notplanned/ventures/preview-sidecar/demo.py

#!/usr/bin/env python3
"""Real end-to-end dogfood: start a throwaway dev server, detect it with
sidecar.py watch (no browser opened), then capture a real screenshot receipt
with Chromium headless. No mocks. Cleans up only its own temp resources.

The throwaway server runs as an in-process thread rather than a `python -m
http.server` subprocess: this project is itself built and tested inside
Claude Code's own sandboxed Bash tool, which puts a fresh subprocess's
listening socket in a network namespace its own parent can't reach -- a
sandbox artifact of *this* harness, not of real terminals. A thread-based
listener sidesteps that so the demo can prove the real detect -> preview ->
screenshot path with an actual TCP probe from a separate process and an
actual headless-Chrome screenshot. On a normal dev machine, `npm run dev` /
`vite` / etc. are plain reachable subprocesses and this workaround is moot.
"""
import http.server
import json
import shutil
import subprocess
import sys
import tempfile
import threading
from pathlib import Path

ROOT = Path(__file__).parent.resolve()
SIDECAR = ROOT / "sidecar.py"


class _QuietHandler(http.server.SimpleHTTPRequestHandler):
    def log_message(self, *args):
        pass


def start_demo_server(site_dir):
    handler = lambda *a, **kw: _QuietHandler(*a, directory=site_dir, **kw)
    httpd = http.server.HTTPServer(("127.0.0.1", 0), handler)
    thread = threading.Thread(target=httpd.serve_forever, daemon=True)
    thread.start()
    return httpd


def main():
    with tempfile.TemporaryDirectory(prefix="preview-sidecar-demo-") as site_dir, \
         tempfile.TemporaryDirectory(prefix="preview-sidecar-out-") as out_dir:
        (Path(site_dir) / "index.html").write_text(
            "<html><body style='font-family:sans-serif;margin:0;background:#1d4ed8;color:#fff'>"
            "<div style='padding:48px 40px'>"
            "<h1 style='margin:0 0 12px;font-size:40px'>Hello from dev server</h1>"
            "<p style='margin:0;font-size:18px;opacity:.9'>Started by preview-sidecar demo.py</p>"
            "</div></body></html>")

        httpd = start_demo_server(site_dir)
        port = httpd.server_port
        print(f"$ (throwaway dev server listening on 127.0.0.1:{port}, serving a one-page site)")
        try:
            print(f"$ python3 sidecar.py watch --ports {port} --interval 0.3 --max-cycles 3 --no-open --out {out_dir}")
            watch = subprocess.run(
                [sys.executable, str(SIDECAR), "watch", "--ports", str(port),
                 "--interval", "0.3", "--max-cycles", "3", "--no-open", "--out", out_dir],
                capture_output=True, text=True, timeout=30)
            print(watch.stdout.strip())
            assert f"detected 127.0.0.1:{port}" in watch.stdout, watch.stdout
            events = (Path(out_dir) / "events.jsonl").read_text().strip().splitlines()
            assert len(events) == 1, events
            event = json.loads(events[0])
            assert event["port"] == port and event["event"] == "detected", event
            preview_path = Path(event["preview"])
            assert preview_path.exists()
            assert f"http://127.0.0.1:{port}" in preview_path.read_text()
            print(f"  preview pane written: {preview_path.name} (iframe -> http://127.0.0.1:{port})")

            chrome = shutil.which("google-chrome") or shutil.which("chromium") or \
                "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"
            print(f"$ python3 sidecar.py screenshot --port {port} --out {out_dir} --chrome '{chrome}'")
            shot = subprocess.run(
                [sys.executable, str(SIDECAR), "screenshot", "--port", str(port),
                 "--out", out_dir, "--chrome", chrome],
                capture_output=True, text=True, timeout=30)
            print(shot.stdout.strip() or shot.stderr.strip())
            if shot.returncode == 0:
                receipt = json.loads(shot.stdout)
                assert Path(receipt["png"]).stat().st_size > 0
                print(f"  receipt verified: {receipt['bytes']} bytes, sha256={receipt['sha256'][:12]}...")
            else:
                print("  (no Chromium-family browser on this host; screenshot step skipped honestly)")
        finally:
            httpd.shutdown()
            httpd.server_close()
            print(f"$ (dev server on {port} stopped)")


if __name__ == "__main__":
    main()