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# A web crawler in Ruby
#
# This script provides a generic Spider class for crawling urls and
# recording data scraped from websites. The Spider is to be used in
# collaboration with a "processor" class that defines which pages to
# visit and how data from those pages should be consumed. In this example
# the processor is ProgrammableWeb.
#
# Usage:
# spider = ProgrammableWeb.new
# spider.results.take(10)
# => [{...}, {...}, ...]
#
# Requirements:
# Ruby 2.0+
#
require "mechanize"
require "pry"
class Spider
REQUEST_INTERVAL = 1
MAX_URLS = 1000
attr_reader :handlers
def initialize(processor, options = {})
@processor = processor
@results = []
@urls = []
@handlers = {}
@interval = options.fetch(:interval, REQUEST_INTERVAL)
@max_urls = options.fetch(:max_urls, MAX_URLS)
enqueue(@processor.root, @processor.handler)
end
def enqueue(url, method, data = {})
return if @handlers[url]
@urls << url
@handlers[url] ||= { method: method, data: data }
end
def record(data = {})
@results << data
end
def results
return enum_for(:results) unless block_given?
i = @results.length
enqueued_urls.each do |url, handler|
begin
log "Handling", url.inspect
@processor.send(handler[:method], agent.get(url), handler[:data])
if block_given? && @results.length > i
yield @results.last
i += 1
end
rescue => ex
log "Error", "#{url.inspect}, #{ex}"
end
sleep @interval if @interval > 0
end
end
private
def enqueued_urls
Enumerator.new do |y|
index = 0
while index < @urls.count && index <= @max_urls
url = @urls[index]
index += 1
next unless url
y.yield url, @handlers[url]
end
end
end
def log(label, info)
warn "%-10s: %s" % [label, info]
end
def agent
@agent ||= Mechanize.new
end
end
class ProgrammableWeb
attr_reader :root, :handler
def initialize(root: "https://programmableweb.com/apis/directory", handler: :process_index, **options)
@root = root
@handler = handler
@options = options
end
def process_index(page, data = {})
page.links_with(href: /\?page=\d+/).each do |link|
spider.enqueue(link.href, :process_index)
end
page.links_with(href: %r{/api/\w+$}).each do |link|
spider.enqueue(link.href, :process_api, name: link.text)
end
end
def process_api(page, data = {})
categories = page.search("article.node-api .tags").first.text.strip.split(/\s+/)
fields = page.search("#tabs-content .field").each_with_object({}) do |tag, results|
key = tag.search("label").text.strip.downcase.gsub(/[^\w]+/, ' ').gsub(/\s+/, "_").to_sym
val = tag.search("span").text
results[key] = val
end
spider.record data.merge(fields).merge(categories: categories)
end
def results(&block)
spider.results(&block)
end
private
def spider
@spider ||= Spider.new(self, @options)
end
end
if __FILE__ == $0
spider = ProgrammableWeb.new
spider.results.lazy.take(5).each_with_index do |result, i|
warn "%-2s: %s" % [i, result.inspect]
end
end
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