dragonflight/services/capture/src/capture-manager.js

import { spawn, execFileSync } from 'child_process';
import { mkdirSync, writeFileSync, createReadStream, statSync, unlinkSync } from 'node:fs';
import { dirname } from 'node:path';
import { v4 as uuidv4 } from 'uuid';
import { createUploadStream } from './s3/client.js';

/**
 * Reads stderr lines from a spawned process until it finds a JSON line.
 * Non-JSON lines (e.g. [board] log messages from the bridge) are logged
 * and skipped. Resolves with the parsed JSON object when a JSON line arrives.
 * Rejects if the process exits before emitting JSON, or if timeoutMs elapses.
 */
function readFirstStderrLine(proc, timeoutMs = 35_000) {
  return new Promise((resolve, reject) => {
    let buf = '';
    let settled = false;
    const settle = (fn) => { if (settled) return; settled = true; fn(); };

    const timer = setTimeout(() => {
      settle(() => reject(new Error(`deltacast-capture: timed out waiting for format JSON after ${timeoutMs}ms`)));
    }, timeoutMs);

    proc.stderr.setEncoding('utf8');
    proc.stderr.on('data', (chunk) => {
      buf += chunk;
      let nl;
      // Process all complete lines in the buffer
      while ((nl = buf.indexOf('\n')) !== -1) {
        const line = buf.slice(0, nl).trim();
        buf = buf.slice(nl + 1);
        if (!line) continue;
        // Skip non-JSON log lines emitted by the bridge (e.g. "[board] waiting...")
        if (!line.startsWith('{')) {
          console.error(`[deltacast-bridge] ${line}`);
          continue;
        }
        clearTimeout(timer);
        try {
          const parsed = JSON.parse(line);
          if (parsed.error) {
            settle(() => reject(new Error(`deltacast-capture: ${parsed.error}`)));
          } else {
            settle(() => resolve(parsed));
          }
        } catch (e) {
          settle(() => reject(new Error(`deltacast-capture: invalid JSON on stderr: ${line}`)));
        }
        return;
      }
    });

    proc.on('exit', (code) => {
      clearTimeout(timer);
      settle(() => reject(new Error(`deltacast-capture: exited with code ${code} before emitting format JSON`)));
    });
  });
}