module Plate
  # Post collection is an enumerable wrapper for the posts in a site.
  class PostCollection
    include Enumerable
    
    attr_accessor :categories, :tags, :archives
    
    def initialize
      @posts = []
      @categories = {}
      @tags = {}
      @archives = {}
    end
    
    # Add a post to the collection
    def <<(post)
      add(post)
    end
    
    # Add a post to the collection, then add its meta data to the summary.
    def add(post)
      return nil unless Post === post      
      @posts << post      
      process_post_meta(post)
    end
    
    # A hash of all categories in this collection with the number of posts using each.
    def category_counts
      return @category_counts if @category_counts
      
      result = {}
      
      categories.keys.each do |key|
        result[key] = categories[key].size
      end
      
      @category_counts = result
    end
    
    # A sorted array of all categories in this collection.
    def category_list
      @category_list ||= categories.keys.sort
    end
    
    # Loop through each Post
    def each
      @posts.each { |post| yield post }
    end
    
    # Returns the last post in the collection.
    #
    # Or, pass in a number to return in descending order that number of posts
    def last(*args)
      result = @posts.last(*args)
      
      if Array === result
        result.reverse!
      end
      
      result
    end
    
    # Any methods called on the collection can be passed through to the Array
    def method_missing(method, *args, &block)      
      @posts.send(method, *args, &block)
    end
    
    # Size of the posts collection
    def size
      @posts.size
    end
    
    # A hash of all tags in this collection with the number of posts using that tag.
    def tag_counts
      return @tag_counts if @tag_counts
      
      result = {}
      
      tags.keys.each do |key|
        result[key] = tags[key].size
      end
      
      @tag_counts = result
    end
    
    # A sorted array of all tag names in this collection.
    def tag_list
      @tag_list ||= tags.keys.sort
    end
    
    def to_a
      @posts
    end
    
    def years
      @years ||= archives.keys.sort
    end
    
    protected
      def process_post_meta(post)
        # load up tags
        post.tags.each do |tag|
          @tags[tag] ||= []
          @tags[tag] << post
        end
        
        # load up category
        @categories[post.category] ||= []
        @categories[post.category] << post
        
        # load up yearly, monthly, and daily archives
        @archives[post.year] ||= {}
        @archives[post.year][post.month] ||= {}
        @archives[post.year][post.month][post.day] ||= []
        @archives[post.year][post.month][post.day] << post
        
        post
      end
  end
end