import type {
  CargoType,
  GameConfig,
  Good,
  Location,
  ScriptedTutorialContract,
  ShipModel,
  Skill,
  Upgrade,
} from "@deadhead/content";
import { MS_PER_MINUTE, type RealTime } from "./clock";
import { contractPayout, type Contract } from "./contract";
import { routeDistance } from "./distance";
import { isCompletable } from "./completable";
import { checkRoute } from "./eligibility";
import { LONG_HAUL_SKILL_ID, skillLevel, type SkillLevels } from "./pilot";
import { createRng, deriveSeed, type Rng, type Seed } from "./rng";
import { travelTimeGameHours } from "./travel";
import { effectiveStats } from "./upgrades";

/** The static data the sim needs. The `content` bundle satisfies this. */
export interface SimContent {
  locations: readonly Location[];
  cargoTypes: readonly CargoType[];
  goods: readonly Good[];
  skills: readonly Skill[];
  shipModels: readonly ShipModel[];
  scriptedTutorialContracts: readonly ScriptedTutorialContract[];
  upgrades: readonly Upgrade[];
  config: GameConfig;
}

export function boardPeriodMs(config: GameConfig): number {
  return config.contractBoardPeriodRealMinutes * MS_PER_MINUTE;
}

/** The board period a real time falls in. */
export function boardPeriodIndex(real: RealTime, config: GameConfig): number {
  return Math.floor(real / boardPeriodMs(config));
}

/** Required Long Haul level: the number of cut-offs the distance exceeds (decision 0.5.7). */
export function requiredLongHaulLevel(distanceMillionKm: number, config: GameConfig): number {
  return config.longHaulCutoffsMillionKm.filter((cutoff) => distanceMillionKm > cutoff).length;
}

export function standardCargo(content: SimContent): CargoType {
  const standard = content.cargoTypes.find((c) => c.requiredSkillId === null);
  if (!standard) throw new Error("Content has no Standard cargo type");
  return standard;
}

export type { FleetMember } from "./completable";
import type { FleetMember } from "./completable";

export interface BoardInput {
  /** The location whose freight market this is; every contract starts here (CR-002). */
  location: Location;
  discoveredIds: ReadonlySet<string>;
  periodIndex: number;
  worldSeed: Seed;
  /**
   * The qualifying fleet (decision 0.5.115): the board keeps only jobs some
   * pair can complete (0.5.114). Absent: an unfiltered board (tools and tests).
   */
  fleet?: readonly FleetMember[];
}

type MassBand = GameConfig["contractMassBands"][number];
type SlotKind = "guaranteed" | "open" | "fit";
interface Crew {
  model: ShipModel;
  skills: SkillLevels;
}

/**
 * Which contracts a board has, band by band (decision 0.5.52). Without a crew
 * every band keeps its count and opens with a guaranteed job. With one, a band
 * no ship can carry shrinks to a preview, its other slots go to the flyable
 * bands (largest first, round-robin), and flyable bands are fit jobs but for
 * `boardOpenSlotsPerBand` open ones.
 */
function planSlots(crews: readonly Crew[], config: GameConfig) {
  const bands = config.contractMassBands;
  const flyable = bands.map((band) => crews.some((c) => c.model.cargoCapacityTonnes >= band.min));
  if (!flyable.some(Boolean)) {
    return bands.flatMap((band) =>
      Array.from({ length: band.count }, (_, k) => ({
        band,
        kind: (k === 0 ? "guaranteed" : "open") as SlotKind,
      })),
    );
  }
  const counts = bands.map((band, i) =>
    flyable[i] ? band.count : Math.min(band.count, config.boardPreviewSlots),
  );
  const targets = bands
    .map((_, i) => i)
    .filter((i) => flyable[i])
    .reverse();
  let freed = bands.reduce((sum, band, i) => sum + band.count - counts[i]!, 0);
  for (let k = 0; freed > 0; k++, freed--) counts[targets[k % targets.length]!]!++;

  return bands.flatMap((band, i) => {
    const fit = flyable[i] ? Math.max(0, counts[i]! - config.boardOpenSlotsPerBand) : 0;
    return Array.from({ length: counts[i]! }, (_, k) => ({
      band,
      kind: (k < fit ? "fit" : !flyable[i] && k === 0 ? "guaranteed" : "open") as SlotKind,
    }));
  });
}

