import { spawnSync } from 'node:child_process';

// Windows 开发栈清理工具。
//
// 背景：Windows 下所有长驻服务都经 `cmd.exe /d /s /c` 包装层启动（Node 的
// `shell: true`），而 Ctrl+C 会先让包装层退出。一旦中间层退出，按父进程链
// 遍历就再也到不了更深的服务进程，`taskkill /T` 也会因为 PID 已消失而失效。
// 因此这里同时提供两种定位方式：
//   1. `selectProcessTreeIds`：按记录下来的根 PID 做父子链遍历（能处理根已退出、
//      但中间层仍留在快照里的情况）。
//   2. `selectWorktreeOwnedProcessIds`：按身份匹配（api-server.exe 的绝对路径、
//      SpacetimeDB 的 --data-dir），不依赖任何仍然存活的包装层。
// 两者结合后，即使 `npm run agc` 的 Ctrl+C 只杀掉了 shell 包装层，也不会留下
// 属于本工作树的后端进程。

function normalizeWindowsPath(value) {
  const raw = String(value ?? '')
    .trim()
    .replace(/^\\\\\?\\/u, '');
  if (!raw) {
    return '';
  }
  return raw.replace(/[\\/]+$/u, '').toLowerCase();
}

function parseWindowsProcessSnapshot(rawText) {
  const raw = String(rawText ?? '').trim();
  if (!raw) {
    return [];
  }

  let parsed;
  try {
    parsed = JSON.parse(raw);
  } catch {
    return [];
  }
  if (!parsed) {
    return [];
  }
  return Array.isArray(parsed) ? parsed : [parsed];
}

// 一次退出流程里会多次清理（每个服务的进程树 + 最后的身份兜底清扫），
// PowerShell 全量进程快照约 1 秒，短时间内复用同一份快照即可，避免 Ctrl+C
// 后清理被拖成十几秒。只在默认实现下缓存，注入实现（测试）始终重新读取。
const PROCESS_SNAPSHOT_TTL_MS = 1000;
let cachedProcessSnapshot = null;
let cachedProcessSnapshotAt = 0;

function readWindowsProcessSnapshot({
  spawnSyncImpl = spawnSync,
  env = process.env,
  now = Date.now,
  ttlMs = PROCESS_SNAPSHOT_TTL_MS,
} = {}) {
  const cacheable = spawnSyncImpl === spawnSync && env === process.env;
  if (
    cacheable &&
    cachedProcessSnapshot &&
    now() - cachedProcessSnapshotAt < ttlMs
  ) {
    return cachedProcessSnapshot;
  }

  const command = [
    '$ErrorActionPreference = "SilentlyContinue"',
    'Get-CimInstance Win32_Process | Select-Object ProcessId,ParentProcessId,Name,ExecutablePath,CommandLine | ConvertTo-Json -Compress',
  ].join('\n');
  const result = spawnSyncImpl(
    'powershell.exe',
    ['-NoProfile', '-ExecutionPolicy', 'Bypass', '-Command', command],
    {
      encoding: 'utf8',
      env,
      maxBuffer: 32 * 1024 * 1024,
    },
  );
  if (result?.error || result?.status !== 0) {
    return [];
  }

  const snapshot = parseWindowsProcessSnapshot(result.stdout);
  if (cacheable) {
    cachedProcessSnapshot = snapshot;
    cachedProcessSnapshotAt = now();
  }
  return snapshot;
}

function selectProcessTreeIds(processes, rootPid) {
  if (!Number.isInteger(rootPid)) {
    return [];
  }

  const childrenByParent = new Map();
  for (const processEntry of processes ?? []) {
    const parentId = Number(processEntry?.ParentProcessId);
    const processId = Number(processEntry?.ProcessId);
    if (!Number.isInteger(parentId) || !Number.isInteger(processId)) {
      continue;
    }
    if (!childrenByParent.has(parentId)) {
      childrenByParent.set(parentId, []);
    }
    childrenByParent.get(parentId).push(processId);
  }

