// Installs the pinned s3d release into Pithos's own bin folder. The digests are
// GitHub's published sha256 for each release asset; a download that does not
// match is discarded before anything is written to the bin folder.

import fs from 'node:fs';
import path from 'node:path';
import crypto from 'node:crypto';
import zlib from 'node:zlib';

export const S3D_VERSION = '0.2.0';

const ASSETS = {
  'win32-x64': { file: 's3d_windows_amd64.zip', sha256: '239356ef55228d03aa1889c7208357b83faf66947ade2cba4f7a3893c632c473' },
  'linux-x64': { file: 's3d_linux_amd64.zip', sha256: 'e537d68be8b6749e3e239d572c497a4f1ebc81ef5a3b70d5ec3cc9ffa6498e73' },
  'linux-arm64': { file: 's3d_linux_arm64.zip', sha256: '76848764f09922f31489c809514cdc928b3882836d6e5b64dcac085a84b4958b' },
  'darwin-x64': { file: 's3d_darwin_amd64.zip', sha256: 'd7fe282efab35242b001ed9040d833334034682225b4c2b6b2eda67ecca8992e' },
  'darwin-arm64': { file: 's3d_darwin_arm64.zip', sha256: '9eb6b73cb30b5b6b54fbbc583af6f7d9e56a30c55247ac70568918a1c98a3353' },
};

export function assetForPlatform() {
  return ASSETS[`${process.platform}-${process.arch}`] || null;
}

export async function installS3d(binDir, onProgress = () => {}) {
  const asset = assetForPlatform();
  if (!asset) throw new Error(`no s3d release for ${process.platform}-${process.arch}`);
  const url = `https://github.com/SiaFoundation/s3d/releases/download/v${S3D_VERSION}/${asset.file}`;
  onProgress({ phase: 'download', url });
  const res = await fetch(url, { redirect: 'follow' });
  if (!res.ok) throw new Error(`download failed: HTTP ${res.status}`);
  const zip = Buffer.from(await res.arrayBuffer());
  const digest = crypto.createHash('sha256').update(zip).digest('hex');
  if (digest !== asset.sha256) throw new Error(`checksum mismatch for ${asset.file} (got ${digest})`);
  onProgress({ phase: 'extract' });

  const exe = process.platform === 'win32' ? 's3d.exe' : 's3d';
  const data = extractFromZip(zip, (name) => path.basename(name) === exe);
  if (!data) throw new Error(`${exe} not found in ${asset.file}`);
  fs.mkdirSync(binDir, { recursive: true });
  const target = path.join(binDir, exe);
  const tmp = target + '.new';
  fs.writeFileSync(tmp, data, { mode: 0o755 });
  fs.renameSync(tmp, target);
  onProgress({ phase: 'done', path: target });
  return target;
}

// Minimal zip reader: walks the central directory and inflates one entry.
function extractFromZip(buf, match) {
  let eocd = -1;
  for (let i = buf.length - 22; i >= Math.max(0, buf.length - 65557); i--) {
    if (buf.readUInt32LE(i) === 0x06054b50) { eocd = i; break; }
  }
  if (eocd < 0) throw new Error('not a zip file');
  const count = buf.readUInt16LE(eocd + 10);
  let p = buf.readUInt32LE(eocd + 16);
  for (let n = 0; n < count; n++) {
    if (buf.readUInt32LE(p) !== 0x02014b50) throw new Error('corrupt zip directory');
    const method = buf.readUInt16LE(p + 10);
    const csize = buf.readUInt32LE(p + 20);
    const nameLen = buf.readUInt16LE(p + 28);
    const extraLen = buf.readUInt16LE(p + 30);
    const commentLen = buf.readUInt16LE(p + 32);
    const local = buf.readUInt32LE(p + 42);
    const name = buf.toString('utf8', p + 46, p + 46 + nameLen);
    p += 46 + nameLen + extraLen + commentLen;
    if (!match(name)) continue;
    const lName = buf.readUInt16LE(local + 26);
    const lExtra = buf.readUInt16LE(local + 28);
    const start = local + 30 + lName + lExtra;
    const raw = buf.subarray(start, start + csize);
    if (method === 0) return Buffer.from(raw);
    if (method === 8) return zlib.inflateRawSync(raw);
    throw new Error(`unsupported zip method ${method}`);
  }
  return null;
}