/**
 * 读取 Windows PE（NSIS 安装包）里的 `VS_VERSION_INFO`。
 *
 * 为什么需要它：AGC 的渠道身份会同时进产物文件名**和**PE 资源里的 `ProductName` /
 * `FileVersion`。只核对文件名等于相信「谁都没改过这个文件」；2026-09-28 的 dev-mac 事故
 * 就是「清单指着一个身份/版本都不对的包」，mac 侧靠解 `Info.plist` 抓到，Windows 侧
 * 需要对称的能力：确认发布出去的 `.exe` 内部确实写着本渠道产品名与本轮版本。
 *
 * 只解析需要的部分：资源目录 → `RT_VERSION` → `VS_FIXEDFILEINFO` 与 `StringFileInfo`。
 */

const SECTION_HEADER_SIZE = 40;
const RESOURCE_DIRECTORY_HEADER_SIZE = 16;
const RESOURCE_DIRECTORY_ENTRY_SIZE = 8;
const RT_VERSION = 16;

function align4(value) {
  return (value + 3) & ~3;
}

/** 读 UTF-16 字符串（含结尾 NUL），并把游标对齐到 4 字节边界。 */
function readUtf16z(buffer, offset, limit) {
  let end = offset;
  const endLimit = limit ?? buffer.length - 1;
  while (end + 1 < endLimit && !(buffer[end] === 0 && buffer[end + 1] === 0)) {
    end += 2;
  }
  return {
    text: buffer.toString('utf16le', offset, end),
    next: align4(end + 2),
  };
}

function readOptionalHeaderLayout(buffer, peOffset) {
  const coffOffset = peOffset + 4;
  const sectionCount = buffer.readUInt16LE(coffOffset + 2);
  const optionalSize = buffer.readUInt16LE(coffOffset + 16);
  const optionalOffset = coffOffset + 20;
  const magic = buffer.readUInt16LE(optionalOffset);
  if (magic !== 0x10b && magic !== 0x20b) {
    throw new Error(`PE 可选头 magic 不受支持：0x${magic.toString(16)}`);
  }
  return {
    sectionCount,
    optionalOffset,
    sectionOffset: optionalOffset + optionalSize,
    dataDirectoryOffset: optionalOffset + (magic === 0x20b ? 112 : 96),
  };
}

function readSections(buffer, layout) {
  const sections = [];
  for (let index = 0; index < layout.sectionCount; index += 1) {
    const base = layout.sectionOffset + index * SECTION_HEADER_SIZE;
    sections.push({
      virtualSize: buffer.readUInt32LE(base + 8),
      virtualAddress: buffer.readUInt32LE(base + 12),
      rawSize: buffer.readUInt32LE(base + 16),
      rawPointer: buffer.readUInt32LE(base + 20),
    });
  }
  return sections;
}

function rvaToOffset(sections, rva) {
  for (const section of sections) {
    const size = Math.max(section.virtualSize, section.rawSize);
    if (rva >= section.virtualAddress && rva < section.virtualAddress + size) {
      return rva - section.virtualAddress + section.rawPointer;
    }
  }
  throw new Error(`资源 RVA 0x${rva.toString(16)} 不属于任何节`);
}

function readDirectoryEntries(buffer, offset) {
  const named = buffer.readUInt16LE(offset + 12);
  const ids = buffer.readUInt16LE(offset + 14);
  const entries = [];
  for (let index = 0; index < named + ids; index += 1) {
    const base =
      offset +
      RESOURCE_DIRECTORY_HEADER_SIZE +
      index * RESOURCE_DIRECTORY_ENTRY_SIZE;
    entries.push({
      id: buffer.readUInt32LE(base),
      offset: buffer.readUInt32LE(base + 4),
    });
  }
  return entries;
}

