"""学习分析。"""
from __future__ import annotations

import json

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

from database import get_db
from dependencies import get_current_user, user_permissions
from models import AttemptSession, ErrorEntry, User
from schemas import AnalyticsOut, DiagnosisOut, MetricItem
from services.mastery_engine import action_for, snapshot


router = APIRouter(tags=["analytics"])


def build_analytics(db: Session, user_id: int) -> AnalyticsOut:
    """按用户聚合学习分析：本人分析与管理员查看指定用户共用同一份逻辑。"""
    sessions = (
        db.query(AttemptSession)
        .filter(AttemptSession.user_id == user_id)
        .order_by(AttemptSession.id.asc())
        .all()
    )
    total_answers = sum(s.total for s in sessions)
    total_correct = sum(s.correct for s in sessions)
    accuracy = total_correct / total_answers * 100 if total_answers else 0.0

    last = sessions[-1] if sessions else None
    errors_count = (
        db.query(ErrorEntry).filter(ErrorEntry.user_id == user_id).count()
    )
    knowledge_rows = snapshot(db, user_id)
    weak_count = sum(1 for k in knowledge_rows if k.mastery < 60)

    metrics = [
        MetricItem(
            label="历史正确率",
            value=f"{accuracy:.1f}%" if total_answers else "0%",
        ),
        MetricItem(
            label="最近一次",
            value=f"{last.correct}/{last.total}" if last else "—",
        ),
        MetricItem(label="错题数量", value=str(errors_count)),
        MetricItem(label="需重点干预", value=str(weak_count)),
    ]

    error_counts: dict[str, int] = {}
    for row in (
        db.query(ErrorEntry.knowledge_name, ErrorEntry.knowledge_names)
        .filter(ErrorEntry.user_id == user_id)
        .all()
    ):
        try:
            names = json.loads(row[1] or "[]")
            if not isinstance(names, list) or not names:
                names = [row[0]]
        except (TypeError, ValueError):
            names = [row[0]]
        for name in {str(name) for name in names}:
            error_counts[name] = error_counts.get(name, 0) + 1

    diagnosis = [
        DiagnosisOut(
            name=k.name,
            mastery=k.mastery,
            error_count=error_counts.get(k.name, 0),
            action=action_for(k.mastery),
        )
        for k in sorted(knowledge_rows, key=lambda x: x.mastery)
    ]
    return AnalyticsOut(metrics=metrics, diagnosis=diagnosis)


@router.get("/analytics", response_model=AnalyticsOut)
def get_analytics(
    user_id: int | None = None,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """默认返回本人学习分析；管理员可用 user_id 查看指定用户（用户管理子页面）。"""
    permissions = user_permissions(db, user)
    target_id = user.id
    if user_id is not None and user_id != user.id:
        if "users:manage" not in permissions:
            raise HTTPException(status_code=403, detail="没有权限查看该用户的学习分析")
        target_id = user_id
    elif "learning:use" not in permissions and "users:manage" not in permissions:
        raise HTTPException(status_code=403, detail="没有权限执行该操作")
    if db.get(User, target_id) is None:
        raise HTTPException(status_code=404, detail="用户不存在")
    return build_analytics(db, target_id)