/**
 * A job one crew can take (decision 0.5.52): within its capacity, to one of
 * `destinations` (discovered places, or undiscovered ones for a first contact) it can reach and land at with its Long Haul, with cargo its
 * pilot is skilled for. Crews are tried from a random start; null if none fits.
 */
function fitJob(
  rng: Rng,
  band: MassBand,
  crews: readonly Crew[],
  origin: Location,
  discovered: readonly Location[],
  offeredAt: RealTime,
  content: SimContent,
) {
  const able = crews.filter((c) => c.model.cargoCapacityTonnes >= band.min);
  if (able.length === 0) return null;
  const start = rng.int(0, able.length - 1);
  for (let k = 0; k < able.length; k++) {
    const { model, skills } = able[(start + k) % able.length]!;
    const reachable = discovered.filter(
      (d) =>
        checkRoute(model, origin, d, content.config).ok &&
        requiredLongHaulLevel(routeDistance(origin, d), content.config) <=
          skillLevel(skills, LONG_HAUL_SKILL_ID),
    );
    if (reachable.length === 0) continue;
    const destination = rng.pick(reachable);
    // Only goods this pilot may carry: a good's own tier must not exceed their skill.
    const qualified = (g: Good) => {
      const skillId = cargoClassOf(g, content).requiredSkillId;
      return skillId === null || skillLevel(skills, skillId) >= (g.tier ?? 1);
    };
    // Any good on this route the crew is qualified for and the ship can carry
    // (CR-008 fix): picking a class first left e.g. a Heavy-skilled Courier at the
    // Moon with nothing but undersized Lunar Titanium lots.
    const fitting = content.goods.filter(
      (g) =>
        g.producedAt.includes(origin.id) &&
        g.demandedAt.includes(destination.id) &&
        qualified(g) &&
        fitsSlot(g, band, content, model.cargoCapacityTonnes),
    );
    let candidates = fitting;
    if (candidates.length === 0) {
      // Nothing on the route fits: a class from the class mix, as a bulk lot if need be.
      const skilled = content.cargoTypes.filter(
        (c) =>
          origin.cargoClassMix.produces.includes(c.id) &&
          destination.cargoClassMix.demands.includes(c.id) &&
          (c.requiredSkillId === null || skillLevel(skills, c.requiredSkillId) >= 1),
      );
      const cargoType = skilled.length > 0 ? rng.pick(skilled) : standardCargo(content);
      candidates = slotGoods(
        cargoType,
        origin,
        destination,
        band,
        content,
        qualified,
        model.cargoCapacityTonnes,
      );
    }
    const { good, massTonnes } = chooseGood(
      rng,
      candidates,
      band,
      content,
      model.cargoCapacityTonnes,
    );
    const skillId = cargoClassOf(good, content).requiredSkillId;
    const tier = tierFor(rng, good, content, skillId ? skillLevel(skills, skillId) : undefined);
    return { destination, good, tier, massTonnes, model };
  }
  return null;
}

/** A mass in [lo, hi]: to 0.1 t under 10 t, whole tonnes from there (CR-007). */
function drawMass(rng: Rng, lo: number, hi: number): number {
  const raw = lo + rng.next() * (hi - lo);
  const rounded = raw < 10 ? Math.round(raw * 10) / 10 : Math.round(raw);
  return Math.min(hi, Math.max(lo, rounded));
}

/**
 * A good and its mass for a slot (CR-007, "the band wins"): a good whose mass
 * range overlaps the slot's band (the lightest band has no floor), with mass in
 * both and within `capacity`; with no overlap, the candidate with the largest
 * range and a mass from the band, a bulk lot.
 */
/** The mass range a good can take in a slot (the lightest band has no floor), within `capacity`. */
function slotRange(good: Good, band: MassBand, content: SimContent, capacity: number) {
  const lightest = Math.min(...content.config.contractMassBands.map((b) => b.min));
  const floor = band.min === lightest ? 0 : band.min;
  return {
    lo: Math.max(floor, good.massTonnes.min),
    hi: Math.min(band.max, capacity, good.massTonnes.max),
  };
}

