#!/usr/bin/env python3
"""
FPGA -> PC stream test with fpga_test/stream loaded into the FPGA: the FPGA
sends a byte counter at exactly 10 Mbaud (1 MB/s) from its own 50 MHz clock.
Checks absolute baud accuracy and that no byte is lost or corrupted.

--switches N first reopens the port N times at other baud rates while the
stream keeps coming (the BL616 receiver used to lock up on such changes).

    python tests/uart_stream_test.py --port COM12 --seconds 20 --switches 10
"""
import argparse
import random
import sys
import time

import serial


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument('--port', required=True)
    ap.add_argument('--baud', type=int, default=10_000_000)
    ap.add_argument('--seconds', type=float, default=10)
    ap.add_argument('--switches', type=int, default=0)
    args = ap.parse_args()

    for i in range(args.switches):
        other = random.choice([9600, 115200, 921600, 3_000_000, 12_000_000])
        with serial.Serial(args.port, other, timeout=0.05) as s:
            time.sleep(random.uniform(0.02, 0.2))
            s.read(65536)

    with serial.Serial(args.port, args.baud, timeout=0.1) as s:
        s.set_buffer_size(rx_size=1 << 20)
        time.sleep(0.3)
        s.reset_input_buffer()
        expect = None
        total = errors = 0
        t0 = time.time()
        while time.time() - t0 < args.seconds:
            buf = s.read(65536)
            for b in buf:
                if expect is not None and b != expect:
                    errors += 1
                expect = (b + 1) & 0xFF
            total += len(buf)
        dt = time.time() - t0

    rate = total / dt
    print(f'received {total} bytes in {dt:.1f} s = {rate / 1e6:.3f} MB/s '
          f'({rate * 10 / 1e6:.2f} Mbaud of 8N1 payload), sequence errors: {errors}')
    ok = errors == 0 and rate > 0.97e6 * args.baud / 10_000_000
    print('PASS' if ok else 'FAIL')
    sys.exit(0 if ok else 1)


if __name__ == '__main__':
    main()