#!/usr/bin/env python3
"""Read the guest's menu state — screen id and cursor — from memory.

Menu navigation in this corpus has always been driven by screenshots. That
breaks under `--gpu=null`, which is the only configuration where the game does
not hit the software-rasterizer freeze
(`docs/re/mission-freeze-heap-exhaustion.md`), so a memory-based signal is what
makes that backend usable as an oracle.

    ./menu_state.py            # print screen/cursor once
    ./menu_state.py watch [n]  # poll n times, one line per change

Found by snapshotting `0x82800000`+3 MB at each menu of a *rendered* run and
keeping the words that change on a screen transition but hold steady when only
the highlight moves.
"""

import os
import struct
import sys
import time

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import gmem  # noqa: E402
import gworld  # noqa: E402

SCREEN = 0x828A690C   # 1 title, 3 main menu, 4 extras
CURSOR = 0x828F38AC   # menu highlight; a second copy lives at 0x828F38BC
MISC = 0x828F37B4     # tracks the screen, distinct values per menu

SCREEN_NAMES = {0: "booting", 1: "title", 3: "main-menu", 4: "extras"}


def read(w, va):
    return struct.unpack(">I", os.pread(w.fd, 4, gmem.va_to_off(va)))[0]


def state(w):
    s, c, m = read(w, SCREEN), read(w, CURSOR), read(w, MISC)
    return s, c, m, SCREEN_NAMES.get(s, f"unknown({s})")


def main():
    w = gworld.World()
    if len(sys.argv) > 1 and sys.argv[1] == "watch":
        n = int(sys.argv[2]) if len(sys.argv) > 2 else 60
        last = None
        for _ in range(n):
            cur = state(w)
            if cur != last:
                print(f"screen={cur[0]} ({cur[3]})  cursor={cur[1]}  misc={cur[2]}",
                      flush=True)
                last = cur
            time.sleep(1)
    else:
        s, c, m, name = state(w)
        print(f"screen={s} ({name})  cursor={c}  misc={m}")


if __name__ == "__main__":
    main()