module Radius
  module LibraryTags
    include Radiant::Taggable
    include TaggableHelper
  
    class TagError < StandardError; end

    ############### tags for use on library pages
                  # usually to build a faceted browser

    tag "library" do |tag|
      raise TagError, "library:* tags can only be used on a LibraryPage" unless tag.locals.page && tag.locals.page.is_a?(LibraryPage)
      tag.expand
    end

    desc %{
      Displays a list of the tags that can be used to narrow the set of results displayed. This begins as a list of 
      all available tags, and as they are chosen it shrinks to show only the coincident tags that will further reduce the set.
      
      This is normally used to display a list or cloud of facets that can be added to a search.
      
      <pre><code>
        <r:library:tags:each><li><r:tag:link /></li></r:library:tags:each>
        <r:library:tags:list />
        <r:library:tags:cloud />
      </code></pre>

      To show only those tags attached to a particular kind of object, supply a 'for' parameter. 
      The parameter can be 'pages', 'assets' or the plural of any asset type. If you're displaying an image gallery,
      you may want to start with a cloud of all the tags that have been applied to images:
      
      <pre><code>
        <r:library:tags for="images" />
      </code></pre>
      
      You can still display pages associated with those tags, but the list will not include tags that only have pages.
    }
    tag "library:tags" do |tag|
      tag.locals.tags = _get_coincident_tags(tag).sort
      tag.expand
    end
    tag "library:tags:each" do |tag|
      tag.render('each_tag', tag.attr.dup, &tag.block)
    end
    tag "library:tags:list" do |tag|
      tag.render('tag_list', tag.attr.dup)
    end
    tag "library:tags:cloud" do |tag|
      tag.render('tag_cloud', tag.attr.dup)
    end
    
    desc %{
      Expands if there are is more than one tag to show. 
      
      *Usage:* 
      <pre><code>
        <r:library:if_tags>
          Displaying items tagged with all of <r:requested_tags />
        <r:library:if_tags>
      </code></pre>
    }
    tag "library:if_tags" do |tag|
      tag.locals.tags = _get_coincident_tags(tag).sort
      tag.expand if tag.locals.tags.length > 1
    end
    desc %{
      Expands if are is one or no tag to show. 
      
      *Usage:* 
      <pre><code>
        <r:library:unless_tags>That's your lot.</r:library:unless_tags>
      </code></pre>
    }
    tag "library:unless_tags" do |tag|
      tag.locals.tags = _get_coincident_tags(tag).sort
      tag.expand if tag.locals.tags.length > 1
    end
        
    desc %{
      Displays a list of the tags requested by the user.
      To offer links that remove the tag from the current set, these will both work:
      
      *Usage:* 
      <pre><code>
        <r:library:requested_tags:each><li><r:tag:unlink /></li></r:library:requested_tags:each>
        <r:library:requested_tags />
      </code></pre>
    }
    tag "library:requested_tags" do |tag|
      tag.locals.tags = _get_requested_tags(tag).sort
      if tag.double?
        tag.expand
      else
        tag.render('tags:unlink_list', tag.attr.dup)
      end
    end
    tag "library:requested_tags:each" do |tag|
      tag.render('each_tag', tag.attr.dup, &tag.block)
    end

    desc %{
      Expands if any tags have been specified:
      
      *Usage:* 
      <pre><code>
        <r:library:if_requested_tags>
          Displaying items tagged with all of <r:requested_tags />
        <r:library:if_requested_tags>
      </code></pre>
    }
    tag "library:if_requested_tags" do |tag|
      tag.locals.tags = _get_requested_tags(tag).sort
      tag.expand if tag.locals.tags.any?
    end
    
    desc %{
      Expands if no tags have been specified:
      
      *Usage:* 
      <pre><code>
        <r:library:unless_requested_tags>
          Showing everything. Choose a tag to start narrowing down the list.
        <r:library:unless_requested_tags>
      </code></pre>
    }
    tag "library:unless_requested_tags" do |tag|
      tag.expand unless _get_requested_tags(tag).any?
    end

    desc %{
      Displays a list of the pages associated with the current tag set. If no tags are specified, this will show all pages.
      You can use all the usual r:page tags within the list.
      
