module Plate
  # A model for each blog post
  class Post < Page
    # Returns the category for this blog post. If no category is given in the meta
    # information, then the value for config[:default_category] is used.
    #
    # If no default category has been given, this will default to "Posts"
    def category
      default = self.meta[:category] || self.site.default_category
    end
    
    # Category for this post, formatted to be URL-friendly
    def category_for_url
      self.category.to_s.dasherize.parameterize
    end
    
    # Returns the date for this post, either from the filename or meta hash.
    # If both are provided, the meta information takes precedence.
    def date
      result = nil
      
      if self.meta[:date]
        result = self.meta[:date].to_s
      elsif self.basename =~ /^(\d{4}-\d{2}-\d{2})-/
        result = $1.to_s
      end
      
      begin
        return Time.parse(result)
      rescue Exception => e
        self.site.log("  ** Problem reading date for file #{relative_file} (#{e.message}). Post skipped.")        
      end
      
      raise NoPostDateProvided
    end
    
    def day
      date.strftime('%d')
    end
    
    # The full file path of where this file will be written to. (Relative to site root)
    def file_path
      "#{permalink}/index.html"
    end
    
    def inspect
      "#<#{self.class}:0x#{object_id.to_s(16)} name=#{name.to_s.inspect} date=#{date.to_s}>"
    end
    
    def month
      date.strftime('%m')  
    end
    
    # Return the [relative] path for this post. Uses the +permalink_template+
    # variable as the method for converting post data into a URL.
    #
    # The permalink_template can be set in the global config named 'permalink'.
    #
    # Available options are:
    # 
    # * `date` - The date of this post, formatted as YYYY-MM-DD
    # * `title` - The title of this post, formatted for URL
    # * `slug` - The filename slug
    # * `year` - The 4-digit year of this post
    # * `month` - The 2-digit month for this post
    # * `day` - The 2-digit day of month for this post
    # * `category` - The category for this post
    #
    # All values are formatted to be URL-safe. (No spaces, underscores or weird characters.)
    def permalink(cache_buster = false)
      return @permalink if @permalink and !cache_buster
      
      date = self.date
  
      # All of these variables can be put into a URL
      permalink_attributes = { 
        "date" => date.strftime('%Y-%m-%d'),
        "slug" => slug,
        "title" => title_for_url,
        "year" => year,
        "month" => month,
        "day" => day,
        "category" => category_for_url
      }
      
      # Copy the permalink template as a starting point
      result = permalink_template.clone
      
      # Replace all variables from the attributes into the template
      permalink_attributes.each { |key, value| result.gsub!(/:#{Regexp.escape(key)}/, value) }
       
      # Remove any double slashes
      result.gsub!(/\/\//, '/')
      
      # Remove file extensions, and cleanup URL
      result = result.split('/').reject{ |segment| segment =~ /^\.+$/ }.join('/')
      
      @permalink = result
    end
    
    # The template to use when generating the permalink.
    def permalink_template
      self.site.options[:permalink] || '/:category/:year/:month/:slug'
    end

    # Returns the URL slug to use for this blog post. 
    #
    # This will convert the file name from a format like:
    #
    #     2012-01-01-post-name.md
    #
    # To simply:
    # 
    #     post-name
    def slug
      name = self.basename.to_s.downcase.gsub(/^(\d{4}-\d{2}-\d{2})-/, '').split('.')[0]
      name.dasherize.parameterize
    end
    
    # Utility method to sanitize tags output. Tags are returned as an array.
    def tags
      @tags ||= (Array === self.meta[:tags] ? self.meta[:tags] : self.meta[:tags].to_s.strip.split(',')).collect(&:strip).sort
    end
    
    def year
      date.strftime('%Y')
    end
    
    # Compare two posts, by date.
    def <=>(other)
      self.date <=> other.date
    end
  end
end