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1# This file is part of astro_metadata_translator.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the LICENSE file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# Use of this source code is governed by a 3-clause BSD-style
10# license that can be found in the LICENSE file.
12"""Classes and support code for metadata translation"""
14__all__ = ("MetadataTranslator", "StubTranslator", "cache_translation")
16from abc import abstractmethod
17import inspect
18import logging
19import warnings
20import math
22import astropy.units as u
23import astropy.io.fits.card
24from astropy.coordinates import Angle
26from .properties import PROPERTIES
28log = logging.getLogger(__name__)
30# Location of the root of the corrections resource files
31CORRECTIONS_RESOURCE_ROOT = "corrections"
34def cache_translation(func, method=None):
35 """Decorator to cache the result of a translation method.
37 Especially useful when a translation uses many other translation
38 methods. Should be used only on ``to_x()`` methods.
40 Parameters
41 ----------
42 func : `function`
43 Translation method to cache.
44 method : `str`, optional
45 Name of the translation method to cache. Not needed if the decorator
46 is used around a normal method, but necessary when the decorator is
47 being used in a metaclass.
49 Returns
50 -------
51 wrapped : `function`
52 Method wrapped by the caching function.
53 """
54 name = func.__name__ if method is None else method
56 def func_wrapper(self):
57 if name not in self._translation_cache:
58 self._translation_cache[name] = func(self)
59 return self._translation_cache[name]
60 func_wrapper.__doc__ = func.__doc__
61 func_wrapper.__name__ = f"{name}_cached"
62 return func_wrapper
65class MetadataTranslator:
66 """Per-instrument metadata translation support
68 Parameters
69 ----------
70 header : `dict`-like
71 Representation of an instrument header that can be manipulated
72 as if it was a `dict`.
73 filename : `str`, optional
74 Name of the file whose header is being translated. For some
75 datasets with missing header information this can sometimes
76 allow for some fixups in translations.
77 """
79 # These are all deliberately empty in the base class.
80 default_search_path = None
81 """Default search path to use to locate header correction files."""
83 default_resource_package = __name__.split(".")[0]
84 """Module name to use to locate the correction resources."""
86 default_resource_root = None
87 """Default package resource path root to use to locate header correction
88 files within the ``default_resource_package`` package."""
90 _trivial_map = {}
91 """Dict of one-to-one mappings for header translation from standard
92 property to corresponding keyword."""
94 _const_map = {}
95 """Dict defining a constant for specified standard properties."""
97 translators = dict()
98 """All registered metadata translation classes."""
100 supported_instrument = None
101 """Name of instrument understood by this translation class."""
103 @classmethod
104 def defined_in_this_class(cls, name):
105 """Report if the specified class attribute is defined specifically in
106 this class.
108 Parameters
109 ----------
110 name : `str`
111 Name of the attribute to test.
113 Returns
114 -------
115 in_class : `bool`
116 `True` if there is a attribute of that name defined in this
117 specific subclass.
118 `False` if the method is not defined in this specific subclass
119 but is defined in a parent class.
120 Returns `None` if the attribute is not defined anywhere
121 in the class hierarchy (which can happen if translators have
122 typos in their mapping tables).
124 Notes
125 -----
126 Retrieves the attribute associated with the given name.
127 Then looks in all the parent classes to determine whether that
128 attribute comes from a parent class or from the current class.
129 Attributes are compared using `id()`.
130 """
131 # The attribute to compare.
132 if not hasattr(cls, name):
133 return None
134 attr_id = id(getattr(cls, name))
136 # Get all the classes in the hierarchy
137 mro = list(inspect.getmro(cls))
139 # Remove the first entry from the list since that will be the
140 # current class
141 mro.pop(0)
143 for parent in mro:
144 # Some attributes may only exist in subclasses. Skip base classes
145 # that are missing the attribute (such as object).
146 if hasattr(parent, name):
147 if id(getattr(parent, name)) == attr_id:
148 return False
149 return True
151 @staticmethod
152 def _make_const_mapping(property_key, constant):
153 """Make a translator method that returns a constant value.
