module Nanoc

  # A Nanoc::Page represents a page in a nanoc site. It has content and
  # attributes, as well as a path. It can also store the modification time to
  # speed up compilation.
  #
  # Each page has a list of page representations or reps (Nanoc::PageRep);
  # compiling a page actually compiles all of its representations.
  class Page

    # Default values for pages.
    DEFAULTS = {
      :custom_path  => nil,
      :extension    => 'html',
      :filename     => 'index',
      :filters_pre  => [],
      :filters_post => [],
      :layout       => 'default',
      :skip_output  => false
    }

    # The Nanoc::Site this page belongs to.
    attr_accessor :site

    # The parent page of this page. This can be nil even for non-root pages.
    attr_accessor :parent

    # The child pages of this page.
    attr_accessor :children

    # This page's raw, uncompiled content.
    attr_reader   :content

    # A hash containing this page's attributes.
    attr_accessor :attributes

    # This page's path.
    attr_reader   :path

    # The time when this page was last modified.
    attr_reader   :mtime

    # This page's list of page representations.
    attr_reader   :reps

    # Creates a new page.
    #
    # +content+:: This page's unprocessed content.
    #
    # +attributes+:: A hash containing this page's attributes.
    #
    # +path+:: This page's path.
    #
    # +mtime+:: The time when this page was last modified.
    def initialize(content, attributes, path, mtime=nil)
      # Set primary attributes
      @attributes     = attributes.clean
      @content        = content
      @path           = path.cleaned_path
      @mtime          = mtime

      # Start disconnected
      @parent         = nil
      @children       = []
      @reps           = []
    end

    # Builds the individual page representations (Nanoc::PageRep) for this
    # page.
    def build_reps
      # Get list of rep names
      rep_names_default = (@site.page_defaults.attributes[:reps] || {}).keys
      rep_names_this    = (@attributes[:reps] || {}).keys + [ :default ]
      rep_names         = rep_names_default | rep_names_this

      # Get list of reps
      reps = rep_names.inject({}) do |memo, rep_name|
        rep = (@attributes[:reps] || {})[rep_name]
        is_bad = (@attributes[:reps] || {}).has_key?(rep_name) && rep.nil?
        is_bad ? memo : memo.merge(rep_name => rep || {})
      end

      # Build reps
      @reps = []
      reps.each_pair do |name, attrs|
        @reps << PageRep.new(self, attrs, name)
      end
    end

    # Returns a proxy (Nanoc::PageProxy) for this page.
    def to_proxy
      @proxy ||= PageProxy.new(self)
    end

    # Returns the attribute with the given name.
    def attribute_named(name)
      return @attributes[name] if @attributes.has_key?(name)
      return @site.page_defaults.attributes[name] if @site.page_defaults.attributes.has_key?(name)
      return DEFAULTS[name]
    end

    # Saves the page in the database, creating it if it doesn't exist yet or
    # updating it if it already exists. Tells the site's data source to save
    # the page.
    def save
      @site.data_source.loading do
        @site.data_source.save_page(self)
      end
    end

    # Moves the page to a new path. Tells the site's data source to move the
    # page.
    def move_to(new_path)
      @site.data_source.loading do
        @site.data_source.move_page(self, new_path)
      end
    end

    # Deletes the page. Tells the site's data source to delete the page.
    def delete
      @site.data_source.loading do
        @site.data_source.delete_page(self)
      end
    end

    def inspect
      "<#{self.class} path=#{self.path}>"
    end

  end

end