"""The zone grid as the companion mod sees it (datapacks/core/data/cobblesurvival/zones/island.json).

zone_at() answers like zone/Zones.kt: a cave biome is its cave zone; otherwise the grid cell's zone.
"""
import json
from pathlib import Path

ROOT = Path(__file__).resolve().parent.parent
ISLAND = ROOT / "datapacks/core/data/cobblesurvival/zones/island.json"


class Grid:
    def __init__(self, data):
        self.radius, self.step, self.size = data["radius"], data["step"], data["size"]
        self.ids = [z["id"] for z in data["zones"]]
        self.caves = {c["biome"]: c["id"] for c in data["caves"]}
        self.cells = [value for value, count in data["grid_rle"] for _ in range(count)]
        if len(self.cells) != self.size * self.size:
            raise ValueError(f"zone grid has {len(self.cells)} cells, expected {self.size ** 2}")

    def zone_at(self, x, z, biome=None):
        if biome in self.caves:
            return self.caves[biome]
        col = (x + self.radius + self.step // 2) // self.step
        row = (z + self.radius + self.step // 2) // self.step
        if not (0 <= col < self.size and 0 <= row < self.size):
            return None
        index = self.cells[row * self.size + col]
        return self.ids[index] if 0 <= index < len(self.ids) else None


def load(path=ISLAND):
    return Grid(json.loads(Path(path).read_text()))