"""Third-level rows for four rashi dashas, on a copy only.

The producer stays free of this key. Printed pages name the sub-period
and not the third level. The split used here is the direct equal-time
rule in the upstream calendar helper: the first child keeps the
sub-period sign, the rest run forward, and the last child ends on the
sub-period end. An empty sub-period list, including a Drig strength tie,
gets no third level.
"""

from __future__ import annotations

from copy import deepcopy
from datetime import datetime

try:
    from rashi_dashas_native import SIGNS
except ImportError:  # pragma: no cover - package import
    from scripts.rashi_dashas_native import SIGNS

FAMILIES = ("sthira", "drig", "shoola", "navamsha")


def attach_rashi_pratyantar(calculated: dict) -> dict:
    """Return a deep copy with third-level rows. The input is not changed."""
    copied = deepcopy(calculated)
    for name in FAMILIES:
        section = copied.get(name)
        if not isinstance(section, dict):
            continue
        for major in section.get("periods") or []:
            if not isinstance(major, dict):
                continue
            children = major.get("antardasha")
            if not isinstance(children, list) or not children:
                continue
            for child in children:
                if not isinstance(child, dict):
                    continue
                third = _equal_forward(child)
                if third:
                    child["pratyantar"] = third
    return copied


def _equal_forward(child: dict) -> list[dict]:
    sign = child.get("sign_index")
    if not isinstance(sign, int):
        label = child.get("sign")
        if label not in SIGNS:
            return []
        sign = SIGNS.index(label)
    try:
        start = datetime.fromisoformat(str(child["start"]))
        end = datetime.fromisoformat(str(child["end"]))
    except (KeyError, TypeError, ValueError):
        return []
    total = (end - start).total_seconds()
    if total <= 0:
        return []
    rows = []
    for offset in range(12):
        moment = end if offset == 11 else start + _seconds(total * (offset + 1) / 12.0)
        opened = start if offset == 0 else start + _seconds(total * offset / 12.0)
        index = (int(sign) + offset) % 12
        rows.append({
            "sign": SIGNS[index],
            "sign_index": index,
            "start": opened.date().isoformat(),
            "end": moment.date().isoformat(),
            "level": "PD",
        })
    rows[-1]["end"] = end.date().isoformat()
    return rows


def _seconds(value: float):
    from datetime import timedelta
    return timedelta(seconds=value)