module Timer
  class TimerNode
    attr_reader :timer
    attr_reader :label

    def initialize(timer, label)
      @timer, @label = timer, label
    end

    def label_width() label&.size || 0 end
    def value_width() raise NotThis end

    def total() raise NotThis end

  protected
    def format(time) sprintf "%.#{timer.scale}f", timer.factor * time end
  end

  class TimerElement < TimerNode
    attr_accessor :time

    def initialize(timer, label, time)
      super(timer, label)
      @time = time
    end

    def value_width() value.size end
    def value() @value ||= format time end

    def total() @time end

  protected
    def dump_element(file, indent, label_width, value_width)
      file.printf "#{indent}%-#{label_width}s: %#{value_width}s#{timer.unit}\n", label, value
    end
  end

  class TimerGroup < TimerNode
    attr_accessor :unit # Currently only :s, or :ms. Default is :ms
    def factor() { s: 1, ms: 1000 }[unit] end
    attr_accessor :scale # Number of digits after the decimal point
    attr_reader :nodes # Array of tuples of label and time or TimerGroup objects

    def initialize(timer, label = nil, unit: :ms, scale: 2)
      super(timer, label)
      @unit = unit.to_sym
      @scale = scale
      @nodes = []
      @nodes_by_label = {}
    end

    def time(label, &block)
      t0 = Time.now
      r = yield
      dt = Time.now - t0
      if @nodes_by_label.key?(label)
        @nodes_by_label[label].time += dt
      else
        element = TimerElement.new(self, label, dt)
        @nodes << element
        @nodes_by_label[label] = element
      end
      r
    end

    def group(label, **opts)
      r = TimerGroup.new(self, label, **{ unit: unit, scale: scale }.merge(opts))
      @nodes << r
      r
    end

    def total()
      @nodes.inject(0) { |a,e| a + e.total }
    end

    def dump(file = $stdout, indent = "")
      dump_element(file, indent, label_width, value_width)
    end

  protected
    def label_width()
      if label
        ([label.size - 2] + @nodes.map { |node| node.send(:label_width) }).max + 2
      else
        @nodes.map { |node| node.send :label_width }.max
      end
    end

    def value_width() @value_width ||= @nodes.map { |node| node.send :value_width }.max end

    def dump_element(file, indent, label_width, value_width)
      if label
        file.puts "#{indent}#{label} (#{format(total)}#{timer.unit})"
        nodes.each { |node|
          node.send :dump_element, file, indent + "  ", label_width - 2, value_width
        }
      else
        nodes.each { |node|
          node.send :dump_element, file, indent, label_width, value_width
        }
      end
    end
  end

  class Timer < TimerGroup
    def initialize(label = nil, **opts)
      super(self, label, **opts)
    end

    def dump(file = $stdout)
      super
      if @nodes.size > 1
        file.printf "%-#{label_width}s: %#{value_width}s#{timer.unit}\n", "Total", format(total)
      end
    end
  end
end