class Battle::AI
  def pbAIRandom(x); return rand(x); end

  def pbStdDev(choices)
    sum = 0
    n   = 0
    choices.each do |c|
      sum += c[1]
      n   += 1
    end
    return 0 if n < 2
    mean = sum.to_f / n
    varianceTimesN = 0
    choices.each do |c|
      next if c[1] <= 0
      deviation = c[1].to_f - mean
      varianceTimesN += deviation * deviation
    end
    # Using population standard deviation
    # [(n-1) makes it a sample std dev, would be 0 with only 1 sample]
    return Math.sqrt(varianceTimesN / n)
  end

  #-----------------------------------------------------------------------------

  # Move's type effectiveness. For switching. Determines the effectiveness of a
  # potential switch-in against an opposing battler.
  # TODO: Unused.
  def pbCalcTypeModPokemon(pkmn, target_battler)
    ret = Effectiveness::NORMAL_EFFECTIVE_MULTIPLIER
    pkmn.types.each do |thisType|
      ret *= Effectiveness.calculate(thisType, *target_battler.types)
    end
    return ret
  end

  # Assumes that pkmn's ability is not negated by a global effect (e.g.
  # Neutralizing Gas).
  # pkmn is either a Battle::AI::AIBattler or a Pokemon. move is a Battle::Move.
  def pokemon_can_absorb_move?(pkmn, move, move_type)
    return false if pkmn.is_a?(Battle::AI::AIBattler) && !pkmn.ability_active?
    # Check pkmn's ability
    # Anything with a Battle::AbilityEffects::MoveImmunity handler
    # TODO: Are there any other absorbing effects? Held item?
    case pkmn.ability_id
    when :BULLETPROOF
      return move.bombMove?
    when :FLASHFIRE
      return move_type == :FIRE
    when :LIGHTNINGROD, :MOTORDRIVE, :VOLTABSORB
      return move_type == :ELECTRIC
    when :SAPSIPPER
      return move_type == :GRASS
    when :SOUNDPROOF
      return move.soundMove?
    when :STORMDRAIN, :WATERABSORB, :DRYSKIN
      return move_type == :WATER
    when :TELEPATHY
      # NOTE: The move is being used by a foe of pkmn.
      return false
    when :WONDERGUARD
      types = pkmn.types
      types = pkmn.pbTypes(true) if pkmn.is_a?(Battle::AI::AIBattler)
      return Effectiveness.super_effective_type?(move_type, *types)
    end
    return false
  end

  #-----------------------------------------------------------------------------

  def each_battler
    @battlers.each_with_index do |battler, i|
      next if !battler || battler.fainted?
      yield battler, i
    end
  end

  def each_foe_battler(side)
    @battlers.each_with_index do |battler, i|
      next if !battler || battler.fainted?
      yield battler, i if i.even? != side.even?
    end
  end

  def each_same_side_battler(side)
    @battlers.each_with_index do |battler, i|
      next if !battler || battler.fainted?
      yield battler, i if i.even? == side.even?
    end
  end

  def each_ally(index)
    @battlers.each_with_index do |battler, i|
      next if !battler || battler.fainted?
      yield battler, i if i != index && i.even? == index.even?
    end
  end
end