class OpenAPIParser::PathItemFinder
  # @param [OpenAPIParser::Schemas::Paths] paths
  def initialize(paths)
    @root = PathNode.new('/')
    @paths = paths

    @paths.path.each { |path, _path_item_object| @root.register_path_node(path.split("/"), path) }
  end

  # @param [String, Symbol] http_method like (get, post .... allow symbol)
  # @param [String] request_path
  # return operation_object, original_path, path_params
  def operation_object(http_method, request_path)
    if (path_item_object = @paths.path[request_path])
      if (op = path_item_object.operation(http_method))
        return op, request_path, {} # find no path_params path
      end
    end

    # check with path_params
    parse_request_path(http_method, request_path)
  end

  class PathNode
    attr_accessor :full_path, :name

    def initialize(name)
      @name = name
      @children = Hash.new {|h, k| h[k] = PathNode.new(k) }
      @path_template_node = nil # we can't initialize because recursive initialize...
      @full_path = nil
    end

    def register_path_node(splited_path, full_path)
      if splited_path.empty?
        @full_path = full_path
        return
      end

      path_name = splited_path.shift

      child = path_template?(path_name) ? path_template_node(path_name) : children[path_name]
      child.register_path_node(splited_path, full_path)
    end

    # @return [String, nil] and Hash
    def find_full_path(splited_path)
      return [@full_path, {}] if splited_path.empty?

      path_name = splited_path.shift

      # when ambiguous matching like this
      # /{entity}/me
      # /books/{id}
      # OpenAPI3 depend on the tooling so we use concrete one (using /books/)

      path_params = {}
      if children.key?(path_name)
        child = children[path_name]
      else
        child = path_template_node(path_name)
        path_params = {"#{child.name}" =>path_name}
      end

      ret, other_path_params = child.find_full_path(splited_path)
      [ret, path_params.merge(other_path_params)]
    end

    private

    attr_reader :children

    def path_template_node(path_name)
      @path_template_node ||= PathNode.new(path_name[1..(path_name.length-2)]) # delete {} from {name}
    end

    def path_template?(path_name)
      path_name.start_with?('{') && path_name.end_with?('}')
    end
  end

  private

  def parse_request_path(http_method, request_path)
    original_path, path_params = @root.find_full_path(request_path.split("/"))
    return nil, nil, {} unless original_path # # can't find

    path_item_object = @paths.path[original_path]
    obj = path_item_object.operation(http_method.to_s)

    [obj, original_path, path_params]
  end
end