from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session
from sqlalchemy import func
from backend.database.postgres.db import get_db
from backend.database.postgres.models import AuditLog, ChatSession as Conversation, GeneratedFile
from datetime import datetime, timedelta

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

@router.get("/health")
async def get_health_metrics(db: Session = Depends(get_db)):
    # 1. Latency Metrics
    latency_stats = db.query(
        func.avg(AuditLog.latency_ms).label("avg"),
        func.max(AuditLog.latency_ms).label("max")
    ).filter(AuditLog.action == "PROCESS_QUERY").first()

    # 2. File Generation Stats
    file_stats = db.query(
        GeneratedFile.file_type, 
        func.count(GeneratedFile.id)
    ).group_by(GeneratedFile.file_type).all()

    # 3. Active Users (24h)
    yesterday = datetime.utcnow() - timedelta(days=1)
    active_users = db.query(func.count(func.distinct(AuditLog.user_hash))).filter(
        AuditLog.created_at > yesterday
    ).scalar()

    # 4. Error Rate
    total_requests = db.query(func.count(AuditLog.id)).scalar() or 1
    errors = db.query(func.count(AuditLog.id)).filter(AuditLog.success == False).scalar() or 0
    error_rate = (errors / total_requests) * 100

    return {
        "status": "healthy",
        "metrics": {
            "avg_latency_ms": round(latency_stats.avg or 0, 2),
            "max_latency_ms": latency_stats.max or 0,
            "active_users_24h": active_users,
            "error_rate_pct": round(error_rate, 2),
            "files_generated": {t: c for t, c in file_stats}
        },
        "system": {
            "timestamp": datetime.utcnow().isoformat(),
            "uptime": "simulated"
        }
    }