"""
Coordinate transformation engine — wraps pyproj for all CRS conversions.
"""
import pyproj
from typing import Tuple

# Well-known EPSG codes
WELL_KNOWN = {
    "WGS84":        "EPSG:4326",
    "CGCS2000":     "EPSG:4490",
    "Xian80":       "EPSG:4610",
    "Beijing54":    "EPSG:4214",
    "WebMercator":  "EPSG:3857",
    "PseudoMercator": "EPSG:3857",
}


def resolve_epsg(name: str) -> str:
    """Resolve a well-known name or return as-is if already EPSG:xxxx."""
    name = name.strip()
    if name.upper() in WELL_KNOWN:
        return WELL_KNOWN[name.upper()]
    if name.upper().startswith("EPSG:"):
        return name.upper()
    return f"EPSG:{name}"


class CoordTransformer:
    """Convert coordinates between any two CRS using pyproj."""

    def __init__(self, from_crs: str, to_crs: str):
        self.from_crs = resolve_epsg(from_crs)
        self.to_crs = resolve_epsg(to_crs)
        if self.from_crs == self.to_crs:
            self._is_identity = True
            self._transformer = None
        else:
            self._is_identity = False
            self._transformer = pyproj.Transformer.from_crs(
                self.from_crs, self.to_crs, always_xy=True
            )

    def transform(self, x: float, y: float) -> Tuple[float, float]:
        if self._is_identity:
            return x, y
        return self._transformer.transform(x, y)

    def transform_batch(self, xs: list[float], ys: list[float]) -> Tuple[list[float], list[float]]:
        if self._is_identity:
            return xs, ys
        results = self._transformer.transform(xs, ys)
        return results[0], results[1]

    @property
    def description(self) -> str:
        if self._is_identity:
            return f"{self.from_crs} (无转换)"
        return f"{self.from_crs} → {self.to_crs}"

    @staticmethod
    def list_supported() -> list[dict]:
        return [
            {"name": "WGS84",       "epsg": "EPSG:4326", "desc": "GPS / Google Earth"},
            {"name": "CGCS2000",    "epsg": "EPSG:4490", "desc": "2000国家大地坐标系"},
            {"name": "Xian80",      "epsg": "EPSG:4610", "desc": "西安80坐标系"},
            {"name": "Beijing54",   "epsg": "EPSG:4214", "desc": "北京54坐标系"},
            {"name": "Web Mercator","epsg": "EPSG:3857", "desc": "互联网地图投影"},
        ]