package main

import (
	"encoding/xml"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"
	"text/tabwriter"
)

type Channel struct {
	ID     string  `xml:"yt:channelId"`
	Name   string  `xml:"title"`
	Videos []Video `xml:"entry"`
}

type Video struct {
	XMLName xml.Name `xml:"entry"`
	ID      string   `xml:"videoId"`
	Title   string   `xml:"title"`
	Date    string   `xml:"published"`
}

var CONFIG_DIR string

func init() {
	// Sets XDG_CONFIG_HOME
	configDir, err := os.UserConfigDir()
	if err != nil {
		log.Fatal(err)
	}

	// Create config dir
	configDir += "/yt-cli"
	err = os.MkdirAll(configDir, 0700)
	if err != nil {
		log.Fatal(err)
		return
	}

	// Check if config file exits
	if _, err = os.Stat(configDir + "/channels"); os.IsNotExist(err) {
		err = ioutil.WriteFile(configDir+"/channels", nil, 0600)
		if err != nil {
			log.Fatal(err)
			return
		}
	}

	// Set global var
	CONFIG_DIR = configDir

}

func main() {
	// set flags
	var add = flag.String("add", "", "Add a channel to subscription list.")
	var list = flag.Bool("list", false, "List all videos from subscriptions.")
	flag.Parse()

	// Print usage if no arguments
	if len(os.Args[1:]) == 0 {
		flag.Usage()
		return
	}

	if *add != "" && *list == true {
		log.Fatal("only one operation may be used at a time")
		return
	}

	// Add a channel if `-add` flag is set
	if *add != "" {
		if err := addSub(*add); err != nil {
			log.Fatal(err)
			return
		}
	}

	// List all channels' videos to stdout
	if *list == true {
		subs, _ := readSubs()
		// minwidth, tabwidth, padding, padchar, flags
		w := new(tabwriter.Writer)
		w.Init(os.Stdout, 5, 0, 1, ' ', 0)
		for _, k := range subs {
			ch, err := getVideos(k)
			if err != nil {
				panic(err)
			}
			for i, v := range ch.Videos {
				if i > 4 {
					break
				}
				fmt.Fprintf(w, "[%.10s]\t%.20s\t- %.50s\t(%.12s)\n", v.Date, ch.Name, v.Title, v.ID)
			}
		}
		w.Flush()
	}
}

// Appends subscription to file
func addSub(id string) (err error) {
	// Open file in append mode only
	file, err := os.OpenFile(CONFIG_DIR+"/channels", os.O_APPEND|os.O_WRONLY, 0600)
	if err != nil {
		return
	}
	defer file.Close()

	// Append the new subscription
	_, err = file.WriteString(id + "\n")
	if err != nil {
		return
	}

	return
}

// Reads subcriptions from file
func readSubs() (subs []string, err error) {
	data, err := ioutil.ReadFile(CONFIG_DIR + "/channels")
	if err != nil {
		return
	}
	subs = strings.Split(string(data), "\n")
	return
}

// Gets videos for subscription
func getVideos(chID string) (ch Channel, err error) {
	url := "https://www.youtube.com/feeds/videos.xml?channel_id=" + chID
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return
	}
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return
	}
	defer res.Body.Close()
	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return
	}

	xml.Unmarshal(body, &ch)
	return
}