/*
Copyright 2026 Lotus Guild

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE in the repository root for full details.
*/

/**
 * [element-call #36] Remember the per-participant volume slider across calls,
 * reloads and reconnects. Keyed by Matrix user id (not device), so "Bob is
 * loud" sticks when Bob switches devices. Local to this browser, never synced.
 * Only voice is remembered; screenshare audio stays per-share.
 */

const STORAGE_KEY = "lotus-per-user-volume";
/** Most recently set entries kept; older ones are dropped. */
export const MAX_REMEMBERED = 50;

type VolumeMap = Record<string, number>;

const isVolume = (v: unknown): v is number =>
  typeof v === "number" && Number.isFinite(v) && v >= 0 && v <= 4;

function load(): VolumeMap {
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (!raw) return {};
    const parsed: unknown = JSON.parse(raw);
    if (typeof parsed !== "object" || parsed === null) return {};
    const out: VolumeMap = {};
    for (const [k, v] of Object.entries(parsed)) if (isVolume(v)) out[k] = v;
    return out;
  } catch {
    return {};
  }
}

function save(map: VolumeMap): void {
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(map));
  } catch {
    // Storage unavailable (private mode, quota): the slider just won't stick.
  }
}

/** The remembered volume for `userId`, or 1 (100 %) if none. */
export function getRememberedVolume(userId: string): number {
  return load()[userId] ?? 1;
}

/**
 * Remember `volume` for `userId`. 1 (the default) forgets the entry. The entry
 * moves to the end so the map is in least-recently-set order, trimmed to
 * MAX_REMEMBERED.
 */
export function rememberVolume(userId: string, volume: number): void {
  if (!isVolume(volume)) return;
  const map = load();
  delete map[userId];
  if (volume !== 1) map[userId] = volume;
  const keys = Object.keys(map);
  for (const k of keys.slice(0, Math.max(0, keys.length - MAX_REMEMBERED)))
    delete map[k];
  save(map);
}