#!/usr/bin/env python3
"""Extract decimated frames from a Blu-ray .m2ts into 256x192 PNGs.

Source is 1920x1080 (16:9). The arcade original is 4:3, so we CENTER-CROP to
1440x1080 by default -- see docs/STATUS.md open question on framing.
"""
import subprocess, sys, os, shutil, getpass

# Where the Dragon's Lair Blu-ray is mounted. Nothing in this repo ships the
# media -- bring your own disc, loop-mount it read-only, and point DLX_BDROM at
# the mount if it is not where udisks puts it:
#   udisksctl loop-setup -r -f DRAGONS_LAIR.iso
BDROM = os.environ.get("DLX_BDROM") or f"/media/{getpass.getuser()}/BDROM"
STREAM_DIR = f"{BDROM}/BDMV/STREAM"
W, H = 256, 192

def duration(path):
    out = subprocess.check_output(["ffprobe","-v","error","-show_entries",
        "format=duration","-of","csv=p=0",path], text=True)
    return float(out.strip())

def extract(stream, outdir, fps=12, mode="crop", start=None, dur=None):
    src = f"{STREAM_DIR}/{stream}.m2ts"
    total = duration(src)
    if start is None: start = 0.0
    if dur is None: dur = total - start
    shutil.rmtree(outdir, ignore_errors=True); os.makedirs(outdir)
    if mode == "crop":      # 4:3 centre crop, arcade framing
        vf = f"crop=1440:1080:240:0,hqdn3d=4:3:0:0,scale={W}:{H}:flags=lanczos"
    elif mode == "squash":  # full 16:9 squeezed into 4:3
        vf = f"hqdn3d=4:3:0:0,scale={W}:{H}:flags=lanczos"
    elif mode == "wide":    # 16:9 preserved, letterboxed later
        vf = f"hqdn3d=4:3:0:0,scale={W}:144:flags=lanczos"
    else: raise ValueError(mode)
    vf = f"fps={fps}," + vf
    subprocess.check_call(["ffmpeg","-v","error","-ss",str(start),"-t",str(dur),
        "-i",src,"-vf",vf,"-vsync","0",f"{outdir}/f%04d.png","-y"])
    n = len(os.listdir(outdir))
    print(f"{stream}: dur={total:.2f}s -> {n} frames @{fps}fps ({mode})")
    return n

if __name__ == "__main__":
    # extract.py <stream> <outdir> [fps] [mode] [start_s] [dur_s]
    # start/dur matter for the long streams: 00223 is 9.4 min and the parts
    # that stress the codec are a few seconds each (tools/analysis/07 finds
    # them). Without them a survey silently averages action into idle scenes.
    stream, outdir = sys.argv[1], sys.argv[2]
    fps = int(sys.argv[3]) if len(sys.argv) > 3 else 12
    mode = sys.argv[4] if len(sys.argv) > 4 else "crop"
    start = float(sys.argv[5]) if len(sys.argv) > 5 else None
    dur = float(sys.argv[6]) if len(sys.argv) > 6 else None
    extract(stream, outdir, fps, mode, start, dur)