/** 找到 `RT_VERSION` 资源并返回它在文件里的偏移与长度。 */
function findVersionResource(buffer) {
  if (buffer.length < 64 || buffer.readUInt16LE(0) !== 0x5a4d) {
    throw new Error('不是 PE 文件（缺少 MZ 头）');
  }
  const peOffset = buffer.readUInt32LE(0x3c);
  if (
    peOffset + 24 > buffer.length ||
    buffer.readUInt32LE(peOffset) !== 0x00004550
  ) {
    throw new Error('不是 PE 文件（缺少 PE 签名）');
  }
  const layout = readOptionalHeaderLayout(buffer, peOffset);
  const sections = readSections(buffer, layout);
  const resourceRva = buffer.readUInt32LE(layout.dataDirectoryOffset + 2 * 8);
  if (!resourceRva) throw new Error('可执行文件没有资源目录');
  const resourceOffset = rvaToOffset(sections, resourceRva);
  const typeEntry = readDirectoryEntries(buffer, resourceOffset).find(
    (entry) => entry.id === RT_VERSION,
  );
  if (!typeEntry) throw new Error('资源目录里没有 RT_VERSION');
  const nameEntry = readDirectoryEntries(
    buffer,
    resourceOffset + (typeEntry.offset & 0x7fffffff),
  )[0];
  const languageEntry = readDirectoryEntries(
    buffer,
    resourceOffset + (nameEntry.offset & 0x7fffffff),
  )[0];
  const dataEntryOffset = resourceOffset + languageEntry.offset;
  const versionRva = buffer.readUInt32LE(dataEntryOffset);
  const versionSize = buffer.readUInt32LE(dataEntryOffset + 4);
  return {
    offset: rvaToOffset(sections, versionRva),
    size: versionSize,
  };
}

function readVersionBlock(buffer, offset, limit) {
  const length = buffer.readUInt16LE(offset);
  const valueLength = buffer.readUInt16LE(offset + 2);
  const key = readUtf16z(buffer, offset + 6, limit);
  return {
    offset,
    length,
    valueLength,
    key: key.text,
    valueOffset: key.next,
  };
}

function formatFixedVersion(ms, ls) {
  return `${(ms >>> 16) & 0xffff}.${ms & 0xffff}.${(ls >>> 16) & 0xffff}.${ls & 0xffff}`;
}

function readStringFileInfo(buffer, block) {
  const strings = {};
  let tableCursor = align4(block.valueOffset + block.valueLength);
  const blockEnd = block.offset + block.length;
  while (tableCursor + 6 <= blockEnd) {
    const table = readVersionBlock(buffer, tableCursor, blockEnd);
    if (table.length === 0) break;
    let entryCursor = align4(table.valueOffset + table.valueLength);
    const tableEnd = table.offset + table.length;
    while (entryCursor + 6 <= tableEnd) {
      const entry = readVersionBlock(buffer, entryCursor, tableEnd);
      if (entry.length === 0) break;
      strings[entry.key] = buffer
        .toString(
          'utf16le',
          entry.valueOffset,
          entry.valueOffset + entry.valueLength * 2,
        )
        .replace(/\0+$/u, '');
      entryCursor = align4(entry.offset + entry.length);
    }
    tableCursor = align4(table.offset + table.length);
  }
  return strings;
}

/**
 * 读出 PE 版本资源里的版本号与字符串表。
 *
 * 返回 `{ fileVersion, productVersion, strings }`；`strings` 通常含
 * `ProductName` / `FileDescription` / `FileVersion` / `ProductVersion`。
 */
export function readPortableExecutableVersionInfo(buffer) {
  if (!Buffer.isBuffer(buffer)) throw new Error('需要传入 PE 文件的 Buffer');
  const resource = findVersionResource(buffer);
  const root = readVersionBlock(
    buffer,
    resource.offset,
    resource.offset + resource.size,
  );
  if (root.key !== 'VS_VERSION_INFO') {
    throw new Error(`版本资源根节点异常：${root.key}`);
  }
  const fixedOffset = root.valueOffset;
  const signature = buffer.readUInt32LE(fixedOffset);
  if (signature !== 0xfeef04bd) {
    throw new Error(`VS_FIXEDFILEINFO 签名异常：0x${signature.toString(16)}`);
  }
  const fixed = {
    fileVersion: formatFixedVersion(
      buffer.readUInt32LE(fixedOffset + 8),
      buffer.readUInt32LE(fixedOffset + 12),
    ),
    productVersion: formatFixedVersion(
      buffer.readUInt32LE(fixedOffset + 16),
      buffer.readUInt32LE(fixedOffset + 20),
    ),
  };
  let strings = {};
  let cursor = align4(fixedOffset + root.valueLength);
  const rootEnd = root.offset + root.length;
  while (cursor + 6 <= rootEnd) {
    const child = readVersionBlock(buffer, cursor, rootEnd);
    if (child.length === 0) break;
    if (child.key === 'StringFileInfo') {
      strings = readStringFileInfo(buffer, child);
    }
    cursor = align4(child.offset + child.length);
  }
  return { ...fixed, strings };
}