/**
 * Goods for a slot of this class (decision 0.5.54): the class's goods on the
 * route. If every one of them is too heavy for the slot (band and ship),
 * Standard goods on the route that fit instead (CR-008 fix: no 8 t lots of a
 * 30 t+ good). Goods too light for a big band stay, and `chooseGood` makes a
 * bulk lot of them ("the band wins").
 */
export function slotGoods(
  cargoType: CargoType,
  origin: Location,
  destination: Location,
  band: MassBand,
  content: SimContent,
  allow: (good: Good) => boolean = () => true,
  capacity = Infinity,
): Good[] {
  const goods = routeGoods(cargoType, origin, destination, content, allow);
  const ceiling = Math.min(band.max, capacity);
  if (!goods.every((g) => g.massTonnes.min > ceiling)) return goods;
  const standard = routeGoods(standardCargo(content), origin, destination, content, allow);
  return standard.some((g) => fitsSlot(g, band, content, capacity)) ? standard : goods;
}

/** Whether a good's own mass range fits the slot's band and the ship. */
export function fitsSlot(good: Good, band: MassBand, content: SimContent, capacity = Infinity) {
  const { lo, hi } = slotRange(good, band, content, capacity);
  return lo <= hi;
}

export function chooseGood(
  rng: Rng,
  candidates: readonly Good[],
  band: MassBand,
  content: SimContent,
  capacity = Infinity,
): { good: Good; massTonnes: number } {
  const ceiling = Math.min(band.max, capacity);
  const overlapping = candidates.filter((g) => fitsSlot(g, band, content, capacity));
  if (overlapping.length > 0) {
    const good = rng.pick(overlapping);
    const { lo, hi } = slotRange(good, band, content, capacity);
    return { good, massTonnes: drawMass(rng, lo, hi) };
  }
  const good = candidates.reduce((a, b) => (b.massTonnes.max > a.massTonnes.max ? b : a));
  return { good, massTonnes: drawMass(rng, band.min, ceiling) };
}

/**
 * A Priority contract's delivery window (decision 0.5.56): the reference
 * ship's trip time for this mass and route at offer time × the window factor.
 */
export function priorityWindow(
  origin: Location,
  destination: Location,
  massTonnes: number,
  content: SimContent,
): number {
  const { config } = content;
  const reference = content.shipModels.find((s) => s.id === config.priorityReferenceShipModelId);
  if (!reference) throw new Error(`Unknown ship model ${config.priorityReferenceShipModelId}`);
  const distance = routeDistance(origin, destination);
  return travelTimeGameHours(reference, distance, massTonnes, config) * config.priorityWindowFactor;
}

/**
 * Rolls Priority for an eligible good (decision 0.5.56). A fit job is Priority
 * only when its own ship (`model`) makes the window.
 */
function rollPriority(
  rng: Rng,
  args: {
    good: Good;
    origin: Location;
    destination: Location;
    massTonnes: number;
    offeredAt: RealTime;
    model?: ShipModel;
  },
  content: SimContent,
): { priority: boolean; deliveryWindowGameHours: number | null } {
  const none = { priority: false, deliveryWindowGameHours: null };
  if (!args.good.priorityEligible || rng.next() >= content.config.priorityChance) return none;
  const window = priorityWindow(args.origin, args.destination, args.massTonnes, content);
  if (args.model) {
    const distance = routeDistance(args.origin, args.destination);
    const trip = travelTimeGameHours(args.model, distance, args.massTonnes, content.config);
    if (trip > window) return none;
  }
  return { priority: true, deliveryWindowGameHours: window };
}

/** A board contract's market rate: uniform within ± `contractPayVariance` of 1 (decision 0.5.60). */
export function payRate(rng: Rng, content: SimContent): number {
  return 1 + content.config.contractPayVariance * (2 * rng.next() - 1);
}

export function cargoClassOf(good: Good, content: SimContent): CargoType {
  const cargoType = content.cargoTypes.find((c) => c.id === good.cargoClassId);
  if (!cargoType) throw new Error(`Unknown cargo class ${good.cargoClassId}`);
  return cargoType;
}