  const collected = new Set();
  const queue = [rootPid];
  while (queue.length > 0) {
    const current = queue.shift();
    if (collected.has(current)) {
      continue;
    }
    collected.add(current);
    for (const childId of childrenByParent.get(current) ?? []) {
      queue.push(childId);
    }
  }
  return [...collected];
}

function selectWorktreeOwnedProcessIds(
  processes,
  { apiServerExePath = '', spacetimeDataDir = '', selfPid = process.pid } = {},
) {
  const expectedExePath = normalizeWindowsPath(apiServerExePath);
  const expectedDataDir = normalizeWindowsPath(spacetimeDataDir);
  if (!expectedExePath && !expectedDataDir) {
    return [];
  }

  const matched = [];
  for (const processEntry of processes ?? []) {
    const processId = Number(processEntry?.ProcessId);
    if (!Number.isInteger(processId) || processId === selfPid) {
      continue;
    }

    const executablePath = normalizeWindowsPath(processEntry?.ExecutablePath);
    if (expectedExePath && executablePath === expectedExePath) {
      matched.push(processId);
      continue;
    }

    if (!expectedDataDir) {
      continue;
    }
    const name = String(processEntry?.Name ?? '').toLowerCase();
    if (!name.startsWith('spacetime')) {
      continue;
    }
    if (
      normalizeWindowsPath(processEntry?.CommandLine).includes(expectedDataDir)
    ) {
      matched.push(processId);
    }
  }
  return matched;
}

function stopWindowsProcessIds(
  processIds,
  { spawnSyncImpl = spawnSync, env = process.env, waitForExitMs = 0 } = {},
) {
  const uniqueIds = [
    ...new Set((processIds ?? []).filter((value) => Number.isInteger(value))),
  ];
  if (uniqueIds.length === 0) {
    return [];
  }

  const command = [
    '$ErrorActionPreference = "SilentlyContinue"',
    '$ids = $env:GENARRATIVE_STOP_PIDS -split ","',
    'foreach ($id in $ids) {',
    '  if ($id) { Stop-Process -Id ([int]$id) -Force -ErrorAction SilentlyContinue }',
    '}',
    ...(waitForExitMs > 0
      ? [
          // 启动前清理旧 api-server 时必须等它真正退出，否则 Windows 仍占用
          // target\debug\api-server.exe，cargo 会报 failed to remove file。
          `Wait-Process -Id $ids -Timeout ${Math.ceil(waitForExitMs / 1000)} -ErrorAction SilentlyContinue`,
        ]
      : []),
  ].join('\n');
  spawnSyncImpl(
    'powershell.exe',
    ['-NoProfile', '-ExecutionPolicy', 'Bypass', '-Command', command],
    {
      env: { ...env, GENARRATIVE_STOP_PIDS: uniqueIds.join(',') },
      stdio: 'ignore',
    },
  );
  return uniqueIds;
}

function stopWindowsProcessTree(
  rootPid,
  { snapshot = null, spawnSyncImpl = spawnSync, env = process.env } = {},
) {
  if (!Number.isInteger(rootPid)) {
    return [];
  }

  const processes =
    snapshot ?? readWindowsProcessSnapshot({ spawnSyncImpl, env });
  return stopWindowsProcessIds(selectProcessTreeIds(processes, rootPid), {
    spawnSyncImpl,
    env,
  });
}

function stopWindowsWorktreeProcesses({
  apiServerExePath = '',
  spacetimeDataDir = '',
  snapshot = null,
  spawnSyncImpl = spawnSync,
  env = process.env,
} = {}) {
  const processes =
    snapshot ?? readWindowsProcessSnapshot({ spawnSyncImpl, env });
  return stopWindowsProcessIds(
    selectWorktreeOwnedProcessIds(processes, {
      apiServerExePath,
      spacetimeDataDir,
    }),
    { spawnSyncImpl, env },
  );
}

export {
  normalizeWindowsPath,
  parseWindowsProcessSnapshot,
  readWindowsProcessSnapshot,
  selectProcessTreeIds,
  selectWorktreeOwnedProcessIds,
  stopWindowsProcessIds,
  stopWindowsProcessTree,
  stopWindowsWorktreeProcesses,
};