require 'multi_json'
require 'jwt'
require 'omniauth/strategies/oauth2'
require 'uri'

module OmniAuth
  module Strategies
    class GoogleOauth2 < OmniAuth::Strategies::OAuth2
      BASE_SCOPE_URL = "https://www.googleapis.com/auth/"
      BASE_SCOPES = %w[profile email openid]
      DEFAULT_SCOPE = "email,profile"

      option :name, 'google_oauth2'
      option :skip_friends, true
      option :skip_image_info, true
      option :skip_jwt, false
      option :jwt_leeway, 60
      option :authorize_options, [:access_type, :hd, :login_hint, :prompt, :request_visible_actions, :scope, :state, :redirect_uri, :include_granted_scopes, :openid_realm]

      option :client_options, {
        :site          => 'https://accounts.google.com',
        :authorize_url => '/o/oauth2/auth',
        :token_url     => '/o/oauth2/token'
      }

      def authorize_params
        super.tap do |params|
          options[:authorize_options].each do |k|
            params[k] = request.params[k.to_s] unless [nil, ''].include?(request.params[k.to_s])
          end

          raw_scope = params[:scope] || DEFAULT_SCOPE
          scope_list = raw_scope.split(" ").map {|item| item.split(",")}.flatten
          scope_list.map! { |s| s =~ /^https?:\/\// || BASE_SCOPES.include?(s) ? s : "#{BASE_SCOPE_URL}#{s}" }
          params[:scope] = scope_list.join(" ")
          params[:access_type] = 'offline' if params[:access_type].nil?
          params['openid.realm'] = params.delete(:openid_realm) unless params[:openid_realm].nil?

          session['omniauth.state'] = params[:state] if params['state']
        end
      end

      uid { raw_info['sub'] || verified_email }

      info do
        prune!({
          :name       => raw_info['name'],
          :email      => verified_email,
          :first_name => raw_info['given_name'],
          :last_name  => raw_info['family_name'],
          :image      => image_url,
          :urls => {
            'Google' => raw_info['profile']
          }
        })
      end

      extra do
        hash = {}
        hash[:id_token] = access_token['id_token']
        if !options[:skip_jwt] && !access_token['id_token'].nil?
          hash[:id_info] = JWT.decode(
            access_token['id_token'], nil, false, {
              :verify_iss => true,
              'iss' => 'accounts.google.com',
              :verify_aud => true,
              'aud' => options.client_id,
              :verify_sub => false,
              :verify_expiration => true,
              :verify_not_before => true,
              :verify_iat => true,
              :verify_jti => false,
              :leeway => options[:jwt_leeway]
            }).first
        end
        hash[:raw_info] = raw_info unless skip_info?
        hash[:raw_friend_info] = raw_friend_info(raw_info['sub']) unless skip_info? || options[:skip_friends]
        hash[:raw_image_info] = raw_image_info(raw_info['sub']) unless skip_info? || options[:skip_image_info]
        prune! hash
      end

      def raw_info
        @raw_info ||= access_token.get('https://www.googleapis.com/plus/v1/people/me/openIdConnect').parsed
      end

      def raw_friend_info(id)
        @raw_friend_info ||= access_token.get("https://www.googleapis.com/plus/v1/people/#{id}/people/visible").parsed
      end

      def raw_image_info(id)
        @raw_image_info ||= access_token.get("https://www.googleapis.com/plus/v1/people/#{id}?fields=image").parsed
      end

      def custom_build_access_token
        access_token =
        if request.xhr? && request.params['code']
          verifier = request.params['code']
          client.auth_code.get_token(verifier, get_token_options('postmessage'), deep_symbolize(options.auth_token_params || {}))
        elsif request.params['code'] && request.params['redirect_uri']
          verifier = request.params['code']
          redirect_uri = request.params['redirect_uri']
          client.auth_code.get_token(verifier, get_token_options(redirect_uri), deep_symbolize(options.auth_token_params || {}))
        elsif verify_token(request.params['access_token'])
          ::OAuth2::AccessToken.from_hash(client, request.params.dup)
        else
          verifier = request.params["code"]
          client.auth_code.get_token(verifier, get_token_options(callback_url), deep_symbolize(options.auth_token_params))
        end

        verify_hd(access_token)
        access_token
      end
      alias_method :build_access_token, :custom_build_access_token

      private

      def callback_url
        options[:redirect_uri] || (full_host + script_name + callback_path)
      end

      def get_token_options(redirect_uri)
        { :redirect_uri => redirect_uri }.merge(token_params.to_hash(:symbolize_keys => true))
      end

      def prune!(hash)
        hash.delete_if do |_, v|
          prune!(v) if v.is_a?(Hash)
          v.nil? || (v.respond_to?(:empty?) && v.empty?)
        end
      end

      def verified_email
        raw_info['email_verified'] ? raw_info['email'] : nil
      end

      def image_url
        return nil unless raw_info['picture']

        u = URI.parse(raw_info['picture'].gsub('https:https', 'https'))

        path_index = u.path.to_s.index('/photo.jpg')

        if path_index && image_size_opts_passed?
          u.path.insert(path_index, image_params)
          u.path = u.path.gsub('//', '/')
        end

        u.query = strip_unnecessary_query_parameters(u.query)

        u.to_s
      end

      def image_size_opts_passed?
        !!(options[:image_size] || options[:image_aspect_ratio])
      end

      def image_params
        image_params = []
        if options[:image_size].is_a?(Integer)
          image_params << "s#{options[:image_size]}"
        elsif options[:image_size].is_a?(Hash)
          image_params << "w#{options[:image_size][:width]}" if options[:image_size][:width]
          image_params << "h#{options[:image_size][:height]}" if options[:image_size][:height]
        end
        image_params << 'c' if options[:image_aspect_ratio] == 'square'

        '/' + image_params.join('-')
      end

      def strip_unnecessary_query_parameters(query_parameters)
        # strip `sz` parameter (defaults to sz=50) which overrides `image_size` options
        return nil if query_parameters.nil?

        params = CGI.parse(query_parameters)
        stripped_params = params.delete_if { |key| key == "sz" }

        # don't return an empty Hash since that would result
        # in URLs with a trailing ? character: http://image.url?
        return nil if stripped_params.empty?

        URI.encode_www_form(stripped_params)
      end

      def verify_token(access_token)
        return false unless access_token
        raw_response = client.request(:get, 'https://www.googleapis.com/oauth2/v3/tokeninfo',
                                      params: { access_token: access_token }).parsed
        raw_response['aud'] == options.client_id
      end

      def verify_hd(access_token)
        return true unless options.hd
        @raw_info ||= access_token.get('https://www.googleapis.com/plus/v1/people/me/openIdConnect').parsed
        allowed_hosted_domains = Array(options.hd)

        raise CallbackError.new(:invalid_hd, "Invalid Hosted Domain") unless allowed_hosted_domains.include? @raw_info['hd']
        true
      end
    end
  end
end