module Jekyll::Hooks

def self.insert_hook(owner, event, priority, &block)
  @hook_priority[block] = [-priority, @hook_priority.size]
  @registry[owner][event] << block
end

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

def self.trigger(owner, event, *args)
  # proceed only if there are hooks to call
  hooks = @registry.dig(owner, event)
  return if hooks.nil? || hooks.empty?
  # 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