from datetime import datetime

import math
from fastapi import HTTPException
from fastapi import status
from sqlalchemy import delete, select, func, update, insert

from models import User
from models.expense import Expense, ExpenseTag
from schemas.base import PaginationSchema
from schemas.expense import *
from services.base import BaseService
from utils.dependecies import is_valid_pagination


class ExpensesService(BaseService):
    async def get_all(self, pagination: PaginationSchema) -> GetAllExpensesResponse:
        if not is_valid_pagination(pagination):
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail='Invalid pagination')
        page = max(0, pagination.page - 1)

        stmt = (
            select(Expense)
            .order_by(Expense.spent_date.desc())
            .offset(page * pagination.items_per_page)
            .limit(pagination.items_per_page)
        )

        total_records = await self.session.scalar(select(func.count()).select_from(Expense))
        if not total_records:
            return GetAllExpensesResponse(
                expenses=[],
                pagination_info=PaginationInfoSchema()
            )
        total_items = total_records
        total_pages = math.ceil(total_records / pagination.items_per_page)

        expenses = await self.session.execute(stmt)
        expenses = expenses.scalars().all()
        response = GetAllExpensesResponse(
            expenses=expenses,
            pagination_info=PaginationInfoSchema(
                total_items=total_items,
                total_pages=total_pages
            )
        )
        return response

    async def get_by_id(self, expense_id: int) -> Optional[Expense]:
        expense = await self.session.get(Expense, expense_id)
        return expense

    async def add_tags(self, expense: Expense, tag_names: list[str]):
        tags = []
        for tag_name in tag_names:
            existing_tag = await self.get_tag_by_name(tag_name)
            if existing_tag:
                tags.append(existing_tag)
            else:
                tag = ExpenseTag(name=tag_name)
                self.session.add(tag)
                tags.append(tag)

        expense.tags = tags

    async def update_expense(self, user: User, request: UpdateExpenseRequest) -> UpdateExpenseResponse:
        expense = await self.get_by_id(request.expense.id or -1)

        if not expense:
            new_expense = Expense(
                created_at=datetime.datetime.now(),
                name=request.expense.name,
                comment=request.expense.comment,
                amount=request.expense.amount,
                spent_date=request.expense.spent_date,
                created_by_user_id=user.id,
            )
            self.session.add(new_expense)
            await self.add_tags(new_expense, request.expense.tags)
            await self.session.commit()
            return UpdateExpenseResponse(ok=True, message='Запись о расходах успешно создана')

        expense.name = request.expense.name
        expense.amount = request.expense.amount
        expense.comment = request.expense.comment
        expense.spent_date = request.expense.spent_date
        self.session.add(expense)
        await self.add_tags(expense, request.expense.tags)
        await self.session.commit()
        return UpdateExpenseResponse(ok=True, message='Запись о расходах успешно изменена')

    async def delete_expense(self, expense_id) -> DeleteExpenseResponse:
        stmt = (
            delete(Expense)
            .where(Expense.id == expense_id)
        )
        await self.session.execute(stmt)
        await self.session.commit()
        return DeleteExpenseResponse(ok=True, message='Запись о расходах успешно удалена')

    async def get_all_tags(self) -> GetAllExpenseTagsResponse:
        stmt = (
            select(ExpenseTag)
            .order_by(ExpenseTag.id)
        )
        tags = await self.session.execute(stmt)
        return GetAllExpenseTagsResponse(tags=tags.scalars().all())

    async def get_tag_by_id(self, expense_tag_id: int) -> Optional[ExpenseTag]:
        return await self.session.get(ExpenseTag, expense_tag_id)

    async def get_tag_by_name(self, expense_tag_name: str) -> Optional[ExpenseTag]:
        stmt = (
            select(ExpenseTag)
            .where(ExpenseTag.name == expense_tag_name)
        )
        tag = await self.session.scalar(stmt)
        return tag

    async def create_tag(self, request: CreateExpenseTagRequest) -> CreateExpenseTagResponse:
        tag = await self.get_tag_by_name(request.tag.name)
        if tag:
            return UpdateExpenseResponse(ok=False, message='Ошибка. Такой тег уже есть.')

        tag_dict = request.tag.model_dump()
        stmt = (
            insert(ExpenseTag)
            .values(**tag_dict)
        )
        await self.session.execute(stmt)
        await self.session.commit()
        return UpdateExpenseResponse(ok=True, message='Тег успешно создан.')

    async def update_tag(self, request: UpdateExpenseTagRequest) -> UpdateExpenseTagResponse:
        tag = await self.get_tag_by_name(request.tag.name)
        if tag:
            return UpdateExpenseTagResponse(ok=False, message='Ошибка. Тег с таким названием уже есть.')

        tag = await self.get_tag_by_id(request.tag.id)
        if not tag:
            return UpdateExpenseTagResponse(ok=False, message='Ошибка. Тег не найден.')

        tag_dict = request.tag.model_dump()
        del tag_dict['id']
        stmt = (
            update(ExpenseTag)
            .where(ExpenseTag.id == request.tag.id)
            .values(**tag_dict)
        )
        await self.session.execute(stmt)
        await self.session.commit()
        return UpdateExpenseResponse(ok=True, message='Тег успешно изменен.')

    async def delete_tag(self, tag_id: int) -> DeleteExpenseTagResponse:
        tag = await self.get_tag_by_id(tag_id)
        if not tag:
            return DeleteExpenseTagResponse(ok=False, message='Ошибка. Тег не найден.')
        if len(tag.expenses) > 0:
            return DeleteExpenseTagResponse(ok=False, message='Ошибка. Тег прикреплен к записи о расходах.')

        stmt = (
            delete(ExpenseTag)
            .where(ExpenseTag.id == tag_id)
        )
        await self.session.execute(stmt)
        await self.session.commit()
        return DeleteExpenseTagResponse(ok=True, message='Тег удален')