package state

import (
	"bytes"
	"fmt"
	"html/template"
	"image"
	"image/color"
	"net/http"

	"github.com/srwiley/oksvg"
	"github.com/srwiley/rasterx"
	"golang.org/x/image/draw"
	"tangled.org/core/appview/pages"
	"tangled.org/core/ico"
)

func (s *State) FaviconSvg(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "image/svg+xml")
	w.Header().Set("Cache-Control", "public, max-age=31536000") // one year
	w.Header().Set("ETag", `"favicon-svg-v1"`)

	if match := r.Header.Get("If-None-Match"); match == `"favicon-svg-v1"` {
		w.WriteHeader(http.StatusNotModified)
		return
	}

	s.pages.Favicon(w)
}

func (s *State) FaviconIco(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "image/x-icon")
	w.Header().Set("Cache-Control", "public, max-age=31536000") // one year
	w.Header().Set("ETag", `"favicon-ico-v1"`)

	if match := r.Header.Get("If-None-Match"); match == `"favicon-ico-v1"` {
		w.WriteHeader(http.StatusNotModified)
		return
	}

	ico, err := dollyIco()
	if err != nil {
		s.logger.Error("failed to render ico", "err", err)
		w.WriteHeader(http.StatusNotFound)
		return
	}

	w.Write(ico)
}

func dollyIco() ([]byte, error) {
	// first, get the bytes from the svg
	tpl, err := template.New("dolly").
		ParseFS(pages.Files, "templates/fragments/dolly/silhouette.html")
	if err != nil {
		return nil, err
	}

	var svgData bytes.Buffer
	if err := tpl.ExecuteTemplate(&svgData, "fragments/dolly/silhouette", "#000000"); err != nil {
		return nil, err
	}

	img, err := svgToImage(svgData.Bytes(), 48, 48)
	if err != nil {
		return nil, err
	}

	ico, err := ico.ImageToIco(img)
	if err != nil {
		return nil, err
	}

	return ico, nil
}

func svgToImage(svgData []byte, w, h int) (image.Image, error) {
	icon, err := oksvg.ReadIconStream(bytes.NewReader(svgData))
	if err != nil {
		return nil, fmt.Errorf("error parsing SVG: %v", err)
	}

	icon.SetTarget(0, 0, float64(w), float64(h))
	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
	draw.Draw(rgba, rgba.Bounds(), &image.Uniform{color.Transparent}, image.Point{}, draw.Src)
	scanner := rasterx.NewScannerGV(w, h, rgba, rgba.Bounds())
	raster := rasterx.NewDasher(w, h, scanner)
	icon.Draw(raster, 1.0)

	return rgba, nil
}