from __future__ import annotations

import uuid

from sqlalchemy.orm import Session
from geoalchemy2.shape import from_shape, to_shape
from shapely.geometry import mapping

from app.core.errors import AppError
from app.models import Area, Project
from app.schemas.area import AreaCreate, AreaRead, AreaUpdate
from app.utils.geometry import area_m2, geometry_bbox_polygon, normalize_to_multipolygon


class AreaService:
    @staticmethod
    def serialize_area(area: Area) -> dict:
        payload = AreaRead.model_validate(area).model_dump()
        payload["geometry"] = mapping(to_shape(area.geometry)) if area.geometry else None
        return payload

    @staticmethod
    def list_areas(db: Session, project_id: uuid.UUID, limit: int = 50, offset: int = 0) -> tuple[list[Area], int]:
        total = db.query(Area).filter(Area.project_id == project_id).count()
        areas = (
            db.query(Area)
            .filter(Area.project_id == project_id)
            .order_by(Area.created_at.desc())
            .offset(offset)
            .limit(limit)
            .all()
        )
        return areas, total

    @staticmethod
    def create_area(db: Session, project_id: uuid.UUID, payload: AreaCreate) -> Area:
        if not db.get(Project, project_id):
            raise AppError(code="PROJECT_NOT_FOUND", message="Project not found", status_code=404)

        try:
            multipolygon = normalize_to_multipolygon(payload.geometry)
        except ValueError as exc:
            raise AppError(code="INVALID_GEOMETRY", message=str(exc), status_code=400) from exc

        area = Area(
            project_id=project_id,
            name=payload.name.strip() or "Unnamed area",
            geometry=from_shape(multipolygon, srid=4326),
            original_crs=payload.crs or "EPSG:4326",
            area_m2=area_m2(multipolygon),
            bbox=from_shape(geometry_bbox_polygon(multipolygon), srid=4326),
        )
        db.add(area)
        db.commit()
        db.refresh(area)
        return area

    @staticmethod
    def get_area(db: Session, area_id: uuid.UUID) -> Area:
        area = db.get(Area, area_id)
        if not area:
            raise AppError(code="AREA_NOT_FOUND", message="Area not found", status_code=404)
        return area

    @staticmethod
    def update_area(db: Session, area_id: uuid.UUID, payload: AreaUpdate) -> Area:
        area = db.get(Area, area_id)
        if not area:
            raise AppError(code="AREA_NOT_FOUND", message="Area not found", status_code=404)

        changed = False
        if payload.name:
            area.name = payload.name.strip() or area.name
            changed = True
        if payload.crs:
            area.original_crs = payload.crs
            changed = True
        if not changed:
            raise AppError(code="NO_CHANGES", message="No updatable fields provided", status_code=422)

        db.add(area)
        db.commit()
        db.refresh(area)
        return area