post votes: fix error handling.

* Clean up javascript.
* Return HTTP 422 instead of HTTP 500 on "you have already voted for
  this post" errors.
* In json/xml error responses, return the error message in the `message`
  field, not `reason`.
* In json/xml success responses, return the post itself instead of a
  plain `{ success: true }` object.

app/controllers/post_votes_controller.rb

@@ -1,20 +1,20 @@
 class PostVotesController < ApplicationController
   before_action :voter_only
   skip_before_action :api_check
+  respond_to :js, :json, :xml
+  rescue_with PostVote::Error, status: 422
 
   def create
     @post = Post.find(params[:post_id])
     @post.vote!(params[:score])
-  rescue PostVote::Error, ActiveRecord::RecordInvalid => x
-    @error = x
-    render status: 500
+
+    respond_with(@post)
   end
 
   def destroy
     @post = Post.find(params[:post_id])
     @post.unvote!
-  rescue PostVote::Error => x
-    @error = x
-    render status: 500
+
+    respond_with(@post)
   end
 end

app/views/post_votes/create.js.erb

@@ -1,9 +1,5 @@
-<% if @error %>
-  $(window).trigger("danbooru:notice", "<%= j @error.to_s %>");
-<% else %>
-  $(window).trigger("danbooru:notice", "Vote saved");
-  $("#score-for-post-<%= @post.id %>").html(<%= @post.score %>);
-<% end %>
+Danbooru.Utility.notice("Vote saved");
+$("#score-for-post-<%= @post.id %>").html(<%= @post.score %>);
 
 $("#vote-links-for-post-<%= @post.id %>").hide();
 $("#unvote-link-for-post-<%= @post.id %>").show();

app/views/post_votes/create.json.erb

@@ -1,5 +0,0 @@
-<% if @error %>
-  {"success": false, "reason": <%= @error.to_s.to_json.html_safe %>}
-<% else %>
-  {"success": true}
-<% end %>

app/views/post_votes/create.xml.erb

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<% if @error %>
-  <response success="false"><%= @error.to_s %></response>
-<% else %>
-  <response success="true"/>
-<% end %>

app/views/post_votes/destroy.js.erb

@@ -1,8 +1,5 @@
-<% if @error %>
-  $(window).trigger("danbooru:notice", "<%= j @error.to_s %>");
-<% else %>
-  $(window).trigger("danbooru:notice", "Unvoted successfully");
-  $("#score-for-post-<%= @post.id %>").html(<%= @post.score %>);
-<% end %>
+Danbooru.Utility.notice("Unvoted successfully");
+$("#score-for-post-<%= @post.id %>").html(<%= @post.score %>);
+
 $("#vote-links-for-post-<%= @post.id %>").show();
 $("#unvote-link-for-post-<%= @post.id %>").hide();

app/views/post_votes/destroy.json.erb

@@ -1,5 +0,0 @@
-<% if @error %>
-  {"success": false, "reason": <%= @error.to_s.to_json.html_safe %>}
-<% else %>
-  {"success": true}
-<% end %>

app/views/post_votes/destroy.xml.erb

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<% if @error %>
-  <response success="false"><%= @error.to_s %></response>
-<% else %>
-  <response success="true"/>
-<% end %>