155 Parameters
156 ----------
157 property_key : `str`
158 Name of the property to be calculated (for the docstring).
159 constant : `str` or `numbers.Number`
160 Value to return for this translator.
162 Returns
163 -------
164 f : `function`
165 Function returning the constant.
166 """
167 def constant_translator(self):
168 return constant
170 if property_key in PROPERTIES: 170 ↛ 173line 170 didn't jump to line 173, because the condition on line 170 was never false
171 property_doc, return_type = PROPERTIES[property_key][:2]
172 else:
173 return_type = type(constant).__name__
174 property_doc = f"Returns constant value for '{property_key}' property"
176 constant_translator.__doc__ = f"""{property_doc}
178 Returns
179 -------
180 translation : `{return_type}`
181 Translated property.
182 """
183 return constant_translator
185 @staticmethod
186 def _make_trivial_mapping(property_key, header_key, default=None, minimum=None, maximum=None,
187 unit=None, checker=None):
188 """Make a translator method returning a header value.
190 The header value can be converted to a `~astropy.units.Quantity`
191 if desired, and can also have its value validated.
193 See `MetadataTranslator.validate_value()` for details on the use
194 of default parameters.
196 Parameters
197 ----------
198 property_key : `str`
199 Name of the translator to be constructed (for the docstring).
200 header_key : `str` or `list` of `str`
201 Name of the key to look up in the header. If a `list` each
202 key will be tested in turn until one matches. This can deal with
203 header styles that evolve over time.
204 default : `numbers.Number` or `astropy.units.Quantity`, `str`, optional
205 If not `None`, default value to be used if the parameter read from
206 the header is not defined or if the header is missing.
207 minimum : `numbers.Number` or `astropy.units.Quantity`, optional
208 If not `None`, and if ``default`` is not `None`, minimum value
209 acceptable for this parameter.
210 maximum : `numbers.Number` or `astropy.units.Quantity`, optional
211 If not `None`, and if ``default`` is not `None`, maximum value
212 acceptable for this parameter.
213 unit : `astropy.units.Unit`, optional
214 If not `None`, the value read from the header will be converted
215 to a `~astropy.units.Quantity`. Only supported for numeric values.
216 checker : `function`, optional
217 Callback function to be used by the translator method in case the
218 keyword is not present. Function will be executed as if it is
219 a method of the translator class. Running without raising an
220 exception will allow the default to be used. Should usually raise
221 `KeyError`.
223 Returns
224 -------
225 t : `function`
226 Function implementing a translator with the specified
227 parameters.
228 """
229 if property_key in PROPERTIES: 229 ↛ 232line 229 didn't jump to line 232, because the condition on line 229 was never false
230 property_doc, return_type = PROPERTIES[property_key][:2]
231 else:
232 return_type = "str` or `numbers.Number"
233 property_doc = f"Map '{header_key}' header keyword to '{property_key}' property"
235 def trivial_translator(self):
236 if unit is not None:
237 q = self.quantity_from_card(header_key, unit,
238 default=default, minimum=minimum, maximum=maximum,
239 checker=checker)
240 # Convert to Angle if this quantity is an angle
241 if return_type == "astropy.coordinates.Angle":
242 q = Angle(q)
243 return q
245 keywords = header_key if isinstance(header_key, list) else [header_key]
246 for key in keywords:
247 if self.is_key_ok(key):
248 value = self._header[key]
249 if default is not None and not isinstance(value, str):
250 value = self.validate_value(value, default, minimum=minimum, maximum=maximum)
251 self._used_these_cards(key)
252 break
253 else:
254 # No keywords found, use default, checking first, or raise
255 # A None default is only allowed if a checker is provided.
256 if checker is not None:
257 try:
258 checker(self)
259 return default
260 except Exception:
261 raise KeyError(f"Could not find {keywords} in header")
262 value = default
263 elif default is not None:
264 value = default
265 else:
266 raise KeyError(f"Could not find {keywords} in header")
268 # If we know this is meant to be a string, force to a string.
269 # Sometimes headers represent items as integers which generically
270 # we want as strings (eg OBSID). Sometimes also floats are
271 # written as "NaN" strings.
272 casts = {"str": str, "float": float, "int": int}
273 if return_type in casts and not isinstance(value, casts[return_type]) and value is not None:
274 value = casts[return_type](value)
276 return value
278 # Docstring inheritance means it is confusing to specify here
279 # exactly which header value is being used.
