package main

import (
	"fmt"
	"log"
	"net/url"
	"os"
	"path"
	"sort"
	"strconv"
	"sync"
	"time"

	"github.com/BurntSushi/toml"
	"github.com/cavaliercoder/grab"
	homedir "github.com/mitchellh/go-homedir"
	"github.com/mmcdole/gofeed"
)

var (
	confFile,dataFile,dstDir string
)

func init() {
	os.Chdir(path.Join()) // go to the root directory
	homeDir,err := homedir.Dir()
	if err != nil {
		log.Fatal("Cannot locate user's home directory")
	}
	confDir := path.Join(homeDir,".config","rssd")
	confFile = path.Join(confDir,"rssd.conf")
	dataFile = path.Join(confDir,"podcasts.conf")
}

type Config struct {
	Workers int
	DestDir string
	Urls []string
}

type Item struct {
	Title, Description, Url, Filename string
	Length int
	Published time.Time
	Podcast *Podcast
}

type Podcast struct {
	Title, Description, Url string
	Items []Item
}

type pcList struct {
	Podcasts []Podcast
}

func newpcList(confs ...string) (ret *pcList) {
	ret = &pcList{}
	ret.Podcasts = make([]Podcast,0)
	if len(confs) > 0 {
		if _, err := toml.DecodeFile(dataFile, &ret); err != nil {
			log.Print("Error reading podcast list:",err)
		}
	}
	return
}

func (p *pcList) Find(x *Podcast) (int, bool) {
	for i,y := range p.Podcasts {
		if y.Title == x.Title {
			return i, true
		}
	}
	return 0, false
}

func (p *pcList) Add(x *Podcast) {
	if x == nil {
		return
	}
	if i,ok := p.Find(x); ok == true {
		log.Print("     Existing podcast")
		p.Podcasts[i].Merge(x)
	} else {
		log.Print("     New podcast")
		p.Podcasts = append((*p).Podcasts,*x)
	}
}

func (p *Podcast) Merge(x *Podcast) {
	for _,item := range x.Items {
		if !p.Has(item) {
			p.Items = append(p.Items,item)
		}
	}
}

func (p *Podcast) Has(i Item) bool {
	for _,x := range p.Items {
		if x.Title == i.Title {
			return true
		}
	}
	return false
}

type Selector func(*gofeed.Item) bool

func AllSelectors(ss ...Selector) Selector {
	return func(i *gofeed.Item) bool {
		for _, s := range ss {
			if !s(i) {
				return false
			}
		}
		return true
	}
}

func AnySelector(ss ...Selector) Selector {
	return func(i *gofeed.Item) bool {
		for _, s := range ss {
			if s(i) {
				return true
			}
		}
		return false
	}
}

func newerThan(t time.Time) Selector {
	return func(i *gofeed.Item) bool {
		if i.PublishedParsed.After(t) {
			return true
		}
		return false
	}
}

func daysAgo(x int) Selector {
	d := time.Now()
	return newerThan(time.Date(d.Year(),d.Month(),d.Day()-x,0,0,0,0,time.Local))
}

func toPodcast(sel Selector, u string, feed *gofeed.Feed) (ret *Podcast) {
	ret = &Podcast{
		Title: feed.Title,
		Description: feed.Description,
		Url: u,
		Items: []Item{},
	}
	for _, i := range feed.Items {
		if sel(i) {
			fn := i.PublishedParsed.Format("20060102--") + i.Title
			it := Item{
				Title: i.Title,
				Description: i.Description,
				Filename: path.Join(ret.Title, fn),
				Published: *i.PublishedParsed,
			}
			for _, n := range i.Enclosures {
				if n.Type == "audio/mpeg" {
					u,err := url.Parse(n.URL)
					if err != nil {
						it.Url = n.URL
					} else {
						it.Url = fmt.Sprintf("%s://%s%s",u.Scheme,u.Host,u.Path)
					}
					if l, err := strconv.Atoi(n.Length); err == nil {
						it.Length = l
					}
				}
			}
			ret.Items = append(ret.Items,it)
		}
	}
	return
}

func readFeed(u string,sel Selector) *Podcast {
	fp := gofeed.NewParser()
	feed, err := fp.ParseURL(u)
	if err != nil {
		log.Print(err)
		return nil
	}
	return toPodcast(sel,u,feed)
}

type dlItem struct {
	Item *Item
	downloading bool
}

type ByDate []*dlItem
func (a ByDate) Len() int		{ return len(a) }
func (a ByDate) Swap(i, j int)		{ a[i], a[j] = a[j], a[i] }
func (a ByDate) Less(i, j int) bool	{ return a[j].Item.Published.After(a[i].Item.Published) }

type dlQueue struct {
	items []*dlItem
	reqch chan *grab.Request
	respch chan *grab.Response
	sync.Mutex
	wg sync.WaitGroup
	wake chan struct{}
}

func (q *dlQueue) Sort() {
	sort.Sort(ByDate(q.items))
}

func (q *dlQueue) Find(x *Item) (int, bool) {
	for i,y := range q.items {
		if y.Item.Title == x.Title {
			return i, true
		}
	}
	return 0, false
}

func (q *dlQueue) Waiting() *dlQueue {
	ret := &dlQueue{
		items: make([]*dlItem,0),
		reqch: q.reqch,
		respch: q.respch,
		Mutex: q.Mutex,
		wg: q.wg,
		wake: q.wake,
	}
	for _,i := range q.items {
		if i.downloading == false {
			ret.items = append(ret.items,i)
		}
	}
	return ret
}

