require 'lotus/utils/class'
require 'lotus/views/default'
require 'lotus/views/null_view'

module Lotus
  # Rendering policy
  #
  # @since 0.1.0
  # @api private
  class RenderingPolicy
    STATUS  = 0
    HEADERS = 1
    BODY    = 2

    LOTUS_ACTION = 'lotus.action'.freeze

    SUCCESSFUL_STATUSES   = (200..201).freeze
    STATUSES_WITHOUT_BODY = Set.new((100..199).to_a << 204 << 205 << 301 << 302 << 304).freeze
    EMPTY_BODY            = Array.new.freeze
    RENDERABLE_FORMATS    = [:all, :html].freeze
    CONTENT_TYPE          = 'Content-Type'.freeze
    REQUEST_METHOD        = 'REQUEST_METHOD'.freeze
    HEAD                  = 'HEAD'.freeze

    def initialize(configuration)
      @controller_pattern = %r{#{ configuration.controller_pattern.gsub(/\%\{(controller|action)\}/) { "(?<#{ $1 }>(.*))" } }}
      @view_pattern       = configuration.view_pattern
      @namespace          = configuration.namespace
      @templates          = configuration.templates
    end

    def render(env, response)
      body = _render(env, response) || _render_head(env)

      response[BODY] = Array(body) unless body.nil?
      response
    end

    private
    def _render(env, response)
      if action = renderable?(env)
        _render_action(action, response) ||
          _render_status_page(action, response)
      end
    end

    def _render_action(action, response)
      if successful?(response)
        view_for(action, response).render(
          action.to_rendering
        )
      end
    end

    def _render_status_page(action, response)
      if render_status_page?(action, response)
        Lotus::Views::Default.render(@templates, response[STATUS], response: response, format: :html)
      end
    end

    def _render_head(env)
      EMPTY_BODY if head?(env)
    end

    def renderable?(env)
      !head?(env) and
        env.delete(LOTUS_ACTION)
    end

    def successful?(response)
      SUCCESSFUL_STATUSES.include?(response[STATUS])
    end

    def head?(env)
      env[REQUEST_METHOD] == HEAD
    end

    def render_status_page?(action, response)
      RENDERABLE_FORMATS.include?(action.format) &&
        !STATUSES_WITHOUT_BODY.include?(response[STATUS])
    end

    def view_for(action, response)
      if response[BODY].empty?
        captures = @controller_pattern.match(action.class.name)
        Utils::Class.load!(@view_pattern % { controller: captures[:controller], action: captures[:action] }, @namespace)
      else
        Views::NullView.new(response[BODY])
      end
    end
  end
end