from datetime import date
from decimal import Decimal
from typing import Any

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.modules.business.models import FundAccount, Project, WorkTask
from app.modules.business.service import serialize_model


class RiskService:
    """Evaluate rule-based business risk signals from internal ledgers."""

    def __init__(self, db: Session):
        self.db = db

    def overdue_tasks(self) -> list[dict[str, Any]]:
        stmt = select(WorkTask).where(
            WorkTask.due_date.is_not(None),
            WorkTask.due_date < date.today(),
            WorkTask.status.notin_(["完成", "已完成", "关闭"]),
        )
        return [serialize_model(item) for item in self.db.execute(stmt).scalars()]

    def delayed_projects(self) -> list[dict[str, Any]]:
        stmt = select(Project).where(
            Project.due_date.is_not(None),
            Project.due_date < date.today(),
            Project.status.notin_(["验收", "已完成", "复盘", "归档", "关闭"]),
        )
        return [serialize_model(item) for item in self.db.execute(stmt).scalars()]

    def over_budget_projects(self) -> list[dict[str, Any]]:
        stmt = select(Project).where(
            Project.budget_amount > 0,
            Project.actual_amount > Project.budget_amount,
        )
        return [serialize_model(item) for item in self.db.execute(stmt).scalars()]

    def fund_risks(self) -> list[dict[str, Any]]:
        stmt = select(FundAccount).where(FundAccount.current_balance < FundAccount.safety_line)
        return [serialize_model(item) for item in self.db.execute(stmt).scalars()]

    def summary(self) -> dict[str, Any]:
        overdue_tasks = self.overdue_tasks()
        delayed_projects = self.delayed_projects()
        over_budget_projects = self.over_budget_projects()
        fund_risks = self.fund_risks()
        risk_score = (
            len(overdue_tasks) * 1
            + len(delayed_projects) * 3
            + len(over_budget_projects) * 4
            + len(fund_risks) * 5
        )
        if risk_score >= 15:
            level = "high"
        elif risk_score >= 5:
            level = "medium"
        else:
            level = "low"
        return {
            "risk_level": level,
            "risk_score": Decimal(risk_score),
            "overdue_tasks": overdue_tasks,
            "delayed_projects": delayed_projects,
            "over_budget_projects": over_budget_projects,
            "fund_risks": fund_risks,
        }