discourse/lib/route_matcher.rb

# frozen_string_literal: true

class RouteMatcher
  PATH_PARAMETERS ||= "_DISCOURSE_REQUEST_PATH_PARAMETERS"

  attr_reader :actions, :params, :methods, :aliases, :formats, :allowed_param_values

  def initialize(
    actions: nil,
    params: nil,
    methods: nil,
    formats: nil,
    aliases: nil,
    allowed_param_values: nil
  )
    @actions = Array(actions) if actions
    @params = Array(params) if params
    @methods = Array(methods) if methods
    @formats = Array(formats) if formats
    @aliases = aliases
    @allowed_param_values = allowed_param_values
  end

  # Return an identical route matcher, with the allowed_param_values replaced
  def with_allowed_param_values(new_allowed_param_values)
    RouteMatcher.new(
      actions: actions,
      params: params,
      methods: methods,
      formats: formats,
      aliases: aliases,
      allowed_param_values: new_allowed_param_values,
    )
  end

  def match?(env:)
    request = ActionDispatch::Request.new(env)

    action_allowed?(request) && params_allowed?(request) && method_allowed?(request) &&
      format_allowed?(request)
  end

  private

  def action_allowed?(request)
    return true if actions.nil? # actions are unrestricted

    # message_bus is not a rails route, special handling
    return true if actions.include?("message_bus") && request.fullpath =~ %r{\A/message-bus/.*/poll}

    path_params = path_params_from_request(request)
    actions.include? "#{path_params[:controller]}##{path_params[:action]}"
  end

  def params_allowed?(request)
    return true if params.nil? || allowed_param_values.blank? # params are unrestricted

    requested_params = request.parameters

    params.all? do |param|
      param_alias = aliases&.[](param)
      allowed_values = [allowed_param_values.fetch(param.to_s, [])].flatten

      value = requested_params[param.to_s]
      alias_value = requested_params[param_alias.to_s]

      return false if value.present? && alias_value.present?

      value = value || alias_value
      value = extract_category_id(value) if param_alias == :category_slug_path_with_id

      allowed_values.blank? || allowed_values.include?(value)
    end
  end

  def extract_category_id(category_slug_with_id)
    parts = category_slug_with_id.split("/")
    !parts.empty? && parts.last =~ /\A\d+\Z/ ? parts.pop : nil
  end

  def method_allowed?(request)
    return true if methods.nil?
    request_method = request.request_method&.downcase&.to_sym
    methods.include?(request_method)
  end

  def format_allowed?(request)
    return true if formats.nil?
    request_format = request.formats&.first&.symbol
    formats.include?(request_format)
  end

  def path_params_from_request(request)
    if request.env[ActionDispatch::Http::Parameters::PARAMETERS_KEY].nil?
      # We need to manually recognize the path when Rails hasn't done that yet. That can happen when
      # the matcher gets called in a Middleware before the controller did its work.
      # We store the result of `recognize_path` in a custom env key, so that we don't change
      # some Rails behavior by accident.
      request.env[PATH_PARAMETERS] ||= begin
        Rails.application.routes.recognize_path(request.path_info)
      rescue ActionController::RoutingError
        {}
      end
    end

    request.path_parameters.presence || request.env[PATH_PARAMETERS] || {}
  end
end