// ── Canonical JSON ───────────────────────────────────────────

function sortKeys(obj: unknown): unknown {
  if (obj === null || obj === undefined || typeof obj !== 'object') return obj;
  if (Array.isArray(obj)) return obj.map(sortKeys);
  const sorted: Record<string, unknown> = {};
  for (const key of Object.keys(obj as Record<string, unknown>).sort()) {
    sorted[key] = sortKeys((obj as Record<string, unknown>)[key]);
  }
  return sorted;
}

export function canonicalJson(obj: unknown): string {
  return JSON.stringify(sortKeys(obj));
}

// ── Hashing ──────────────────────────────────────────────────

export async function sha256Hex(data: string): Promise<string> {
  const buf = await crypto.subtle.digest(
    'SHA-256',
    new TextEncoder().encode(data),
  );
  return Array.from(new Uint8Array(buf))
    .map((b) => b.toString(16).padStart(2, '0'))
    .join('');
}

// ── Event filenames ──────────────────────────────────────────

const HASH_PREFIX_LEN = 12;

export function eventFilename(ts: number, fullHash: string): string {
  return `${ts}_${fullHash.slice(0, HASH_PREFIX_LEN)}.json`;
}

const EVENT_FILE_RE = /^(\d+)_([0-9a-f]+)\.json$/;

export function parseEventFilename(
  name: string,
): { ts: number; hash: string } | null {
  const m = EVENT_FILE_RE.exec(name);
  if (!m) return null;
  return { ts: Number(m[1]), hash: m[2] };
}

// ── Client ID ────────────────────────────────────────────────

export function generateClientId(): string {
  return crypto.randomUUID();
}

// ── Index value extraction ───────────────────────────────────

export function extractIndexValue(
  data: unknown,
  fields: string[],
): IDBValidKey | undefined {
  if (!data || typeof data !== 'object') return undefined;
  const rec = data as Record<string, unknown>;

  if (fields.length === 1) {
    const v = getNestedValue(rec, fields[0]);
    if (v === undefined || v === null) return undefined;
    return toIDBKey(v);
  }

  const parts: IDBValidKey[] = [];
  for (const f of fields) {
    const v = getNestedValue(rec, f);
    if (v === undefined || v === null) return undefined;
    parts.push(toIDBKey(v));
  }
  return parts;
}

function getNestedValue(obj: Record<string, unknown>, path: string): unknown {
  let cur: unknown = obj;
  for (const seg of path.split('.')) {
    if (cur === null || cur === undefined || typeof cur !== 'object') {
      return undefined;
    }
    cur = (cur as Record<string, unknown>)[seg];
  }
  return cur;
}

function toIDBKey(v: unknown): IDBValidKey {
  if (typeof v === 'string' || typeof v === 'number') return v;
  if (v instanceof Date) return v;
  if (Array.isArray(v)) return v.map(toIDBKey);
  // Fallback: stringify
  return String(v);
}