from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy.orm import Session
from pydantic import BaseModel
from typing import List, Optional

from app.database.database import get_db
from app.database.models import User
from app.middleware.cache import cache

# Import AI helper engines
from app.ai.forecasting import predict_future_balance, forecast_savings_and_investments, simulate_future_scenarios
from app.ai.simulation import simulate_purchase_impact, simulate_investment_impact, simulate_subscription_cancellation
from app.ai.behavior import analyze_spending_behavior
from app.ai.coaching import calculate_financial_health_score, generate_daily_briefing
from app.ai.subscriptions import analyze_subscriptions
from app.ai.fraud import evaluate_transaction_for_fraud, get_user_fraud_alerts
from app.ai.chat import get_chat_response

router = APIRouter(prefix="/api/ai", tags=["AI Intelligence"])

# Fallback helper to retrieve a valid user ID for demonstration
def get_user_id_fallback(db: Session, user_id: Optional[str] = None) -> str:
    if user_id:
        return user_id
    user = db.query(User).first()
    if not user:
        raise HTTPException(status_code=404, detail="No users found in database. Please seed the database first.")
    return user.id

# Pydantic Schemas for input
class PurchaseRequest(BaseModel):
    amount: float
    merchant: str
    category: str

class InvestmentRequest(BaseModel):
    monthly_sip: float
    asset_type: str
    lump_sum: float = 0.0

class SubscriptionSimulationRequest(BaseModel):
    subscription_ids: List[str]

class ChatMessageRequest(BaseModel):
    message: str

# ─── FINANCIAL TWIN FORECASTS ──────────────────────────────────────────────────

@router.get("/twin/predict")
def get_twin_predict(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:twin:predict:{uid}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = predict_future_balance(db, uid)
    cache.set(cache_key, result, ttl=300) # cache for 5 minutes
    return result

@router.get("/twin/future")
def get_twin_future(user_id: Optional[str] = None, months: int = Query(default=12, ge=1, le=60), db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:twin:future:{uid}:{months}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = forecast_savings_and_investments(db, uid, months)
    cache.set(cache_key, result, ttl=300)
    return result

@router.get("/twin/scenarios")
def get_twin_scenarios(user_id: Optional[str] = None, months: int = Query(default=6, ge=1, le=24), db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:twin:scenarios:{uid}:{months}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = simulate_future_scenarios(db, uid, months)
    cache.set(cache_key, result, ttl=300)
    return result

# ─── SIMULATION ENDPOINTS ──────────────────────────────────────────────────────

@router.post("/simulate/purchase")
def post_simulate_purchase(req: PurchaseRequest, user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    return simulate_purchase_impact(db, uid, req.amount, req.category, req.merchant)

@router.post("/simulate/investment")
def post_simulate_investment(req: InvestmentRequest, user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    return simulate_investment_impact(db, uid, req.monthly_sip, req.asset_type, req.lump_sum)

@router.post("/simulate/subscription")
def post_simulate_subscription(req: SubscriptionSimulationRequest, user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    return simulate_subscription_cancellation(db, uid, req.subscription_ids)

# ─── BEHAVIORAL ANALYTICS ─────────────────────────────────────────────────────

@router.get("/behavior/insights")
def get_behavior_insights(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:behavior:insights:{uid}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = analyze_spending_behavior(db, uid)
    cache.set(cache_key, result, ttl=600) # cache for 10 minutes
    return result

# ─── COACHING & BRIEFINGS ─────────────────────────────────────────────────────

@router.get("/coaching/briefing")
def get_coaching_briefing(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    # Cache briefings for 1 hour to prevent excessive LLM costs
    cache_key = f"ai:coaching:briefing:{uid}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = generate_daily_briefing(db, uid)
    cache.set(cache_key, result, ttl=3600)
    return result

@router.get("/coaching/score")
def get_coaching_score(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:coaching:score:{uid}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = calculate_financial_health_score(db, uid)
    cache.set(cache_key, result, ttl=600)
    return result

# ─── SUBSCRIPTION OPTIMIZATION ────────────────────────────────────────────────

@router.get("/subscriptions/optimize")
def get_subscriptions_optimize(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:subs:optimize:{uid}"
    
    cached = cache.get(cache_key)
    if cached:
        return cached
        
    result = analyze_subscriptions(db, uid)
    cache.set(cache_key, result, ttl=600)
    return result

# ─── FRAUD & SECURITY ─────────────────────────────────────────────────────────

@router.get("/fraud/analysis")
def get_fraud_analysis(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    return get_user_fraud_alerts(db, uid)

@router.post("/fraud/evaluate/{transaction_id}")
def post_fraud_evaluate(transaction_id: str, db: Session = Depends(get_db)):
    return evaluate_transaction_for_fraud(db, transaction_id)

# ─── CONTEXTUAL CHAT ENDPOINT ──────────────────────────────────────────────────

@router.post("/chat")
def post_chat(req: ChatMessageRequest, user_id: Optional[str] = None, db: Session = Depends(get_db)):
    uid = get_user_id_fallback(db, user_id)
    response_msg = get_chat_response(db, uid, req.message)
    return {"response": response_msg}