"""rio-tiler dynamic tile server for Mars MGS MOLA ClrShade global basemap"""

import math
from pathlib import Path

from fastapi import FastAPI, HTTPException
from starlette.requests import Request
from starlette.responses import Response

from pyproj import CRS
from morecantile import TileMatrixSet

from rio_tiler.errors import TileOutsideBounds
from rio_tiler.io import Reader
from rio_tiler.profiles import img_profiles

DATA_PATH = str(
    Path(__file__).parent / "data" / "Mars_MGS_MOLA_ClrShade_merge_global_463m.tif"
)

# TIF 的原生 CRS 是 SimpleCylindrical Mars（等距柱状投影，单位：米）
# 用 proj4 字符串定义，直接匹配 TIF —— 参考 lunaserv-python 的 proj4 字符串方式
#
# 关键设计决策：TMS 与 TIF 使用同一个 CRS（eqc 米制），rio-tiler 读取时无需任何跨 CRS 转换。
# 若改用 longlat（度），PROJ 会尝试通过 WGS84 做 datum shift：火星球体(R=3396km) vs
# 地球椭球(R=6378km) 差异极大，导致中间计算出现 "PROJ: eqc: Invalid latitude" 错误。
MARS_CRS = CRS.from_proj4(
    "+proj=eqc +lat_ts=0 +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 +a=3396190 +b=3396190 +units=m +no_defs"
)

# 火星球体在等距柱状投影下的全球范围（米）
# 等距柱状: x = R × lon_rad, y = R × lat_rad
# → max_x = R × π（对应 180°），max_y = R × π/2（对应 90°）
_R = 3396190
_MAX_X = _R * math.pi        # ≈ 10,669,442 m
_MAX_Y = _R * math.pi / 2    # ≈  5,334,721 m

# WorldCRS84Quad 等效 TMS（米制版本）：
# - 范围覆盖全球等距柱状投影
# - matrix_scale=[2, 1] → zoom 0 有 2×1 个瓦片，与 Cesium GeographicTilingScheme(2×1) 对齐
# - 瓦片编号 (z, x, y) 与地理位置的对应关系和经纬度版完全一致，Cesium 无需任何修改
MARS_TMS = TileMatrixSet.custom(
    crs=MARS_CRS,
    extent=(-_MAX_X, -_MAX_Y, _MAX_X, _MAX_Y),
    matrix_scale=[2, 1],
)

app = FastAPI(
    title="rio-tiler Mars",
    description="Mars MGS MOLA Color-Shaded Relief global tile server",
)


@app.get(
    "/tiles/{z}/{x}/{y}.png",
    responses={
        200: {"content": {"image/png": {}}, "description": "Return a PNG tile."},
        404: {"description": "Tile outside bounds."},
    },
    response_class=Response,
    description="Read Mars tile and return PNG (uint8 RGB, no rescaling needed)",
)
def tile(z: int, x: int, y: int):
    """Return a map tile for the given z/x/y coordinates."""
    try:
        with Reader(DATA_PATH, tms=MARS_TMS) as cog:
            img = cog.tile(x, y, z)
    except TileOutsideBounds:
        raise HTTPException(status_code=404, detail="Tile outside bounds")

    content = img.render(
        img_format="PNG",
        **img_profiles.get("png", {}),
    )
    return Response(content, media_type="image/png")


@app.get("/tilejson.json", responses={200: {"description": "Return a TileJSON document"}})
def tilejson(request: Request):
    """Return a TileJSON 2.2.0 document."""
    with Reader(DATA_PATH, tms=MARS_TMS) as cog:
        bounds = cog.get_geographic_bounds(cog.tms.rasterio_geographic_crs)
        minzoom = cog.minzoom
        maxzoom = cog.maxzoom

    base_url = str(request.base_url).rstrip("/")
    tile_url = f"{base_url}/tiles/{{z}}/{{x}}/{{y}}.png"

    return {
        "tilejson": "2.2.0",
        "name": "Mars MGS MOLA ClrShade",
        "description": "Mars MGS MOLA Color-Shaded Relief Global Mosaic 463m/px",
        "tiles": [tile_url],
        "bounds": list(bounds),
        "minzoom": minzoom,
        "maxzoom": maxzoom,
        "center": [0, 0, minzoom],
    }