# @!visibility private
module GamesDice::ComplexDieHelpers

  private

  def recursive_probabilities probabilities={},prior_probability=1.0,depth=0,prior_result=nil,rerolls_left=nil,roll_reason=:basic,subtracting=false
    each_probability = prior_probability / @basic_die.sides
    depth += 1
    if depth >= 20 || each_probability < 1.0e-16
      @probabilities_complete = false
      stop_recursing = true
    end

    @basic_die.each_value do |v|
      recurse_probs_for_value( v, roll_reason, probabilities, each_probability, depth, prior_result, rerolls_left, subtracting, stop_recursing )
    end
    probabilities
  end

  def recurse_probs_for_value v, roll_reason, probabilities, each_probability, depth, prior_result, rerolls_left, subtracting, stop_recursing
    # calculate value, recurse if there is a reroll
    result_so_far, rerolls_remaining = calc_result_so_far(prior_result, rerolls_left, v, roll_reason )

    # Find which rule, if any, is being triggered
    rule_idx = find_matching_reroll_rule( v, result_so_far.rolls.length, rerolls_remaining )

    if rule_idx && ! stop_recursing
      recurse_probs_with_rule( probabilities, each_probability, depth, result_so_far, rerolls_remaining, rule_idx, subtracting )
    else
      t = result_so_far.total
      probabilities[ t ] ||= 0.0
      probabilities[ t ] += each_probability
    end
  end

  def recurse_probs_with_rule probabilities, each_probability, depth, result_so_far, rerolls_remaining, rule_idx, subtracting
    rule = @rerolls[ rule_idx ]
    rerolls_remaining[ rule_idx ] -= 1
    is_subtracting = true if subtracting || rule.type == :reroll_subtract

    # Apply the rule (note reversal for additions, after a subtract)
    if subtracting && rule.type == :reroll_add
      recursive_probabilities probabilities, each_probability, depth, result_so_far, rerolls_remaining, :reroll_subtract, is_subtracting
    else
      recursive_probabilities probabilities, each_probability, depth, result_so_far, rerolls_remaining, rule.type, is_subtracting
    end
  end

  def calc_result_so_far prior_result, rerolls_left, v, roll_reason
    if prior_result
      result_so_far = prior_result.clone
      result_so_far.add_roll(v,roll_reason)
      rerolls_remaining = rerolls_left.clone
    else
      result_so_far = GamesDice::DieResult.new(v,roll_reason)
      rerolls_remaining = @rerolls.map { |rule| rule.limit }
    end
    [result_so_far, rerolls_remaining]
  end
end