cpolis/cmd/data/rss.go

package data

import (
	"encoding/gob"
	"fmt"
	"os"
	"sync"

	"git.streifling.com/jason/rss"
)

type Channel struct {
	addCh   chan *rss.Item
	setCh   chan rss.Channel
	getCh   chan rss.Channel
	channel rss.Channel
	wg      sync.WaitGroup
}

func initChannel() *Channel {
	return &Channel{
		addCh: make(chan *rss.Item),
		setCh: make(chan rss.Channel),
		getCh: make(chan rss.Channel),
		channel: rss.Channel{
			Items: make([]*rss.Item, 0),
		},
	}
}

func (c *Channel) start() {
	c.wg.Done()
	for {
		select {
		case item := <-c.addCh:
			c.channel.Items = append(c.channel.Items, item)
		case c.getCh <- c.channel:
		case c.channel = <-c.setCh:
		}
	}
}

func NewChannel(title, link, desc string) *Channel {
	channel := initChannel()
	channel.channel = rss.Channel{
		Title:       title,
		Link:        link,
		Description: desc,
	}

	channel.wg.Add(1)
	go channel.start()
	channel.wg.Wait()

	return channel
}

func (c *Channel) Get() rss.Channel {
	return <-c.getCh
}

func (f *Channel) Set(channel rss.Channel) {
	f.setCh <- channel
}

func LoadChannel(filename string) (*Channel, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, fmt.Errorf("error opening file %v: %v", filename, err)
	}
	defer file.Close()

	channel := initChannel()
	channel.wg.Add(1)
	go channel.start()
	channel.wg.Wait()

	tmpChannel := new(rss.Channel)
	if err = gob.NewDecoder(file).Decode(tmpChannel); err != nil {
		return nil, fmt.Errorf("error decoding channel from file %v: %v", filename, err)
	}

	channel.Set(*tmpChannel)
	return channel, nil
}

func (c *Channel) Save(filename string) error {
	file, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("error creating file %v: %v", filename, err)
	}
	defer file.Close()

	channel := c.Get()
	if err = gob.NewEncoder(file).Encode(channel); err != nil {
		return fmt.Errorf("error encoding file %v: %v", filename, err)
	}

	return nil
}

func (c *Channel) Add(i *rss.Item) {
	c.addCh <- i
}