#!/usr/bin/env python3
"""Generate deterministic v1 little-endian OfflineFixture field payloads."""

from pathlib import Path
import struct


GRID = 16
ROOT = Path(__file__).resolve().parents[1] / "particle-fixtures"
ANDROID_ASSETS = (
    Path(__file__).resolve().parents[1]
    / "platform/android/MapLibreAndroidTestApp/src/main/assets/integration/particle-fixtures"
)


def velocity(fixture: str, x: int, y: int) -> tuple[float, float]:
    if fixture == "uniform-east":
        return 1.0, 0.0
    if fixture == "uniform-north":
        return 0.0, 1.0
    if fixture == "nodata":
        return (-9999.0, -9999.0) if (x, y) == (3, 4) else (1.0, 0.0)
    local_x = (x + 0.5) / GRID - 0.5
    local_y = (y + 0.5) / GRID - 0.5
    return -2.0 * local_y, 2.0 * local_x


for fixture in ("uniform-east", "uniform-north", "vortex", "nodata"):
    payload = bytearray()
    for y in range(GRID):
        for x in range(GRID):
            payload.extend(struct.pack("<ff", *velocity(fixture, x, y)))
    (ROOT / fixture / "field.f32").write_bytes(payload)
    asset_path = ANDROID_ASSETS / fixture / "field.f32"
    asset_path.parent.mkdir(parents=True, exist_ok=True)
    asset_path.write_bytes(payload)
    (asset_path.parent / "metadata.json").write_bytes((ROOT / fixture / "metadata.json").read_bytes())