"""Aufteilung (Ausbaustufe 13): Brücke DB -> engine/breakdown.py.

scenario=None ist „System-Plan" (reine Planung, alle Kredite, keine
Modifikatoren) - dieselbe Datenbasis wie load_scenario_inputs(None).
"""
from dataclasses import dataclass
from datetime import date
from decimal import Decimal

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.engine.breakdown import (BreakdownRow, Filters, PlainLoan, Summary,
                                  breakdown_rows, summarize)
from app.engine.loans import loan_schedule
from app.models.tables import Category, Scenario
from app.reserved import SYSTEM_PREFIX
from app.services.double_count import Konflikt, all_conflicts
from app.services.planning_chart import KREDITRATEN, UNKATEGORISIERT
from app.services.projection_service import load_scenario_inputs

PLAN_NAME = f"{SYSTEM_PREFIX}Plan"


@dataclass(frozen=True)
class Breakdown:
    month: date
    rows: list[BreakdownRow]
    summary: Summary
    conflicts: list[Konflikt]


def compute_breakdown(session: Session, month: date, scenario: Scenario | None,
                      filters: Filters) -> Breakdown:
    inputs = load_scenario_inputs(session, scenario)
    names = {c.id: c.name for c in session.execute(select(Category)).scalars()}
    loans = [PlainLoan(l.id, l.name,
                       loan_schedule(Decimal(l.principal), Decimal(l.annual_rate_pct),
                                     l.term_months, l.payout_date, l.repayment_type))
             for l in inputs.loans]
    rows = breakdown_rows(month, inputs.recurring, inputs.planned, loans,
                          inputs.modifiers, filters, category_names=names,
                          loan_category=KREDITRATEN, uncategorized=UNKATEGORISIERT)
    # Doppelzählungs-Hinweis nur, wenn Fixposten UND Kredit hier als Zeile stehen.
    posten = {r.recurring_id for r in rows if r.recurring_id is not None}
    kredite = {r.loan_id for r in rows if r.loan_id is not None}
    conflicts = [k for k in all_conflicts(session)
                 if k.posten_id in posten and k.kredit_id in kredite]
    return Breakdown(month.replace(day=1), rows, summarize(rows), conflicts)