func (q *dlQueue) Add(i *Item) {
	if _, ok := q.Find(i); ok == true {
		return
	}
	di := &dlItem{Item: &Item{} }
	*di.Item = *i
	q.items = append(q.items,di)
}

type Daemon struct {
	conf Config
	g *grab.Client
	pl *pcList
	queue *dlQueue
	sync.Mutex
	workers int
	dlwake chan struct{}
}

func NewDaemon(conf Config, pl *pcList) *Daemon {
	return &Daemon{
		conf: conf,
		g: grab.NewClient(),
		pl: pl,
		queue: &dlQueue{ wake: make(chan struct{}) },
		dlwake: make(chan struct{}),
	}
}

func (d *Daemon) Update(urls []string) {
	sel := daysAgo(30)
	for _,url := range urls {
		log.Print("  -> ",url)
		f := readFeed(url,sel) // do not lock around IO
		d.Lock()
		d.pl.Add(f)
		d.Unlock()
	}
}

func (d *Daemon) Monitor() {
	status := func(resp *grab.Response) {
		log.Printf("  %s: %v bytes (%.2f%%)\n",
			resp.Filename,
			resp.BytesComplete(),
			100*resp.Progress())
	}
	mon := func(resp *grab.Response) {
		t := time.NewTicker(5 * time.Second)
		defer t.Stop()
		Loop:
		for {
			select {
			case <-t.C:
				status(resp)
			case <-resp.Done:
				status(resp)
				break Loop
			}
		}
		if err := resp.Err(); err != nil {
			log.Printf("Download failed for %s (%s)\n",resp.Filename,err)
		}
	}
	for {
		mon(<-d.queue.respch)
	}
}

func (d *Daemon) StartDownloader() {
	log.Print("Downloader(): starting")
	d.queue.reqch = make(chan *grab.Request)
	d.queue.respch = make(chan *grab.Response)
	log.Print("Downloader(): spawning workers")
	for i := 0; i < d.workers; i++ {
		d.queue.wg.Add(1)
		go func() {
			d.g.DoChannel(d.queue.reqch,d.queue.respch)
			d.queue.wg.Done()
		}()
	}
	log.Print("Downloader(): starting monitor")
	go d.Monitor()

	if d.queue.items == nil {
		d.queue.Lock()
		d.queue.items = make([]*dlItem,0)
		d.queue.Unlock()
	}
	go d.QueueUpdater()
	go d.queue.Downloader()
}

func (d *Daemon) QueueUpdater() {
	t := time.NewTicker(30 * time.Minute)
	defer t.Stop()
	for {
		// lock Podcast list and update download queue
		log.Print("QueueUpdater(): Updating download queue")
		d.queue.Lock()
		for _,p := range d.pl.Podcasts {
			for _,i := range p.Items {
				d.queue.Add(&i)
			}
		}
		log.Print("QueueUpdater(): Done updating download queue")
		d.queue.Unlock()
		d.queue.wake<- struct{}{}
		log.Print("QueueUpdater(): Sleeping")
		select {
		case <-t.C:
			continue
		case <-d.dlwake:
			continue
		}
	}
}

func (q *dlQueue) Downloader() {
	t := time.NewTicker(30 * time.Minute)
	defer t.Stop()
	LOOP:
	for {
		// launch requests for files we are not yet downloading
		q.Lock()
		waiting := q.Waiting()
		q.Unlock()
		log.Print("Download queue length: ",len(waiting.items))
		for _,i := range waiting.items {
			if !i.downloading {
				dst := path.Join(dstDir,i.Item.Filename) + path.Ext(i.Item.Url)
				req,err := grab.NewRequest(dst,i.Item.Url)
				if err != nil {
					log.Print("Request error: ",err)
					continue
				}
				i.downloading = true
				t := time.Now()
				q.reqch <- req
				if time.Now().After(t.Add(5 * time.Second)) {
					continue LOOP // refresh list
				}
			}
		}
		log.Print("Downloader(): sleeping")
		select {
		case <-t.C:
			continue
		case <-q.wake:
			continue
		}
	}
}

func (d *Daemon) Updater() {
	log.Print("Updater(): starting")
	d.StartDownloader()
	for {
		time.Sleep(1 * time.Second)
		d.Update(d.conf.Urls)
		of,err := os.Create(dataFile)
		if err != nil {
			log.Print("Updater(): Cannot open output file")
		} else {
			enc := toml.NewEncoder(of)
			log.Print("Updater(): writing output")
			d.Lock()
			enc.Encode(d.pl)
			d.Unlock()
			of.Close()
		}
		d.dlwake <-struct{}{}
		time.Sleep(30 * time.Minute)
	}
}

func (d *Daemon) Start() {
	go d.Updater()
}

func main() {
	log.Print("rssd")
	log.Print("reading configuration")
	var conf Config
	var err error
	if _, err = toml.DecodeFile(confFile, &conf); err != nil {
		log.Fatal("Error reading config file:",err)
	}

	pl := newpcList(dataFile)
	d := NewDaemon(conf,pl)
	if d.conf.Workers != 0 {
		d.workers = d.conf.Workers
	} else {
		d.workers = 3
	}
	dstDir,err = homedir.Expand(conf.DestDir)
	if err != nil {
		log.Fatal("Error locating DestDir.")
	}
	d.Start()
	select { }
}