app/routers/analytics.py

from fastapi import APIRouter, Query, Depends, HTTPException
from app.mongodb import chat_logs
from datetime import datetime
from app.verify_access import verify_access

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

@router.get("/overview")
async def get_analytics_overview(
    chatbot_id: str,
    start_date: str | None = Query(None, description="Start date YYYY-MM-DD"),
    end_date: str | None = Query(None, description="End date YYYY-MM-DD"),
    access=Depends(verify_access)
):
    """
    Returns aggregated analytics data for charts:
    - sessions_per_day
    - requests_per_day
    - avg_latency_per_day
    """

    # --- Build match filter ---
    match_filter = {"chatbot_id": chatbot_id}

    if start_date:
        try:
            match_filter["timestamp"] = match_filter.get("timestamp", {})
            match_filter["timestamp"]["$gte"] = datetime.strptime(start_date, "%Y-%m-%d")
        except ValueError:
            raise HTTPException(status_code=400, detail="Invalid start_date format. Use YYYY-MM-DD")

    if end_date:
        try:
            match_filter["timestamp"] = match_filter.get("timestamp", {})
            match_filter["timestamp"]["$lte"] = datetime.strptime(end_date, "%Y-%m-%d")
        except ValueError:
            raise HTTPException(status_code=400, detail="Invalid end_date format. Use YYYY-MM-DD")

    # --- Sessions per day ---
    pipeline_sessions = [
        {"$match": match_filter},
        {
            "$group": {
                "_id": {
                    "$dateToString": {"format": "%Y-%m-%d", "date": "$timestamp", "timezone": "America/Los_Angeles"}
                },
                "unique_sessions": {"$addToSet": "$session_id"}
            }
        },
        {"$project": {"date": "$_id", "count": {"$size": "$unique_sessions"}, "_id": 0}},
        {"$sort": {"date": 1}}
    ]
    sessions_per_day = await chat_logs.aggregate(pipeline_sessions).to_list(length=None)

    # --- Requests per day ---
    pipeline_requests = [
        {"$match": match_filter},
        {
            "$group": {
                "_id": {
                    "$dateToString": {"format": "%Y-%m-%d", "date": "$timestamp", "timezone": "America/Los_Angeles"}
                },
                "count": {"$sum": 1}
            }
        },
        {"$project": {"date": "$_id", "count": 1, "_id": 0}},
        {"$sort": {"date": 1}}
    ]
    requests_per_day = await chat_logs.aggregate(pipeline_requests).to_list(length=None)

    # --- Average latency per day ---
    latency_filter = match_filter.copy()
    latency_filter["latency_ms"] = {"$exists": True}

    pipeline_latency = [
        {"$match": latency_filter},
        {
            "$group": {
                "_id": {
                    "$dateToString": {"format": "%Y-%m-%d", "date": "$timestamp", "timezone": "America/Los_Angeles"}
                },
                "avg_latency": {"$avg": "$latency_ms"}
            }
        },
        {"$project": {"date": "$_id", "avg_latency": {"$divide": ["$avg_latency", 1000]}, "_id": 0}},
        {"$sort": {"date": 1}}
    ]
    avg_latency_per_day = await chat_logs.aggregate(pipeline_latency).to_list(length=None)

    return {
        "sessions_per_day": sessions_per_day,
        "requests_per_day": requests_per_day,
        "avg_latency_per_day": avg_latency_per_day
    }