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# Copyright (c) Facebook, Inc. and its affiliates.
from typing import Any, Dict, Optional, Tuple
class EntrySelector:
"""
Base class for entry selectors
"""
@staticmethod
def from_string(spec: str) -> "EntrySelector":
if spec == "*":
return AllEntrySelector()
return FieldEntrySelector(spec)
class AllEntrySelector(EntrySelector):
"""
Selector that accepts all entries
"""
SPECIFIER = "*"
def __call__(self, entry):
return True
class FieldEntrySelector(EntrySelector):
"""
Selector that accepts only entries that match provided field
specifier(s). Only a limited set of specifiers is supported for now:
<specifiers>::=<specifier>[<comma><specifiers>]
<specifier>::=<field_name>[<type_delim><type>]<equal><value_or_range>
<field_name> is a valid identifier
<type> ::= "int" | "str"
<equal> ::= "="
<comma> ::= ","
<type_delim> ::= ":"
<value_or_range> ::= <value> | <range>
<range> ::= <value><range_delim><value>
<range_delim> ::= "-"
<value> is a string without spaces and special symbols
(e.g. <comma>, <equal>, <type_delim>, <range_delim>)
"""
_SPEC_DELIM = ","
_TYPE_DELIM = ":"
_RANGE_DELIM = "-"
_EQUAL = "="
_ERROR_PREFIX = "Invalid field selector specifier"
class _FieldEntryValuePredicate:
"""
Predicate that checks strict equality for the specified entry field
"""
def __init__(self, name: str, typespec: Optional[str], value: str):
import builtins
self.name = name
self.type = getattr(builtins, typespec) if typespec is not None else str
self.value = value
def __call__(self, entry):
return entry[self.name] == self.type(self.value)
class _FieldEntryRangePredicate:
"""
Predicate that checks whether an entry field falls into the specified range
"""
def __init__(self, name: str, typespec: Optional[str], vmin: str, vmax: str):
import builtins
self.name = name
self.type = getattr(builtins, typespec) if typespec is not None else str
self.vmin = vmin
self.vmax = vmax
def __call__(self, entry):
return (entry[self.name] >= self.type(self.vmin)) and (
entry[self.name] <= self.type(self.vmax)
)
def __init__(self, spec: str):
self._predicates = self._parse_specifier_into_predicates(spec)
def __call__(self, entry: Dict[str, Any]):
for predicate in self._predicates:
if not predicate(entry):
return False
return True
def _parse_specifier_into_predicates(self, spec: str):
predicates = []
specs = spec.split(self._SPEC_DELIM)
for subspec in specs:
eq_idx = subspec.find(self._EQUAL)
if eq_idx > 0:
field_name_with_type = subspec[:eq_idx]
field_name, field_type = self._parse_field_name_type(field_name_with_type)
field_value_or_range = subspec[eq_idx + 1 :]
if self._is_range_spec(field_value_or_range):
vmin, vmax = self._get_range_spec(field_value_or_range)
predicate = FieldEntrySelector._FieldEntryRangePredicate(
field_name, field_type, vmin, vmax
)
else:
predicate = FieldEntrySelector._FieldEntryValuePredicate(
field_name, field_type, field_value_or_range
)
predicates.append(predicate)
elif eq_idx == 0:
self._parse_error(f'"{subspec}", field name is empty!')
else:
self._parse_error(f'"{subspec}", should have format ' "<field>=<value_or_range>!")
return predicates
def _parse_field_name_type(self, field_name_with_type: str) -> Tuple[str, Optional[str]]:
type_delim_idx = field_name_with_type.find(self._TYPE_DELIM)
if type_delim_idx > 0:
field_name = field_name_with_type[:type_delim_idx]
field_type = field_name_with_type[type_delim_idx + 1 :]
elif type_delim_idx == 0:
self._parse_error(f'"{field_name_with_type}", field name is empty!')
else:
field_name = field_name_with_type
field_type = None
# pyre-fixme[61]: `field_name` may not be initialized here.
# pyre-fixme[61]: `field_type` may not be initialized here.
return field_name, field_type
def _is_range_spec(self, field_value_or_range):
delim_idx = field_value_or_range.find(self._RANGE_DELIM)
return delim_idx > 0
def _get_range_spec(self, field_value_or_range):
if self._is_range_spec(field_value_or_range):
delim_idx = field_value_or_range.find(self._RANGE_DELIM)
vmin = field_value_or_range[:delim_idx]
vmax = field_value_or_range[delim_idx + 1 :]
return vmin, vmax
else:
self._parse_error('"field_value_or_range", range of values expected!')
def _parse_error(self, msg):
raise ValueError(f"{self._ERROR_PREFIX}: {msg}")
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