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from __future__ import annotations
import itertools
from collections import namedtuple
from typing import (
TYPE_CHECKING,
Callable,
Generic,
Iterable,
Iterator,
Mapping,
NamedTuple,
Sequence,
TypeVar,
Union,
)
KT = TypeVar("KT") # Identifier.
RT = TypeVar("RT") # Requirement.
CT = TypeVar("CT") # Candidate.
Matches = Union[Iterable[CT], Callable[[], Iterable[CT]]]
if TYPE_CHECKING:
from .resolvers.criterion import Criterion
class RequirementInformation(NamedTuple, Generic[RT, CT]):
requirement: RT
parent: CT | None
class State(NamedTuple, Generic[RT, CT, KT]):
"""Resolution state in a round."""
mapping: dict[KT, CT]
criteria: dict[KT, Criterion[RT, CT]]
backtrack_causes: list[RequirementInformation[RT, CT]]
else:
RequirementInformation = namedtuple(
"RequirementInformation", ["requirement", "parent"]
)
State = namedtuple("State", ["mapping", "criteria", "backtrack_causes"])
class DirectedGraph(Generic[KT]):
"""A graph structure with directed edges."""
def __init__(self) -> None:
self._vertices: set[KT] = set()
self._forwards: dict[KT, set[KT]] = {} # <key> -> Set[<key>]
self._backwards: dict[KT, set[KT]] = {} # <key> -> Set[<key>]
def __iter__(self) -> Iterator[KT]:
return iter(self._vertices)
def __len__(self) -> int:
return len(self._vertices)
def __contains__(self, key: KT) -> bool:
return key in self._vertices
def copy(self) -> DirectedGraph[KT]:
"""Return a shallow copy of this graph."""
other = type(self)()
other._vertices = set(self._vertices)
other._forwards = {k: set(v) for k, v in self._forwards.items()}
other._backwards = {k: set(v) for k, v in self._backwards.items()}
return other
def add(self, key: KT) -> None:
"""Add a new vertex to the graph."""
if key in self._vertices:
raise ValueError("vertex exists")
self._vertices.add(key)
self._forwards[key] = set()
self._backwards[key] = set()
def remove(self, key: KT) -> None:
"""Remove a vertex from the graph, disconnecting all edges from/to it."""
self._vertices.remove(key)
for f in self._forwards.pop(key):
self._backwards[f].remove(key)
for t in self._backwards.pop(key):
self._forwards[t].remove(key)
def connected(self, f: KT, t: KT) -> bool:
return f in self._backwards[t] and t in self._forwards[f]
def connect(self, f: KT, t: KT) -> None:
"""Connect two existing vertices.
Nothing happens if the vertices are already connected.
"""
if t not in self._vertices:
raise KeyError(t)
self._forwards[f].add(t)
self._backwards[t].add(f)
def iter_edges(self) -> Iterator[tuple[KT, KT]]:
for f, children in self._forwards.items():
for t in children:
yield f, t
def iter_children(self, key: KT) -> Iterator[KT]:
return iter(self._forwards[key])
def iter_parents(self, key: KT) -> Iterator[KT]:
return iter(self._backwards[key])
class IteratorMapping(Mapping[KT, Iterator[CT]], Generic[RT, CT, KT]):
def __init__(
self,
mapping: Mapping[KT, RT],
accessor: Callable[[RT], Iterable[CT]],
appends: Mapping[KT, Iterable[CT]] | None = None,
) -> None:
self._mapping = mapping
self._accessor = accessor
self._appends: Mapping[KT, Iterable[CT]] = appends or {}
def __repr__(self) -> str:
return "IteratorMapping({!r}, {!r}, {!r})".format(
self._mapping,
self._accessor,
self._appends,
)
def __bool__(self) -> bool:
return bool(self._mapping or self._appends)
def __contains__(self, key: object) -> bool:
return key in self._mapping or key in self._appends
def __getitem__(self, k: KT) -> Iterator[CT]:
try:
v = self._mapping[k]
except KeyError:
return iter(self._appends[k])
return itertools.chain(self._accessor(v), self._appends.get(k, ()))
def __iter__(self) -> Iterator[KT]:
more = (k for k in self._appends if k not in self._mapping)
return itertools.chain(self._mapping, more)
def __len__(self) -> int:
more = sum(1 for k in self._appends if k not in self._mapping)
return len(self._mapping) + more
class _FactoryIterableView(Iterable[RT]):
"""Wrap an iterator factory returned by `find_matches()`.
Calling `iter()` on this class would invoke the underlying iterator
factory, making it a "collection with ordering" that can be iterated
through multiple times, but lacks random access methods presented in
built-in Python sequence types.
"""
def __init__(self, factory: Callable[[], Iterable[RT]]) -> None:
self._factory = factory
self._iterable: Iterable[RT] | None = None
def __repr__(self) -> str:
return f"{type(self).__name__}({list(self)})"
def __bool__(self) -> bool:
try:
next(iter(self))
except StopIteration:
return False
return True
def __iter__(self) -> Iterator[RT]:
iterable = self._factory() if self._iterable is None else self._iterable
self._iterable, current = itertools.tee(iterable)
return current
class _SequenceIterableView(Iterable[RT]):
"""Wrap an iterable returned by find_matches().
This is essentially just a proxy to the underlying sequence that provides
the same interface as `_FactoryIterableView`.
"""
def __init__(self, sequence: Sequence[RT]):
self._sequence = sequence
def __repr__(self) -> str:
return f"{type(self).__name__}({self._sequence})"
def __bool__(self) -> bool:
return bool(self._sequence)
def __iter__(self) -> Iterator[RT]:
return iter(self._sequence)
def build_iter_view(matches: Matches[CT]) -> Iterable[CT]:
"""Build an iterable view from the value returned by `find_matches()`."""
if callable(matches):
return _FactoryIterableView(matches)
if not isinstance(matches, Sequence):
matches = list(matches)
return _SequenceIterableView(matches)
IterableView = Iterable
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