Extract and refactor filters into filters.py

This will help in implementing __in as a filter, refs #433

datasette/utils.py

@@ -584,143 +584,6 @@ def table_columns(conn, table):
     ]
 
 
-class Filter:
-    def __init__(self, key, display, sql_template, human_template, format='{}', numeric=False, no_argument=False):
-        self.key = key
-        self.display = display
-        self.sql_template = sql_template
-        self.human_template = human_template
-        self.format = format
-        self.numeric = numeric
-        self.no_argument = no_argument
-
-    def where_clause(self, table, column, value, param_counter):
-        converted = self.format.format(value)
-        if self.numeric and converted.isdigit():
-            converted = int(converted)
-        if self.no_argument:
-            kwargs = {
-                'c': column,
-            }
-            converted = None
-        else:
-            kwargs = {
-                'c': column,
-                'p': 'p{}'.format(param_counter),
-                't': table,
-            }
-        return self.sql_template.format(**kwargs), converted
-
-    def human_clause(self, column, value):
-        if callable(self.human_template):
-            template = self.human_template(column, value)
-        else:
-            template = self.human_template
-        if self.no_argument:
-            return template.format(c=column)
-        else:
-            return template.format(c=column, v=value)
-
-
-class Filters:
-    _filters = [
-        # key, display, sql_template, human_template, format=, numeric=, no_argument=
-        Filter('exact', '=', '"{c}" = :{p}', lambda c, v: '{c} = {v}' if v.isdigit() else '{c} = "{v}"'),
-        Filter('not', '!=', '"{c}" != :{p}', lambda c, v: '{c} != {v}' if v.isdigit() else '{c} != "{v}"'),
-        Filter('contains', 'contains', '"{c}" like :{p}', '{c} contains "{v}"', format='%{}%'),
-        Filter('endswith', 'ends with', '"{c}" like :{p}', '{c} ends with "{v}"', format='%{}'),
-        Filter('startswith', 'starts with', '"{c}" like :{p}', '{c} starts with "{v}"', format='{}%'),
-        Filter('gt', '>', '"{c}" > :{p}', '{c} > {v}', numeric=True),
-        Filter('gte', '\u2265', '"{c}" >= :{p}', '{c} \u2265 {v}', numeric=True),
-        Filter('lt', '<', '"{c}" < :{p}', '{c} < {v}', numeric=True),
-        Filter('lte', '\u2264', '"{c}" <= :{p}', '{c} \u2264 {v}', numeric=True),
-        Filter('glob', 'glob', '"{c}" glob :{p}', '{c} glob "{v}"'),
-        Filter('like', 'like', '"{c}" like :{p}', '{c} like "{v}"'),
-    ] + ([Filter('arraycontains', 'array contains', """rowid in (
-            select {t}.rowid from {t}, json_each({t}.{c}) j
-            where j.value = :{p}
-        )""", '{c} contains "{v}"')
-    ] if detect_json1() else []) + [
-        Filter('isnull', 'is null', '"{c}" is null', '{c} is null', no_argument=True),
-        Filter('notnull', 'is not null', '"{c}" is not null', '{c} is not null', no_argument=True),
-        Filter('isblank', 'is blank', '("{c}" is null or "{c}" = "")', '{c} is blank', no_argument=True),
-        Filter('notblank', 'is not blank', '("{c}" is not null and "{c}" != "")', '{c} is not blank', no_argument=True),
-    ]
-    _filters_by_key = {
-        f.key: f for f in _filters
-    }
-
-    def __init__(self, pairs, units={}, ureg=None):
-        self.pairs = pairs
-        self.units = units
-        self.ureg = ureg
-
-    def lookups(self):
-        "Yields (lookup, display, no_argument) pairs"
-        for filter in self._filters:
-            yield filter.key, filter.display, filter.no_argument
-
-    def human_description_en(self, extra=None):
-        bits = []
-        if extra:
-            bits.extend(extra)
-        for column, lookup, value in self.selections():
-            filter = self._filters_by_key.get(lookup, None)
-            if filter:
-                bits.append(filter.human_clause(column, value))
-        # Comma separated, with an ' and ' at the end
-        and_bits = []
-        commas, tail = bits[:-1], bits[-1:]
-        if commas:
-            and_bits.append(', '.join(commas))
-        if tail:
-            and_bits.append(tail[0])
-        s = ' and '.join(and_bits)
-        if not s:
-            return ''
-        return 'where {}'.format(s)
-
-    def selections(self):
-        "Yields (column, lookup, value) tuples"
-        for key, value in self.pairs:
-            if '__' in key:
-                column, lookup = key.rsplit('__', 1)
-            else:
-                column = key
-                lookup = 'exact'
-            yield column, lookup, value
-
-    def has_selections(self):
-        return bool(self.pairs)
-
-    def convert_unit(self, column, value):
-        "If the user has provided a unit in the query, convert it into the column unit, if present."
-        if column not in self.units:
-            return value
-
-        # Try to interpret the value as a unit
-        value = self.ureg(value)
-        if isinstance(value, numbers.Number):
-            # It's just a bare number, assume it's the column unit
-            return value
-
-        column_unit = self.ureg(self.units[column])
-        return value.to(column_unit).magnitude
-
-    def build_where_clauses(self, table):
-        sql_bits = []
-        params = {}
-        for i, (column, lookup, value) in enumerate(self.selections()):
-            filter = self._filters_by_key.get(lookup, None)
-            if filter:
-                sql_bit, param = filter.where_clause(table, column, self.convert_unit(column, value), i)
-                sql_bits.append(sql_bit)
-                if param is not None:
-                    param_id = 'p{}'.format(i)
-                    params[param_id] = param
-        return sql_bits, params
-
-
 filter_column_re = re.compile(r'^_filter_column_\d+$')