/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/shares/shares.mjs
 *  Purpose : Share links — base58 tokens, expiry, passwords, limits, logging
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { randomBytes, timingSafeEqual } from 'node:crypto';
import argon2 from 'argon2';
import { getDb, logActivity } from '../db/db.mjs';
import { mustGetNode } from '../storage/nodes.mjs';

// 58^10 ≈ 4.3e17 ≈ 58.6 bits of entropy — matches the security checklist.
const BASE58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';
const TOKEN_LEN = 10;

/** Uniform base58 token of the given length (default: share length). */
export function makeToken(len = TOKEN_LEN) {
  const bytes = randomBytes(len * 2);
  let out = '';
  for (let i = 0; out.length < len && i < bytes.length; i += 1) {
    // Rejection sampling keeps the distribution uniform across the alphabet.
    if (bytes[i] < 232) out += BASE58[bytes[i] % 58];
  }
  while (out.length < len) out += BASE58[randomBytes(1)[0] % 58];
  return out;
}

/**
 * Create a share for a node.
 * @param {{expiresAt?: number|null, password?: string|null, maxDownloads?: number|null,
 *          allowDownload?: boolean, label?: string|null, ip?: string}} opts
 */
export async function createShare(nodeId, opts = {}) {
  const node = mustGetNode(nodeId);
  if (node.trashed_at) throw Object.assign(new Error('Cannot share a trashed item'), { statusCode: 400 });
  const token = makeToken();
  const passwordHash = opts.password
    ? await argon2.hash(opts.password, { type: argon2.argon2id })
    : null;
  const info = getDb()
    .prepare(
      `INSERT INTO shares (token, node_id, created, expires_at, password_hash, max_downloads, allow_download, label)
       VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
    )
    .run(
      token, nodeId, Date.now(), opts.expiresAt ?? null, passwordHash,
      opts.maxDownloads ?? null, opts.allowDownload === false ? 0 : 1, opts.label ?? null,
    );
  logActivity('share.create', { nodeId, detail: token, ip: opts.ip ?? '' });
  return getShareById(Number(info.lastInsertRowid));
}

/** Update share options (expiry, password, limits, label). */
export async function updateShare(id, opts = {}) {
  const db = getDb();
  const share = getShareById(id);
  if (!share) return null;
  const passwordHash = opts.password === undefined
    ? share.password_hash
    : opts.password
      ? await argon2.hash(opts.password, { type: argon2.argon2id })
      : null;
  db.prepare(
    `UPDATE shares SET expires_at = ?, password_hash = ?, max_downloads = ?, allow_download = ?, label = ?
     WHERE id = ?`,
  ).run(
    opts.expiresAt !== undefined ? opts.expiresAt : share.expires_at,
    passwordHash,
    opts.maxDownloads !== undefined ? opts.maxDownloads : share.max_downloads,
    opts.allowDownload !== undefined ? (opts.allowDownload ? 1 : 0) : share.allow_download,
    opts.label !== undefined ? opts.label : share.label,
    id,
  );
  return getShareById(id);
}

export function getShareById(id) {
  return getDb().prepare('SELECT * FROM shares WHERE id = ?').get(id) ?? null;
}

/**
 * Constant-time token lookup.
 * @returns {object|null} the share row (regardless of validity)
 */
export function getShareByToken(token) {
  if (typeof token !== 'string' || token.length !== TOKEN_LEN) return null;
  // Indexed fetch, then constant-time comparison of the candidate.
  const row = getDb().prepare('SELECT * FROM shares WHERE token = ?').get(token);
  if (!row) return null;
  const a = Buffer.from(row.token);
  const b = Buffer.from(token);
  if (a.length !== b.length || !timingSafeEqual(a, b)) return null;
  return row;
}

/**
 * Validity check used by every public route.
 * @returns {{ok: true} | {ok: false, reason: 'revoked'|'expired'|'exhausted'|'missing'}}
 */
export function shareValidity(share) {
  if (!share) return { ok: false, reason: 'missing' };
  if (share.revoked_at) return { ok: false, reason: 'revoked' };
  if (share.expires_at && share.expires_at < Date.now()) return { ok: false, reason: 'expired' };
  if (share.max_downloads !== null && share.downloads >= share.max_downloads) {
    return { ok: false, reason: 'exhausted' };
  }
  return { ok: true };
}

/** Check a visitor-supplied password against the share. */
export async function verifySharePassword(share, password) {
  if (!share.password_hash) return true;
  try {
    return await argon2.verify(share.password_hash, password ?? '');
  } catch {
    return false;
  }
}

/** Record a visit or download (also mirrored into the activity log). */
export function recordShareEvent(shareId, kind, { ip = '', ua = '' } = {}) {
  const db = getDb();
  db.prepare('INSERT INTO share_events (share_id, ts, kind, ip, ua) VALUES (?, ?, ?, ?, ?)')
    .run(shareId, Date.now(), kind, ip, ua.slice(0, 300));
  db.prepare(
    kind === 'download'
      ? 'UPDATE shares SET downloads = downloads + 1 WHERE id = ?'
      : 'UPDATE shares SET visits = visits + 1 WHERE id = ?',
  ).run(shareId);
  const share = getShareById(shareId);
  logActivity(`share.${kind}`, { nodeId: share?.node_id, detail: share?.token, ip });
}

/** All shares with node info, newest first (share manager). */
export function listShares() {
  return getDb()
    .prepare(
      `SELECT s.*, n.name AS node_name, n.type AS node_type, n.size AS node_size, n.mime AS node_mime
       FROM shares s JOIN nodes n ON n.id = s.node_id
       ORDER BY s.created DESC`,
    )
    .all();
}

/** Shares attached to one node (info panel). */
export function sharesForNode(nodeId) {
  return getDb().prepare('SELECT * FROM shares WHERE node_id = ? AND revoked_at IS NULL ORDER BY created DESC').all(nodeId);
}

/** Recent visit/download events for one share. */
export function shareEvents(shareId, limit = 100) {
  return getDb()
    .prepare('SELECT ts, kind, ip, ua FROM share_events WHERE share_id = ? ORDER BY ts DESC LIMIT ?')
    .all(shareId, limit);
}

/** Revoke immediately (public link dies on the next request). */
export function revokeShare(id, { ip = '' } = {}) {
  const share = getShareById(id);
  if (!share) return false;
  getDb().prepare('UPDATE shares SET revoked_at = ? WHERE id = ?').run(Date.now(), id);
  logActivity('share.revoke', { nodeId: share.node_id, detail: share.token, ip });
  return true;
}

/** Delete revoked/expired shares older than 90 days (daily job). */
export function pruneShares() {
  const cutoff = Date.now() - 90 * 86_400_000;
  return getDb()
    .prepare(
      `DELETE FROM shares WHERE (revoked_at IS NOT NULL AND revoked_at < ?)
       OR (expires_at IS NOT NULL AND expires_at < ?)`,
    )
    .run(cutoff, cutoff).changes;
}