280 trivial_translator.__doc__ = f"""{property_doc}
282 Returns
283 -------
284 translation : `{return_type}`
285 Translated value derived from the header.
286 """
287 return trivial_translator
289 @classmethod
290 def __init_subclass__(cls, **kwargs):
291 """Register all subclasses with the base class and create dynamic
292 translator methods.
294 The method provides two facilities. Firstly, every subclass
295 of `MetadataTranslator` that includes a ``name`` class property is
296 registered as a translator class that could be selected when automatic
297 header translation is attempted. Only name translator subclasses that
298 correspond to a complete instrument. Translation classes providing
299 generic translation support for multiple instrument translators should
300 not be named.
302 The second feature of this method is to convert simple translations
303 to full translator methods. Sometimes a translation is fixed (for
304 example a specific instrument name should be used) and rather than
305 provide a full ``to_property()`` translation method the mapping can be
306 defined in a class variable named ``_constMap``. Similarly, for
307 one-to-one trivial mappings from a header to a property,
308 ``_trivialMap`` can be defined. Trivial mappings are a dict mapping a
309 generic property to either a header keyword, or a tuple consisting of
310 the header keyword and a dict containing key value pairs suitable for
311 the `MetadataTranslator.quantity_from_card()` method.
312 """
313 super().__init_subclass__(**kwargs)
315 # Only register classes with declared names
316 if hasattr(cls, "name") and cls.name is not None:
317 if cls.name in MetadataTranslator.translators: 317 ↛ 318line 317 didn't jump to line 318, because the condition on line 317 was never true
318 log.warning("%s: Replacing %s translator with %s",
319 cls.name, MetadataTranslator.translators[cls.name], cls)
320 MetadataTranslator.translators[cls.name] = cls
322 # Check that we have not inherited constant/trivial mappings from
323 # parent class that we have already applied. Empty maps are always
324 # assumed okay
325 const_map = cls._const_map if cls._const_map and cls.defined_in_this_class("_const_map") else {}
326 trivial_map = cls._trivial_map \
327 if cls._trivial_map and cls.defined_in_this_class("_trivial_map") else {}
329 # Check for shadowing
330 trivials = set(trivial_map.keys())
331 constants = set(const_map.keys())
332 both = trivials & constants
333 if both: 333 ↛ 334line 333 didn't jump to line 334, because the condition on line 333 was never true
334 log.warning("%s: defined in both const_map and trivial_map: %s",
335 cls.__name__, ", ".join(both))
337 all = trivials | constants
338 for name in all:
339 if cls.defined_in_this_class(f"to_{name}"): 339 ↛ 342line 339 didn't jump to line 342, because the condition on line 339 was never true
340 # Must be one of trivial or constant. If in both then constant
341 # overrides trivial.
342 location = "by _trivial_map"
343 if name in constants:
344 location = "by _const_map"
345 log.warning("%s: %s is defined explicitly but will be replaced %s",
346 cls.__name__, name, location)
348 # Go through the trival mappings for this class and create
349 # corresponding translator methods
350 for property_key, header_key in trivial_map.items():
351 kwargs = {}
352 if type(header_key) == tuple:
353 kwargs = header_key[1]
354 header_key = header_key[0]
355 translator = cls._make_trivial_mapping(property_key, header_key, **kwargs)
356 method = f"to_{property_key}"
357 translator.__name__ = f"{method}_trivial_in_{cls.__name__}"
358 setattr(cls, method, cache_translation(translator, method=method))
359 if property_key not in PROPERTIES: 359 ↛ 360line 359 didn't jump to line 360, because the condition on line 359 was never true
360 log.warning(f"Unexpected trivial translator for '{property_key}' defined in {cls}")
362 # Go through the constant mappings for this class and create
363 # corresponding translator methods
364 for property_key, constant in const_map.items():
365 translator = cls._make_const_mapping(property_key, constant)
366 method = f"to_{property_key}"
367 translator.__name__ = f"{method}_constant_in_{cls.__name__}"
368 setattr(cls, method, translator)
369 if property_key not in PROPERTIES: 369 ↛ 370line 369 didn't jump to line 370, because the condition on line 369 was never true
370 log.warning(f"Unexpected constant translator for '{property_key}' defined in {cls}")
372 def __init__(self, header, filename=None):
373 self._header = header
374 self.filename = filename
375 self._used_cards = set()
377 # Prefix to use for warnings about failed translations
378 self._log_prefix_cache = None
380 # Cache assumes header is read-only once stored in object
381 self._translation_cache = {}
383 @classmethod
384 @abstractmethod
385 def can_translate(cls, header, filename=None):
386 """Indicate whether this translation class can translate the
387 supplied header.
