require 'sitediff/uriwrapper'
require 'typhoeus'

class SiteDiff
class Fetch
  # Cache is a cache object, see sitediff/cache
  # Paths is a list of sub-paths
  # Tags is a hash of tag names => base URLs.
  def initialize(cache, paths, tags)
    @cache = cache
    @paths = paths
    @tags = tags
  end

  # Fetch all the paths, once per tag.
  # When a path has been fetched for every tag, block will be called with the
  # path, and a hash of tag => UriWrapper::ReadResult objects.
  def run(&block)
    @callback = block
    @hydra = Typhoeus::Hydra.new(max_concurrency: 3)
    @paths.each { |path| queue_path(path) }
    @hydra.run
  end

private
  # Queue a path for fetching
  def queue_path(path)
    results = {}

    @tags.each do |tag, base|
      if res = @cache.get(tag, path)
        results[tag] = res
        process_results(path, results)
      elsif !base
        # We only have the cache, but this item isn't cached!
        results[tag] = UriWrapper::ReadResult.error("Not cached")
        process_results(path, results)
      else
        uri = UriWrapper.new(base + path)
        uri.queue(@hydra) do |res|
          @cache.set(tag, path, res)
          results[tag] = res
          process_results(path, results)
        end
      end
    end
  end

  # Process fetch results
  def process_results(path, results)
    return unless results.size == @tags.size
    @callback[path, results]
  end
end
end