      :by, :order, :limit, :offset, :status and all the usual list-control attributes are obeyed.
      
      To paginate the list, set paginated="true" and, optionally, per_page="xx".
      
      *Usage:* 
      <pre><code>
        <r:library:pages:each><li><r:link /><br /><r:content part="description" /></li></r:library:pages:each>
      </code></pre>
    }
    tag "library:pages" do |tag|
      tag.locals.pages = _get_pages(tag)
      tag.expand
    end
    tag "library:pages:each" do |tag|
      tag.render('page_list', tag.attr.dup, &tag.block)       # r:page_list is defined in taggable
    end

    desc %{
      Expands if there are any pages associated with all of the current tag set.
      
      *Usage:* 
      <pre><code>
        <r:library:if_pages><h2>Pages</h2>...</r:library:if_pages>
      </code></pre>
    }
    tag "library:if_pages" do |tag|
      tag.expand if _get_pages(tag).any?
    end

    desc %{
      Displays a list of the assets associated with the current tag set. If no tags are specified, this will show all assets.
      You can use all the usual r:assets tags within the list.
      
      By, order, limit and offset attributes are obeyed. The default is to sort by creation date, descending.
      
      To paginate the list, set paginated="true" and, optionally, per_page="xx".
      
      *Usage:* 
      <pre><code>
        <r:library:assets:each><li><r:assets:thumbnail /></li></r:library:assets:each>
      </code></pre>
    }
    tag "library:assets" do |tag|
      tag.expand
    end
    tag "library:assets:each" do |tag|
      tag.locals.assets = _get_assets(tag)
      tag.render('asset_list', tag.attr.dup, &tag.block)
    end

    desc %{
      Expands if there are any assets associated with all of the current tag set.
      
      *Usage:* 
      <pre><code>
        <r:library:if_assets><h2>Assets</h2>...</r:library:if_assets>
      </code></pre>
    }
    tag "library:if_assets" do |tag|
      tag.expand if _get_assets(tag).any?
    end

    Asset.known_types.each do |type|
      these = type.to_s.pluralize
      
      desc %{
        Displays a list of the all the #{these} associated with the current tag set. If no tags are specified, this will show all such assets.
        You can use all the usual r:assets tags within the list.

        *Usage:* 
        <pre><code>
          <r:library:#{these}:each><li><r:assets:link /></li></r:library:#{these}:each>
        </code></pre>
      }
      tag "library:#{these}" do |tag|
        tag.expand
      end
      tag "library:#{these}:each" do |tag|
        tag.locals.assets = _get_assets(tag).send(these.to_sym)
        tag.render('asset_list', tag.attr.dup, &tag.block)
      end

      desc %{
        Expands if there are any #{these} associated with all of the current tag set.

        *Usage:* 
        <pre><code>
          <r:library:if_#{these}><h2>#{these.titlecase}</h2>...</r:library:if_#{these}>
        </code></pre>
      }
      tag "library:if_#{these}" do |tag|
        tag.locals.assets = _get_assets(tag).send(these.to_sym)
        tag.expand if tag.locals.assets.any?
      end
    end

    ############### extra tags:* tags that only make sense on library or other faceting pages

    desc %{
      Makes a link that adds the current tag to the active set. Other options are passed through as usual.
      If the present page is not a library page, or similar, the link will be directed to the first available
      library page. You can override this behavior by specifying a 'base' parameter, which will force that  
      path prefix regardless of what page it designates, if any. Remote urls are also possible.

