// Pure helpers for the offline hotseat (pass-and-play) creation roster: keeping a last-valid name as
// a row is edited, and turning the finished roster into engine seats. Kept out of the component so it
// is unit-testable; the form itself is exercised by the e2e layer.

import { validDisplayName } from './profileValidation';
import type { PinLock } from './pin';
import type { Seat } from './localgame/serialize';

/** RosterRow is one editable player row: the live input, the last valid name kept when the input
 *  goes invalid, and the optional per-seat PIN lock. */
export interface RosterRow {
  name: string;
  committed: string;
  pin?: PinLock;
}

/** commitName returns the new last-valid name: the trimmed input when it is a valid display name,
 *  otherwise prevCommitted unchanged — so editing a set name into an invalid one keeps the old one. */
export function commitName(input: string, prevCommitted: string): string {
  return validDisplayName(input) ? input.trim() : prevCommitted;
}

/** rosterReady reports whether the roster can start a game: 2-4 rows, each with a committed name. */
export function rosterReady(rows: RosterRow[]): boolean {
  return rows.length >= 2 && rows.length <= 4 && rows.every((r) => r.committed !== '');
}

/** buildSeats turns committed roster rows into engine seats — all human, account-less (local
 *  players sharing a device), carrying each row's optional PIN. */
export function buildSeats(rows: RosterRow[]): Seat[] {
  return rows.map((r): Seat => ({ kind: 'human', name: r.committed, pin: r.pin }));
}

/**
 * shuffleSeeded returns a deterministic shuffle of items driven by seed — a Fisher-Yates over a small
 * in-house PRNG (a distinct seed derivation from the tile bag, so the seating is not correlated with
 * the tile draws). Used to randomise the hotseat seating at game start, so the first mover is random;
 * being seed-driven keeps it reproducible for replay and tests.
 */
export function shuffleSeeded<T>(items: readonly T[], seed: bigint): T[] {
  const out = [...items];
  let a = (Number(BigInt.asUintN(32, seed ^ 0x9e3779b9n)) >>> 0) || 1;
  const rand = (): number => {
    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;
  };
  for (let i = out.length - 1; i > 0; i--) {
    const j = Math.floor(rand() * (i + 1));
    [out[i], out[j]] = [out[j], out[i]];
  }
  return out;
}