iqdb: delete leftover unused code.

* Delete unused Iqdb::Download module.
* Fix N+1 query in decorate_posts.
* /iqdb_queries: Raise max value of `limit` param to 1000.

app/logical/iqdb_proxy.rb

@@ -1,19 +1,24 @@
 class IqdbProxy
-  def self.search(params)
-    raise NotImplementedError unless Danbooru.config.iqdbs_server.present?
+  class Error < StandardError; end
 
-    limit = params[:limit].presence || 20
-    limit = limit.to_i.clamp(1, 100)
+  def self.enabled?
+    Danbooru.config.iqdbs_server.present?
+  end
+
+  def self.search(params)
+    raise NotImplementedError, "the IQDBs service isn't configured" unless enabled?
+
+    limit = params[:limit]&.to_i&.clamp(1, 1000) || 20
     similarity = params[:similarity].to_f.clamp(0.0, 100.0)
 
     if params[:file].present?
-      results = query_file(params[:file], limit)
+      results = query(file: params[:file], limit: limit)
     elsif params[:url].present?
       url = Sources::Strategies.find(params[:url]).image_url
-      results = query_url(url, limit)
+      results = query(url: url, limit: limit)
     elsif params[:post_id].present?
       url = Post.find(params[:post_id]).preview_file_url
-      results = query_url(url, limit)
+      results = query(url: url, limit: limit)
     else
       results = []
     end
@@ -22,26 +27,19 @@ class IqdbProxy
     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
-
-  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)
+  def self.query(params)
+    response = HTTParty.post("#{Danbooru.config.iqdbs_server}/similar", body: params, **Danbooru.config.httparty_options)
+    raise Error, "HTTP error: #{response.code} #{response.message}" unless response.success?
     response.parsed_response
   end
 
   def self.decorate_posts(json)
-    json.map do |x|
-      begin
-        x["post"] = Post.find(x["post_id"])
-        x
-      rescue ActiveRecord::RecordNotFound
-        nil
-      end
+    post_ids = json.map { |match| match["post_id"] }
+    posts = Post.where(id: post_ids).group_by(&:id).transform_values(&:first)
+
+    json.map do |match|
+      post = posts.fetch(match["post_id"], nil)
+      match.with_indifferent_access.merge(post: post) if post
     end.compact
   end
 end