mirror of https://github.com/zulip/zulip.git
75 lines
1.5 KiB
Python
75 lines
1.5 KiB
Python
from collections.abc import Callable
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from typing import Generic, TypeVar
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"""
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This module helps you set up a bunch
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of sequences, similar to how database
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sequences work.
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You need to be a bit careful here, since
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you're dealing with a big singleton, but
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for data imports that's usually easy to
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manage.
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"""
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T = TypeVar("T")
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def _seq() -> Callable[[], int]:
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i = 0
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def next_one() -> int:
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nonlocal i
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i += 1
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return i
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return next_one
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def sequencer() -> Callable[[str], int]:
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"""
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Use like this:
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NEXT_ID = sequencer()
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message_id = NEXT_ID('message')
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"""
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seq_dict: dict[str, Callable[[], int]] = {}
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def next_one(name: str) -> int:
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if name not in seq_dict:
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seq_dict[name] = _seq()
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seq = seq_dict[name]
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return seq()
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return next_one
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"""
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NEXT_ID is a singleton used by an entire process, which is
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almost always reasonable. If you want to have two parallel
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sequences, just use different `name` values.
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This object gets created once and only once during the first
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import of the file.
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"""
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NEXT_ID = sequencer()
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class IdMapper(Generic[T]):
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def __init__(self) -> None:
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self.map: dict[T, int] = {}
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self.cnt = 0
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def has(self, their_id: T) -> bool:
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return their_id in self.map
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def get(self, their_id: T) -> int:
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if their_id in self.map:
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return self.map[their_id]
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self.cnt += 1
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our_id = self.cnt
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self.map[their_id] = our_id
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return our_id
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