389 Parameters
390 ----------
391 header : `dict`-like
392 Header to convert to standardized form.
393 filename : `str`, optional
394 Name of file being translated.
396 Returns
397 -------
398 can : `bool`
399 `True` if the header is recognized by this class. `False`
400 otherwise.
401 """
402 raise NotImplementedError()
404 @classmethod
405 def can_translate_with_options(cls, header, options, filename=None):
406 """Helper method for `can_translate` allowing options.
408 Parameters
409 ----------
410 header : `dict`-like
411 Header to convert to standardized form.
412 options : `dict`
413 Headers to try to determine whether this header can
414 be translated by this class. If a card is found it will
415 be compared with the expected value and will return that
416 comparison. Each card will be tried in turn until one is
417 found.
418 filename : `str`, optional
419 Name of file being translated.
421 Returns
422 -------
423 can : `bool`
424 `True` if the header is recognized by this class. `False`
425 otherwise.
427 Notes
428 -----
429 Intended to be used from within `can_translate` implementations
430 for specific translators. Is not intended to be called directly
431 from `determine_translator`.
432 """
433 for card, value in options.items():
434 if card in header:
435 return header[card] == value
436 return False
438 @classmethod
439 def determine_translator(cls, header, filename=None):
440 """Determine a translation class by examining the header
442 Parameters
443 ----------
444 header : `dict`-like
445 Representation of a header.
446 filename : `str`, optional
447 Name of file being translated.
449 Returns
450 -------
451 translator : `MetadataTranslator`
452 Translation class that knows how to extract metadata from
453 the supplied header.
455 Raises
456 ------
457 ValueError
458 None of the registered translation classes understood the supplied
459 header.
460 """
461 for name, trans in cls.translators.items():
462 if trans.can_translate(header, filename=filename):
463 log.debug(f"Using translation class {name}")
464 return trans
465 else:
466 raise ValueError(f"None of the registered translation classes {list(cls.translators.keys())}"
467 " understood this header")
469 @classmethod
470 def fix_header(cls, header, instrument, obsid, filename=None):
471 """Apply global fixes to a supplied header.
473 Parameters
474 ----------
475 header : `dict`
476 The header to correct. Correction is in place.
477 instrument : `str`
478 The name of the instrument.
479 obsid : `str`
480 Unique observation identifier associated with this header.
481 Will always be provided.
482 filename : `str`, optional
483 Filename associated with this header. May not be set since headers
484 can be fixed independently of any filename being known.
486 Returns
487 -------
488 modified : `bool`
489 `True` if a correction was applied.
491 Notes
492 -----
493 This method is intended to support major discrepancies in headers
494 such as:
496 * Periods of time where headers are known to be incorrect in some
497 way that can be fixed either by deriving the correct value from
498 the existing value or understanding the that correction is static
499 for the given time. This requires that the date header is
500 known.
501 * The presence of a certain value is always wrong and should be
502 corrected with a new static value regardless of date.
504 It is assumed that one off problems with headers have been applied
505 before this method is called using the per-obsid correction system.
507 Usually called from `astro_metadata_translator.fix_header`.
509 For log messages, do not assume that the filename will be present.
510 Always write log messages to fall back on using the ``obsid`` if
511 ``filename`` is `None`.
512 """
513 return False
515 @staticmethod
516 def _construct_log_prefix(obsid, filename=None):
517 """Construct a log prefix string from the obsid and filename.
519 Parameters
520 ----------
521 obsid : `str`
522 The observation identifier.
523 filename : `str`, optional
524 The filename associated with the header being translated.
525 Can be `None`.
526 """
527 if filename:
528 return f"{filename}({obsid})"
529 return obsid
531 @property
532 def _log_prefix(self):
533 """Standard prefix that can be used for log messages to report
534 useful context.
536 Will be either the filename and obsid, or just the obsid depending
537 on whether a filename is known.
539 Returns
540 -------
541 prefix : `str`
542 The prefix to use.
543 """
544 if self._log_prefix_cache is None:
545 # Protect against the unfortunate event of the obsid failing to
546 # be calculated. This should be rare but should not prevent a log
547 # message from appearing.
