i.Bounds().Max.Y
		log.Printf("%s Encoded GIF image: %s, Size: %s, Colors: %d, Res: %dx%d, Time: %vms\n", rq.r.RemoteAddr, imgPath, sSize, rq.colors, iW, iH, time.Since(st).Milliseconds())
	case "jpg":
		i, err := png.Decode(bytes.NewReader(pngCap))
		if err != nil {
			log.Printf("%s Failed to decode PNG screenshot: %s\n", rq.r.RemoteAddr, err)
			fmt.Fprintf(rq.w, "<BR>Unable to decode page PNG screenshot:<BR>%s<BR>\n", err)
			return
		}
		st := time.Now()
		var jpgBuf bytes.Buffer
		err = jpeg.Encode(&jpgBuf, i, &jpeg.Options{Quality: *jpgQual})
		if err != nil {
			log.Printf("%s Failed to encode JPG: %s\n", rq.r.RemoteAddr, err)
			fmt.Fprintf(rq.w, "<BR>Unable to encode JPG:<BR>%s<BR>\n", err)
			return
		}
		img[imgPath] = jpgBuf
		sSize = fmt.Sprintf("%.0f KB", float32(len(jpgBuf.Bytes()))/1024.0)
		iW = i.Bounds().Max.X
		iH = i.Bounds().Max.Y
		log.Printf("%s Encoded JPG image: %s, Size: %s, Quality: %d, Res: %dx%d, Time: %vms\n", rq.r.RemoteAddr, imgPath, sSize, *jpgQual, iW, iH, time.Since(st).Milliseconds())
	}
	rq.printHTML(printParams{
		bgColor:    fmt.Sprintf("#%02X%02X%02X", r, g, b),
		pageHeight: fmt.Sprintf("%d PX", h),
		imgSize:    sSize,
		imgURL:     imgPath,
		mapURL:     mapPath,
		imgWidth:   iW,
		imgHeight:  iH,
	})
	log.Printf("%s Done with capture for %s\n", rq.r.RemoteAddr, rq.url)
}

// Process HTTP requests to WRP '/' url
func pageServer(w http.ResponseWriter, r *http.Request) {
	log.Printf("%s Page Request for %s [%+v]\n", r.RemoteAddr, r.URL.Path, r.URL.RawQuery)
	rq := wrpReq{
		r: r,
		w: w,
	}
	rq.parseForm()
	if len(rq.url) < 4 {
		rq.printHTML(printParams{bgColor: "#FFFFFF"})
		return
	}
	rq.navigate() // TODO: if error from navigate do not capture
	rq.capture()
}

// Process HTTP requests to ISMAP '/map/' url
func mapServer(w http.ResponseWriter, r *http.Request) {
	log.Printf("%s ISMAP Request for %s [%+v]\n", r.RemoteAddr, r.URL.Path, r.URL.RawQuery)
	rq, ok := ismap[r.URL.Path]
	rq.r = r
	rq.w = w
	if !ok {
		fmt.Fprintf(w, "Unable to find map %s\n", r.URL.Path)
		log.Printf("Unable to find map %s\n", r.URL.Path)
		return
	}
	if !*noDel {
		defer delete(ismap, r.URL.Path)
	}
	n, err := fmt.Sscanf(r.URL.RawQuery, "%d,%d", &rq.mouseX, &rq.mouseY)
	if err != nil || n != 2 {
		fmt.Fprintf(w, "n=%d, err=%s\n", n, err)
		log.Printf("%s ISMAP n=%d, err=%s\n", r.RemoteAddr, n, err)
		return
	}
	log.Printf("%s WrpReq from ISMAP: %+v\n", r.RemoteAddr, rq)
	if len(rq.url) < 4 {
		rq.printHTML(printParams{bgColor: "#FFFFFF"})
		return
	}
	rq.navigate() // TODO: if error from navigate do not capture
	rq.capture()
}

// Process HTTP requests for images '/img/' url
func imgServer(w http.ResponseWriter, r *http.Request) {
	log.Printf("%s IMG Request for %s\n", r.RemoteAddr, r.URL.Path)
	imgBuf, ok := img[r.URL.Path]
	if !ok || imgBuf.Bytes() == nil {
		fmt.Fprintf(w, "Unable to find image %s\n", r.URL.Path)
		log.Printf("%s Unable to find image %s\n", r.RemoteAddr, r.URL.Path)
		return
	}
	if !*noDel {
		defer delete(img, r.URL.Path)
	}
	switch {
	case strings.HasPrefix(r.URL.Path, ".gif"):
		w.Header().Set("Content-Type", "image/gif")
	case strings.HasPrefix(r.URL.Path, ".png"):
		w.Header().Set("Content-Type", "image/png")
	case strings.HasPrefix(r.URL.Path, ".jpg"):
		w.Header().Set("Content-Type", "image/jpeg")
	}
	w.Header().Set("Content-Length", strconv.Itoa(len(imgBuf.Bytes())))
	w.Header().Set("Cache-Control", "max-age=0")
	w.Header().Set("Expires", "-1")
	w.Header().Set("Pragma", "no-cache")
	w.Write(imgBuf.Bytes())
	w.(http.Flusher).Flush()
}

