from fastapi import APIRouter, Depends
from sqlalchemy.orm import Session
from sqlalchemy import func
from typing import List, Optional

from database import get_db
from models import Student, Class, Score, Employment

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


@router.get("/classes")
def class_stats(db: Session = Depends(get_db)):
    """按班级统计学生人数和性别分布"""
    results = (
        db.query(
            Student.class_id,
            Class.name.label("class_name"),
            func.count(Student.id).label("total"),
            func.sum(func.if_(Student.sex == 1, 1, 0)).label("male"),
            func.sum(func.if_(Student.sex == 2, 1, 0)).label("female"),
        )
        .join(Class, Student.class_id == Class.id)
        .filter(Student.is_deleted == False, Class.is_deleted == False)
        .group_by(Student.class_id, Class.name)
        .all()
    )
    return [
        {
            "class_id": r.class_id,
            "class_name": r.class_name,
            "total_students": r.total,
            "male_count": r.male,
            "female_count": r.female,
        }
        for r in results
    ]


@router.get("/scores")
def score_stats(class_id: Optional[int] = None, score_num: Optional[str] = None, db: Session = Depends(get_db)):
    """成绩统计：平均分、最高分、最低分、人数"""
    query = (
        db.query(
            Score.num.label("score_num"),
            Student.class_id,
            func.avg(Score.score).label("avg_score"),
            func.max(Score.score).label("max_score"),
            func.min(Score.score).label("min_score"),
            func.count(Score.id).label("count"),
        )
        .join(Student, Score.sid == Student.id)
        .filter(Student.is_deleted == False, Score.is_deleted == False)
        .group_by(Score.num, Student.class_id)
    )
    if class_id:
        query = query.filter(Student.class_id == class_id)
    if score_num:
        query = query.filter(Score.num == score_num)
    results = query.all()
    return [
        {
            "score_num": r.score_num,
            "class_id": r.class_id,
            "avg_score": float(r.avg_score),
            "max_score": float(r.max_score),
            "min_score": float(r.min_score),
            "count": r.count,
        }
        for r in results
    ]


@router.get("/employment")
def employment_stats(class_id: Optional[int] = None, db: Session = Depends(get_db)):
    """就业统计：已就业人数、总人数、平均薪资、平均签约周期"""
    from sqlalchemy import cast, Integer

    query = (
        db.query(
            Employment.class_id,
            Class.name.label("class_name"),
            func.count(Employment.id).label("employed_count"),
            func.count(Student.id).label("total_count"),
            func.avg(Employment.employment_salary).label("avg_salary"),
        )
        .join(Class, Employment.class_id == Class.id)
        .join(Student, Employment.sid == Student.id)
        .filter(Employment.is_deleted == False, Student.is_deleted == False, Class.is_deleted == False)
        .group_by(Employment.class_id, Class.name)
    )
    if class_id:
        query = query.filter(Employment.class_id == class_id)
    results = query.all()

    output = []
    for r in results:
        # 计算平均签约周期（天数）
        durations = (
            db.query(
                func.ceil(
                    func.cast(func.julianday(Employment.offer_recived_time) - func.julianday(Employment.employment_open_time), Integer)
                )
            )
            .filter(
                Employment.class_id == r.class_id,
                Employment.is_deleted == False,
                Employment.employment_open_time.isnot(None),
                Employment.offer_recived_time.isnot(None),
            )
            .all()
        )
        avg_days = sum(d[0] for d in durations if d[0] is not None) / len(durations) if durations else None
        output.append({
            "class_id": r.class_id,
            "class_name": r.class_name,
            "employed_count": r.employed_count,
            "total_count": r.total_count,
            "avg_salary": float(r.avg_salary) if r.avg_salary else None,
            "avg_duration_days": round(avg_days, 1) if avg_days is not None else None,
        })
    return output