from datetime import datetime
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Path, Query
from pydantic import BaseModel
from sqlmodel import Session, select

from app.auth import get_current_user
from app.db import get_session
from app.models.models import (
    BalanceOverride,
    BalanceOverrideCreate,
    BalanceOverrideRead,
    RecurringItem,
    RecurringItemCreate,
    RecurringItemRead,
    RecurringItemType,
    RecurringItemUpdate,
)
from app.services.budget_projection import (
    FRESH_START_MONTH,
    FRESH_START_YEAR,
    MAX_YEAR,
    MIN_YEAR,
    compute_monthly_projection,
    compute_yearly_projection_with_cumulative,
)

router = APIRouter(prefix="/budget", tags=["budget"])


# --- Recurring Item CRUD ---


@router.get("/recurring", response_model=list[RecurringItemRead])
def list_recurring_items(
    item_type: Optional[RecurringItemType] = None,
    is_active: Optional[bool] = None,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    query = select(RecurringItem)
    if item_type:
        query = query.where(RecurringItem.item_type == item_type)
    if is_active is not None:
        query = query.where(RecurringItem.is_active == is_active)
    query = query.order_by(RecurringItem.item_type, RecurringItem.name)
    return session.exec(query).all()


@router.post("/recurring", response_model=RecurringItemRead, status_code=201)
def create_recurring_item(
    data: RecurringItemCreate,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    item = RecurringItem.model_validate(data)
    session.add(item)
    session.commit()
    session.refresh(item)
    return item


@router.patch("/recurring/{item_id}", response_model=RecurringItemRead)
def update_recurring_item(
    item_id: int,
    data: RecurringItemUpdate,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    item = session.get(RecurringItem, item_id)
    if not item:
        raise HTTPException(status_code=404, detail="Recurring item not found")
    update_data = data.model_dump(exclude_unset=True)
    for key, value in update_data.items():
        setattr(item, key, value)
    session.add(item)
    session.commit()
    session.refresh(item)
    return item


@router.delete("/recurring/{item_id}", status_code=204)
def delete_recurring_item(
    item_id: int,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    item = session.get(RecurringItem, item_id)
    if not item:
        raise HTTPException(status_code=404, detail="Recurring item not found")
    session.delete(item)
    session.commit()


# --- Projection Endpoints ---


class MonthlyProjectionResponse(BaseModel):
    month: int
    year: int
    projected_income: float
    projected_fixed_expenses: float
    projected_savings: float
    actual_credit_card: float
    actual_cash: float
    actual_transfers: float
    uncovered_actual: float
    gran_total_egresos: float
    net_balance: float
    carryover_balance: float = 0.0
    cumulative_balance: float = 0.0
    balance_overridden: bool = False


class YearlyProjectionResponse(BaseModel):
    year: int
    months: list[MonthlyProjectionResponse]
    annual_income: float
    annual_expenses: float
    annual_savings: float
    annual_net: float


@router.get("/projection/{year}", response_model=YearlyProjectionResponse)
def get_yearly_projection(
    year: int,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    if year < MIN_YEAR or year > MAX_YEAR:
        raise HTTPException(
            status_code=400,
            detail=f"Year must be between {MIN_YEAR} and {MAX_YEAR}",
        )

    months_data = compute_yearly_projection_with_cumulative(session, year)
    months = []
    annual_income = 0.0
    annual_expenses = 0.0
    annual_savings = 0.0
    annual_net = 0.0

    for data in months_data:
        monthly = MonthlyProjectionResponse(
            month=data["month"],
            year=data["year"],
            projected_income=data["projected_income"],
            projected_fixed_expenses=data["projected_fixed_expenses"],
            projected_savings=data["projected_savings"],
            actual_credit_card=data["actual_credit_card"],
            actual_cash=data["actual_cash"],
            actual_transfers=data["actual_transfers"],
            uncovered_actual=data["uncovered_actual"],
            gran_total_egresos=data["gran_total_egresos"],
            net_balance=data["net_balance"],
            carryover_balance=data["carryover_balance"],
            cumulative_balance=data["cumulative_balance"],
            balance_overridden=data["balance_overridden"],
        )
        months.append(monthly)
        annual_income += data["projected_income"]
        annual_expenses += data["gran_total_egresos"]
        annual_savings += data["projected_savings"]
        annual_net += data["net_balance"]

