satbd-explorer/album_description_cache.go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/PuerkitoBio/goquery"
	"github.com/nightlyone/lockfile"
)

// An AlbumDescriptionCache is used to fetch and cache AlbumDescription from www.bedetheque.com
type AlbumDescriptionCache struct {
	basepath string
	lock     lockfile.Lockfile
	getter   HTTPGetter
	// time to live of the cache, data which is older than this TTL will be automatically removed
	TTL time.Duration
}

// NewAlbumDescriptionCache is creating a new album description at specified location
func NewAlbumDescriptionCache(path string, maxRequest uint, window time.Duration) (*AlbumDescriptionCache, error) {
	res := &AlbumDescriptionCache{
		basepath: path,
		getter:   NewRateLimitedGetter(maxRequest, window),
		TTL:      3 * 31 * 24 * time.Hour, // 3 Months
	}
	var err error
	res.lock, err = lockfile.New(filepath.Join(path, "global.lock"))
	if err != nil {
		return nil, fmt.Errorf("DescriptionCache: could not create lock: %s", err)
	}

	err = os.MkdirAll(filepath.Join(res.basepath, "albums"), 0755)
	if err != nil {
		return nil, err
	}

	err = os.MkdirAll(filepath.Join(res.basepath, "covers"), 0755)
	if err != nil {
		return nil, err
	}

	return res, nil
}

func (c *AlbumDescriptionCache) unlockOrPanic() {
	if err := c.lock.Unlock(); err != nil {
		panic(fmt.Sprintf("Could not unlock '%s': %s", c.lock, err))
	}
}

func (c *AlbumDescriptionCache) albumPath(ID AlbumID) string {
	return filepath.Join(c.basepath, "albums", fmt.Sprintf("%d.json", ID))
}

// CoverPath gets the path of the cover in the cache
func (c *AlbumDescriptionCache) CoverPath(ID AlbumID, ext string) string {
	return filepath.Join(c.basepath, "covers", fmt.Sprintf("%d%s", ID, ext))
}

var noteRx = regexp.MustCompile(`Note:\s*([0-9\.]+)\s*/\s*[0-9\.]+`)

func linkFromSelection(s *goquery.Selection) Link {
	target, _ := s.Attr("href")
	return Link{
		Title:  strings.TrimSpace(s.Text()),
		Target: target,
	}
}

func (c *AlbumDescriptionCache) fetchAndCache(ID AlbumID) (*AlbumDescription, error) {
	URL := path.Join("www.bedetheque.com", fmt.Sprintf("BD--%d.html", ID))
	resp, err := c.getter.Get("http://" + URL)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	doc, err := goquery.NewDocumentFromReader(resp.Body)
	if err != nil {
		return nil, err
	}
	res := &AlbumDescription{}
	principal := doc.Find("div.bandeau-principal")
	errors := make(chan error)
	waitSize := 0
	waitSize++
	go func() {
		cover := principal.Find(".bandeau-image img.image_album")
		if cover.Size() != 1 {
			errors <- fmt.Errorf("could not find a single cover, found (%d)", cover.Size())
			return
		}

		src, ok := cover.Attr("src")
		if ok == false {
			errors <- fmt.Errorf("Could not find src attribute for cover")
			return
		}

		resp, err := c.getter.Get(src)
		if err != nil {
			errors <- err
			return
		}

		defer resp.Body.Close()

		savePath := c.CoverPath(ID, path.Ext(src))

		f, err := os.Create(savePath)
		if err != nil {
			errors <- err
			return
		}
		defer f.Close()
		_, err = io.Copy(f, resp.Body)
		if err != nil {
			errors <- err
			return
		}
		res.CoverExt = path.Ext(src)
		errors <- nil
	}()

	waitSize++
	go func() {
		description := principal.Find(".bandeau-info p.auto-height span")
		if description.Size() != 1 {
			errors <- fmt.Errorf("Could not find a single description, found %d", description.Size())
			return
		}
		res.Description = description.Text()
		errors <- nil
	}()
	waitSize++
	go func() {
		note := principal.Find(".bandeau-info .etoiles p.message")
		if note.Size() != 1 {
			errors <- fmt.Errorf("Could not find a single note, found %d", note.Size())
			return
		}
		m := noteRx.FindStringSubmatch(note.Text())
		if m == nil {
			errors <- fmt.Errorf("Could not parse note with regexp %s", noteRx)
			return
		}
		noteTmp, err := strconv.ParseFloat(m[1], 64)
		if err != nil {
			errors <- fmt.Errorf("Could not parse note in `%s`", m[0])
			return
		}
		res.Note = noteTmp
		errors <- nil
	}()

	details := map[string][]*goquery.Selection{}
	previous := ""
	doc.Find("div.detail-album ul.infos-albums li").Each(func(i int, s *goquery.Selection) {
		labelSelection := s.Find("label")
		if labelSelection.Size() != 1 {
			return
		}
		label := strings.TrimSpace(labelSelection.Text())
		if len(label) == 0 {
			details[previous] = append(details[previous], s)
		}
		details[label] = []*goquery.Selection{s}
		previous = label
	})
	waitSize++
	go func() {
		sList, ok := details["Scénario :"]
		if ok == false {
			errors <- fmt.Errorf("Could not find Scenarist")
			return
		}
		for _, s := range sList {
			res.Scenarist = append(res.Scenarist, linkFromSelection(s.Find("a")))
		}
		errors <- nil
	}()

	waitSize++
	go func() {
		sList, ok := details["Dessin :"]
		if ok == false {
			errors <- fmt.Errorf("Could not find Designe")
			return
		}
		for _, s := range sList {
			res.Designer = append(res.Designer, linkFromSelection(s.Find("a")))
		}
		errors <- nil
	}()

	waitSize++
	go func() {
		sList, ok := details["Couleurs :"]
		if ok == false {
			errors <- fmt.Errorf("Could not find Colorist")
			return
		}
		for _, s := range sList {
			res.Colorist = append(res.Colorist, linkFromSelection(s.Find("a")))
		}
		errors <- nil
	}()

	errorList := make([]string, 0, waitSize)
	for i := 0; i < waitSize; i++ {
		err := <-errors
		if err != nil {
			errorList = append(errorList, err.Error())
		}
	}

	if len(errorList) != 0 {
		return nil, fmt.Errorf("Could not parse description from http://%s:%s",
			URL,
			strings.Join(append([]string{""}, errorList...), "\n * "))
	}

	f, err := os.Create(c.albumPath(ID))
	if err != nil {
		return res, err
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	return res, enc.Encode(res)
}

// GetDescription retrieves from the cache or either from www.bedetheque.com the AlbumDescription of an album
func (c *AlbumDescriptionCache) GetDescription(ID AlbumID) (*AlbumDescription, error) {
	// we should lock the cache while we are using it
	if err := c.lock.TryLock(); err != nil {
		return nil, fmt.Errorf("Could not lock %s: %s", c.lock, err)
	}
	defer c.unlockOrPanic()

	info, err := os.Stat(c.albumPath(ID))
	if err != nil {
		if os.IsNotExist(err) == false {
			return nil, err
		}
		return c.fetchAndCache(ID)
	}

	// check TTL
	if info.ModTime().Before(time.Now().Add(-c.TTL)) == true {
		return c.fetchAndCache(ID)
	}

	f, err := os.Open(c.albumPath(ID))
	if err != nil {
		return nil, err
	}
	defer f.Close()

	dec := json.NewDecoder(f)
	res := &AlbumDescription{}
	err = dec.Decode(&res)
	if err != nil {
		return nil, err
	}

	return res, nil
}