prawnpdf/prawn

# frozen_string_literal: true

require_relative 'bounding_box'

module Prawn
  class Document # rubocop: disable Style/Documentation
    # @group Experimental API

    # A column box is a bounding box with the additional property that when
    # text flows past the bottom, it will wrap first to another column on the
    # same page, and only flow to the next page when all the columns are
    # filled.
    #
    # `column_box` accepts the same parameters as {bounding_box}, as well as the
    # number of `:columns` and a `:spacer` (in points) between columns. If
    # resetting the top margin is desired on a new page (e.g. to allow for
    # initial page wide column titles) the option `reflow_margins: true` can be
    # set.
    #
    # @overload column_box(point, options = {})
    #   @param point [Array(Number, Number)]
    #   @param options [Hash{Symbol => any}]
    #   @option options :width [Number]
    #     width of the new column box, must be specified.
    #   @option options :height [Number]
    #     height of the new column box, stretchy box if omitted.
    #   @option options :hold_position [Boolean]
    #     whether to put cursor at the bottom of the column box.
    #   @option options :columns [Integer] (3)
    #   @option options :spacer [Number] (font_size)
    #   @option options :reflow_margins [Boolean] (false)
    #   @yieldparam parent_box [BoundingBox] parent bounding box
    #   @return [void]
    def column_box(*args, &block)
      init_column_box(block) do |parent_box|
        map_to_absolute!(args[0])
        @bounding_box = ColumnBox.new(self, parent_box, *args)
      end
    end

    private

    def init_column_box(user_block, options = {})
      parent_box = @bounding_box

      yield(parent_box)

      self.y = @bounding_box.absolute_top
      user_block.call
      self.y = @bounding_box.absolute_bottom unless options[:hold_position]

      @bounding_box = parent_box
    end

    # Implements the necessary functionality to allow {Document#column_box} to
    # work.
    #
    class ColumnBox < BoundingBox
      # @param point [Array(Number, Number)]
      # @param options [Hash{Symbol => any}]
      # @option options :width [Number]
      #   width of the new column box, must be specified.
      # @option options :height [Number]
      #   height of the new column box, stretchy box if omitted.
      # @option options :columns [Integer] (3)
      # @option options :spacer [Number] (font_size)
      # @option options :reflow_margins [Boolean] (false)
      def initialize(document, parent, point, options = {})
        super
        @columns = options[:columns] || 3
        @spacer = options[:spacer] || @document.font_size
        @current_column = 0
        @reflow_margins = options[:reflow_margins]
      end

      # The column width, not the width of the whole box, before left and/or
      # right padding.
      #
      # @return [Number]
      def bare_column_width
        (@width - (@spacer * (@columns - 1))) / @columns
      end

      # The column width after padding. Used to calculate how long a line of
      # text can be.
      #
      # @return [Number]
      def width
        bare_column_width - (@total_left_padding + @total_right_padding)
      end

      # Column width including the spacer.
      #
      # @return [Number]
      def width_of_column
        bare_column_width + @spacer
      end

      # x coordinate of the left edge of the current column.
      #
      # @return [Number]
      def left_side
        absolute_left + (width_of_column * @current_column)
      end

      # Relative position of the left edge of the current column.
      #
      # @return [Number]
      def left
        width_of_column * @current_column
      end

      # x coordinate of the right edge of the current column.
      #
      # @return [Number]
      def right_side
        columns_from_right = @columns - (1 + @current_column)
        absolute_right - (width_of_column * columns_from_right)
      end

      # Relative position of the right edge of the current column.
      #
      # @return [Number]
      def right
        left + width
      end

      # Moves to the next column or starts a new page if currently positioned at
      # the rightmost column.
      #
      # @return [void]
      def move_past_bottom
        @current_column = (@current_column + 1) % @columns
        @document.y = @y
        if @current_column.zero?
          if @reflow_margins
            @y = @parent.absolute_top
          end
          @document.start_new_page
        end
      end

      # Override the padding functions so as not to split the padding amount
      # between all columns on the page.

      # @private
      # @param left_padding [Number]
      # @return [void]
      def add_left_padding(left_padding)
        @total_left_padding += left_padding
        @x += left_padding
      end

      # @private
      # @param left_padding [Number]
      # @return [void]
      def subtract_left_padding(left_padding)
        @total_left_padding -= left_padding
        @x -= left_padding
      end

      # @private
      # @param right_padding [Number]
      # @return [void]
      def add_right_padding(right_padding)
        @total_right_padding += right_padding
      end

      # @private
      # @param right_padding [Number]
      # @return [void]
      def subtract_right_padding(right_padding)
        @total_right_padding -= right_padding
      end
    end
  end
end