/**
 * Presentation helpers for the profile picker.
 *
 * Pure, and separate from the component, because this is the half worth testing
 * and a component cannot be unit-tested without mounting it.
 *
 * Note what is *not* here: nothing decides whether a profile is locked, whether
 * a PIN is correct, or how many attempts remain. Those come from the backend as
 * an opaque `unlockMethod` and an `UnlockOutcome`. A child's profile is simply
 * one with no PIN — the app models no roles and infers no ages.
 *
 * TRACES: UR-082, UR-083 | DR-276
 */

import type { Profile } from "$lib/api/bindings";

/**
 * Order tiles as people expect to find them: whoever used the device last is
 * leftmost, and profiles that have never been used sort after those that have.
 *
 * TRACES: UR-082 | DR-276
 */
export function orderProfiles(profiles: Profile[]): Profile[] {
  return [...profiles].sort((a, b) => {
    if (a.lastUsedAt && b.lastUsedAt) return b.lastUsedAt.localeCompare(a.lastUsedAt);
    if (a.lastUsedAt) return -1;
    if (b.lastUsedAt) return 1;
    return a.username.localeCompare(b.username);
  });
}

/**
 * Initials for a tile with no avatar. At most two letters, because three fills
 * a circle badly at tile size.
 *
 * TRACES: UR-082 | DR-276
 */
export function initialsFor(username: string): string {
  const words = username
    .trim()
    .split(/[\s._-]+/)
    .filter(Boolean);
  if (words.length === 0) return "?";
  if (words.length === 1) return words[0].slice(0, 2).toUpperCase();
  return (words[0][0] + words[words.length - 1][0]).toUpperCase();
}

/**
 * A stable tile colour per profile, so a family learns to recognise their tile
 * by colour before they read the name. Derived from the user id rather than the
 * name, so renaming does not move someone's colour.
 *
 * TRACES: UR-082 | DR-276
 */
const TILE_COLOURS = ["#7b68ee", "#00a4dc", "#e8734a", "#3ba55d", "#d95f8e", "#c9a227"] as const;

export function tileColour(userId: string): string {
  let hash = 0;
  for (let i = 0; i < userId.length; i++) {
    hash = (hash * 31 + userId.charCodeAt(i)) >>> 0;
  }
  return TILE_COLOURS[hash % TILE_COLOURS.length];
}

/**
 * How long a lockout has left, phrased for a person rather than a log line.
 *
 * TRACES: UR-083 | DR-276
 */
export function lockoutMessage(until: string, now: Date = new Date()): string {
  const remainingMs = new Date(until).getTime() - now.getTime();
  if (!Number.isFinite(remainingMs) || remainingMs <= 0) return "Try again now";
  const minutes = Math.ceil(remainingMs / 60000);
  if (minutes <= 1) return "Try again in less than a minute";
  return `Try again in ${minutes} minutes`;
}