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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"
)
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type restaurant struct {
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name string
address string
url string
features map[string]float64
latitude float64
longitude float64
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closestStnName string
closestStnDist float64
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}
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type scraper interface {
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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
}
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func decodeReviews(in chan restaurant, out chan restaurant, gc *geoCache) {
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for {
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if res, ok := <-in; ok {
pos, err := gc.decode(res.address)
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if err == nil {
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res.latitude = pos.Latitude
res.longitude = pos.Longitude
out <- res
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} else {
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log.Printf("failed to decode address for %s (%v)", res.url, err)
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}
} else {
close(out)
return
}
}
}
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func scrapeReview(url string, out chan restaurant, wc *webCache, group *sync.WaitGroup, scr scraper) {
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defer group.Done()
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doc, err := wc.load(url)
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if err != nil {
log.Printf("failed to load review at %s (%v)", url, err)
return
}
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name, address, features, err := scr.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 <- restaurant{
name: name,
address: address,
features: features,
url: url}
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}
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func scrapeIndex(indexUrl string, out chan restaurant, wc *webCache, scr scraper) {
doc, err := wc.load(indexUrl)
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if err != nil {
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log.Printf("failed to load index at %s (%v)", indexUrl, err)
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return
}
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nextIndexUrl, reviewUrls := scr.index(doc)
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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)
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go scrapeReview(absUrl, out, wc, &group, scr)
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}
group.Wait()
if nextIndexUrl == "" {
close(out)
} else {
absUrl, err := makeAbsUrl(nextIndexUrl, indexUrl)
if err != nil {
log.Fatal(err)
}
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scrapeIndex(absUrl, out, wc, scr)
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}
}
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func scrape(url string, wc *webCache, gc *geoCache, scr scraper) []restaurant {
out := make(chan restaurant)
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in := make(chan restaurant)
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go scrapeIndex(url, in, wc, scr)
go decodeReviews(in, out, gc)
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var results []restaurant
for {
if res, ok := <-out; ok {
results = append(results, res)
} else {
return results
}
}
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}