// Process HTTP requests for Shutdown via '/shutdown/' url
func haltServer(w http.ResponseWriter, r *http.Request) {
	log.Printf("%s Shutdown Request for %s\n", r.RemoteAddr, r.URL.Path)
	w.Header().Set("Cache-Control", "max-age=0")
	w.Header().Set("Expires", "-1")
	w.Header().Set("Pragma", "no-cache")
	w.Header().Set("Content-Type", "text/plain")
	fmt.Fprintf(w, "Shutting down WRP...\n")
	w.(http.Flusher).Flush()
	time.Sleep(time.Second * 2)
	cncl()
	acncl()
	srv.Shutdown(context.Background())
	os.Exit(1)
}

// returns html template, either from html file or built-in
func tmpl(t string) string {
	var tmpl []byte
	fh, err := os.Open(t)
	if err != nil {
		goto builtin
	}
	defer fh.Close()

	tmpl, err = ioutil.ReadAll(fh)
	if err != nil {
		goto builtin
	}
	log.Printf("Got HTML UI template from %v file, size %v \n", t, len(tmpl))
	return string(tmpl)

builtin:
	fhs, err := fs.Open("wrp.html")
	if err != nil {
		log.Fatal(err)
	}
	defer fhs.Close()

	tmpl, err = ioutil.ReadAll(fhs)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("Got HTML UI template from embed\n")
	return string(tmpl)
}

// Print my own IP addresses
func printIPs(b string) {
	ap := strings.Split(b, ":")
	if len(ap) < 1 {
		log.Fatal("Wrong format of ipaddress:port")
	}
	log.Printf("Listen address: %v", b)
	if ap[0] != "" && ap[0] != "0.0.0.0" {
		return
	}
	a, err := net.InterfaceAddrs()
	if err != nil {
		log.Print("Unable to get interfaces: ", err)
		return
	}
	var m string
	for _, i := range a {
		n, ok := i.(*net.IPNet)
		if !ok || n.IP.IsLoopback() || strings.Contains(n.IP.String(), ":") {
			continue
		}
		m = m + n.IP.String() + " "
	}
	log.Print("My IP addresses: ", m)
}

// Main
func main() {
	var err error
	flag.Parse()
	log.Printf("Web Rendering Proxy Version %s\n", version)
	log.Printf("Args: %q", os.Args)
	if len(os.Getenv("PORT")) > 0 {
		*addr = ":" + os.Getenv(("PORT"))
	}
	printIPs(*addr)
	n, err := fmt.Sscanf(*fgeom, "%dx%dx%d", &defGeom.w, &defGeom.h, &defGeom.c)
	if err != nil || n != 3 {
		log.Fatalf("Unable to parse -g geometry flag / %s", err)
	}

	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.Flag("headless", *headless),
		chromedp.Flag("hide-scrollbars", false),
		chromedp.Flag("enable-automation", false),
		chromedp.Flag("disable-blink-features", "AutomationControlled"),
	)
	if *userAgent != "" {
		opts = append(opts, chromedp.UserAgent(*userAgent))
	}
	actx, acncl = chromedp.NewExecAllocator(context.Background(), opts...)
	defer acncl()
	ctx, cncl = chromedp.NewContext(actx)
	defer cncl()

	rand.Seed(time.Now().UnixNano())

	c := make(chan os.Signal)
	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-c
		log.Printf("Interrupt - shutting down.")
		cncl()
		acncl()
		srv.Shutdown(context.Background())
		os.Exit(1)
	}()

	http.HandleFunc("/", pageServer)
	http.HandleFunc("/map/", mapServer)
	http.HandleFunc("/img/", imgServer)
	http.HandleFunc("/shutdown/", haltServer)
	http.HandleFunc("/favicon.ico", http.NotFound)

	log.Printf("Default Img Type: %v, Geometry: %+v", *defType, defGeom)

	htmlTmpl, err = template.New("wrp.html").Parse(tmpl(*htmFnam))
	if err != nil {
		log.Fatal(err)
	}

	log.Print("Starting WRP http server")
	srv.Addr = *addr
	err = srv.ListenAndServe()
	if err != nil {
		log.Fatal(err)
	}
}