/**
 * Guns: the damage table and what a shot does with it. Pure functions —
 * nothing here knows about a match.
 *
 * Distance is in world units; fifty units is a metre, so the map is about
 * forty-eight metres across and the Phantom's fifteen-metre falloff lands
 * where it should. The rule that matters: a Vandal head shot kills through
 * full armour at any range, a Phantom head shot does not.
 */

export type WeaponId =
  | "classic"
  | "ghost"
  | "sheriff"
  | "spectre"
  | "phantom"
  | "vandal"
  | "operator";

export type Zone = "head" | "body" | "legs";

export type Band = { upTo: number; head: number; body: number; legs: number };

export type Weapon = {
  id: WeaponId;
  name: string;
  cost: number;
  /** Shots a second. */
  rate: number;
  magazine: number;
  reload: number;
  /** Cone half-angle in radians when standing still, and the walking penalty. */
  spread: number;
  movePenalty: number;
  range: number;
  auto: boolean;
  bands: Band[];
};

const METRE = 50;

export const WEAPONS: Record<WeaponId, Weapon> = {
  classic: {
    id: "classic",
    name: "Classic",
    cost: 0,
    rate: 6.75,
    magazine: 12,
    reload: 1.75,
    spread: 0.022,
    movePenalty: 0.05,
    range: 1600,
    auto: false,
    bands: [{ upTo: Infinity, head: 78, body: 26, legs: 22 }],
  },
  ghost: {
    id: "ghost",
    name: "Ghost",
    cost: 500,
    rate: 6.75,
    magazine: 15,
    reload: 1.5,
    spread: 0.016,
    movePenalty: 0.05,
    range: 1800,
    auto: false,
    bands: [
      { upTo: 30 * METRE, head: 105, body: 30, legs: 26 },
      { upTo: Infinity, head: 88, body: 25, legs: 21 },
    ],
  },
  sheriff: {
    id: "sheriff",
    name: "Sheriff",
    cost: 800,
    rate: 4,
    magazine: 6,
    reload: 2.25,
    spread: 0.02,
    movePenalty: 0.09,
    range: 2000,
    auto: false,
    bands: [
      { upTo: 30 * METRE, head: 159, body: 55, legs: 46 },
      { upTo: Infinity, head: 145, body: 50, legs: 42 },
    ],
  },
  spectre: {
    id: "spectre",
    name: "Spectre",
    cost: 1600,
    rate: 13.33,
    magazine: 30,
    reload: 2.5,
    spread: 0.03,
    movePenalty: 0.03,
    range: 1600,
    auto: true,
    bands: [
      { upTo: 20 * METRE, head: 78, body: 26, legs: 22 },
      { upTo: Infinity, head: 66, body: 22, legs: 18 },
    ],
  },
  phantom: {
    id: "phantom",
    name: "Phantom",
    cost: 2900,
    rate: 11,
    magazine: 30,
    reload: 2.5,
    spread: 0.021,
    movePenalty: 0.06,
    range: 2400,
    auto: true,
    bands: [
      { upTo: 15 * METRE, head: 156, body: 39, legs: 33 },
      { upTo: 30 * METRE, head: 140, body: 35, legs: 29 },
      { upTo: Infinity, head: 124, body: 31, legs: 26 },
    ],
  },
  vandal: {
    id: "vandal",
    name: "Vandal",
    cost: 2900,
    rate: 9.75,
    magazine: 25,
    reload: 2.5,
    spread: 0.024,
    movePenalty: 0.07,
    range: 2400,
    auto: true,
    bands: [{ upTo: Infinity, head: 160, body: 40, legs: 34 }],
  },
  operator: {
    id: "operator",
    name: "Operator",
    cost: 4700,
    rate: 0.6,
    magazine: 5,
    reload: 3.7,
    spread: 0.004,
    movePenalty: 0.2,
    range: 2800,
    auto: false,
    bands: [{ upTo: Infinity, head: 255, body: 150, legs: 120 }],
  },
};

export const weaponIds = (): WeaponId[] => Object.keys(WEAPONS) as WeaponId[];

export const isWeaponId = (value: unknown): value is WeaponId =>
  typeof value === "string" && value in WEAPONS;

/** Raw damage for a hit: the band the distance falls in, by zone. */
export function damage(id: WeaponId, zone: Zone, distance: number): number {
  const weapon = WEAPONS[id];
  const band = weapon.bands.find((b) => distance <= b.upTo) ?? weapon.bands[weapon.bands.length - 1]!;
  return band[zone];
}

/**
 * Armour absorbs point for point — a hundred health behind fifty armour is a
 * hundred and fifty to chew through — but it takes two thirds of each hit,
 * so it runs out before health does.
 */
export function applyDamage(
  hp: number,
  armour: number,
  amount: number,
): { hp: number; armour: number } {
  const toArmour = Math.min(armour, Math.ceil(amount * (2 / 3)));
  return { hp: Math.max(0, hp - (amount - toArmour)), armour: armour - toArmour };
}

/** True when this hit kills outright: the test the Vandal exists to pass. */
export const isLethal = (hp: number, armour: number, amount: number): boolean =>
  applyDamage(hp, armour, amount).hp <= 0;

/**
 * Where a shot lands, from how close the ray passes the target's centre.
 * Top-down has no vertical, so precision stands in for it: dead centre is a
 * head shot, the outer edge is legs.
 */
export function zoneFromMiss(miss: number, radius: number): Zone {
  if (miss <= radius * 0.33) return "head";
  if (miss <= radius * 0.75) return "body";
  return "legs";
}

/** Cone half-angle for a shot: standing still is accurate, running is not. */
export const shotSpread = (id: WeaponId, speedFraction: number): number =>
  WEAPONS[id].spread + WEAPONS[id].movePenalty * Math.min(1, Math.max(0, speedFraction));

export const SHIELD = { light: { cost: 400, armour: 25 }, heavy: { cost: 1000, armour: 50 } };