/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/web/http-helpers.mjs
 *  Purpose : Range-aware blob responses, rate limiting, content-type policy
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { blobPath, blobStream } from '../storage/blobs.mjs';
import { stat } from 'node:fs/promises';

/** MIME types that are safe to render inline; everything else downloads. */
const INLINE_SAFE = /^(image\/(?!svg)|video\/|audio\/|application\/pdf|text\/plain$)/;

/** RFC7233 single-range parser. Returns null when absent/invalid. */
export function parseRange(header, size) {
  if (!header || !header.startsWith('bytes=')) return null;
  const m = header.slice(6).split(',')[0].trim().match(/^(\d*)-(\d*)$/);
  if (!m || (m[1] === '' && m[2] === '')) return null;
  let start;
  let end;
  if (m[1] === '') {
    // suffix range: last N bytes
    const n = Number(m[2]);
    if (n === 0) return null;
    start = Math.max(0, size - n);
    end = size - 1;
  } else {
    start = Number(m[1]);
    end = m[2] === '' ? size - 1 : Number(m[2]);
  }
  if (Number.isNaN(start) || Number.isNaN(end) || start > end || start >= size) return null;
  return { start, end: Math.min(end, size - 1) };
}

/** RFC5987 filename* encoding for Content-Disposition. */
function contentDisposition(kind, filename) {
  const ascii = filename.replace(/[^\x20-\x7e]/g, '_').replace(/"/g, "'");
  return `${kind}; filename="${ascii}"; filename*=UTF-8''${encodeURIComponent(filename)}`;
}

/**
 * Stream a blob with full Range support (instant video seeking).
 * @param {{download?: boolean, mime?: string, filename?: string}} opts
 *   download=true forces attachment; inline is only allowed for safe types
 *   (uploaded HTML/SVG never executes same-origin — security checklist).
 */
export async function sendBlob(req, reply, { sha, mime, filename, download = false }) {
  const size = (await stat(blobPath(sha))).size;
  const type = mime || 'application/octet-stream';
  const inline = !download && INLINE_SAFE.test(type);
  const servedType = inline ? type : type === 'text/html' || type === 'image/svg+xml'
    ? type // still declared, but forced to attachment below
    : type;

  reply.header('Accept-Ranges', 'bytes');
  reply.header('X-Content-Type-Options', 'nosniff');
  reply.header('Content-Disposition', contentDisposition(inline ? 'inline' : 'attachment', filename));
  reply.header('Cache-Control', 'private, max-age=3600');
  reply.type(servedType);

  const range = parseRange(req.headers.range, size);
  if (range) {
    reply.code(206);
    reply.header('Content-Range', `bytes ${range.start}-${range.end}/${size}`);
    reply.header('Content-Length', range.end - range.start + 1);
    return reply.send(blobStream(sha, range));
  }
  reply.header('Content-Length', size);
  return reply.send(blobStream(sha));
}

/**
 * Serve an SVG blob inline but fully sandboxed (CSP sandbox, no scripts run).
 */
export async function sendSandboxedSvg(req, reply, { sha, filename }) {
  const size = (await stat(blobPath(sha))).size;
  reply.header('Content-Security-Policy', "sandbox; default-src 'none'; style-src 'unsafe-inline'");
  reply.header('X-Content-Type-Options', 'nosniff');
  reply.header('Content-Disposition', contentDisposition('inline', filename));
  reply.header('Cache-Control', 'private, max-age=3600');
  reply.header('Content-Length', size);
  reply.type('image/svg+xml');
  return reply.send(blobStream(sha));
}

/**
 * Fixed-window in-memory rate limiter.
 * @returns {(req, reply) => boolean} true when the request may proceed
 */
export function makeRateLimiter({ windowMs = 60_000, max = 100 } = {}) {
  const hits = new Map();
  setInterval(() => hits.clear(), windowMs).unref();
  return (req, reply) => {
    const key = req.ip;
    const count = (hits.get(key) ?? 0) + 1;
    hits.set(key, count);
    if (count > max) {
      reply.code(429).send({ error: { code: 'rate_limited', message: 'Too many requests' } });
      return false;
    }
    return true;
  };
}

/** Standard API error payload. */
export function apiError(reply, statusCode, code, message) {
  return reply.code(statusCode).send({ error: { code, message } });
}