"""Umrechnung zwischen gtadb-Weltkoordinaten, Kacheln und Mosaikpixeln.

Spiegelt src/world/coords.js. Beide Seiten müssen dieselben Werte liefern.
"""
import re

TILE_PX = 256
WORLD_HALF = 16384
CHUNK_SIZE = 250
SLICE = {"x0": -1000, "x1": 2000, "y0": -500, "y1": 2500}


def tile_for_world(x: float, y: float) -> tuple[int, int]:
    return (int((WORLD_HALF - y) // TILE_PX), int((x + WORLD_HALF) // TILE_PX))


def slice_tiles() -> list[tuple[int, int]]:
    r0, c0 = tile_for_world(SLICE["x0"], SLICE["y1"])
    r1, c1 = tile_for_world(SLICE["x1"] - 1, SLICE["y0"] + 1)
    return [(r, c) for r in range(r0, r1 + 1) for c in range(c0, c1 + 1)]


def mosaic_origin_px() -> tuple[int, int]:
    """Pixelversatz der Ausschnittsecke innerhalb des ungeschnittenen Kachelrasters."""
    r0, c0 = tile_for_world(SLICE["x0"], SLICE["y1"])
    return (SLICE["x0"] + WORLD_HALF - c0 * TILE_PX, (WORLD_HALF - SLICE["y1"]) - r0 * TILE_PX)


def pixel_to_world(px: int, py: int) -> tuple[float, float]:
    return (SLICE["x0"] + px, SLICE["y1"] - py)


CHUNKS_PER_SIDE = (SLICE["x1"] - SLICE["x0"]) // CHUNK_SIZE   # 12
CHUNK_COLUMNS = "ABCDEFGHIJKL"
# [0-9] statt \d: in Python passt \d auch auf andere Ziffernzeichen wie ١ oder １, in JavaScript nicht.
_CHUNK_NAME = re.compile(r"([A-La-l])([1-9][0-9]?)")


def _is_index(k) -> bool:
    return isinstance(k, int) and not isinstance(k, bool) and 0 <= k < CHUNKS_PER_SIDE


def chunk_name(i: int, j: int) -> str | None:
    """Planquadrat-Name wie src/world/coords.js: Spalte A–L aus i, Zeile 1–12 aus j. A1 = Nordwest."""
    if not (_is_index(i) and _is_index(j)):
        return None
    return f"{CHUNK_COLUMNS[i]}{j + 1}"


def parse_chunk_name(name: str) -> tuple[int, int] | None:
    """Umkehrung von chunk_name. Akzeptiert Kleinschreibung, None außerhalb A1–L12."""
    match = _CHUNK_NAME.fullmatch(str(name))
    if not match or int(match.group(2)) > CHUNKS_PER_SIDE:
        return None
    return CHUNK_COLUMNS.index(match.group(1).upper()), int(match.group(2)) - 1


def chunk_for_world(x: float, y: float) -> tuple[int, int]:
    """Spiegel von chunkForWorld in src/world/coords.js: i nach Osten, j von der Nordkante nach Süden."""
    return int((x - SLICE["x0"]) // CHUNK_SIZE), int((SLICE["y1"] - y) // CHUNK_SIZE)