// localStorage layer for the export "Advanced options" panel. Independent
// of exportFilterStorage so filter resets / profile switches don't disturb
// advanced settings (and vice versa). Strict parser — malformed value
// resets storage and returns null so the UI falls back to defaults.

const KEY = "ytdlp-tb:export-advanced";
const VERSION = 1;

export type AdvancedSnapshot = {
  hitBatchValue: number;
  hitBatchUnlimited: boolean;
  fetchConcurrency: number;
  flushIntervalMs: number;
};

type StoredAdvanced = {
  v: 1;
  s: AdvancedSnapshot;
};

function clampInt(
  v: unknown,
  min: number,
  max: number,
  fallback: number,
): number {
  if (typeof v !== "number" || !Number.isFinite(v)) return fallback;
  const n = Math.floor(v);
  if (n < min) return min;
  if (n > max) return max;
  return n;
}

// Tolerates v1 records that still carry the now-removed `groupsBatch*`
// fields — they're silently ignored. Only `hitBatchUnlimited` is required.
function parseSnapshot(raw: unknown): AdvancedSnapshot | null {
  if (!raw || typeof raw !== "object") return null;
  const r = raw as Record<string, unknown>;
  if (typeof r.hitBatchUnlimited !== "boolean") return null;
  return {
    hitBatchValue: clampInt(r.hitBatchValue, 1, 1_000_000, 500),
    hitBatchUnlimited: r.hitBatchUnlimited,
    fetchConcurrency: clampInt(r.fetchConcurrency, 1, 32, 6),
    flushIntervalMs: clampInt(r.flushIntervalMs, 16, 2000, 120),
  };
}

function parseStored(raw: string): AdvancedSnapshot | null {
  let parsed: unknown;
  try {
    parsed = JSON.parse(raw);
  } catch {
    return null;
  }
  if (!parsed || typeof parsed !== "object") return null;
  const r = parsed as Record<string, unknown>;
  if (r.v !== VERSION) return null;
  return parseSnapshot(r.s);
}

export function loadAdvanced(): AdvancedSnapshot | null {
  if (typeof window === "undefined") return null;
  let raw: string | null = null;
  try {
    raw = window.localStorage.getItem(KEY);
  } catch {
    return null;
  }
  if (raw === null) return null;
  const parsed = parseStored(raw);
  if (!parsed) {
    try {
      window.localStorage.removeItem(KEY);
    } catch {
      /* ignore */
    }
    return null;
  }
  return parsed;
}

export function saveAdvanced(snapshot: AdvancedSnapshot): void {
  if (typeof window === "undefined") return;
  const stored: StoredAdvanced = { v: VERSION, s: snapshot };
  try {
    window.localStorage.setItem(KEY, JSON.stringify(stored));
  } catch {
    /* quota/serialization errors are non-fatal */
  }
}

export function clearAdvanced(): void {
  if (typeof window === "undefined") return;
  try {
    window.localStorage.removeItem(KEY);
  } catch {
    /* ignore */
  }
}