#!/usr/bin/env python3
"""Source-bounded Tribhagi Dasha producer.

Tribhagi divides each Vimshottari lord's years across its three nakshatras.
The full 27-nakshatra traversal is 120 years; each nine-nakshatra bhaga is
40 years.  This module emits birth-forward major rows only.
"""

from __future__ import annotations

from datetime import datetime, timedelta
from typing import Any


YEAR_DAYS = 365.25636
NAKSHATRA_SPAN = 360.0 / 27.0
VIMSHOTTARI_SEQUENCE = (
    ("Ketu", 7),
    ("Venus", 20),
    ("Sun", 6),
    ("Moon", 10),
    ("Mars", 7),
    ("Rahu", 18),
    ("Jupiter", 16),
    ("Saturn", 19),
    ("Mercury", 17),
)
NAKSHATRA_NAMES = (
    "Ashwini",
    "Bharani",
    "Krittika",
    "Rohini",
    "Mrigashira",
    "Ardra",
    "Punarvasu",
    "Pushya",
    "Ashlesha",
    "Magha",
    "Purva Phalguni",
    "Uttara Phalguni",
    "Hasta",
    "Chitra",
    "Swati",
    "Vishakha",
    "Anuradha",
    "Jyeshtha",
    "Mula",
    "Purva Ashadha",
    "Uttara Ashadha",
    "Shravana",
    "Dhanishtha",
    "Shatabhisha",
    "Purva Bhadrapada",
    "Uttara Bhadrapada",
    "Revati",
)
FULL_CYCLE_YEARS = 120
BHAGA_CYCLE_YEARS = 40


def _nakshatra_index(moon_longitude: float) -> int:
    return int(float(moon_longitude) % 360.0 // NAKSHATRA_SPAN)


def _nakshatra_fraction_elapsed(moon_longitude: float) -> float:
    return (float(moon_longitude) % NAKSHATRA_SPAN) / NAKSHATRA_SPAN


def _lord_for_nakshatra(index: int) -> tuple[str, float]:
    lord, years = VIMSHOTTARI_SEQUENCE[index % len(VIMSHOTTARI_SEQUENCE)]
    return lord, years / 3.0


def _cycle_indices(start: int, mode: str) -> list[int]:
    if mode == "full_120":
        return [(start + offset) % 27 for offset in range(27)]
    if mode == "single_bhaga_40":
        bhaga_start = (start // 9) * 9
        return [(start + offset - bhaga_start) % 9 + bhaga_start for offset in range(9)]
    raise ValueError("mode must be full_120 or single_bhaga_40")


def calculate_tribhagi_dasha(birth_info: dict[str, Any]) -> dict[str, Any]:
    """Return birth-forward Tribhagi rows; child-period boundaries stay blocked."""
    required = ("birth_datetime", "moon_longitude")
    missing = [field for field in required if birth_info.get(field) is None]
    if missing:
        return {
            "applicable": False,
            "execution_status": "blocked",
            "confidence_status": "blocked",
            "reason": "Missing required input: " + ", ".join(missing),
            "major": [],
        }
    mode = str(birth_info.get("mode") or "full_120")
    try:
        indices = _cycle_indices(_nakshatra_index(float(birth_info["moon_longitude"])), mode)
    except ValueError as exc:
        return {
            "applicable": False,
            "execution_status": "blocked",
            "confidence_status": "blocked",
            "reason": str(exc),
            "major": [],
        }
    birth = birth_info["birth_datetime"]
    if isinstance(birth, str):
        birth = datetime.fromisoformat(birth)
    year_days = float(birth_info.get("dasha_year_days") or YEAR_DAYS)
    fraction_elapsed = _nakshatra_fraction_elapsed(float(birth_info["moon_longitude"]))
    rows = []
    cursor = birth
    for offset, nakshatra_index in enumerate(indices):
        lord, full_years = _lord_for_nakshatra(nakshatra_index)
        years = full_years * (1.0 - fraction_elapsed) if offset == 0 else full_years
        end = cursor + timedelta(days=years * year_days)
        rows.append(
            {
                "level": "mahadasha",
                "lord": lord,
                "planet": lord,
                "nakshatra_index": nakshatra_index,
                "nakshatra": NAKSHATRA_NAMES[nakshatra_index],
                "years": years,
                "full_years": full_years,
                "is_birth_balance": offset == 0,
                "start_date": cursor.isoformat(timespec="seconds"),
                "end_date": end.isoformat(timespec="seconds"),
            }
        )
        cursor = end
    return {
        "schema": "tribhagi_dasha_v1",
        "applicable": True,
        "execution_status": "executed",
        "confidence_status": "parameter_sensitive",
        "verification_status": "source_bounded_local_candidate",
        "period_depth_status": "mahadasha_executed_ad_pd_blocked_pending_row_level_replay",
        "mode": mode,
        "total_cycle": FULL_CYCLE_YEARS if mode == "full_120" else BHAGA_CYCLE_YEARS,
        "dasha_year_days": year_days,
        "starting_nakshatra_index": indices[0],
        "starting_lord": rows[0]["lord"] if rows else None,
        "dasha_balance_at_birth_years": rows[0]["years"] if rows else 0.0,
        "major": rows,
        "reason": "Local source-bounded Tribhagi MD calculation; AD/PD and PL9 semantic mapping remain blocked pending row-level replay.",
        "source_locator": "Public Tribhagi explanations: Vimshottari lord years divided across three ruled nakshatras; full 120-year cycle or single 40-year bhaga view.",
    }