module Jekyll::Hooks

def self.insert_hook(owner, event, priority, &block)
  @hook_priority[block] = "#{priority}.#{@hook_priority.size}".to_f
  @registry[owner][event] << block
end

def self.priority_value(priority)
  return priority if priority.is_a?(Fixnum)
  PRIORITY_MAP[priority] || DEFAULT_PRIORITY
end

def self.register(owners, event, priority: DEFAULT_PRIORITY, &block)
  Array(owners).each do |owner|
    register_one(owner, event, priority_value(priority), &block)
  end
end

def self.register_one(owner, event, priority, &block)
  @registry[owner] ||={
    :post_init   => [],
    :pre_render  => [],
    :post_render => [],
    :post_write  => []
  }
  unless @registry[owner][event]
    raise NotAvailable, "Invalid hook. #{owner} supports only the " \
      "following hooks #{@registry[owner].keys.inspect}"
  end
  unless block.respond_to? :call
    raise Uncallable, "Hooks must respond to :call"
  end
  insert_hook owner, event, priority, &block
end

def self.trigger(owner, event, *args)
  # proceed only if there are hooks to call
  return unless @registry[owner]
  return unless @registry[owner][event]
  # hooks to call for this owner and event
  hooks = @registry[owner][event]
  # sort and call hooks according to priority and load order
  hooks.sort_by { |h| @hook_priority[h] }.each do |hook|
    hook.call(*args)
  end
end