"use strict";

const fs = require("node:fs");
const fsp = require("node:fs/promises");
const { spawnSync } = require("node:child_process");

const WINDOWS_DIRECTORY_FLUSH = [
  "$ErrorActionPreference='Stop'",
  "$source='using System; using System.Runtime.InteropServices; public static class AasDirectoryFlush { [DllImport(\"kernel32.dll\", CharSet=CharSet.Unicode, SetLastError=true)] public static extern IntPtr CreateFileW(string n, uint a, uint s, IntPtr p, uint c, uint f, IntPtr t); [DllImport(\"kernel32.dll\", SetLastError=true)] public static extern bool FlushFileBuffers(IntPtr h); [DllImport(\"kernel32.dll\", SetLastError=true)] public static extern bool CloseHandle(IntPtr h); }'",
  "Add-Type -TypeDefinition $source",
  // FlushFileBuffers requires a handle opened with GENERIC_WRITE. Keep all
  // sharing flags so the durability probe does not become an exclusivity lock.
  "$h=[AasDirectoryFlush]::CreateFileW($args[0],0x40000000,7,[IntPtr]::Zero,3,0x02000000,[IntPtr]::Zero)",
  "if($h -eq [IntPtr](-1)){throw 'CreateFileW failed'}",
  "try{if(-not [AasDirectoryFlush]::FlushFileBuffers($h)){throw 'FlushFileBuffers failed'}}finally{[void][AasDirectoryFlush]::CloseHandle($h)}",
].join(";");

function durabilityError(cause) {
  const error = new Error("AAS_DURABILITY_CAPABILITY_UNAVAILABLE", { cause });
  error.code = "AAS_DURABILITY_CAPABILITY_UNAVAILABLE";
  error.category = "filesystem";
  error.details = {};
  return error;
}

function flushWindowsDirectory(directoryPath, cause) {
  if (process.platform !== "win32") throw cause;
  const result = spawnSync("powershell.exe", [
    "-NoProfile", "-NonInteractive", "-Command", WINDOWS_DIRECTORY_FLUSH, directoryPath,
  ], { encoding: "utf8", windowsHide: true, timeout: 15000, maxBuffer: 64 * 1024 });
  if (result.status !== 0 || result.error) throw durabilityError(result.error || cause);
}

function fsyncDirectorySync(directoryPath) {
  let descriptor;
  try {
    descriptor = fs.openSync(directoryPath, fs.constants.O_RDONLY);
    fs.fsyncSync(descriptor);
  } catch (error) {
    flushWindowsDirectory(directoryPath, error);
  } finally {
    if (descriptor !== undefined) fs.closeSync(descriptor);
  }
}

async function fsyncDirectoryAsync(directoryPath) {
  let handle;
  try {
    handle = await fsp.open(directoryPath, "r");
    await handle.sync();
  } catch (error) {
    flushWindowsDirectory(directoryPath, error);
  } finally {
    if (handle) await handle.close();
  }
}

module.exports = { fsyncDirectoryAsync, fsyncDirectorySync };