module Nanoc::Int
  # Represents a cache than can be used to store already compiled content,
  # to prevent it from being needlessly recompiled.
  #
  # @api private
  class CompiledContentCache < ::Nanoc::Int::Store
    def initialize(env_name: nil, items:)
      super(Nanoc::Int::Store.tmp_path_for(env_name: env_name, store_name: 'compiled_content'), 2)

      @items = items
      @cache = {}
    end

    # Returns the cached compiled content for the given item
    # representation. This cached compiled content is a hash where the keys
    # are the snapshot names and the values the compiled content at the
    # given snapshot.
    #
    # @param [Nanoc::Int::ItemRep] rep The item rep to fetch the content for
    #
    # @return [Hash<Symbol,String>] A hash containing the cached compiled
    #   content for the given item representation
    def [](rep)
      item_cache = @cache[rep.item.identifier] || {}
      item_cache[rep.name]
    end

    # Sets the compiled content for the given representation.
    #
    # @param [Nanoc::Int::ItemRep] rep The item representation for which to set
    #   the compiled content
    #
    # @param [Hash<Symbol,String>] content A hash containing the compiled
    #   content of the given representation
    #
    # @return [void]
    def []=(rep, content)
      @cache[rep.item.identifier] ||= {}
      @cache[rep.item.identifier][rep.name] = content
    end

    protected

    def data
      @cache
    end

    def data=(new_data)
      @cache = {}

      item_identifiers = Set.new(@items.map(&:identifier))

      new_data.each_pair do |item_identifier, content_per_rep|
        if item_identifiers.include?(item_identifier)
          @cache[item_identifier] ||= content_per_rep
        end
      end
    end
  end
end