      *Usage:* 
      <pre><code><r:tag:link base='/library' /></code></pre>
    }
    tag 'tag:link' do |tag|
      options = tag.attr.dup
      options['class'] ||= 'facet'
      anchor = options['anchor'] ? "##{options.delete('anchor')}" : ''
      attributes = options.inject(' ') { |s, (k, v)| s << %{#{k.downcase}="#{v}" } }.strip
      text = tag.double? ? tag.expand : tag.render('tag:name')
      if tag.locals.page.respond_to?(:requested_tags)
        href = tag.locals.page.path(tag.locals.page.requested_tags + [tag.locals.tag])
      elsif base_path = options.delete('base') 
        href = clean_path(base_path + '/-' + tag.locals.tag.clean_title)
      elsif library = LibraryPage.first
        href = library.path([tag.locals.tag])
      else 
        raise TagError "cannot find a LibraryPage to link to."
      end
      
      %{<a href="#{href}#{anchor}"#{attributes}>#{text}</a>}
    end

    desc %{
      Summarises in a sentence the list of attached, with each one presented as a faceting link.
    }    
    tag 'tags:link_list' do |tag| 
      _get_requested_tags(tag).map { |t|
        tag.locals.tag = t
        tag.render('tag:link', tag.attr.dup)
      }.join(' | ')
    end

    desc %{
      Makes a link that removes the current tag from the active set. Other options as for tag:link. 
      This only really makes sense in the context of a requested_tags list, since no other tag can be unlinked.

      *Usage:* 
      <pre><code><r:requested_tags:each><r:tag:unlink base='/library' /></r:requested_tags:each></code></pre>
    }
    tag 'tag:unlink' do |tag|
      raise TagError "unlinking a tag requires a library page or similar" unless tag.locals.page.respond_to?(:requested_tags)

      options = tag.attr.dup
      options['class'] ||= 'defacet'
      anchor = options['anchor'] ? "##{options.delete('anchor')}" : ''
      attributes = options.inject(' ') { |s, (k, v)| s << %{#{k.downcase}="#{v}" } }.strip
      text = tag.double? ? tag.expand : tag.render('tag:name')
      href = tag.locals.page.path(tag.locals.page.requested_tags - [tag.locals.tag])
      %{<a href="#{href}#{anchor}"#{attributes}>#{text}</a>}
    end

    desc %{
      Summarises in a sentence the list of tags currently active, with each one presented as a defaceting link.
    }    
    tag 'tags:unlink_list' do |tag| 
      requested = _get_requested_tags(tag)     
      if requested.any?
        requested.map { |t|
          tag.locals.tag = t
          tag.render('tag:unlink', tag.attr.dup)
        }.to_sentence
      else
        ""
      end
    end

  private

    def _get_requested_tags(tag)
      tag.locals.page.requested_tags
    end

    def _get_coincident_tags(tag)
      requested = _get_requested_tags(tag)
      limit = tag.attr['limit'] || 50
      if requested.any?
        Tag.coincident_with(requested)
      else
        Tag.most_popular(limit)
      end
    end

    # a bit of extra logic so that in the absence of any requested tags we default to all, not none
  
    def _default_library_find_options
      {
        :by => 'created_at',
        :order => 'desc'
      }
    end
  
    def _get_pages(tag)
      options = children_find_options(tag)
      requested = _get_requested_tags(tag)
      pages = Page.scoped(options)
      pages = pages.tagged_with(requested) if requested.any?
      pages
    end

    def _get_assets(tag)
      options = asset_find_options(tag)
      requested = _get_requested_tags(tag)
      assets = Asset.scoped(options)
      assets = assets.tagged_with(requested) if requested.any?
      assets
    end
  
    # duplicate of children_find_options except:
    # no virtual or status options
    # defaults to chronological descending
  
    def asset_find_options(tag)
      attr = tag.attr.symbolize_keys

      options = {}

      [:limit, :offset].each do |symbol|
        if number = attr[symbol]
          if number =~ /^\d{1,4}$/
            options[symbol] = number.to_i
          else
            raise TagError.new("`#{symbol}' attribute of `each' tag must be a positive number between 1 and 4 digits")
          end
        end
      end

      by = (attr[:by] || 'created_at').strip
      order = (attr[:order] || 'desc').strip
      order_string = ''
      if self.attributes.keys.include?(by)
        order_string << by
      else
        raise TagError.new("`by' attribute of `each' tag must be set to a valid field name")
      end
      if order =~ /^(asc|desc)$/i
        order_string << " #{$1.upcase}"
      else
        raise TagError.new(%{`order' attribute of `each' tag must be set to either "asc" or "desc"})
      end
      options[:order] = order_string
      options
    end

  end
end