class_name UpgradeDef
extends Resource
## One upgrade, as data. Every field here is a modifier the simulation already
## knows how to apply, so adding an upgrade is a table entry and never a branch
## in [SimWorld] -- the same rule bosses follow.
##
## Note what is NOT here: the flat +5% damage every upgrade carries. That is a
## property of *taking an upgrade*, not of any particular one, so it lives in
## [PlayerStats] where it is applied once per upgrade held. Baking it into each
## definition would mean seven places to change it and seven places to get it
## wrong.

enum Rarity { COMMON, UNCOMMON, RARE, LEGENDARY }

@export var id: StringName = &"upgrade"
@export var display_name: String = "Upgrade"
## Shown on the choice card. Says what it does, in the player's terms.
@export var description: String = ""
@export var rarity: Rarity = Rarity.COMMON

# --- Damage -----------------------------------------------------------------
## Added to the additive pool: base x (1 + sum of these) x product of the
## multiplicative ones. Negative for the upgrades that trade damage away.
@export var damage_add: float = 0.0
## Multiplied in after the pool. Sniper is the only thing that uses this, and
## the brief calls it out as multiplicative specifically so it stays sharp no
## matter how many additive percentages have piled up.
@export var damage_mult: float = 1.0

# --- Everything else --------------------------------------------------------
## Multiplies the character's levelled maximum health, so the cost of trading
## health away scales instead of fading out by level 15.
@export var max_hp_mult: float = 1.0
## Below 1.0 means slower. Applied to the cooldown as a division, so 0.5 here is
## genuinely half the shots per second.
@export var fire_rate_mult: float = 1.0
@export var bullet_speed_mult: float = 1.0
## Extra projectiles fanned out to the sides of the aim.
@export var side_shots: int = 0
## Extra projectiles parallel to the aim, offset sideways.
@export var parallel_shots: int = 0
## How many times one shot may split on hitting something. The brief's "cannot
## split twice unless the upgrade is taken again" is exactly this being a count
## rather than a flag.
@export var split_charges: int = 0
## Fraction of a hit's damage dealt again over the poison window.
@export var poison_fraction: float = 0.0
## Chance, per tick, that a shot deletes an enemy projectile it is passing
## through.
@export var erase_chance: float = 0.0


static func rarity_name(r: Rarity) -> String:
	match r:
		Rarity.COMMON: return "common"
		Rarity.UNCOMMON: return "uncommon"
		Rarity.RARE: return "rare"
		Rarity.LEGENDARY: return "legendary"
	return "?"