#!/usr/bin/env python3
"""Determinism guard for planet_simulation.simulate() (#963).

The 1024×512 elevation bump (D-202 amended) claims to be deterministic — the
271-body heightmap bake cannot be re-run cheaply, so a silent non-determinism
means a full regeneration. This asserts that simulating the same body twice
yields a bit-identical elevation array.

Run:  uv run python tooling/planet-gen/test_sim_determinism.py
Exit: 0 = deterministic, 1 = drift detected, 2 = could not find a test body.
"""
import hashlib
import sqlite3
import sys
from pathlib import Path

REPO = Path(__file__).resolve().parent.parent.parent
sys.path.insert(0, str(REPO / "tooling" / "planet-gen"))

import numpy as np  # noqa: E402

from body_definition_parser import parse_system  # noqa: E402
from planet_simulation import GRID_H, GRID_W, simulate  # noqa: E402


def _elev_hash(terrain) -> str:
    arr = np.ascontiguousarray(terrain["elevation"], dtype=np.float32)
    return hashlib.sha256(arr.tobytes()).hexdigest()


def main() -> int:
    conn = sqlite3.connect(str(REPO / "server" / "data" / "systems.db"))
    rows = conn.execute(
        "SELECT body_id, terrain_reference FROM bodies "
        "WHERE inhabited=1 AND terrain_reference IS NOT NULL AND population>0 "
        "AND system_id != 'GJ 0' ORDER BY body_id LIMIT 30"
    ).fetchall()

    checked = 0
    for body_id, tref in rows:
        if checked >= 3:
            break
        sys_index = tref.split("/bodies/")[0] + "/index.md"
        try:
            defs = parse_system(sys_index)
        except Exception:
            continue
        bd = next((d for d in defs if d.get("id") == body_id), None)
        if bd is None:
            continue
        t1 = simulate(bd)
        t2 = simulate(bd)
        if not t1 or "elevation" not in t1:
            continue
        h1, h2 = _elev_hash(t1), _elev_hash(t2)
        ok = h1 == h2 and t1["elevation"].shape == (GRID_H, GRID_W)
        print(f"  {body_id}: {'OK' if ok else 'DRIFT'}  {h1[:16]}  shape={t1['elevation'].shape}")
        if not ok:
            print(f"FAIL: {body_id} elevation is non-deterministic ({h1[:16]} != {h2[:16]})")
            return 1
        checked += 1

    if checked == 0:
        print("SKIP: no testable body found")
        return 2
    print(f"PASS: {checked} bodies simulate deterministically at {GRID_W}×{GRID_H}")
    return 0


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