import type { SimContent } from "./board";
import type { RealTime } from "./clock";
import type { Contract } from "./contract";
import {
  contractTripGameHours,
  findLocation,
  findShipModel,
  tripFuel,
  wouldStrand,
  type DispatchFailure,
} from "./dispatch";
import { checkRoute } from "./eligibility";
import { checkPilotEligibility, type SkillLevels } from "./pilot";
import { effectiveStats, type UpgradeLevels } from "./upgrades";

/**
 * One ship-and-pilot pair's lasting capabilities (decision 0.5.115): the ship's
 * model and upgrades, its pilot's skills, and the fuel on board (which counts
 * only where the job's origin sells no fuel).
 */
export interface FleetMember {
  modelId: string;
  skills: SkillLevels;
  /** Installed upgrades: effective stats count (CR-009). */
  upgrades?: UpgradeLevels;
  /** Fuel on board; absent means a full tank. */
  fuelFu?: number;
}

/** The permanent checks, in order (decision 0.5.116): the dispatch reasons that can't be waited out. */
export const PERMANENT_FAILURES = [
  "over-capacity",
  "cannot-land",
  "out-of-range",
  "would-strand",
  "too-slow",
  "cargo-skill-too-low",
  "long-haul-too-low",
] as const satisfies readonly DispatchFailure[];
export type PermanentFailure = (typeof PERMANENT_FAILURES)[number];

/**
 * The first permanent check a pair fails for a contract, or null when it could
 * fly it once rested, out of the shop and refuelled (decision 0.5.116). Same
 * rules and order as `validateDispatch`, but the tank counts as full wherever
 * the origin sells fuel.
 */
export function permanentFailure(
  contract: Contract,
  member: FleetMember,
  discoveredIds: ReadonlySet<string> | undefined,
  content: SimContent,
): PermanentFailure | null {
  const model = effectiveStats(
    findShipModel(member.modelId, content),
    member.upgrades ?? {},
    content,
  );
  const origin = findLocation(contract.originId, content);
  const destination = findLocation(contract.destinationId, content);

  if (contract.massTonnes > model.cargoCapacityTonnes) return "over-capacity";
  const route = checkRoute(model, origin, destination, content.config);
  if (!route.ok) return route.reason;
  // Where the origin sells fuel the tank can be filled first; elsewhere only what's aboard.
  const available = origin.sellsFuel
    ? model.tankCapacityFu
    : Math.min(member.fuelFu ?? model.tankCapacityFu, model.tankCapacityFu);
  const leg = tripFuel(model, origin, destination, content.config);
  if (leg > available) return "out-of-range";
  if (wouldStrand(model, destination, available - leg, discoveredIds, content)) {
    return "would-strand";
  }
  if (
    contract.priority &&
    contract.deliveryWindowGameHours !== null &&
    contractTripGameHours(model, contract, content) > contract.deliveryWindowGameHours
  ) {
    return "too-slow";
  }
  const pilot = checkPilotEligibility(member.skills, contract);
  return pilot.ok ? null : pilot.reason;
}

export interface Completability {
  /** At least one pair passes every permanent check (decision 0.5.114). */
  completable: boolean;
  /** Per pair, in order: the first failing permanent check, or null. */
  failures: (PermanentFailure | null)[];
}

/** Whether any pair in `fleet` could complete `contract` (decisions 0.5.114, 0.5.116). */
export function completability(
  contract: Contract,
  fleet: readonly FleetMember[],
  discoveredIds: ReadonlySet<string> | undefined,
  content: SimContent,
): Completability {
  const failures = fleet.map((m) => permanentFailure(contract, m, discoveredIds, content));
  return { completable: failures.some((f) => f === null), failures };
}

/** Shorthand: true when some pair could complete the contract. */
export function isCompletable(
  contract: Contract,
  fleet: readonly FleetMember[],
  discoveredIds: ReadonlySet<string> | undefined,
  content: SimContent,
): boolean {
  return fleet.some((m) => permanentFailure(contract, m, discoveredIds, content) === null);
}

/** An owned ship as the qualifying-fleet rule sees it. */
export interface FleetShip {
  id: string;
  modelId: string;
  upgrades?: UpgradeLevels;
  fuelFu?: number;
  /** Where it is; null in flight. */
  locationId: string | null;
  /** In flight: where to, and when it lands. */
  destinationId?: string | null;
  arrivalAt?: RealTime | null;
}

/** A pilot as the qualifying-fleet rule sees it. */
export interface FleetPilot {
  id: string;
  skills: SkillLevels;
  assignedShipId: string | null;
  /** Where an unassigned pilot is; null otherwise. */
  locationId: string | null;
}

export interface QualifyingFleetInput {
  locationId: string;
  /** In a stable order: the snapshot (and so the board) follows it. */
  ships: readonly FleetShip[];
  pilots: readonly FleetPilot[];
  /** Locations with a player bay: unassigned pilots there can be assigned. */
  bayLocationIds: ReadonlySet<string>;
  /** The end of the board period: ships landing before then count. */
  periodEndsAt: RealTime;
}

export interface QualifyingFleet {
  members: FleetMember[];
  /** No pair qualified at the location, so this is the whole fleet. */
  wholeFleet: boolean;
}

const member = (ship: FleetShip, pilot: FleetPilot): FleetMember => ({
  modelId: ship.modelId,
  skills: pilot.skills,
  ...(ship.upgrades ? { upgrades: ship.upgrades } : {}),
  ...(ship.fuelFu !== undefined ? { fuelFu: ship.fuelFu } : {}),
});

/**
 * The pairs a location's board is made for (decision 0.5.115): ships there, or
 * landing there before the period ends, each with its assigned pilot, or with
 * any unassigned pilot there when the player has a bay there. With no such
 * pair, every ship with its pilot, or with any unassigned pilot, anywhere.
 */
export function qualifyingFleet(input: QualifyingFleetInput): QualifyingFleet {
  const { locationId, ships, pilots } = input;
  const unassigned = pilots.filter((p) => p.assignedShipId === null);
  const pairsFor = (ship: FleetShip, spare: readonly FleetPilot[]) => [
    ...pilots.filter((p) => p.assignedShipId === ship.id).map((p) => member(ship, p)),
    ...spare.map((p) => member(ship, p)),
  ];

  const here = ships.filter(
    (s) =>
      s.locationId === locationId ||
      (s.locationId === null &&
        s.destinationId === locationId &&
        s.arrivalAt != null &&
        s.arrivalAt < input.periodEndsAt),
  );
  const spareHere = input.bayLocationIds.has(locationId)
    ? unassigned.filter((p) => p.locationId === locationId)
    : [];
  const local = here.flatMap((s) => pairsFor(s, spareHere));
  if (local.length > 0) return { members: local, wholeFleet: false };
  return { members: ships.flatMap((s) => pairsFor(s, unassigned)), wholeFleet: true };
}