548 try:
549 obsid = self.to_observation_id()
550 except Exception:
551 obsid = "unknown_obsid"
552 self._log_prefix_cache = self._construct_log_prefix(obsid, self.filename)
553 return self._log_prefix_cache
555 def _used_these_cards(self, *args):
556 """Indicate that the supplied cards have been used for translation.
558 Parameters
559 ----------
560 args : sequence of `str`
561 Keywords used to process a translation.
562 """
563 self._used_cards.update(set(args))
565 def cards_used(self):
566 """Cards used during metadata extraction.
568 Returns
569 -------
570 used : `frozenset` of `str`
571 Cards used when extracting metadata.
572 """
573 return frozenset(self._used_cards)
575 @staticmethod
576 def validate_value(value, default, minimum=None, maximum=None):
577 """Validate the supplied value, returning a new value if out of range
579 Parameters
580 ----------
581 value : `float`
582 Value to be validated.
583 default : `float`
584 Default value to use if supplied value is invalid or out of range.
585 Assumed to be in the same units as the value expected in the
586 header.
587 minimum : `float`
588 Minimum possible valid value, optional. If the calculated value
589 is below this value, the default value will be used.
590 maximum : `float`
591 Maximum possible valid value, optional. If the calculated value
592 is above this value, the default value will be used.
594 Returns
595 -------
596 value : `float`
597 Either the supplied value, or a default value.
598 """
599 if value is None or math.isnan(value):
600 value = default
601 else:
602 if minimum is not None and value < minimum:
603 value = default
604 elif maximum is not None and value > maximum:
605 value = default
606 return value
608 @staticmethod
609 def is_keyword_defined(header, keyword):
610 """Return `True` if the value associated with the named keyword is
611 present in the supplied header and defined.
613 Parameters
614 ----------
615 header : `dict`-lik
616 Header to use as reference.
617 keyword : `str`
618 Keyword to check against header.
620 Returns
621 -------
622 is_defined : `bool`
623 `True` if the header is present and not-`None`. `False` otherwise.
624 """
625 if keyword not in header:
626 return False
628 if header[keyword] is None:
629 return False
631 # Special case Astropy undefined value
632 if isinstance(header[keyword], astropy.io.fits.card.Undefined):
633 return False
635 return True
637 def resource_root(self):
638 """Package resource to use to locate correction resources within an
639 installed package.
641 Returns
642 -------
643 resource_package : `str`
644 Package resource name. `None` if no package resource are to be
645 used.
646 resource_root : `str`
647 The name of the resource root. `None` if no package resources
648 are to be used.
649 """
650 return (self.default_resource_package, self.default_resource_root)
652 def search_paths(self):
653 """Search paths to use when searching for header fix up correction
654 files.
656 Returns
657 -------
658 paths : `list`
659 Directory paths to search. Can be an empty list if no special
660 directories are defined.
662 Notes
663 -----
664 Uses the classes ``default_search_path`` property if defined.
665 """
666 if self.default_search_path is not None:
667 return [self.default_search_path]
668 return []
670 def is_key_ok(self, keyword):
671 """Return `True` if the value associated with the named keyword is
672 present in this header and defined.
674 Parameters
675 ----------
676 keyword : `str`
677 Keyword to check against header.
679 Returns
680 -------
681 is_ok : `bool`
682 `True` if the header is present and not-`None`. `False` otherwise.
683 """
684 return self.is_keyword_defined(self._header, keyword)
686 def are_keys_ok(self, keywords):
687 """Are the supplied keys all present and defined?
689 Parameters
690 ----------
691 keywords : iterable of `str`
692 Keywords to test.
694 Returns
695 -------
696 all_ok : `bool`
697 `True` if all supplied keys are present and defined.
698 """
699 for k in keywords:
700 if not self.is_key_ok(k):
701 return False
702 return True
704 def quantity_from_card(self, keywords, unit, default=None, minimum=None, maximum=None, checker=None):
705 """Calculate a Astropy Quantity from a header card and a unit.
707 Parameters
708 ----------
709 keywords : `str` or `list` of `str`
710 Keyword to use from header. If a list each keyword will be tried
711 in turn until one matches.
