import { spawnSync, type SpawnSyncOptions } from 'node:child_process';
import * as fs from 'node:fs';
import * as path from 'node:path';
import { fileURLToPath } from 'node:url';

const DATA_DIR = process.env.DATA_DIR || '/data';

export function stepParseCacheDir(modelId: number, cadFileId: number): string {
  return path.join(DATA_DIR, 'models', String(modelId), 'cad', '.step_parse', String(cadFileId));
}

function scriptPath(): string {
  const here = path.dirname(fileURLToPath(import.meta.url));
  return path.join(here, '..', 'scripts', 'step_parse_mvp.py');
}

/**
 * 不依赖 existsSync：挂载/命名空间下路径探测可能不准；子进程 PATH 过短会导致 `python3` ENOENT。
 * 顺序尝试可执行文件，仅对 ENOENT 换下一个。
 */
function python3Candidates(): string[] {
  const fromEnv = process.env.PYTHON3_PATH?.trim();
  const list: string[] = [];
  if (fromEnv) list.push(fromEnv);
  if (process.platform !== 'win32') {
    list.push('/usr/bin/python3', '/usr/local/bin/python3');
  }
  list.push('python3');
  return Array.from(new Set(list));
}

function spawnStepParseSync(script: string, stepAbsolutePath: string, outDir: string) {
  const envBase: NodeJS.ProcessEnv = {
    ...process.env,
    PYTHONUNBUFFERED: '1',
    // 保证按名查找 python3 时能找到 Debian/Ubuntu 常见路径
    PATH: `/usr/bin:/usr/local/bin:/bin:/usr/sbin:${process.env.PATH ?? ''}`,
  };
  const opts: SpawnSyncOptions = {
    encoding: 'utf-8',
    maxBuffer: 64 * 1024 * 1024,
    timeout: 60 * 60 * 1000,
    env: envBase,
  };

  const args = [script, stepAbsolutePath, outDir];
  let lastErr: NodeJS.ErrnoException | undefined;

  for (const py of python3Candidates()) {
    const r = spawnSync(py, args, opts);
    if (!r.error) {
      return r;
    }
    lastErr = r.error as NodeJS.ErrnoException;
    if (lastErr.code !== 'ENOENT') {
      throw new Error(
        `无法启动 Python（${py}）：${lastErr.message}。PYTHON3_PATH=${process.env.PYTHON3_PATH ?? '(未设置)'}`,
      );
    }
  }

  throw new Error(
    `无法启动 Python（已尝试: ${python3Candidates().join(' → ')}）：${lastErr?.message ?? 'ENOENT'}。` +
      `请确认镜像已安装 python3（docker/Dockerfile.dev），或设置 PYTHON3_PATH 为实际解释器路径。`,
  );
}

export type StepManifestPart = { id: string; name: string; stlRelative: string };

export type StepManifest = {
  ok: boolean;
  parts: StepManifestPart[];
  sourceStep?: string;
};

/** cadquery/OCP 可能在 stdout 打印非 JSON 日志，不能只取最后一行 */
function parseJsonResultFromProcessOutput(stdout: string, stderr: string): {
  ok?: boolean;
  error?: string;
  parts?: StepManifestPart[];
} | null {
  const text = `${stdout || ''}\n${stderr || ''}`;
  let last: { ok?: boolean; error?: string; parts?: StepManifestPart[] } | null = null;
  for (const line of text.split('\n')) {
    const t = line.trim();
    if (!t.startsWith('{') || !t.endsWith('}')) continue;
    try {
      const o = JSON.parse(t) as { ok?: boolean };
      if (typeof o.ok === 'boolean') {
        last = o as { ok?: boolean; error?: string; parts?: StepManifestPart[] };
      }
    } catch {
      /* 单行非完整 JSON */
    }
  }
  return last;
}

/**
 * 调用 Python cadquery 将 STEP 三角化为每零件 STL，并写入 manifest.json。
 * @returns manifest 或抛出带 message 的错误
 */
export function runStepParseMvp(stepAbsolutePath: string, outDir: string): StepManifest {
  fs.mkdirSync(outDir, { recursive: true });
  const script = scriptPath();
  if (!fs.existsSync(script)) {
    throw new Error(`未找到 STEP 解析脚本: ${script}`);
  }
  const r = spawnStepParseSync(script, stepAbsolutePath, outDir);

  const out = (v: string | Buffer | null | undefined) =>
    v == null ? '' : typeof v === 'string' ? v : v.toString('utf-8');
  const combined = `${out(r.stdout)}\n${out(r.stderr)}`;
  let parsed = parseJsonResultFromProcessOutput(out(r.stdout), out(r.stderr));

  const resultFile = path.join(outDir, '_parse_result.json');
  if ((!parsed || typeof parsed.ok !== 'boolean') && fs.existsSync(resultFile)) {
    try {
      parsed = JSON.parse(fs.readFileSync(resultFile, 'utf-8')) as typeof parsed;
    } catch {
      /* ignore */
    }
  }

  if (!parsed || typeof parsed.ok !== 'boolean') {
    const sig = r.signal != null ? ` signal=${r.signal}` : '';
    throw new Error(
      `STEP 解析无有效 JSON 结果（exit=${r.status ?? 'null'}${sig}）。` +
        `请确认 cadquery 可用。输出摘录：\n${combined.trim().slice(-2500)}`,
    );
  }

  if (!parsed.ok) {
    throw new Error(parsed.error || 'STEP 解析失败');
  }

  const manFile = path.join(outDir, 'manifest.json');
  if (!fs.existsSync(manFile)) {
    throw new Error(`未生成 manifest.json: ${manFile}`);
  }
  const raw = JSON.parse(fs.readFileSync(manFile, 'utf-8')) as StepManifest;
  return raw;
}