# -*- coding: utf-8 -*-
# Copyright 2026 Nexa Systems Inc.
# License OPL-1 (Odoo Proprietary License v1.0)
"""Pay-period date math shared by reports, attendance filters and the period
picker. Pure functions (no ORM) so they unit-test trivially and never drift
between callers."""

from datetime import date, timedelta


def period_length_days(frequency):
    """Fixed window length for grid frequencies; None for calendar-based ones."""
    return {'weekly': 7, 'biweekly': 14}.get(frequency)


def compute_pay_period(frequency, anchor_str, reference_date):
    """Return (start_date, end_date) for the period containing reference_date.

    ``anchor_str`` is a 'YYYY-MM-DD' string or falsy (falls back to
    first-of-month). Mirrors the original
    fusion.clock.report._calculate_current_period logic, including floor
    division so dates before the anchor resolve to the correct earlier period.
    """
    if anchor_str:
        try:
            # Truncate to 'YYYY-MM-DD' first, matching Odoo's fields.Date.from_string
            # (Date.to_date), so a stored datetime-ish anchor like
            # "2026-05-04 00:00:00" still parses instead of silently falling back.
            anchor = date.fromisoformat(anchor_str[:10])
        except (ValueError, TypeError):
            anchor = reference_date.replace(day=1)
    else:
        anchor = reference_date.replace(day=1)

    if frequency == 'weekly':
        period_num = (reference_date - anchor).days // 7
        start = anchor + timedelta(days=period_num * 7)
        end = start + timedelta(days=6)
    elif frequency == 'semi_monthly':
        if reference_date.day <= 15:
            start = reference_date.replace(day=1)
            end = reference_date.replace(day=15)
        else:
            start = reference_date.replace(day=16)
            next_month = reference_date.replace(day=28) + timedelta(days=4)
            end = next_month - timedelta(days=next_month.day)
    elif frequency == 'monthly':
        start = reference_date.replace(day=1)
        next_month = reference_date.replace(day=28) + timedelta(days=4)
        end = next_month - timedelta(days=next_month.day)
    else:  # 'biweekly' and default
        period_num = (reference_date - anchor).days // 14
        start = anchor + timedelta(days=period_num * 14)
        end = start + timedelta(days=13)
    return start, end


def current_prev_next(frequency, anchor_str, today):
    """Return {'current','previous','next'} (start,end) windows. Previous/next
    are derived by stepping the reference date one day outside the current
    window, which works for grid AND calendar frequencies."""
    cur = compute_pay_period(frequency, anchor_str, today)
    prev = compute_pay_period(frequency, anchor_str, cur[0] - timedelta(days=1))
    nxt = compute_pay_period(frequency, anchor_str, cur[1] + timedelta(days=1))
    return {'current': cur, 'previous': prev, 'next': nxt}