#!/usr/bin/env python3
# SPDX-License-Identifier: BSD-3-Clause
# frame_reader.py - read the GPU-rendered frames the guest publishes into the
# kvmfr ivshmem BAR (see tools/cuda-ab/frame_producer.cu) and save them on the
# host as PPM/PNG. This is the host half of the guest frame-producer path:
# the QEMU ivshmem-plain device is backed by /dev/shm/kvmfr-<uuid>, which the
# guest maps through /sys/bus/pci/devices/0000:00:03.0/resource2.
#
# Usage: frame_reader.py [--shm /dev/shm/kvmfr-<uuid>] [--frames N] [--out DIR]
import argparse
import mmap
import os
import struct
import sys
import time

MAGIC = 0x4B564D46
FRAME_OFFSET = 0x100000
# magic, version, width, height, stride, format, seq, reserved, timestamp_ns
HDR = struct.Struct("<IIIIIIIIQ")


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--shm", default=None)
    ap.add_argument("--frames", type=int, default=5)
    ap.add_argument("--out", default="/tmp/opencode/frames")
    ap.add_argument("--timeout", type=float, default=120.0)
    args = ap.parse_args()

    if not args.shm:
        import glob
        cands = [p for p in glob.glob("/dev/shm/kvmfr-*")
                 if os.path.getsize(p) > 0]
        if not cands:
            print("NO_SHM_FILE", file=sys.stderr)
            return 1
        args.shm = max(cands, key=os.path.getsize)
    os.makedirs(args.out, exist_ok=True)
    print("SHM %s" % args.shm)

    fd = os.open(args.shm, os.O_RDWR)
    size = os.fstat(fd).st_size
    mm = mmap.mmap(fd, size, mmap.MAP_SHARED,
                   mmap.PROT_READ | mmap.PROT_WRITE)

    deadline = time.time() + args.timeout
    saved = 0
    last_seq = 0
    while saved < args.frames and time.time() < deadline:
        mm.seek(FRAME_OFFSET)
        magic, ver, w, h, stride, fmt, seq, _res, ts = HDR.unpack(
            mm.read(HDR.size))
        if magic != MAGIC or seq == 0 or seq == last_seq or w == 0:
            time.sleep(0.05)
            continue
        fb = mm.read(w * h * 4)
        last_seq = seq
        path = os.path.join(args.out, "frame-%04d.ppm" % seq)
        with open(path, "wb") as f:
            f.write(b"P6\n%d %d\n255\n" % (w, h))
            # RGBA -> RGB
            rgb = bytearray(w * h * 3)
            rgb[0::3] = fb[0::4]
            rgb[1::3] = fb[1::4]
            rgb[2::3] = fb[2::4]
            f.write(bytes(rgb))
        saved += 1
        print("SAVED seq=%d %dx%d fmt=%d -> %s" % (seq, w, h, fmt, path))
    mm.close()
    os.close(fd)
    print("READER_DONE saved=%d last_seq=%d" % (saved, last_seq))
    return 0 if saved else 2


if __name__ == "__main__":
    sys.exit(main())