package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"os/user"
	"path"
	"path/filepath"
	"time"

	"github.com/gocolly/colly"
)

var format = flag.String("format", "epub", "format to download")
var output = flag.String("output", "epub", "output directory")
var store = flag.String("store", "~/.tal-scraper.json", "data store")

func main() {
	flag.Parse()

	*output = fixpath(*output)
	*store = fixpath(*store)

	os.MkdirAll(*output, os.ModePerm)

	oldMostRecent := ""
	newMostRecent := ""

	data, _ := ioutil.ReadFile(*store)
	_ = json.Unmarshal(data, &oldMostRecent)

	done := false

	c := colly.NewCollector()

	c.OnHTML("div.amw-listing-item a[href]", func(e *colly.HTMLElement) {
		url := e.Attr("href") + "." + *format

		if newMostRecent == "" {
			newMostRecent = url
		}

		if newMostRecent == oldMostRecent {
			done = true
			return
		}

		fmt.Println(url)

		name := filenameForUrl(url)
		path := *output + "/" + name

		data, err := HTTPGet(url, time.Second*3)
		if err != nil {
			fmt.Println(url)
			fmt.Println(err)
			return
		}

		err = ioutil.WriteFile(path, data, 0644)
		if err != nil {
			fmt.Println(err)
		}
	})

	c.OnHTML("a[href] i.fa-chevron-right", func(e *colly.HTMLElement) {
		next, _ := e.DOM.Parent().Attr("href")

		if !done {
			e.Request.Visit(next)
		}
	})

	c.OnRequest(func(r *colly.Request) {
		fmt.Println("Checking", r.URL)
	})

	c.Visit("https://theanarchistlibrary.org/latest")

	data, _ = json.Marshal(newMostRecent)
	_ = ioutil.WriteFile(*store, data, 0644)
}

func fixpath(path string) string {
	path = filepath.FromSlash(path)
	if (path)[0] == '~' {
		user, err := user.Current()
		if err != nil {
			fmt.Fprintln(os.Stderr, err.Error())
			os.Exit(10)
		}
		path = filepath.Join(user.HomeDir, (path)[1:])
	}
	path, _ = filepath.Abs(path)
	return path
}

func filenameForUrl(url string) string {
	return path.Base(url)
}

func HTTPGet(url string, timeout time.Duration) (content []byte, err error) {
	request, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return
	}

	ctx, cancel_func := context.WithTimeout(context.Background(), timeout)
	request = request.WithContext(ctx)

	response, err := http.DefaultClient.Do(request)
	if err != nil {
		return
	}
	defer response.Body.Close()

	if response.StatusCode != 200 {
		cancel_func()
		return nil, fmt.Errorf("INVALID RESPONSE; status: %s", response.Status)
	}

	return ioutil.ReadAll(response.Body)
}

func fileExists(path string) bool {
	info, err := os.Stat(path)
	if os.IsNotExist(err) {
		return false
	}
	return !info.IsDir()
}