From a8acad865622c6e5e4e4615f0d9c82522c4f12b8 Mon Sep 17 00:00:00 2001
From: Simon Perkins <simon.perkins@gmail.com>
Date: Fri, 5 Apr 2024 17:16:21 +0200
Subject: [PATCH] Address review comments

---
 xarrayfits/grid.py | 77 +++++++++++++++++++++++++---------------------
 1 file changed, 42 insertions(+), 35 deletions(-)

diff --git a/xarrayfits/grid.py b/xarrayfits/grid.py
index 1cf0b03..4a1cac2 100644
--- a/xarrayfits/grid.py
+++ b/xarrayfits/grid.py
@@ -1,52 +1,31 @@
 from collections.abc import Mapping
 import numpy as np
 
-HEADER_PREFIXES = ["NAXIS", "CTYPE", "CRPIX", "CRVAL", "CDELT", "CUNIT", "CNAME"]
-
 
 class UndefinedGridError(ValueError):
     pass
 
 
-def property_factory(prefix: str):
-    def impl(self):
-        return getattr(self, f"_{prefix}")
-
-    return property(impl)
-
-
-class AffineGridMetaclass(type):
-    def __new__(cls, name, bases, dct):
-        for prefix in (p.lower() for p in HEADER_PREFIXES):
-            dct[prefix] = property_factory(prefix)
-        return type.__new__(cls, name, bases, dct)
-
-
-class AffineGrid(metaclass=AffineGridMetaclass):
+class AffineGrid:
     """Presents a C-ordered view over FITS Header grid attributes"""
 
     def __init__(self, header: Mapping):
-        self._ndims = ndims = header["NAXIS"]
-        axr = tuple(range(1, ndims + 1))
         h = header
 
         # Read headers into C-order
-        for prefix in HEADER_PREFIXES:
-            values = reversed([header.get(f"{prefix}{n}") for n in axr])
-            values = [s.strip() if isinstance(s, str) else s for s in values]
-            setattr(self, f"_{prefix.lower()}", values)
-
-        # We must have all NAXIS
-        for i, a in enumerate(self.naxis):
-            if a is None:
-                raise UndefinedGridError(f"NAXIS{ndims - i} undefined")
-
-        # Fill in any missing CRVAL
-        self._crval = [0.0 if v is None else v for v in self._crval]
-        # Fill in any missing CRPIX
-        self._crpix = [1 if p is None else p for p in self._crpix]
-        # Fill in any missing CDELT
-        self._cdelt = [1.0 if d is None else d for d in self._cdelt]
+        try:
+            self._ndims = ndims = h["NAXIS"]
+            axr = tuple(range(1, ndims + 1))
+            self._naxis = list(reversed([h[f"NAXIS{n}"] for n in axr]))
+        except KeyError as e:
+            raise UndefinedGridError(f"{e} undefined") from e
+
+        self._ctype = list(reversed([h.get(f"CTYPE{n}") for n in axr]))
+        self._crpix = list(reversed([h.get(f"CRPIX{n}", 1) for n in axr]))
+        self._crval = list(reversed([h.get(f"CRVAL{n}", 0.0) for n in axr]))
+        self._cdelt = list(reversed([h.get(f"CDELT{n}", 1.0) for n in axr]))
+        self._cunit = list(reversed([h.get(f"CUNIT{n}") for n in axr]))
+        self._cname = list(reversed([h.get(f"CNAME{n}") for n in axr]))
 
         self._grid = []
 
@@ -56,10 +35,38 @@ def __init__(self, header: Mapping):
                 (pixels - self._crpix[d]) * self._cdelt[d] + self._crval[d]
             )
 
+    @property
+    def naxis(self):
+        return self._naxis
+
     @property
     def ndims(self):
         return self._ndims
 
+    @property
+    def ctype(self):
+        return self._ctype
+
+    @property
+    def crpix(self):
+        return self._crpix
+
+    @property
+    def crval(self):
+        return self._crval
+
+    @property
+    def cdelt(self):
+        return self._cdelt
+
+    @property
+    def cunit(self):
+        return self._cunit
+
+    @property
+    def cname(self):
+        return self._cname
+
     def name(self, dim: int):
         """Return a name for dimension :code:`dim`"""
         if result := self.cname[dim]: