module SecureHeaders
  SCRIPT_HASH_CONFIG_FILE = 'config/script_hashes.yml'
  HASHES_ENV_KEY = 'secure_headers.script_hashes'

  module Configuration
    class << self
      attr_accessor :hsts, :x_frame_options, :x_content_type_options,
        :x_xss_protection, :csp, :x_download_options, :script_hashes,
        :x_permitted_cross_domain_policies

      def configure &block
        instance_eval &block
        if File.exists?(SCRIPT_HASH_CONFIG_FILE)
          ::SecureHeaders::Configuration.script_hashes = YAML.load(File.open(SCRIPT_HASH_CONFIG_FILE))
        end
      end
    end
  end

  class << self
    def append_features(base)
      base.module_eval do
        extend ClassMethods
        include InstanceMethods
      end
    end
  end

  module ClassMethods
    attr_writer :secure_headers_options
    def secure_headers_options
      if @secure_headers_options
        @secure_headers_options
      elsif superclass.respond_to?(:secure_headers_options) # stop at application_controller
        superclass.secure_headers_options
      else
        {}
      end
    end

    def ensure_security_headers options = {}
      self.secure_headers_options = options
      before_filter :prep_script_hash
      before_filter :set_hsts_header
      before_filter :set_x_frame_options_header
      before_filter :set_csp_header
      before_filter :set_x_xss_protection_header
      before_filter :set_x_content_type_options_header
      before_filter :set_x_download_options_header
      before_filter :set_x_permitted_cross_domain_policies_header
    end

    # we can't use ||= because I'm overloading false => disable, nil => default
    # both of which trigger the conditional assignment
    def options_for(type, options)
      options.nil? ? ::SecureHeaders::Configuration.send(type) : options
    end
  end

  module InstanceMethods
    def set_security_headers(options = self.class.secure_headers_options)
      set_csp_header(request, options[:csp])
      set_hsts_header(options[:hsts])
      set_x_frame_options_header(options[:x_frame_options])
      set_x_xss_protection_header(options[:x_xss_protection])
      set_x_content_type_options_header(options[:x_content_type_options])
      set_x_download_options_header(options[:x_download_options])
      set_x_permitted_cross_domain_policies_header(options[:x_permitted_cross_domain_policies])
    end

    # set_csp_header - uses the request accessor and SecureHeader::Configuration settings
    # set_csp_header(+Rack::Request+) - uses the parameter and and SecureHeader::Configuration settings
    # set_csp_header(+Hash+) - uses the request accessor and options from parameters
    # set_csp_header(+Rack::Request+, +Hash+)
    def set_csp_header(req = nil, config=nil)
      if req.is_a?(Hash) || req.is_a?(FalseClass)
        config = req
      end

      config = self.class.secure_headers_options[:csp] if config.nil?
      config = self.class.options_for :csp, config

      return if config == false

      if config && config[:script_hash_middleware]
        ContentSecurityPolicy.add_to_env(request, self, config)
      else
        csp_header = ContentSecurityPolicy.new(config, :request => request, :controller => self)
        set_header(csp_header)
      end
    end


    def prep_script_hash
      if ::SecureHeaders::Configuration.script_hashes
        @script_hashes = ::SecureHeaders::Configuration.script_hashes.dup
        ActiveSupport::Notifications.subscribe("render_partial.action_view") do |event_name, start_at, end_at, id, payload|
          save_hash_for_later payload
        end

        ActiveSupport::Notifications.subscribe("render_template.action_view") do |event_name, start_at, end_at, id, payload|
          save_hash_for_later payload
        end
      end
    end

    def save_hash_for_later payload
      matching_hashes = @script_hashes[payload[:identifier].gsub(Rails.root.to_s + "/", "")] || []

      if payload[:layout]
        # We're assuming an html.erb layout for now. Will need to handle mustache too, just not sure of the best way to do this
        layout_hashes = @script_hashes[File.join("app", "views", payload[:layout]) + '.html.erb']

        matching_hashes << layout_hashes if layout_hashes
      end

      if matching_hashes.any?
        request.env[HASHES_ENV_KEY] = ((request.env[HASHES_ENV_KEY] || []) << matching_hashes).flatten
      end
    end

    def set_x_frame_options_header(options=self.class.secure_headers_options[:x_frame_options])
      set_a_header(:x_frame_options, XFrameOptions, options)
    end

    def set_x_content_type_options_header(options=self.class.secure_headers_options[:x_content_type_options])
      set_a_header(:x_content_type_options, XContentTypeOptions, options)
    end

    def set_x_xss_protection_header(options=self.class.secure_headers_options[:x_xss_protection])
      set_a_header(:x_xss_protection, XXssProtection, options)
    end

    def set_hsts_header(options=self.class.secure_headers_options[:hsts])
      return unless request.ssl?
      set_a_header(:hsts, StrictTransportSecurity, options)
    end

    def set_x_download_options_header(options=self.class.secure_headers_options[:x_download_options])
      set_a_header(:x_download_options, XDownloadOptions, options)
    end

    def set_x_permitted_cross_domain_policies_header(options=self.class.secure_headers_options[:x_permitted_cross_domain_policies])
      set_a_header(:x_permitted_cross_domain_policies, XPermittedCrossDomainPolicies, options)
    end

    private

    def set_a_header(name, klass, options=nil)
      options = self.class.options_for name, options
      return if options == false

      header = klass.new(options)
      set_header(header)
    end

    def set_header(name_or_header, value=nil)
      if name_or_header.is_a?(Header)
        header = name_or_header
        response.headers[header.name] = header.value
      else
        response.headers[name_or_header] = value
      end
    end
  end
end


require "secure_headers/version"
require "secure_headers/header"
require "secure_headers/headers/content_security_policy"
require "secure_headers/headers/x_frame_options"
require "secure_headers/headers/strict_transport_security"
require "secure_headers/headers/x_xss_protection"
require "secure_headers/headers/x_content_type_options"
require "secure_headers/headers/x_download_options"
require "secure_headers/headers/x_permitted_cross_domain_policies"
require "secure_headers/railtie"
require "secure_headers/hash_helper"
require "secure_headers/view_helper"