712 unit : `astropy.units.UnitBase`
713 Unit of the item in the header.
714 default : `float`, optional
715 Default value to use if the header value is invalid. Assumed
716 to be in the same units as the value expected in the header. If
717 None, no default value is used.
718 minimum : `float`, optional
719 Minimum possible valid value, optional. If the calculated value
720 is below this value, the default value will be used.
721 maximum : `float`, optional
722 Maximum possible valid value, optional. If the calculated value
723 is above this value, the default value will be used.
724 checker : `function`, optional
725 Callback function to be used by the translator method in case the
726 keyword is not present. Function will be executed as if it is
727 a method of the translator class. Running without raising an
728 exception will allow the default to be used. Should usually raise
729 `KeyError`.
731 Returns
732 -------
733 q : `astropy.units.Quantity`
734 Quantity representing the header value.
736 Raises
737 ------
738 KeyError
739 The supplied header key is not present.
740 """
741 keywords = keywords if isinstance(keywords, list) else [keywords]
742 for k in keywords:
743 if self.is_key_ok(k):
744 value = self._header[k]
745 keyword = k
746 break
747 else:
748 if checker is not None:
749 try:
750 checker(self)
751 value = default
752 if value is not None:
753 value = u.Quantity(value, unit=unit)
754 return value
755 except Exception:
756 pass
757 raise KeyError(f"Could not find {keywords} in header")
758 if isinstance(value, str):
759 # Sometimes the header has the wrong type in it but this must
760 # be a number if we are creating a quantity.
761 value = float(value)
762 self._used_these_cards(keyword)
763 if default is not None:
764 value = self.validate_value(value, default, maximum=maximum, minimum=minimum)
765 return u.Quantity(value, unit=unit)
767 def _join_keyword_values(self, keywords, delim="+"):
768 """Join values of all defined keywords with the specified delimiter.
770 Parameters
771 ----------
772 keywords : iterable of `str`
773 Keywords to look for in header.
774 delim : `str`, optional
775 Character to use to join the values together.
777 Returns
778 -------
779 joined : `str`
780 String formed from all the keywords found in the header with
781 defined values joined by the delimiter. Empty string if no
782 defined keywords found.
783 """
784 values = []
785 for k in keywords:
786 if self.is_key_ok(k):
787 values.append(self._header[k])
788 self._used_these_cards(k)
790 if values:
791 joined = delim.join(str(v) for v in values)
792 else:
793 joined = ""
795 return joined
797 @cache_translation
798 def to_detector_unique_name(self):
799 """Return a unique name for the detector.
801 Base class implementation attempts to combine ``detector_name`` with
802 ``detector_group``. Group is only used if not `None`.
804 Can be over-ridden by specialist translator class.
806 Returns
807 -------
808 name : `str`
809 ``detector_group``_``detector_name`` if ``detector_group`` is
810 defined, else the ``detector_name`` is assumed to be unique.
811 If neither return a valid value an exception is raised.
813 Raises
814 ------
815 NotImplementedError
816 Raised if neither detector_name nor detector_group is defined.
817 """
818 name = self.to_detector_name()
819 group = self.to_detector_group()
821 if group is None and name is None:
822 raise NotImplementedError("Can not determine unique name from detector_group and detector_name")
824 if group is not None:
825 return f"{group}_{name}"
827 return name
829 @cache_translation
830 def to_exposure_group(self):
831 """Return the group label associated with this exposure.
833 Base class implementation returns the ``exposure_id`` in string
834 form. A subclass may do something different.
836 Returns
837 -------
838 name : `str`
839 The ``exposure_id`` converted to a string.
840 """
841 exposure_id = self.to_exposure_id()
842 if exposure_id is None:
843 return None
844 else:
845 return str(exposure_id)
847 @cache_translation
848 def to_observation_reason(self):
849 """Return the reason this observation was taken.
851 Base class implementation returns the ``science`` if the
852 ``observation_type`` is science, else ``unknown``.
853 A subclass may do something different.
855 Returns
856 -------
857 name : `str`
858 The reason for this observation.
859 """
860 obstype = self.to_observation_type()
861 if obstype == "science":
862 return "science"
863 return "unknown"
865 @cache_translation
866 def to_observing_day(self):
867 """Return the YYYYMMDD integer corresponding to the observing day.
869 Base class implementation uses the TAI date of the start of the
870 observation.
872 Returns
873 -------
874 day : `int`
875 The observing day as an integer of form YYYYMMDD. If the header
876 is broken and is unable to obtain a date of observation, ``0``
877 is returned and the assumption is made that the problem will
878 be caught elsewhere.
