class_name PlayerStats
extends RefCounted
## A player's combat numbers, computed from the upgrades they hold.
##
## Derived, never stored: the character record keeps the list of upgrade ids and
## this is rebuilt from it. One source of truth means a saved stat can never
## disagree with the upgrades that produced it -- the same reasoning that makes
## [Progression] derive level from experience rather than storing both.

## The damage formula, settled with the user:
##
##     base x (1 + sum of additive) x product of multiplicative
##
## The +5% every upgrade carries, Spread's −10%, Doubleshot's −50% and Glass
## Cannon's +100% all pool into the additive term. Sniper's 2x multiplies the
## result, which is why it stays worth taking however many percentages have
## already piled up -- and why two Snipers is 4x rather than +200%.

var damage: int = SimConfig.PLAYER_BULLET_DAMAGE
var fire_cooldown: int = SimConfig.PLAYER_FIRE_COOLDOWN
var bullet_speed: float = SimConfig.PLAYER_BULLET_SPEED
## Multiplies the level's maximum health. See SimPlayer.recompute_max_hp().
var max_hp_mult: float = 1.0
var side_shots: int = 0
var parallel_shots: int = 0
var split_charges: int = 0
var poison_fraction: float = 0.0
var erase_chance: float = 0.0
## How many upgrades produced these numbers, duplicates included. Only used for
## display, but it is the number a player counts.
var upgrade_count: int = 0
## True when the bullet-speed ceiling actually bit. Surfaced so the choice
## screen can say a second Sniper buys no more speed instead of silently
## selling one.
var speed_capped: bool = false


static func build(ids: Array[StringName]) -> PlayerStats:
	var s := PlayerStats.new()
	var additive := 0.0
	var multiplicative := 1.0
	var fire_rate := 1.0
	var speed := 1.0
	var hp := 1.0

	for id in ids:
		var def := Upgrades.get_def(id)
		if def == null:
			continue  # an upgrade this build no longer has: ignored, not fatal
		s.upgrade_count += 1
		# Every upgrade carries this, whatever else it does.
		additive += SimConfig.UPGRADE_DAMAGE_BONUS
		additive += def.damage_add
		multiplicative *= def.damage_mult
		fire_rate *= def.fire_rate_mult
		speed *= def.bullet_speed_mult
		hp *= def.max_hp_mult
		s.side_shots += def.side_shots
		s.parallel_shots += def.parallel_shots
		s.split_charges += def.split_charges
		s.poison_fraction += def.poison_fraction
		s.erase_chance += def.erase_chance

	# Floored at 1 rather than allowed to reach zero. Stacking Doubleshot and
	# Spread can in principle drive the additive pool below −100%, and a shot
	# that deals nothing is indistinguishable from a bug.
	s.damage = maxi(1, roundi(float(SimConfig.PLAYER_BULLET_DAMAGE)
		* (1.0 + additive) * multiplicative))
	# A division, so "half the fire rate" is half the shots per second rather
	# than half the cooldown.
	s.fire_cooldown = maxi(1, roundi(float(SimConfig.PLAYER_FIRE_COOLDOWN)
		/ maxf(fire_rate, 0.01)))
	var wanted := SimConfig.PLAYER_BULLET_SPEED * speed
	s.bullet_speed = minf(wanted, SimConfig.MAX_BULLET_SPEED)
	s.speed_capped = wanted > SimConfig.MAX_BULLET_SPEED
	s.max_hp_mult = maxf(hp, 0.01)
	s.erase_chance = clampf(s.erase_chance, 0.0, 1.0)
	return s