"""Meals router (spec §3.2). Thin handlers — business logic in services/meals.py."""

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session

from database import get_db
from schemas import (
    LogEntryRead,
    MealComponentsUpdateRequest,
    MealFromLogRequest,
    MealFromLogResponse,
    MealRead,
    MealUnpackRequest,
    MealUnpackResponse,
)
from services import meals as svc

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


@router.post("/from-log", response_model=MealFromLogResponse, status_code=201)
def create_meal_from_log(data: MealFromLogRequest, db: Session = Depends(get_db)):
    """Create a meal food from selected daily log entries (§4.3).

    Runs as one transaction: creates the meal + components, deletes source
    entries, inserts one replacement entry.  Rolls back entirely on failure.
    """
    try:
        meal, entry = svc.create_meal_from_log(
            db, data.date, data.entry_ids, data.name,
        )
    except svc.EntryNotFoundError as e:
        raise HTTPException(status_code=404, detail=str(e))
    except svc.EntryDateMismatchError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))

    return MealFromLogResponse(meal=meal, entry=entry)


@router.post("/{meal_id}/unpack", response_model=MealUnpackResponse)
def unpack_meal(
    meal_id: int,
    data: MealUnpackRequest,
    db: Session = Depends(get_db),
):
    """Replace a logged meal entry with its leaf component entries (§4.4).

    Components are resolved recursively — nested meals are flattened to
    leaf foods with their scaling factors multiplied down.

    Runs as one transaction.  If multiple entries match the meal on this
    date, specify ``entry_id`` to disambiguate.
    """
    try:
        entries = svc.unpack_meal(db, meal_id, data.date, data.entry_id)
    except svc.EntryNotFoundError as e:
        raise HTTPException(status_code=404, detail=str(e))
    except svc.AmbiguousMealEntryError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))

    return MealUnpackResponse(entries=entries)


@router.put("/{meal_id}/components", response_model=MealRead)
def update_meal_components(
    meal_id: int,
    data: MealComponentsUpdateRequest,
    db: Session = Depends(get_db),
):
    """Replace a meal's component list (§3.2 PUT). Cycle-checked.

    Components are validated for cycles (direct or transitive self-reference).
    A 422 is returned when the update would create a cycle.

    This is a full replacement — all existing components are removed and
    replaced with the provided list.
    """
    comps = [{"food_id": c.food_id, "quantity": c.quantity} for c in data.components]

    try:
        return svc.update_meal_components(db, meal_id, comps)
    except svc.MealNotFoundError as e:
        raise HTTPException(status_code=404, detail=str(e))
    except svc.ComponentFoodNotFoundError as e:
        raise HTTPException(status_code=404, detail=str(e))
    except svc.MealCycleError as e:
        raise HTTPException(status_code=422, detail=str(e))