iqdb: proxy iqdb searches through danbooru.

Previously the search form on the /iqdb_queries page submitted directly
to the iqdb service (karasuma.donmai.us), which redirected back to
Danbooru with the search results.

This was different than API requests, which submitted to
/iqdb_queries.json which proxied the call to iqdb through Danbooru.
Because of this, searches on the /iqdb_queries page had different
behavior than API requests. Things like filesize limits and referrer
spoofing were handled differently.

Now searches on the /iqdb_queries page submit directly to Danbooru. This
is simpler and it means that API requests and HTML requests have the
same behavior.

app/logical/iqdb_proxy.rb

@@ -1,15 +1,37 @@
 class IqdbProxy
-  def self.query(url, limit, similarity)
+  def self.search(params)
     raise NotImplementedError unless Danbooru.config.iqdbs_server.present?
 
-    limit ||= 20
-    similarity ||= 0.0
+    limit = params[:limit].presence || 20
+    limit = limit.to_i.clamp(1, 100)
+    similarity = params[:similarity].to_f.clamp(0.0, 100.0)
+
+    if params[:file].present?
+      results = query_file(params[:file], limit)
+    elsif params[:url].present?
+      url = Sources::Strategies.find(params[:url]).image_url
+      results = query_url(url, limit)
+    elsif params[:post_id].present?
+      url = Post.find(params[:post_id]).preview_file_url
+      results = query_url(url, limit)
+    else
+      results = []
+    end
+
+    results = results.select { |result| result["score"] >= similarity }.take(limit)
+    decorate_posts(results)
+  end
+
+  def self.query_url(url, limit)
     query = { url: url, limit: limit }
     response = HTTParty.get("#{Danbooru.config.iqdbs_server}/similar", query: query, **Danbooru.config.httparty_options)
+    response.parsed_response
+  end
 
-    json = decorate_posts(response.parsed_response)
-    json = json.select { |result| result["score"] >= similarity.to_f }.take(limit.to_i)
-    json
+  def self.query_file(file, limit)
+    body = { file: file, limit: limit }
+    response = HTTParty.post("#{Danbooru.config.iqdbs_server}/similar", body: body, **Danbooru.config.httparty_options)
+    response.parsed_response
   end
 
   def self.decorate_posts(json)