#!/usr/bin/env python3
"""Read a USB CDC tty on macOS using only Python's standard library."""
import argparse
import codecs
from datetime import datetime
import glob
import os
from pathlib import Path
import select
import sys
import termios
import time
import tty


def available_ports():
    return sorted(set(glob.glob('/dev/cu.usbmodem*') + glob.glob('/dev/cu.usbserial*')))


def open_port(path):
    fd = os.open(path, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
    try:
        saved = termios.tcgetattr(fd)
        tty.setraw(fd, termios.TCSANOW)
        config = termios.tcgetattr(fd)
        config[2] |= termios.CLOCAL | termios.CREAD
        config[2] &= ~(termios.PARENB | termios.CSTOPB | termios.CSIZE)
        config[2] |= termios.CS8
        if hasattr(termios, 'CRTSCTS'):
            config[2] &= ~termios.CRTSCTS
        config[4] = config[5] = termios.B115200
        termios.tcsetattr(fd, termios.TCSANOW, config)
        return fd, saved
    except BaseException:
        os.close(fd)
        raise


def read_session(path, output, diag_only=False):
    fd, saved = open_port(path)
    decoder = codecs.getincrementaldecoder('utf-8')(errors='replace')
    pending = ''

    def emit(line):
        line = line.rstrip('\r')
        if not line or (diag_only and '[现场诊断]' not in line and '[USB日志]' not in line):
            return
        stamped = f'{datetime.now().astimezone().isoformat(timespec="milliseconds")} {line}\n'
        output.write(stamped)
        output.flush()
        sys.stdout.write(stamped)
        sys.stdout.flush()

    print(f'已连接 {path}，UTF-8 / 115200 8N1；Ctrl+C 结束。', file=sys.stderr)
    try:
        while True:
            readable, _, _ = select.select([fd], [], [], 1)
            if not readable:
                continue
            try:
                block = os.read(fd, 4096)
            except BlockingIOError:
                continue
            if not block:
                raise OSError('USB端口已关闭')
            pending += decoder.decode(block)
            while '\n' in pending:
                line, pending = pending.split('\n', 1)
                emit(line)
            if len(pending) > 8192:
                emit(pending + ' [未换行，分段保存]')
                pending = ''
    finally:
        pending += decoder.decode(b'', final=True)
        if pending:
            emit(pending)
        try:
            termios.tcsetattr(fd, termios.TCSANOW, saved)
        except termios.error:
            pass
        os.close(fd)


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--list', action='store_true', help='列出 USB 串口，不打开设备')
    parser.add_argument('--port', help='例如 /dev/cu.usbmodemXXXX；仅一个USB串口时可省略')
    parser.add_argument('--output', type=Path, help='日志路径；默认 usb-logs/banban-时间.log')
    parser.add_argument('--diag-only', action='store_true', help='只保存现场诊断与USB状态行')
    parser.add_argument('--reconnect', action='store_true', help='拔插后等待同名端口重连；端口改名需重新指定')
    args = parser.parse_args()
    ports = available_ports()
    if args.list:
        print('\n'.join(ports) if ports else '未发现 USB 串口；检查数据线和设备枚举。')
        return 0
    path = args.port
    if not path:
        if len(ports) != 1:
            print('请用 --port 指定设备 CDC 口；先运行 --list 并对比拔插前后的列表。', file=sys.stderr)
            for port in ports:
                print(port, file=sys.stderr)
            return 2
        path = ports[0]
    destination = args.output or Path('usb-logs') / f'banban-{datetime.now():%Y%m%d-%H%M%S}.log'
    destination.parent.mkdir(parents=True, exist_ok=True)
    print(f'日志保存到 {destination.resolve()}；时间戳是电脑接收时间。', file=sys.stderr)
    try:
        with destination.open('a', encoding='utf-8') as output:
            while True:
                try:
                    read_session(path, output, args.diag_only)
                except (OSError, termios.error) as error:
                    notice = f'[电脑读取] {datetime.now().astimezone().isoformat(timespec="milliseconds")} 连接中断：{error}'
                    print(notice, file=sys.stderr)
                    output.write(notice + '\n')
                    output.flush()
                    if not args.reconnect:
                        return 1
                    print('等待同名USB端口重连……', file=sys.stderr)
                    time.sleep(1)
    except KeyboardInterrupt:
        print('\n已停止，日志已保存。', file=sys.stderr)
    return 0


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