26 lines
857 B
Python
26 lines
857 B
Python
import calendar
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from datetime import date
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STEP = {"monthly": 1, "quarterly": 3, "yearly": 12}
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def _clamp(y: int, m: int, day: int) -> date:
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return date(y, m, min(day, calendar.monthrange(y, m)[1]))
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def occurrences(rhythm: str, due_day: int, window_start: date, window_end: date,
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item_start: date | None = None, item_end: date | None = None) -> list[date]:
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step = STEP[rhythm]
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lo = max(window_start, item_start) if item_start else window_start
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hi = min(window_end, item_end) if item_end else window_end
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anchor = item_start or window_start
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d = _clamp(anchor.year, anchor.month, due_day)
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out: list[date] = []
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while d <= hi:
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if d >= lo:
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out.append(d)
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total = d.year * 12 + d.month - 1 + step
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y, m0 = divmod(total, 12)
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d = _clamp(y, m0 + 1, due_day)
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return out
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