/**
 * A contract's tier (decision 0.5.55): Standard is 0, High-Value and Dangerous
 * take the good's tier, and Heavy rolls 1 to `maxTier` (the skill's maximum,
 * or a pilot's level for a fit job).
 */
export function tierFor(rng: Rng, good: Good, content: SimContent, maxTier?: number): number {
  const cargoType = cargoClassOf(good, content);
  if (cargoType.requiredSkillId === null) return 0;
  if (good.tier !== undefined) return good.tier;
  return maxTier === undefined ? pickTier(rng, cargoType, content) : rng.int(1, maxTier);
}

/** Builds one contract from a chosen route, good, tier and mass. */
export function buildContract(
  args: {
    id: string;
    origin: Location;
    destination: Location;
    good: Good;
    tier: number;
    massTonnes: number;
    firstContact: boolean;
    periodIndex: number;
    shipper: string;
    priority: boolean;
    deliveryWindowGameHours: number | null;
    /** Market rate (decision 0.5.60); 1 when absent, as on the tutorial board. */
    payRate?: number;
  },
  content: SimContent,
): Contract {
  const { config } = content;
  const cargoType = cargoClassOf(args.good, content);
  const offeredAt = args.periodIndex * boardPeriodMs(config);
  const distance = routeDistance(args.origin, args.destination);
  return {
    id: args.id,
    originId: args.origin.id,
    destinationId: args.destination.id,
    cargoTypeId: cargoType.id,
    goodId: args.good.id,
    shipper: args.shipper,
    priority: args.priority,
    deliveryWindowGameHours: args.priority ? args.deliveryWindowGameHours : null,
    tier: args.tier,
    massTonnes: args.massTonnes,
    payout: contractPayout(
      {
        cargoType,
        payMultiplier: args.good.payMultiplier,
        tier: args.tier,
        massTonnes: args.massTonnes,
        distanceMillionKm: distance,
        firstContact: args.firstContact,
        priority: args.priority,
        marketRate: args.payRate ?? 1,
      },
      config,
    ),
    requiredSkill:
      cargoType.requiredSkillId === null
        ? null
        : { skillId: cargoType.requiredSkillId, level: args.tier },
    requiredLongHaulLevel: requiredLongHaulLevel(distance, config),
    offeredAt,
    expiresAt: offeredAt + boardPeriodMs(config),
    firstContact: args.firstContact,
  };
}

/**
 * The goods a contract of this class can carry on this route (decision 0.5.54):
 * that class's goods made at the origin and wanted at the destination; else
 * Standard goods on the route; else any Standard good made at the origin.
 * `allow` filters out goods a crew can't take (fit jobs).
 */
export function routeGoods(
  cargoType: CargoType,
  origin: Location,
  destination: Location,
  content: SimContent,
  allow: (good: Good) => boolean = () => true,
): Good[] {
  const made = content.goods.filter((g) => g.producedAt.includes(origin.id) && allow(g));
  const onRoute = made.filter((g) => g.demandedAt.includes(destination.id));
  const ofClass = onRoute.filter((g) => g.cargoClassId === cargoType.id);
  if (ofClass.length > 0) return ofClass;
  const standardId = standardCargo(content).id;
  const standardOnRoute = onRoute.filter((g) => g.cargoClassId === standardId);
  if (standardOnRoute.length > 0) return standardOnRoute;
  const anyStandard = content.goods.filter(
    (g) => g.producedAt.includes(origin.id) && g.cargoClassId === standardId,
  );
  if (anyStandard.length === 0) throw new Error(`${origin.id} makes no Standard good`);
  return anyStandard;
}

function pickCargo(rng: Rng, origin: Location, destination: Location, content: SimContent) {
  const matching = content.cargoTypes.filter(
    (c) =>
      origin.cargoClassMix.produces.includes(c.id) &&
      destination.cargoClassMix.demands.includes(c.id),
  );
  // Decision 0.5.17: fall back to Standard when no produced cargo is demanded.
  return matching.length > 0 ? rng.pick(matching) : standardCargo(content);
}

function pickTier(rng: Rng, cargoType: CargoType, content: SimContent): number {
  if (cargoType.requiredSkillId === null) return 0;
  const skill = content.skills.find((s) => s.id === cargoType.requiredSkillId);
  if (!skill) throw new Error(`Unknown skill ${cargoType.requiredSkillId}`);
  return rng.int(1, skill.maxLevel);
}

