module ActionDispatch
  module Journey
    # The Formatter class is used for formatting URLs. For example, parameters
    # passed to +url_for+ in rails will eventually call Formatter#generate.
    class Formatter # :nodoc:
      attr_reader :routes

      def initialize(routes)
        @routes = routes
        @cache  = nil
      end

      def generate(type, name, options, recall = {}, parameterize = nil)
        constraints = recall.merge(options)
        missing_keys = []

        match_route(name, constraints) do |route|
          parameterized_parts = extract_parameterized_parts(route, options, recall, parameterize)
          next if !name && route.requirements.empty? && route.parts.empty?

          missing_keys = missing_keys(route, parameterized_parts)
          next unless missing_keys.empty?
          params = options.dup.delete_if do |key, _|
            parameterized_parts.key?(key) || route.defaults.key?(key)
          end

          return [route.format(parameterized_parts), params]
        end

        raise Router::RoutingError.new "missing required keys: #{missing_keys}"
      end

      def clear
        @cache = nil
      end

      private

        def extract_parameterized_parts(route, options, recall, parameterize = nil)
          constraints = recall.merge(options)
          data = constraints.dup

          keys_to_keep = route.parts.reverse.drop_while { |part|
            !options.key?(part) || (options[part] || recall[part]).nil?
          } | route.required_parts

          (data.keys - keys_to_keep).each do |bad_key|
            data.delete(bad_key)
          end

          parameterized_parts = data.dup

          if parameterize
            parameterized_parts.each do |k, v|
              parameterized_parts[k] = parameterize.call(k, v)
            end
          end

          parameterized_parts.keep_if { |_, v| v  }
          parameterized_parts
        end

        def named_routes
          routes.named_routes
        end

        def match_route(name, options)
          if named_routes.key?(name)
            yield named_routes[name]
          else
            routes = non_recursive(cache, options.to_a)

            hash = routes.group_by { |_, r| r.score(options) }

            hash.keys.sort.reverse_each do |score|
              next if score < 0

              hash[score].sort_by { |i, _| i }.each do |_, route|
                yield route
              end
            end
          end
        end

        def non_recursive(cache, options)
          routes = []
          stack  = [cache]

          while stack.any?
            c = stack.shift
            routes.concat(c[:___routes]) if c.key?(:___routes)

            options.each do |pair|
              stack << c[pair] if c.key?(pair)
            end
          end

          routes
        end

        # Returns an array populated with missing keys if any are present.
        def missing_keys(route, parts)
          missing_keys = []
          tests = route.path.requirements
          route.required_parts.each { |key|
            if tests.key?(key)
              missing_keys << key unless /\A#{tests[key]}\Z/ === parts[key]
            else
              missing_keys << key unless parts[key]
            end
          }
          missing_keys
        end

        def possibles(cache, options, depth = 0)
          cache.fetch(:___routes) { [] } + options.find_all { |pair|
            cache.key?(pair)
          }.map { |pair|
            possibles(cache[pair], options, depth + 1)
          }.flatten(1)
        end

        # Returns +true+ if no missing keys are present, otherwise +false+.
        def verify_required_parts!(route, parts)
          missing_keys(route, parts).empty?
        end

        def build_cache
          root = { ___routes: [] }
          routes.each_with_index do |route, i|
            leaf = route.required_defaults.inject(root) do |h, tuple|
              h[tuple] ||= {}
            end
            (leaf[:___routes] ||= []) << [i, route]
          end
          root
        end

        def cache
          @cache ||= build_cache
        end
    end
  end
end