    return YearlyProjectionResponse(
        year=year,
        months=months,
        annual_income=annual_income,
        annual_expenses=annual_expenses,
        annual_savings=annual_savings,
        annual_net=annual_net,
    )


class RecurringItemDetail(BaseModel):
    id: int
    name: str
    amount: float
    projected_amount: float | None = None
    used_actual: bool = False
    item_type: str
    frequency: str
    category_name: str | None = None
    category_id: int | None = None


class ActualsBySource(BaseModel):
    source: str
    total_compra: float
    total_devolucion: float
    net: float
    count: int


class CCCategorySpending(BaseModel):
    category_name: str
    amount: float


class MonthlyDetailResponse(BaseModel):
    year: int
    month: int
    income_items: list[RecurringItemDetail]
    expense_items: list[RecurringItemDetail]
    savings_items: list[RecurringItemDetail]
    actuals_by_source: list[ActualsBySource]
    total_projected_income: float
    total_projected_expenses: float
    total_projected_savings: float
    uncovered_actual: float
    gran_total_egresos: float
    net_balance: float
    cc_by_category: list[CCCategorySpending]


@router.get("/month/{year}/{month}", response_model=MonthlyDetailResponse)
def get_monthly_detail(
    year: int,
    month: int = Path(ge=1, le=12),
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    data = compute_monthly_projection(session, year, month)
    return MonthlyDetailResponse(
        year=data["year"],
        month=data["month"],
        income_items=[RecurringItemDetail(**i) for i in data["income_items"]],
        expense_items=[RecurringItemDetail(**i) for i in data["expense_items"]],
        savings_items=[RecurringItemDetail(**i) for i in data["savings_items"]],
        actuals_by_source=[ActualsBySource(**a) for a in data["actuals_by_source"]],
        total_projected_income=data["projected_income"],
        total_projected_expenses=data["projected_fixed_expenses"],
        total_projected_savings=data["projected_savings"],
        uncovered_actual=data["uncovered_actual"],
        gran_total_egresos=data["gran_total_egresos"],
        net_balance=data["net_balance"],
        cc_by_category=[CCCategorySpending(**c) for c in data["cc_by_category"]],
    )


# --- Balance Override CRUD ---


@router.put(
    "/balance-override/{year}/{month}",
    response_model=BalanceOverrideRead,
)
def upsert_balance_override(
    year: int,
    month: int = Path(ge=1, le=12),
    data: BalanceOverrideCreate = ...,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    if year < MIN_YEAR or year > MAX_YEAR:
        raise HTTPException(400, f"Year must be between {MIN_YEAR} and {MAX_YEAR}")
    if year == FRESH_START_YEAR and month < FRESH_START_MONTH:
        raise HTTPException(400, f"Cannot override before {FRESH_START_YEAR}-{FRESH_START_MONTH:02d}")

    existing = session.exec(
        select(BalanceOverride).where(
            BalanceOverride.year == year, BalanceOverride.month == month
        )
    ).first()

    if existing:
        existing.override_balance = data.override_balance
        existing.updated_at = datetime.utcnow()
        session.add(existing)
        session.commit()
        session.refresh(existing)
        return existing

    override = BalanceOverride(
        year=year, month=month, override_balance=data.override_balance
    )
    session.add(override)
    session.commit()
    session.refresh(override)
    return override


@router.delete("/balance-override/{year}/{month}", status_code=204)
def delete_balance_override(
    year: int,
    month: int = Path(ge=1, le=12),
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    existing = session.exec(
        select(BalanceOverride).where(
            BalanceOverride.year == year, BalanceOverride.month == month
        )
    ).first()
    if not existing:
        raise HTTPException(404, "No override found for this month")
    session.delete(existing)
    session.commit()