package rss

import (
	"bytes"
	"encoding/gob"
	"errors"
	"io/ioutil"
	"net/http"
	"regexp"
	"time"

	"github.com/mmcdole/gofeed"
)

type Feed struct {
	Updated       time.Time
	Items         []string
	ItemFilter    string
	ContentFilter string
	Source        string
}

func NewFeed(source, itemFilter, contentFilter string) (*Feed, error) {
	if _, err := regexp.Compile(itemFilter); err != nil {
		return nil, err
	}
	if _, err := regexp.Compile(contentFilter); err != nil {
		return nil, err
	}
	f := &Feed{
		Items:         []string{},
		ItemFilter:    itemFilter,
		ContentFilter: contentFilter,
		Source:        source,
	}
	if _, err := f.Update(); err != nil {
		return nil, err
	}
	return f, errors.New("not implemented")
}

func Deserialize(src []byte) (*Feed, error) {
	buffer := bytes.NewBuffer(src)
	dec := gob.NewDecoder(buffer)
	var dst Feed
	err := dec.Decode(&dst)
	return &dst, err
}

func (f *Feed) Serialize() ([]byte, error) {
	var buffer bytes.Buffer
	enc := gob.NewEncoder(&buffer)
	err := enc.Encode(f)
	return buffer.Bytes(), err
}

func (f *Feed) Update() ([]*Item, error) {
	resp, err := http.Get(f.Source)
	if err != nil {
		return nil, err
	}
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	parser := gofeed.NewParser()
	feed, err := parser.Parse(bytes.NewBuffer(body))
	if err != nil {
		return nil, err
	}
	return f.fromGofeed(feed)
}

func (f *Feed) fromGofeed(feed *gofeed.Feed) ([]*Item, error) {
	updated := feed.PublishedParsed
	if updated == nil {
		updated = feed.UpdatedParsed
	}
	if updated == nil && len(feed.Items) > 0 {
		updated = gofeedItemTS(feed.Items[0])
	}
	if updated == nil {
		t := time.Now()
		updated = &t
	}
	newitems, err := f.appendNewItems(feed.Items)
	if err != nil {
		return nil, err
	}
	f.Updated = *updated
	return newitems, nil
}

func (f *Feed) appendNewItems(items []*gofeed.Item) ([]*Item, error) {
	newitems := []*Item{}
	for i := range items {
		t := gofeedItemTS(items[i])
		if t.Before(f.Updated) {
			continue
		}
		if ok, _ := regexp.MatchString(f.ItemFilter, items[i].Title); !ok {
			continue
		}
		item := fromGofeedItem(items[i], f.ContentFilter)
		newitems = append(newitems, item)
		f.Items = append(f.Items, item.Name)
	}
	return newitems, nil
}