879 """
880 datetime_begin = self.to_datetime_begin()
881 if datetime_begin is None:
882 return 0
883 return int(datetime_begin.tai.strftime("%Y%m%d"))
885 @cache_translation
886 def to_observation_counter(self):
887 """Return an integer corresponding to how this observation relates
888 to other observations.
890 Base class implementation returns ``0`` to indicate that it is not
891 known how an observatory will define a counter. Some observatories
892 may not use the concept, others may use a counter that increases
893 for every observation taken for that instrument, and others may
894 define it to be a counter within an observing day.
896 Returns
897 -------
898 sequence : `int`
899 The observation counter. Always ``0`` for this implementation.
900 """
901 return 0
904def _make_abstract_translator_method(property, doc, return_typedoc, return_type):
905 """Create a an abstract translation method for this property.
907 Parameters
908 ----------
909 property : `str`
910 Name of the translator for property to be created.
911 doc : `str`
912 Description of the property.
913 return_typedoc : `str`
914 Type string of this property (used in the doc string).
915 return_type : `class`
916 Type of this property.
918 Returns
919 -------
920 m : `function`
921 Translator method for this property.
922 """
923 def to_property(self):
924 raise NotImplementedError(f"Translator for '{property}' undefined.")
926 to_property.__doc__ = f"""Return value of {property} from headers.
928 {doc}
930 Returns
931 -------
932 {property} : `{return_typedoc}`
933 The translated property.
934 """
935 return to_property
938# Make abstract methods for all the translators methods.
939# Unfortunately registering them as abstractmethods does not work
940# as these assignments come after the class has been created.
941# Assigning to __abstractmethods__ directly does work but interacts
942# poorly with the metaclass automatically generating methods from
943# _trivialMap and _constMap.
945# Allow for concrete translator methods to exist in the base class
946# These translator methods can be defined in terms of other properties
947CONCRETE = set()
949for name, description in PROPERTIES.items():
950 method = f"to_{name}"
951 if not MetadataTranslator.defined_in_this_class(method):
952 setattr(MetadataTranslator, f"to_{name}",
953 abstractmethod(_make_abstract_translator_method(name, *description[:3])))
954 else:
955 CONCRETE.add(method)
958class StubTranslator(MetadataTranslator):
959 """Translator where all the translations are stubbed out and issue
960 warnings.
962 This translator can be used as a base class whilst developing a new
963 translator. It allows testing to proceed without being required to fully
964 define all translation methods. Once complete the class should be
965 removed from the inheritance tree.
967 """
968 pass
971def _make_forwarded_stub_translator_method(cls, property, doc, return_typedoc, return_type):
972 """Create a stub translation method for this property that calls the
973 base method and catches `NotImplementedError`.
975 Parameters
976 ----------
977 cls : `class`
978 Class to use when referencing `super()`. This would usually be
979 `StubTranslator`.
980 property : `str`
981 Name of the translator for property to be created.
982 doc : `str`
983 Description of the property.
984 return_typedoc : `str`
985 Type string of this property (used in the doc string).
986 return_type : `class`
987 Type of this property.
989 Returns
990 -------
991 m : `function`
992 Stub translator method for this property.
993 """
994 method = f"to_{property}"
996 def to_stub(self):
997 parent = getattr(super(cls, self), method, None)
998 try:
999 if parent is not None:
1000 return parent()
1001 except NotImplementedError:
1002 pass
1004 warnings.warn(f"Please implement translator for property '{property}' for translator {self}",
1005 stacklevel=3)
1006 return None
1008 to_stub.__doc__ = f"""Unimplemented forwarding translator for {property}.
1010 {doc}
1012 Calls the base class translation method and if that fails with
1013 `NotImplementedError` issues a warning reminding the implementer to
1014 override this method.
1016 Returns
1017 -------
1018 {property} : `None` or `{return_typedoc}`
1019 Always returns `None`.
1020 """
1021 return to_stub
1024# Create stub translation methods for each property. These stubs warn
1025# rather than fail and should be overridden by translators.
1026for name, description in PROPERTIES.items():
1027 setattr(StubTranslator, f"to_{name}", _make_forwarded_stub_translator_method(StubTranslator,
1028 name, *description[:3]))