#!/usr/bin/env python3
"""Capture a line-oriented bare-metal UART stream with host timestamps."""

from __future__ import annotations

import argparse
import csv
import time
from pathlib import Path

import serial


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser()
    parser.add_argument("--port", default="/dev/ttyUSB2")
    parser.add_argument("--baud", type=int, default=115200)
    parser.add_argument("--duration", type=float, default=60.0)
    parser.add_argument("--output", type=Path, required=True)
    parser.add_argument(
        "--stop-text",
        help="stop early after a line containing this text (duration remains a limit)",
    )
    return parser.parse_args()


def main() -> int:
    args = parse_args()
    args.output.parent.mkdir(parents=True, exist_ok=True)

    line_count = 0
    byte_count = 0
    start_wall_ns = time.time_ns()
    start_mono_ns = time.monotonic_ns()
    deadline_ns = start_mono_ns + int(args.duration * 1e9)

    with serial.Serial(args.port, args.baud, timeout=0.1) as uart, args.output.open(
        "w", newline="", encoding="utf-8"
    ) as stream:
        writer = csv.writer(stream)
        writer.writerow(["host_monotonic_s", "host_unix_s", "uart_line"])
        uart.reset_input_buffer()

        while time.monotonic_ns() < deadline_ns:
            raw = uart.readline()
            if not raw:
                continue
            now_mono_ns = time.monotonic_ns()
            now_wall_ns = time.time_ns()
            byte_count += len(raw)
            line = raw.decode("utf-8", errors="replace").rstrip("\r\n")
            writer.writerow(
                [
                    f"{(now_mono_ns - start_mono_ns) / 1e9:.9f}",
                    f"{now_wall_ns / 1e9:.9f}",
                    line,
                ]
            )
            line_count += 1
            if args.stop_text and args.stop_text in line:
                break

    elapsed_s = (time.monotonic_ns() - start_mono_ns) / 1e9
    print(
        f"captured lines={line_count} bytes={byte_count} "
        f"elapsed={elapsed_s:.3f}s output={args.output} "
        f"start_unix={start_wall_ns / 1e9:.6f}"
    )
    return 0


if __name__ == "__main__":
    raise SystemExit(main())