#!/usr/bin/env node
import fs from 'node:fs';
import fsp from 'node:fs/promises';
import os from 'node:os';
import path from 'node:path';
import { recordError } from '../src/util/errorLogger.js';

const logDir = process.env.PM2_ERROR_LOG_DIR || path.join(os.homedir(), '.pm2', 'logs');
const stateFile = process.env.PM2_ERROR_LOG_STATE_FILE || path.join(process.cwd(), '.pm2-error-log-cursors.json');
const pollIntervalMs = Number(process.env.PM2_ERROR_LOG_POLL_INTERVAL_MS || 30000);
const readExisting = process.env.PM2_ERROR_LOG_READ_EXISTING === 'true';

async function loadState() {
  try {
    return JSON.parse(await fsp.readFile(stateFile, 'utf8'));
  } catch (error) {
    return {};
  }
}

async function saveState(state) {
  await fsp.writeFile(stateFile, JSON.stringify(state, null, 2));
}

async function listPm2ErrorLogs() {
  try {
    const files = await fsp.readdir(logDir);
    return files
      .filter((file) => file.endsWith('-error.log'))
      .map((file) => path.join(logDir, file));
  } catch (error) {
    console.error(`[pm2-error-log-collector] cannot read log dir ${logDir}:`, error.message || error);
    return [];
  }
}

async function readRange(filePath, start, end) {
  if (end < start) {
    return '';
  }

  let content = '';
  const stream = fs.createReadStream(filePath, {
    start,
    end,
    encoding: 'utf8',
  });

  for await (const chunk of stream) {
    content += chunk;
  }

  return content;
}

function splitErrorBlocks(content) {
  const lines = content.replace(/\r\n/g, '\n').split('\n');
  const blocks = [];
  let current = [];

  const startsNewBlock = (line) => {
    return (
      /^\d{4}-\d{2}-\d{2}[ T]\d{2}:\d{2}:\d{2}/.test(line) ||
      /^(Error|TypeError|ReferenceError|SyntaxError|RangeError|UnhandledPromiseRejection|uncaughtException|unhandledRejection)\b/.test(line)
    );
  };

  for (const line of lines) {
    if (startsNewBlock(line) && current.length > 0) {
      blocks.push(current.join('\n').trim());
      current = [];
    }
    current.push(line);
  }

  if (current.length > 0) {
    blocks.push(current.join('\n').trim());
  }

  return blocks.filter(Boolean);
}

function getMessageFromBlock(block) {
  const line = block
    .split('\n')
    .map((item) => item.trim())
    .find((item) => item && !item.startsWith('at '));

  return line
    ? line.replace(/^\d{4}-\d{2}-\d{2}[ T]\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+-]\d{2}:?\d{2})?\s*/, '')
    : 'PM2 error log';
}

async function collectOnce(state) {
  const files = await listPm2ErrorLogs();

  for (const filePath of files) {
    let stat;
    try {
      stat = await fsp.stat(filePath);
    } catch (error) {
      continue;
    }

    const previousOffset = state[filePath];
    if (previousOffset === undefined && !readExisting) {
      state[filePath] = stat.size;
      continue;
    }

    const start = Math.min(previousOffset || 0, stat.size);
    const content = await readRange(filePath, start, stat.size - 1);
    state[filePath] = stat.size;

    for (const block of splitErrorBlocks(content)) {
      await recordError(new Error(getMessageFromBlock(block)), null, {
        source: 'pm2-log',
        stack: block,
        message: getMessageFromBlock(block),
        extra: { logFile: filePath },
      });
    }
  }

  await saveState(state);
}

async function main() {
  console.log(`[pm2-error-log-collector] watching ${logDir}`);
  const state = await loadState();

  await collectOnce(state);
  setInterval(() => {
    collectOnce(state).catch((error) => {
      console.error('[pm2-error-log-collector] collect failed:', error);
    });
  }, pollIntervalMs);
}

main().catch((error) => {
  console.error('[pm2-error-log-collector] fatal:', error);
  process.exit(1);
});