Add raster support for fvcom layers without nearest neighbor metadata (…

…#70)

* Breakout grids to module

* Get all grids working for getmap

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* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* satisfy black

* Fix GFI for fvcom

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---------

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xpublish_wms/grids/__init__.py

@@ -0,0 +1,150 @@
+from typing import Optional, Sequence, Tuple, Union
+
+import cf_xarray  # noqa
+import numpy as np
+import xarray as xr
+
+from xpublish_wms.grids.fvcom import FVCOMGrid
+from xpublish_wms.grids.grid import Grid, RenderMethod
+from xpublish_wms.grids.hycom import HYCOMGrid
+from xpublish_wms.grids.irregular import IrregularGrid
+from xpublish_wms.grids.regular import RegularGrid
+from xpublish_wms.grids.roms import ROMSGrid
+from xpublish_wms.grids.selfe import SELFEGrid
+
+_grid_impls = [
+    HYCOMGrid,
+    FVCOMGrid,
+    SELFEGrid,
+    ROMSGrid,
+    IrregularGrid,
+    RegularGrid,
+]
+
+
+def register_grid_impl(grid_impl: Grid, priority: int = 0):
+    """
+    Register a new grid implementation.
+    :param grid_impl: The grid implementation to register
+    :param priority: The priority of the implementation. Highest priority is 0. Default is 0.
+    """
+    _grid_impls.insert(grid_impl, priority)
+
+
+def grid_factory(ds: xr.Dataset) -> Optional[Grid]:
+    for grid_impl in _grid_impls:
+        if grid_impl.recognize(ds):
+            return grid_impl(ds)
+
+    return None
+
+
+@xr.register_dataset_accessor("gridded")
+class GridDatasetAccessor:
+    _ds: xr.Dataset
+    _grid: Optional[Grid]
+
+    def __init__(self, ds: xr.Dataset):
+        self._ds = ds
+        self._grid = grid_factory(ds)
+
+    @property
+    def grid(self) -> Grid:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid
+
+    @property
+    def name(self) -> str:
+        if self._grid is None:
+            return "unsupported"
+        else:
+            return self.grid.name
+
+    @property
+    def render_method(self) -> RenderMethod:
+        if self._grid is None:
+            return RenderMethod.Quad
+        else:
+            return self._grid.render_method
+
+    @property
+    def crs(self) -> str:
+        if self._grid is None:
+            return None
+        else:
+            return self.grid.crs
+
+    def bbox(self, var) -> Tuple[float, float, float, float]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.bbox(var)
+
+    def has_elevation(self, da: xr.DataArray) -> bool:
+        if self._grid is None:
+            return False
+        else:
+            return self._grid.has_elevation(da)
+
+    def elevation_units(self, da: xr.DataArray) -> Optional[str]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.elevation_units(da)
+
+    def elevation_positive_direction(self, da: xr.DataArray) -> Optional[str]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.elevation_positive_direction(da)
+
+    def elevations(self, da: xr.DataArray) -> Optional[xr.DataArray]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.elevations(da)
+
+    def select_by_elevation(
+        self,
+        da: xr.DataArray,
+        elevations: Optional[Sequence[float]],
+    ) -> xr.DataArray:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.select_by_elevation(da, elevations)
+
+    def mask(
+        self,
+        da: Union[xr.DataArray, xr.Dataset],
+    ) -> Union[xr.DataArray, xr.Dataset]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.mask(da)
+
+    def project(self, da: xr.DataArray, crs: str) -> xr.DataArray:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.project(da, crs)
+
+    def tessellate(self, da: Union[xr.DataArray, xr.Dataset]) -> np.ndarray:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.tessellate(da)
+
+    def sel_lat_lng(
+        self,
+        subset: xr.Dataset,
+        lng,
+        lat,
+        parameters,
+    ) -> Tuple[xr.Dataset, list, list]:
+        if self._grid is None:
+            return None
+        else:
+            return self._grid.sel_lat_lng(subset, lng, lat, parameters)