# frozen_string_literal: true

require 'multi_range/version'
require 'roulette-wheel-selection'
require 'interval_tree'

if not Range.method_defined?(:size)
  warn "Please backports Range#size method to use multi_range gem.\n" \
       "You can use backports gem and add the following lines to your program:\n" \
       "require 'backports/1.9.2/float/infinity'\n" \
       "require 'backports/2.0.0/range/size'"
end

if not Enumerable.method_defined?(:to_h)
  warn "Please backports Enumerable#to_h method to use multi_range gem.\n" \
       "You can use backports gem and add the following lines to your program:\n" \
       "require 'backports/2.1.0/enumerable/to_h'"
end

class MultiRange
  INDEX_WITH_DEFAULT = Object.new

  attr_reader :ranges

  def initialize(ranges)
    if ranges.is_a? MultiRange
      @ranges = ranges.ranges
      @is_float = ranges.is_float?
    else
      @ranges = ranges.map{|s| s.is_a?(Numeric) ? s..s : s }.sort_by(&:begin).freeze
      @is_float = @ranges.any?{|range| range.begin.is_a?(Float) || range.end.is_a?(Float) }
    end
  end

  def is_float?
    @is_float
  end

  def merge_overlaps(merge_same_value = true)
    return MultiRange.new([]) if @ranges.size == 0

    new_ranges = []
    current_range = nil

    @ranges.each do |range|
      next current_range = range if current_range == nil
      next if range.end <= current_range.end

      if can_combine?(current_range, range, merge_same_value)
        current_range = range.exclude_end? ? current_range.begin...range.end : current_range.begin..range.end
      else
        new_ranges << current_range
        current_range = range
      end
    end

    new_ranges << current_range
    return MultiRange.new(new_ranges)
  end

  def &(other)
    other_ranges = MultiRange.new(other).merge_overlaps.ranges
    tree = IntervalTree::Tree.new(other_ranges)
    intersected_ranges = merge_overlaps.ranges.flat_map do |range|
      # A workaround for the issue: https://github.com/greensync/interval-tree/issues/17
      query = (range.first == range.last) ? range.first : range
      matching_ranges_converted_to_exclusive = tree.search(query) || []

      # The interval tree converts interval endings to exclusive, so we need to restore the original
      matching_ranges = matching_ranges_converted_to_exclusive.map do |matching_range_converted_to_exclusive|
        other_ranges.find do |other_range|
          # Having merged overlaps in each multi_range, there's no need to check the endings,
          # since there will only be one range with each beginning
          other_range.begin == matching_range_converted_to_exclusive.begin
        end
      end

      matching_ranges.map do |matching_range|
        intersect_two_ranges(range, matching_range)
      end
    end
    MultiRange.new(intersected_ranges)
  end

  alias intersection &

  def -(other)
    return difference_with_other_multi_range(other) if other.is_a?(MultiRange)

    new_ranges = @ranges.dup
    return MultiRange.new(new_ranges) if not overlaps_with_range?(other)

    changed_size = 0
    @ranges.each_with_index do |range, idx|
      # when this range is smaller than and not overlaps with `other`
      #      range          other
      #   |---------|    |---------|
      next if other.begin > range.end

      # when this range is larger than and not overlaps with `other`
      #      other          range
      #   |---------|    |---------|
      break if other.end < range.begin

      sub_ranges = possible_sub_ranges_of(range, other)
      new_ranges[idx + changed_size, 1] = sub_ranges
      changed_size += sub_ranges.size - 1

      # when the maximum value of this range is larger than that of `other`
      #     range
      # -------------|
      #   other
      # ---------|
      break if other.end <= range.end
    end

    return MultiRange.new(new_ranges)
  end

  alias difference -

  def |(other)
    other_ranges = other.is_a?(MultiRange) ? other.ranges : [other]
    return MultiRange.new(@ranges + other_ranges).merge_overlaps
  end

  alias union |

  def overlaps?(other)
    multi_range = merge_overlaps
    return multi_range.ranges != (multi_range - other).ranges
  end

  def sample
    range = RouletteWheelSelection.sample(@ranges.map{|s| [s, s.size] }.to_h)
    return nil if range == nil
    return rand(range)
  end

  def size
    @ranges.inject(0){|sum, v| sum + v.size }
  end

  def any?
    @ranges.any?
  end

  def index_with(default = INDEX_WITH_DEFAULT)
    if block_given?
      fail ArgumentError, 'wrong number of arguments (given 1, expected 0)' if default != INDEX_WITH_DEFAULT
      return map{|s| [s, yield(s)] }.to_h
    end

    return to_enum(:index_with){ size } if default == INDEX_WITH_DEFAULT
    return map{|s| [s, default] }.to_h
  end

  def each
    return to_enum(:each){ size } if !block_given?

    ranges.each do |range|
      range.each{|s| yield(s) }
    end
  end

  def map
    return to_enum(:map){ size } if !block_given?
    return each.map{|s| yield(s) }
  end

  def to_a
    each.to_a
  end

  def min
    range = @ranges.first
    return range.min if range
  end

  def max
    range = @ranges.last
    return range.max if range
  end

  def contain_overlaps?
    merge_overlaps(false).ranges != ranges
  end

  private

  # make sure that range1.begin <= range2.begin
  def can_combine?(range1, range2, merge_same_value)
    return merge_same_value if range1.end == range2.begin and range1.exclude_end?
    return range1.end >= range2.begin if @is_float
    return range1.end + 1 >= range2.begin
  end

  def difference_with_other_multi_range(other)
    new_multi_range = dup
    other.ranges.each{|range| new_multi_range -= range }
    return new_multi_range
  end

  def possible_sub_ranges_of(range, other)
    sub_range1 = range.begin...other.begin

    sub_range2_begin = if other.exclude_end?
                         other.end
                       else
                         other.end.is_a?(Float) ? other.end.next_float : other.end + 1
                       end

    sub_range2 = range.exclude_end? ? sub_range2_begin...range.end : sub_range2_begin..range.end

    sub_ranges = []
    sub_ranges << sub_range1 if not empty_range?(sub_range1)
    sub_ranges << sub_range2 if not empty_range?(sub_range2)
    return sub_ranges
  end

  def overlaps_with_range?(range)
    return false if @ranges.empty?
    return false if range.begin > @ranges.last.end # larger than maximum
    return false if range.end < @ranges.first.begin # smaller than minimum
    return true
  end

  def intersect_two_ranges(range_a, range_b)
    ranges = [range_a, range_b]
    start = ranges.map(&:begin).max
    finish = ranges.map(&:end).min
    if ranges.sort_by{|range| [range.end, range.exclude_end? ? 1 : 0] }.first.exclude_end?
      start...finish
    else
      start..finish
    end
  end

  def empty_range?(range)
    range.begin > range.end || (range.begin == range.end && range.exclude_end?)
  end
end