Add an undate converter to wire in hijri date parsing capability

src/undate/converters/calendars/__init__.py

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+from undate.converters.calendars.hijri import HijriDateConverter
+
+__all__ = ["HijriDateConverter"]

src/undate/converters/calendars/hijri/__init__.py

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+from undate.converters.calendars.hijri.converter import HijriDateConverter
+
+__all__ = ["HijriDateConverter"]

src/undate/converters/calendars/hijri/converter.py

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+from typing import Union
+
+from lark.exceptions import UnexpectedCharacters
+
+from undate.converters.base import BaseDateConverter
+from undate.converters.calendars.hijri.parser import hijri_parser
+from undate.converters.calendars.hijri.transformer import HijriDateTransformer
+from undate.undate import Undate, UndateInterval
+
+
+class HijriDateConverter(BaseDateConverter):
+    """
+    Converter for Hijri / Islamic calendar.
+
+    Support for parsing Hijri dates and converting to Undate and UndateInterval
+    objects in the Gregorian calendar.
+    """
+
+    #: converter name: Hijri
+    name: str = "Hijri"
+    calendar_name: str = "Hijrī"
+
+    def __init__(self):
+        self.transformer = HijriDateTransformer()
+
+    def parse(self, value: str) -> Union[Undate, UndateInterval]:
+        """
+        Parse a Hijri date string and return an :class:`~undate.undate.Undate` or
+        :class:`~undate.undate.UndateInterval` in Gregorian calendar.
+        The Hijri date string is preserved in the undate label
+        """
+        if not value:
+            raise ValueError("Parsing empty string is not supported")
+
+        # parse the input string, then transform to undate object
+        try:
+            # parse the string with our Hijri date parser
+            parsetree = hijri_parser.parse(value)
+            # transform the parse tree into an undate or undate interval
+            undate_obj = self.transformer.transform(parsetree)
+            # set the original date as a label, with the calendar name
+            undate_obj.label = f"{value} {self.calendar_name}"
+            return undate_obj
+        except UnexpectedCharacters:
+            raise ValueError("Could not parse '%s' as a Hijri date" % value)
+
+    # do we need to support conversion the other direction?
+    # i.e., generate a Hijri date from an abitrary undate or undate interval?

tests/test_converters/test_calendars/test_hijri/test_hijri_converter.py

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+import pytest
+from undate.converters.calendars import HijriDateConverter
+from undate.undate import Undate, UndateInterval
+
+
+class TestHijriDateConverter:
+    def test_parse_(self):
+        # day
+        date_str = "7 Jumādā I 1243"
+        date = HijriDateConverter().parse(date_str)
+        assert date == Undate(1827, 11, 26)
+        assert date.label == f"{date_str} {HijriDateConverter.calendar_name}"
+
+        # month
+        date_str = "Rajab 495"
+        date = HijriDateConverter().parse(date_str)
+        assert date == UndateInterval(Undate(1102, 4, 28), Undate(1102, 5, 27))
+        assert date.label == f"{date_str} {HijriDateConverter.calendar_name}"
+
+        # year
+        date_str = "441"
+        date = HijriDateConverter().parse(date_str)
+        assert date == UndateInterval(Undate(1049, 6, 11), Undate(1050, 5, 31))
+        assert date.label == f"{date_str} {HijriDateConverter.calendar_name}"
+
+    def test_parse_error(self):
+        # a string we can't parse should raise an error
+        with pytest.raises(ValueError):
+            HijriDateConverter().parse("January 2, 1991")
+        # empty string should also error
+        with pytest.raises(ValueError):
+            HijriDateConverter().parse("")