Release 2: Add validation support

After a challenge from Mike on the last version, I tried to do this
without building a whole, separate validation class.

I couldn't get message to work on the 'presence' validation, so I did a
separate validation function for it. I could have combined all of these
into one large validation function, but I decided it was more
interesting to make a number of simple validation functions instead.

source/app/assets/stylesheets/urls.css.scss

@@ -1,3 +1,6 @@
 // Place all the styles related to the Urls controller here.
 // They will automatically be included in application.css.
 // You can use Sass (SCSS) here: http://sass-lang.com/
+.error {
+    color: red;
+}

source/app/controllers/urls_controller.rb

@@ -6,16 +6,27 @@ def index
 
   def new
     # default behavior looks good
+    @target = ''
+    @save_errors = nil
   end
 
   def create
     # Actually create the new shortened url
-    target= params[:target]
+    @target = params[:target]
+    @errors = nil
 
-    @url = Url.new(target_link: target)
+    @url = Url.new(target_link: @target)
     if !@url.save
-      flash[:save_error] = ['Unable to save URL. Please try another.'];
-      flash[:target] = target
+      case
+      when @url.errors[:target_link].any?
+        @errors = @url.errors[:target_link]
+      when @url.errors[:linkid].any?
+        @errors = @url.errors[:linkid]
+      when @url.errors[:base].any?
+        @errors = @url.errors[:base]
+      else
+        @errors = ['Unable to save URL. Please try another.'];
+      end
       render 'new'
     else
       redirect_to url_path(@url.linkid)

source/app/models/url.rb

@@ -1,8 +1,43 @@
+require 'uri'
+require 'net/http'
+
 class Url < ActiveRecord::Base
   before_save   :ensure_short_link
+  validates :linkid, uniqueness: true
+  validate :target_link_not_empty, :target_link_must_be_http, :target_link_must_be_reachable
+
+  def target_link_not_empty
+    return unless errors.empty?
+    if target_link.empty?
+      errors[:target_link] << 'Target URL cannot be blank';
+    end
+  end
+
+  def target_link_must_be_http
+    return unless errors.empty?
+    unless target_link.match(%r{^https?://})
+      errors[:target_link] << 'Target URL has an unrecognized scheme';
+    end
+  end
+
+  def target_link_must_be_reachable
+    return unless errors.empty?
+    begin
+      uri = URI.parse(target_link)
+      resp = Net::HTTP.get_response(uri)
+      if resp.code.to_i >= 400
+        errors[:target_link] << 'Target URL is not found'
+      end
+    rescue URI::InvalidURIError
+      errors[:target_link] << 'Target URL is not valid'
+      return
+    rescue
+      errors[:target_link] << 'Target URL is not reachable'
+    end
+  end
 
   def ensure_short_link
-    if self.linkid.nil? || self.linkid.length == 0
+    if self.linkid.nil? || self.linkid.empty?
       self.linkid = UrlsHelper.shortened_linkid(self.target_link)
     end
   end

source/app/views/urls/new.html.erb

@@ -1,11 +1,13 @@
 <h1>URL Shortener</h1>
-<% if flash[:save_error] %>
-  <p class="error"><%= flash[:save_error] %></p>
+<% if !@errors.nil? && @errors.size > 0 %>
+  <%   @errors.each do |err| %>
+  <p class="error"><%= err %></p>
+  <% end %>
 <% end %>
 <form id="new_url" method="post" action="<%= urls_path %>">
   <input name="authenticity_token" type="hidden" value="<%= form_authenticity_token %>"/>
   <label for="#target">Target:</label>
-  <input type="text" name="target" id="target" size="100" placeholder="http://example.com/cool_page.html" value="<%= flash[:target] || '' %>">
+  <input type="text" name="target" id="target" size="100" placeholder="http://example.com/cool_page.html" value="<%= @target || '' %>">
   <button class="btn btn-primary" type="submit">Shorten</button>
 </form>
 <a href="<%= urls_path %>">Back to list</a>