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restaurant-search/scraper.go

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/*
* Copyright (c) 2015 Alex Yatskov <alex@foosoft.net>
* Author: Alex Yatskov <alex@foosoft.net>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package main
import (
"log"
"net/url"
"sync"
"github.com/PuerkitoBio/goquery"
)
type review struct {
name string
address string
url string
features map[string]float64
latitude float64
longitude float64
}
type profiler interface {
index(doc *goquery.Document) (string, []string)
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review(doc *goquery.Document) (string, string, map[string]float64, error)
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}
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func makeAbsUrl(ref, base string) (string, error) {
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b, err := url.Parse(base)
if err != nil {
return "", err
}
r, err := url.Parse(ref)
if err != nil {
return "", err
}
return b.ResolveReference(r).String(), nil
}
func decodeReviews(in chan review, out chan review, cache *geoCache) {
for {
if r, ok := <-in; ok {
pos, err := cache.decode(r.address)
if err == nil {
r.latitude = pos.Latitude
r.longitude = pos.Longitude
out <- r
} else {
log.Printf("failed to decode address for %s (%v)", r.url, err)
}
} else {
close(out)
return
}
}
}
func scrapeReview(url string, out chan review, cache *webCache, group *sync.WaitGroup, prof profiler) {
defer group.Done()
doc, err := cache.load(url)
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if err != nil {
log.Printf("failed to load review at %s (%v)", url, err)
return
}
name, address, features, err := prof.review(doc)
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if err != nil {
log.Printf("failed to scrape review at %s (%v)", url, err)
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return
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}
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out <- review{name: name, address: address, features: features, url: url}
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}
func scrapeIndex(indexUrl string, out chan review, cache *webCache, prof profiler) {
doc, err := cache.load(indexUrl)
if err != nil {
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log.Printf("failed to load index at %s (%v)", indexUrl, err)
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return
}
nextIndexUrl, reviewUrls := prof.index(doc)
if err != nil {
log.Fatal(err)
}
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var group sync.WaitGroup
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for _, reviewUrl := range reviewUrls {
absUrl, err := makeAbsUrl(reviewUrl, indexUrl)
if err != nil {
log.Fatal(err)
}
group.Add(1)
go scrapeReview(absUrl, out, cache, &group, prof)
}
group.Wait()
if nextIndexUrl == "" {
close(out)
} else {
absUrl, err := makeAbsUrl(nextIndexUrl, indexUrl)
if err != nil {
log.Fatal(err)
}
scrapeIndex(absUrl, out, cache, prof)
}
}
func scrape(url string, wc *webCache, gc *geoCache, prof profiler) []review {
scrapeChan := make(chan review)
decodeChan := make(chan review)
go scrapeIndex(url, scrapeChan, wc, prof)
go decodeReviews(scrapeChan, decodeChan, gc)
var reviews []review
for {
if r, ok := <-decodeChan; ok {
reviews = append(reviews, r)
} else {
return reviews
}
}
}