/**
 * Generates a location's contract board for one period (any discovered
 * location, bay or not, CR-002): `contractMassBands` decide how
 * many contracts fall in each ship-size mass band, shaped by the player's fleet
 * when given (CR-006). With a fleet, only jobs some pair can complete are kept
 * (decision 0.5.114): candidates are drawn slot by slot, round and round, until
 * the board is full or `boardMaxAttempts` candidates have been tried, so a
 * fleet that can do little gets a smaller board. Same inputs always give the
 * same board.
 */
export function generateContractBoard(input: BoardInput, content: SimContent): Contract[] {
  const { location: origin, discoveredIds, periodIndex, worldSeed } = input;
  const { config } = content;
  const rng = createRng(deriveSeed(worldSeed, `board:${origin.id}:${periodIndex}`));

  const others = content.locations.filter((l) => l.id !== origin.id);
  const discovered = others.filter((l) => discoveredIds.has(l.id));
  const undiscovered = others.filter((l) => !discoveredIds.has(l.id));

  const crews: Crew[] = (input.fleet ?? []).flatMap((f) => {
    const model = content.shipModels.find((m) => m.id === f.modelId);
    return model
      ? [{ model: effectiveStats(model, f.upgrades ?? {}, content), skills: f.skills }]
      : [];
  });
  const offeredAt = periodIndex * boardPeriodMs(config);

  // One slot per contract, band by band. A guaranteed slot is Standard cargo
  // (no skill) to a discovered place, so every ship size always has something
  // a new pilot can fly; fit slots are built for the player's own ships.
  // One fit slot per board is a first contact the fleet can fly, while anywhere
  // reachable is undiscovered (decision 0.5.85): exploring never waits on luck.
  let firstContactOffered = false;
  const candidate = ({ band, kind }: { band: MassBand; kind: SlotKind }, id: string) => {
    const explore =
      kind === "fit" && !firstContactOffered && undiscovered.length > 0
        ? fitJob(rng, band, crews, origin, undiscovered, offeredAt, content)
        : null;
    const fit =
      explore ??
      (kind === "fit" ? fitJob(rng, band, crews, origin, discovered, offeredAt, content) : null);
    if (fit) {
      const { model, ...job } = fit;
      const contract = buildContract(
        {
          id,
          origin,
          ...job,
          firstContact: explore !== null,
          periodIndex,
          ...rollPriority(rng, { ...job, origin, offeredAt, model }, content),
          shipper: rng.pick(origin.shippers),
          payRate: payRate(rng, content),
        },
        content,
      );
      return { contract, explored: explore !== null };
    }
    const guaranteed = kind !== "open";
    const plain = guaranteed && discovered.length > 0;
    const firstContact =
      !plain &&
      undiscovered.length > 0 &&
      (discovered.length === 0 || rng.next() < config.firstContactChance);
    const destination = rng.pick(firstContact ? undiscovered : discovered);
    const cargoType = plain ? standardCargo(content) : pickCargo(rng, origin, destination, content);
    const { good, massTonnes } = chooseGood(
      rng,
      slotGoods(cargoType, origin, destination, band, content),
      band,
      content,
    );
    const contract = buildContract(
      {
        id,
        origin,
        destination,
        good,
        tier: tierFor(rng, good, content),
        massTonnes,
        firstContact,
        periodIndex,
        ...rollPriority(rng, { good, origin, destination, massTonnes, offeredAt }, content),
        shipper: rng.pick(origin.shippers),
        payRate: payRate(rng, content),
      },
      content,
    );
    return { contract, explored: false };
  };

  const slots = planSlots(crews, config);
  const fleet = input.fleet;
  if (!fleet)
    return slots.map((slot, i) => candidate(slot, `${origin.id}:${periodIndex}:${i}`).contract);
  const board: Contract[] = [];
  for (
    let attempt = 0;
    board.length < slots.length && attempt < config.boardMaxAttempts;
    attempt++
  ) {
    const { contract, explored } = candidate(
      slots[attempt % slots.length]!,
      `${origin.id}:${periodIndex}:${board.length}`,
    );
    if (!isCompletable(contract, fleet, discoveredIds, content)) continue;
    board.push(contract);
    if (explored) firstContactOffered = true;
  }
  return board;
}