Refactor Reportbooru API clients.

* Combine MissedSearchService, PostViewCountService, and
  PopularSearchService into single ReportbooruService class.
* Use Danbooru::Http for these services instead of HTTParty.

app/logical/reportbooru_service.rb

@@ -0,0 +1,49 @@
+class ReportbooruService
+  attr_reader :http, :reportbooru_server
+
+  def initialize(http: Danbooru::Http.new, reportbooru_server: Danbooru.config.reportbooru_server)
+    @reportbooru_server = reportbooru_server
+    @http = http
+  end
+
+  def enabled?
+    reportbooru_server.present?
+  end
+
+  def missed_search_rankings(expires_in: 1.minutes)
+    raise NotImplementedError, "Reportbooru not configured, missed searches not available." unless enabled?
+
+    response = http.cache(expires_in).get("#{reportbooru_server}/missed_searches")
+    return [] if response.status != 200
+
+    body = response.to_s.force_encoding("utf-8")
+    body.lines.map(&:split).map { [_1, _2.to_i] }
+  end
+
+  def post_search_rankings(date = Date.today, expires_in: 1.minutes)
+    raise NotImplementedError, "Reportbooru not configured, popular searches not available." unless enabled?
+
+    response = http.cache(expires_in).get("#{reportbooru_server}/post_searches/rank?date=#{date}")
+    return [] if response.status != 200
+    JSON.parse(response.to_s.force_encoding("utf-8"))
+  end
+
+  def post_view_rankings(date = Date.today, expires_in: 1.minutes)
+    raise NotImplementedError, "Reportbooru not configured, post views not available." unless enabled?
+
+    response = http.get("#{reportbooru_server}/post_views/rank?date=#{date}")
+    return [] if response.status != 200
+    JSON.parse(response.to_s.force_encoding("utf-8"))
+  end
+
+  def popular_searches(date = Date.today, limit: 100)
+    ranking = post_search_rankings(date)
+    ranking = post_search_rankings(date.yesterday) if ranking.blank?
+    ranking.take(limit).map(&:first)
+  end
+
+  def popular_posts(date = Date.today, limit: 100)
+    ranking = post_view_rankings(date)
+    ranking.take(limit).map { |x| Post.find(x[0]) }
+  end
+end