//! Balancing data (ADR-0001).
//!
//! This module holds **only data and data structures**. No gameplay logic, no Bevy systems.
//! Gameplay reads `Res<Balance>` and never sees the constants in [`values`].
//!
//! The numbers themselves live in [`values`] and are all placeholders; this file only gives
//! them their shape. `Balance` is deliberately built from plain fields, numbers and vectors —
//! no `Handle`, no `Entity` — so it could be serialized without a redesign if the revision
//! triggers of ADR-0001 ever fire. A `serde` derive is explicitly *not* added now.

mod values;

use bevy::prelude::*;

/// The numeric type of every stat and balancing value (ADR-0002 §4).
///
/// An alias, not a newtype. `f32` carries seven significant digits, which is enough for the
/// slice; ADR-0002 revision trigger 1 says when this is reconsidered.
pub type Stat = f32;

/// All balancing data of the game, in one place.
///
/// Built by exactly one function, [`Balance::from_constants`]. Nothing else constructs a
/// `Balance`, which is what makes that function the seam an asset loading path would replace.
#[derive(Resource, Debug, Clone)]
pub struct Balance {
    pub arena: ArenaBalance,
    pub tower: TowerBalance,
    pub enemy: EnemyBalance,
    pub combat: CombatBalance,
    pub meta: MetaBalance,
    pub caps: Caps,
}

/// The playing field.
#[derive(Debug, Clone)]
pub struct ArenaBalance {
    /// Distance from the tower in the centre to the rim enemies spawn on, in world units.
    pub radius: Stat,
}

/// Base values of the tower, before any modifier from ADR-0002 is applied.
#[derive(Debug, Clone)]
pub struct TowerBalance {
    /// Damage of a single shot.
    pub damage: Stat,
    /// Seconds between two shots — an interval, not a rate (ADR-0002 §3).
    pub attack_interval: Stat,
    /// Tower health. The tower dying is what ends a run.
    pub health: Stat,
}

/// Base values of the single enemy archetype the skeleton knows.
#[derive(Debug, Clone)]
pub struct EnemyBalance {
    /// Movement speed in world units per second.
    pub speed: Stat,
    /// Health at wave 1.
    pub health: Stat,
    /// Distance from the tower centre at which an enemy stops walking.
    pub attack_range: Stat,
    /// Enemies closer than this push each other apart (ADR-0004 §5).
    pub separation_radius: Stat,
    /// ‹k›: how many neighbours one enemy takes into account (ADR-0004 §5).
    pub separation_neighbours: usize,
    /// ‹f› < 1: the separation offset is clamped to `f x (speed x dt)` (ADR-0004 §5).
    pub separation_clamp: Stat,
    /// Living enemies the spawner fills the field up to. Becomes `target_population(wave)`.
    pub target_population: usize,
    /// `HARD_ENEMY_CAP`: the measured performance limit, never exceeded by anything.
    pub hard_cap: usize,
}

/// Values that describe how things touch each other.
#[derive(Debug, Clone)]
pub struct CombatBalance {
    /// A projectile within this distance of an enemy counts as a hit, in world units.
    pub hit_radius: Stat,
}

/// Meta progression income — the currency that survives a run.
#[derive(Debug, Clone)]
pub struct MetaBalance {
    /// Meta currency granted per killed enemy.
    pub gain_per_kill: Stat,
}

/// Upper bounds for the percentage-point sums of the stat pipeline (ADR-0002 §2).
///
/// Empty on purpose. ADR-0002 §2 requires every clamp limit to be a balancing value living
/// here — one per clamped stat — with no global clamp and no default in code. The skeleton
/// has none of the stats that carry a cap (`crit_chance`, `defense_percent`,
/// `cooldown_reduction`, `wave_cooldown_reduction`, `free_upgrade_chance`), so there is
/// nothing to put in yet.
///
// ponytail: an empty struct rather than five caps nothing reads. It exists so the place is
// named and reachable as `balance.caps.*`; the fields land with the stats that need them in
// the thickening phase, and the compiler will point at this struct when they do.
#[derive(Debug, Clone, Default)]
pub struct Caps {}

impl Balance {
    /// Builds `Balance` from the constants in [`values`].
    ///
    /// **The one and only constructor** (ADR-0001, decision point 3). Everything that wants
    /// balancing data goes through the resource this returns; nothing else assembles a
    /// `Balance`. That makes this function the single seam a later asset loading path — or a
    /// debug panel that mutates `Balance` in the running process — attaches to.
    pub fn from_constants() -> Self {
        Self {
            arena: ArenaBalance {
                radius: values::ARENA_RADIUS,
            },
            tower: TowerBalance {
                damage: values::TOWER_DAMAGE,
                attack_interval: values::TOWER_ATTACK_INTERVAL,
                health: values::TOWER_HEALTH,
            },
            enemy: EnemyBalance {
                speed: values::ENEMY_SPEED,
                health: values::ENEMY_HEALTH,
                attack_range: values::ENEMY_ATTACK_RANGE,
                separation_radius: values::ENEMY_SEPARATION_RADIUS,
                separation_neighbours: values::ENEMY_SEPARATION_NEIGHBOURS,
                separation_clamp: values::ENEMY_SEPARATION_CLAMP,
                target_population: values::ENEMY_TARGET_POPULATION,
                hard_cap: values::HARD_ENEMY_CAP,
            },
            combat: CombatBalance {
                hit_radius: values::HIT_RADIUS,
            },
            meta: MetaBalance {
                gain_per_kill: values::META_GAIN_PER_KILL,
            },
            caps: Caps::default(),
        }
    }
}