import { haversineKm } from '@/lib/geo';
import { PLANE_TYPES, STARTER_MODEL } from './catalog';

// First-run seed. Everything here is a pure function of (airports, rng, nowMs)
// so it is fully deterministic and unit-testable: the RNG is injected, never
// read internally. Production calls this with a crypto-random seed; tests use
// mulberry32(fixed).

export interface SeedAirport {
  icao: string;
  name: string;
  lat: number;
  lon: number;
}

export type Rng = () => number;

// Small deterministic PRNG (mulberry32) — good enough for game seeding, and it
// makes tests reproducible. Returns floats in [0, 1).
export function mulberry32(seed: number): Rng {
  let a = seed >>> 0;
  return () => {
    a |= 0;
    a = (a + 0x6d2b79f5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

export interface SeedPlane {
  id: string;
  model: string;
  status: 'available' | 'flying';
  fuel: number;
  maxFuel: number;
  locationIcao: string;
  contractId: null;
  lat: number;
  lon: number;
}

export interface SeedContract {
  id: string;
  originIcao: string;
  destIcao: string;
  reward: number;
  cargoType: string;
  cargoCount: number;
  deadlineSimTime: number;
  status: 'open';
  planeId: null;
  createdSimTime: number;
}

export interface SeedData {
  plane: SeedPlane;
  contracts: SeedContract[];
  account: { cash: number; reputation: number };
  simState: { clockMs: number; timeScale: number; paused: false; lastRealTickMs: number };
}

// --- Tunables (documented so future revenue/cost work can build on them) ---

export const STARTING_CASH = 20_000;
export const STARTING_REPUTATION = 10;

// The starter plane grounds at a large central-European hub. If the ICAO is
// ever missing from the dataset we fall back to the first airport rather than
// failing first run. (EDDF = Frankfurt; EDDM is Munich — don't mix them up.)
export const HUB_ICAO = 'EDDF'; // Frankfurt Main

export const CONTRACT_COUNT_MIN = 8;
export const CONTRACT_COUNT_MAX = 12; // inclusive

// Market target (v0.7.0): the sim engine tops open contracts back up to this
// count after expiries, so the job board never runs dry.
export const MARKET_TARGET_OPEN_CONTRACTS = 10;

// Reward formula (v0.6.0 — deliberately simple; real revenue/cost modeling is a
// later increment): reward = BASE_REWARD + REWARD_PER_KM * great-circle km.
export const BASE_REWARD = 500;
export const REWARD_PER_KM = 2.5;

// Contract deadlines: now + a plausible game-time window of 6–72 hours.
const DEADLINE_MIN_HOURS = 6;
const DEADLINE_MAX_HOURS = 72;

const CARGO_TYPES = ['Passengers', 'Mail', 'Perishables', 'Electronics', 'Auto parts'] as const;

export function rewardForDistanceKm(km: number): number {
  return Math.round(BASE_REWARD + REWARD_PER_KM * km);
}

// Shared contract generator, used by BOTH the first-run seed and the runtime
// market spawn (v0.7.0) so spawned contracts match seeded ones exactly: random
// distinct airports from the dataset, distance-based reward, cargo flavor,
// deadline now + 6–72h game time (or now + deadlineOffsetMs when given — used by
// the e2e test hook to force a near-term expiry). The RNG call order per contract
// is fixed: origin, dest, cargoType, cargoCount, [deadline window].
// v0.8.0: originIcao/destIcao optionally FORCE an endpoint (spawn coverage rule +
// the e2e create-contract hook); a forced endpoint consumes no RNG draws, so
// callers that omit both get byte-identical behavior to before.
export function generateContract(input: {
  id: string;
  airports: SeedAirport[];
  rng: Rng;
  nowMs: number;
  deadlineOffsetMs?: number;
  originIcao?: string;
  destIcao?: string;
}): SeedContract {
  const { airports, rng, nowMs } = input;
  if (airports.length < 2) throw new Error('contract generation needs at least two airports');

  let oi: number;
  if (input.originIcao !== undefined) {
    oi = airports.findIndex((a) => a.icao === input.originIcao);
    if (oi < 0) throw new Error(`unknown origin airport ${input.originIcao}`);
  } else {
    oi = Math.floor(rng() * airports.length);
  }
  let di: number;
  if (input.destIcao !== undefined) {
    di = airports.findIndex((a) => a.icao === input.destIcao);
    if (di < 0) throw new Error(`unknown destination airport ${input.destIcao}`);
    // A RANDOM origin may have landed on the forced destination — shift it (no
    // extra RNG draw), mirroring the unforced collision handling below.
    if (oi === di && input.originIcao === undefined) oi = (oi + 1) % airports.length;
  } else {
    di = Math.floor(rng() * airports.length);
    if (di === oi) di = (di + 1) % airports.length;
  }
  if (oi === di) throw new Error('origin and destination must differ'); // both forced identical
  const origin = airports[oi];
  const dest = airports[di];

  const km = haversineKm(origin.lat, origin.lon, dest.lat, dest.lon);
  const cargoType = CARGO_TYPES[Math.floor(rng() * CARGO_TYPES.length)];
  // Passengers up to the ATR 72's ~68 seats; other cargo in pallets.
  const cargoCount =
    cargoType === 'Passengers' ? 1 + Math.floor(rng() * 68) : 1 + Math.floor(rng() * 50);
  const deadlineMs =
    input.deadlineOffsetMs ?? (DEADLINE_MIN_HOURS + rng() * (DEADLINE_MAX_HOURS - DEADLINE_MIN_HOURS)) * 3_600_000;

  return {
    id: input.id,
    originIcao: origin.icao,
    destIcao: dest.icao,
    reward: rewardForDistanceKm(km),
    cargoType,
    cargoCount,
    deadlineSimTime: Math.round(nowMs + deadlineMs),
    status: 'open',
    planeId: null,
    createdSimTime: nowMs,
  };
}

function pickHub(airports: SeedAirport[]): SeedAirport {
  return airports.find((a) => a.icao === HUB_ICAO) ?? airports[0];
}

export function buildSeed(input: {
  airports: SeedAirport[];
  rng: Rng;
  nowMs: number;
}): SeedData {
  const { airports, rng, nowMs } = input;
  if (airports.length < 2) throw new Error('seed needs at least two airports');

  const type = PLANE_TYPES[STARTER_MODEL];
  const hub = pickHub(airports);

  const plane: SeedPlane = {
    id: 'plane-starter',
    model: STARTER_MODEL,
    status: 'available',
    fuel: type.maxFuel, // starts full
    maxFuel: type.maxFuel,
    locationIcao: hub.icao,
    contractId: null,
    lat: hub.lat,
    lon: hub.lon,
  };

  const count = CONTRACT_COUNT_MIN + Math.floor(rng() * (CONTRACT_COUNT_MAX - CONTRACT_COUNT_MIN + 1));
  // Stable index-based ids for the seed set; runtime-generated entities must use
  // random UUIDs to avoid colliding with these.
  const contracts: SeedContract[] = [];
  for (let i = 0; i < count; i++) {
    contracts.push(generateContract({ id: `contract-${i + 1}`, airports, rng, nowMs }));
  }

  return {
    plane,
    contracts,
    account: { cash: STARTING_CASH, reputation: STARTING_REPUTATION },
    // lastRealTickMs starts at the seed moment so the first tick-on-read advances
    // by ~0 instead of treating "time since install" as elapsed play time.
    simState: { clockMs: nowMs, timeScale: 1, paused: false, lastRealTickMs: nowMs },
  };
}