#!/usr/bin/env python3
"""--scan's walk and report logic, no simulator: the probe order, the rate
arithmetic, and the advice's direction. The rate physics itself is not
sim-testable — a pty carries bytes at any termios rate — so what the wire
would arbitrate is pinned here as logic instead.

Usage: test_scan.py <tool_py>
"""

import os
import sys


def fail(message):
    print(f"FAIL: {message}")
    sys.exit(1)


def main():
    sys.path.insert(0, os.path.dirname(os.path.abspath(sys.argv[1])))
    import pureboot as pb

    walk = pb.scan_ratios()
    if walk != [0, -2, 2, -4, 4, -6, 6, -8, 8, -10, 10]:
        fail(f"probe walk is not built-rate-first, nearest-out: {walk}")

    if pb.scan_rate(9600, 4) != 9984 or pb.scan_rate(9600, -4) != 9216:
        fail("probe rate arithmetic")
    if pb.scan_rate(115200, 0) != 115200:
        fail("the built rate must probe unchanged")

    # A loader answering fast means a fast oscillator: the trim goes down.
    report = "\n".join(pb.scan_report(9600, 4, 6))
    for needle in ("9984", "+4 %", "--baud 9984", "4 steps lower", "pureboot 6"):
        if needle not in report:
            fail(f"+4 % report lacks {needle!r}:\n{report}")
    report = "\n".join(pb.scan_report(9600, -6, 6))
    if "6 steps higher" not in report:
        fail(f"-6 % report advises the wrong direction:\n{report}")

    report = "\n".join(pb.scan_report(9600, 0, 6))
    if "none" not in report or "steps" in report:
        fail(f"an on-rate answer must advise no trim:\n{report}")

    report = "\n".join(pb.scan_report(9600, 4, 6, clock=9600000))
    if "9984000" not in report:
        fail(f"the absolute clock must scale with the found ratio:\n{report}")

    # The walk's rates mostly have no termios B-constant, so the POSIX port
    # must set them through termios2 — probed on a pty, which accepts the
    # ioctl without caring about the speed. Without this every off-nominal
    # probe would abort the walk on the platform --scan matters most on.
    if os.name == "posix":
        import pty

        master, slave = pty.openpty()
        try:
            port = pb.Port(os.ttyname(slave), pb.scan_rate(9600, 4))
            port.set_baud(pb.scan_rate(9600, -4))
            port.close()
        except pb.Error as error:
            fail(f"PosixPort refused an off-nominal probe rate: {error}")
        finally:
            os.close(master)
            os.close(slave)

    print("OK")


if __name__ == "__main__":
    main()