text_run.rb

# coding: utf-8
# typed: strict
# frozen_string_literal: true

class PDF::Reader
  # A value object that represents one or more consecutive characters on a page.
  class TextRun
    include Comparable

    attr_reader :origin
    attr_reader :width
    attr_reader :font_size
    attr_reader :text

    alias :to_s :text

    def initialize(x, y, width, font_size, text)
      @origin = PDF::Reader::Point.new(x, y)
      @width = width
      @font_size = font_size
      @text = text
    end

    # Allows collections of TextRun objects to be sorted. They will be sorted
    # in order of their position on a cartesian plain - Top Left to Bottom Right
    def <=>(other)
      if x == other.x && y == other.y
        0
      elsif y < other.y
        1
      elsif y > other.y
        -1
      elsif x < other.x
        -1
      elsif x > other.x
        1
      end
    end

    def x
      @origin.x
    end

    def y
      @origin.y
    end

    def endx
      @endx ||= @origin.x + width
    end

    def endy
      @endy ||= @origin.y + font_size
    end

    def mean_character_width
      @width / character_count
    end

    def mergable?(other)
      y.to_i == other.y.to_i && font_size == other.font_size && mergable_range.include?(other.x)
    end

    def +(other)
      raise ArgumentError, "#{other} cannot be merged with this run" unless mergable?(other)

      if (other.x - endx) <( font_size * 0.2)
        TextRun.new(x, y, other.endx - x, font_size, text + other.text)
      else
        TextRun.new(x, y, other.endx - x, font_size, "#{text} #{other.text}")
      end
    end

    def inspect
      "#{text} w:#{width} f:#{font_size} @#{x},#{y}"
    end

    def intersect?(other_run)
      x <= other_run.endx && endx >= other_run.x &&
        endy >= other_run.y && y <= other_run.endy
    end

    # return what percentage of this text run is overlapped by another run
    def intersection_area_percent(other_run)
      return 0 unless intersect?(other_run)

      dx = [endx, other_run.endx].min - [x, other_run.x].max
      dy = [endy, other_run.endy].min - [y, other_run.y].max
      intersection_area = dx*dy

      intersection_area.to_f / area
    end

    # return what percentage of this text run is overlapped by another run horizontally
    def horizontal_overlap(other_run)
      # rectangles do not overlap (we are on the left side)
      return 0 if [x, endx].max < [other_run.x, other_run.endx].min
      # rectangles do not overlap (other_run is on the left side)
      return 0 if [other_run.x, other_run.endx].max < [x, endx].min
      a = [ [x, endx].min, [other_run.x, other_run.endx].min ].max
      b = [ [x, endx].max, [other_run.x, other_run.endx].max ].min
      return (a - b).abs
    end

    private

    def area
      (endx - x) * (endy - y)
    end

    def mergable_range
      @mergable_range ||= Range.new(endx - 3, endx + font_size)
    end

    # Assume string encoding is marked correctly and we can trust String#size to return a
    # character count
    def character_count
      @text.size.to_f
    end
  end
end