Add British Columbia PHN

Closes #421

stdnum/ca/bc_phn.py

@@ -0,0 +1,103 @@
+# bc_phn.py - functions for handling British Columbia Personal Health Numbers (PHNs)
+# coding: utf-8
+#
+# Copyright (C) 2023 Ömer Boratav
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301 USA
+
+"""BC PHN (British Columbia Personal Health Number).
+
+A unique, numerical, lifetime identifier used in the specific identification
+of an individual client or patient who has had any interaction with the
+British Columbia health system. It is assigned only to and used by one person
+and will not be assigned to any other person.
+
+The existence of a PHN does not imply eligibility for health care services in
+BC or provide any indication of an individual’s benefit status.
+
+The PNH is a 10-digit number where the first digit is always 9, and the last
+digit is a MOD-11 check digit.
+
+More information:
+
+* https://www2.gov.bc.ca/gov/content/health/health-drug-coverage/msp/bc-residents/personal-health-identification
+* https://www2.gov.bc.ca/assets/gov/health/practitioner-pro/software-development-guidelines/conformance-standards/vol-4b-app-rules-client-registry.pdf
+
+
+>>> validate('9698 658 215')
+'9698658215'
+>>> format('9698658215')
+'9698 658 215'
+>>> validate('9698648215')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('5736504210')
+Traceback (most recent call last):
+    ...
+InvalidComponent: ...
+>>> validate('9736A04212')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+"""  # noqa: E501
+
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+def compact(number):
+    """Convert the number to the minimal representation. This strips the
+    number of any valid separators and removes surrounding whitespace."""
+    return clean(number, '- ').strip()
+
+
+def calc_check_digit(number):
+    """Calculate the check digit. The number passed should not have the check
+    digit included."""
+    weights = (2, 4, 8, 5, 10, 9, 7, 3)
+    s = sum((w * int(n)) % 11 for w, n in zip(weights, number))
+    return str((11 - s) % 11)
+
+
+def validate(number):
+    """Check if the number is a valid PHN. This checks the length,
+    formatting and check digit."""
+    number = compact(number)
+    if len(number) != 10:
+        raise InvalidLength()
+    if not isdigits(number):
+        raise InvalidFormat()
+    if number[0] != '9':
+        raise InvalidComponent()
+    if number[9] != calc_check_digit(number[1:9]):
+        raise InvalidChecksum()
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid PHN."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    return ' '.join((number[0:4], number[4:7], number[7:]))