/*
Copyright © 2019 Darko Luketic <info@icod.de>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package server

import (
	"bytes"
	"fmt"
	"net/http"
	"os/exec"
	"syscall"
	"time"

	"github.com/allegro/bigcache"
	"github.com/sirupsen/logrus"
)

type Handler struct {
	binary     string
	baseParams []string
	uid        int
	logger     *logrus.Logger
	cache      *bigcache.BigCache
}

func NewHandler(binary string, eviction time.Duration, maxmem int) *Handler {
	h := new(Handler)
	h.binary = binary
	h.uid = syscall.Getuid()
	h.baseParams = []string{
		"--disable-client-side-phishing-detection",
		"--disable-cloud-import",
		"--disable-default-apps",
		"--disable-dinosaur-easter-egg",
		"--disable-new-tab-first-run",
		"--disable-offer-upload-credit-cards",
		"--disable-signin-promo",
		"--disable-sync",
		"--disable-translate",
		"--hide-scrollbars",
		"--incognito",
		"--mute-audio",
		"--no-default-browser-check",
		"--no-first-run",
		"--noerrdialogs",
		"--password-store=basic",
		"--window-size=1280,1696",
		"--headless",
		"--disable-gpu",
		"--disable-software-rasterizer",
		"--dump-dom",
	}
	h.logger = logrus.StandardLogger()
	cacheConf := bigcache.DefaultConfig(eviction)
	cacheConf.HardMaxCacheSize = maxmem
	cache, e := bigcache.NewBigCache(cacheConf)
	if e != nil {
		h.logger.Fatal(e.Error())
		return nil
	}
	h.cache = cache
	return h
}

func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	b, e := h.FetchDom(fmt.Sprintf("https://%s%s", r.Host, r.RequestURI))
	if e != nil {
		h.logger.Error(e)
		if _, err := fmt.Fprintln(w, e.Error()); err != nil {
			h.logger.Error(e)
			return
		}
		return
	}
	if _, e := w.Write(b.Bytes()); e != nil {
		h.logger.Error(e)
	}

}

func (h *Handler) FetchDom(url string) (*bytes.Buffer, error) {
	b, e := h.cache.Get(url)
	if e != nil {
		if e == bigcache.ErrEntryNotFound {
			var params []string
			if h.uid == 0 {
				params = append(h.baseParams, "--no-sandbox")
			} else {
				params = h.baseParams
			}
			params = append(params, url)
			cmd := exec.Command(h.binary, params...)
			buf := bytes.NewBuffer(nil)
			cmd.Stdout = buf
			if e := cmd.Run(); e != nil {
				return nil, e
			}
			if e := h.cache.Set(url, buf.Bytes()); e != nil {
				h.logger.Error(e)
			}
			return buf, nil
		} else {
			return nil, e
		}
	}
	return bytes.NewBuffer(b), nil
}