filters.py

import re


class FilteringFailedException(Exception):
    pass


class BasicFilterer(object):
    """Filter that reads in a dictionary and filters based on feature properties"""

    def __init__(self, filter_def, filter_operator):
        super(BasicFilterer, self).__init__()
        self.filter_def = filter_def
        self.operator = filter_operator
        if not self.operator in ["and", "or"]:
            raise FilteringFailedException(
                "Unknown filter operator:%s" % filter_operator
            )

    def keep(self, feature):
        for item in self.filter_def:
            if not "expression" in item:
                raise FilteringFailedException(
                    "Expression missing from filter definition" % (key, value)
                )
            if item["expression"] == "not null":
                test_success = (
                    item["key"] in feature["properties"]
                    and feature["properties"][item["key"]] is not None
                )
            elif item["expression"] == "=":
                test_success = (
                    item["key"] in feature["properties"]
                    and feature["properties"][item["key"]] == item["value"]
                )
            elif item["expression"] == "!=":
                test_success = (
                    item["key"] not in feature["properties"]
                    or feature["properties"][item["key"]] != item["value"]
                )
            elif item["expression"] == "match" or item["expression"] == "not match":
                test_success = (
                    item["key"] in feature["properties"]
                    and feature["properties"][item["key"]] is not None
                    and re.match(item["value"], feature["properties"][item["key"]])
                )
                if item["expression"] == "not match":
                    test_success = not test_success
            else:
                raise FilteringFailedException(
                    "Unhandled filtering expression:%s" % (item["expression"])
                )

            if self.operator == "and" and not test_success:
                return False
            elif self.operator == "or" and test_success:
                return True

        if self.operator == "or":
            return False
        else:
            return True