import fs from 'node:fs/promises';

import { session } from 'electron';

import { asAssetId } from '../../shared/types/ids';
import type { ZipProjectStore } from '../project/zipStore';

/**
 * Обслуживает `dnd://asset?...` — без этого `<img src="file://...">` в рендерере часто ломается.
 */
export function registerDndAssetProtocol(projectStore: ZipProjectStore): void {
  session.defaultSession.protocol.handle('dnd', async (request) => {
    const url = new URL(request.url);
    if (url.hostname !== 'asset') {
      return new Response(null, { status: 404 });
    }
    const id = url.searchParams.get('id');
    if (!id) {
      return new Response(null, { status: 404 });
    }
    const info = projectStore.getAssetReadInfo(asAssetId(id));
    if (!info) {
      return new Response(null, { status: 404 });
    }
    try {
      const stat = await fs.stat(info.absPath);
      const total = stat.size;
      const range = request.headers.get('range') ?? request.headers.get('Range');

      if (range) {
        const m = /^bytes=(\d+)-(\d+)?$/iu.exec(range.trim());
        if (m) {
          const start = Number(m[1]);
          const endRaw = m[2] ? Number(m[2]) : total - 1;
          const end = Math.min(endRaw, total - 1);
          if (!Number.isFinite(start) || !Number.isFinite(end) || start < 0 || end < start) {
            return new Response(null, { status: 416 });
          }
          const len = end - start + 1;
          const fh = await fs.open(info.absPath, 'r');
          try {
            const buf = Buffer.alloc(len);
            await fh.read(buf, 0, len, start);
            return new Response(buf, {
              status: 206,
              headers: {
                'Content-Type': info.mime,
                'Accept-Ranges': 'bytes',
                'Content-Range': `bytes ${String(start)}-${String(end)}/${String(total)}`,
                'Content-Length': String(len),
                'Cache-Control': 'public, max-age=300',
              },
            });
          } finally {
            await fh.close();
          }
        }
      }

      const buf = await fs.readFile(info.absPath);
      return new Response(buf, {
        headers: {
          'Content-Type': info.mime,
          'Accept-Ranges': 'bytes',
          'Content-Length': String(buf.length),
          'Cache-Control': 'public, max-age=300',
        },
      });
    } catch {
      return new Response(null, { status: 404 });
    }
  });
}