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, chat_memory
from app.ai.intelligence import generate_weekly_coaching, explain_fraud_alert, generate_spending_narrative

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
    session_id: Optional[str] = None
    language: str = "English"

class ChatSessionCreateRequest(BaseModel):
    title: Optional[str] = "New chat"

# ─── 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.get("/chat/sessions")
def list_chat_sessions(
    user_id: Optional[str] = None,
    limit: int = Query(30, ge=1, le=50),
    db: Session = Depends(get_db),
):
    uid = get_user_id_fallback(db, user_id)
    sessions = chat_memory.list_sessions(db, uid, limit=limit)
    return {"sessions": sessions, "count": len(sessions)}


@router.post("/chat/sessions")
def create_chat_session(
    body: ChatSessionCreateRequest,
    user_id: Optional[str] = None,
    db: Session = Depends(get_db),
):
    uid = get_user_id_fallback(db, user_id)
    session = chat_memory.create_session(db, uid, title=body.title or "New chat")
    return {
        "id": session.id,
        "title": session.title,
        "created_at": session.created_at.isoformat() if session.created_at else None,
        "updated_at": session.updated_at.isoformat() if session.updated_at else None,
        "message_count": 0,
        "preview": "",
    }


@router.delete("/chat/sessions/{session_id}")
def delete_chat_session(
    session_id: str,
    user_id: Optional[str] = None,
    db: Session = Depends(get_db),
):
    uid = get_user_id_fallback(db, user_id)
    if not chat_memory.delete_session(db, uid, session_id):
        raise HTTPException(status_code=404, detail="Chat session not found")
    return {"ok": True, "message": "Chat deleted"}


@router.get("/chat/history")
def get_chat_history(
    session_id: str = Query(..., description="Chat session ID"),
    user_id: Optional[str] = None,
    limit: int = Query(100, ge=1, le=200),
    db: Session = Depends(get_db),
):
    uid = get_user_id_fallback(db, user_id)
    if not chat_memory.get_session(db, uid, session_id):
        raise HTTPException(status_code=404, detail="Chat session not found")
    messages = chat_memory.list_messages(db, session_id, limit=limit)
    return {"session_id": session_id, "messages": messages, "count": len(messages)}


@router.delete("/chat/history")
def delete_chat_history(
    session_id: str = Query(..., description="Chat session ID"),
    user_id: Optional[str] = None,
    db: Session = Depends(get_db),
):
    uid = get_user_id_fallback(db, user_id)
    if not chat_memory.clear_session_messages(db, uid, session_id):
        raise HTTPException(status_code=404, detail="Chat session not found")
    return {"ok": True, "message": "Conversation cleared", "session_id": session_id}


@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, session_id = get_chat_response(db, uid, req.message, req.session_id, req.language)
    return {"response": response_msg, "session_id": session_id}


# ─── FINANCIAL COACH MODE ──────────────────────────────────────────────────────

@router.get("/coach/weekly")
def get_weekly_coaching(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    """
    Proactive weekly coaching report: summary, budget coaching, savings nudge,
    anomaly explanations, and top 3 actions — all grounded in real account data.
    """
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:coach:weekly:{uid}"
    cached = cache.get(cache_key)
    if cached:
        return cached
    result = generate_weekly_coaching(db, uid)
    cache.set(cache_key, result, ttl=3600)  # cache 1 hour
    return result


# ─── AI FRAUD EXPLANATION ──────────────────────────────────────────────────────

@router.get("/fraud/explain/{fraud_log_id}")
def get_fraud_explanation(fraud_log_id: str, db: Session = Depends(get_db)):
    """
    Returns a human-readable AI explanation of exactly why a specific
    transaction was flagged, with context about the user's normal patterns.
    """
    return explain_fraud_alert(db, fraud_log_id)


# ─── SPENDING NARRATIVE ────────────────────────────────────────────────────────

@router.get("/narrative/monthly")
def get_monthly_narrative(user_id: Optional[str] = None, db: Session = Depends(get_db)):
    """
    Monthly spending narrative: what changed, what improved, what to watch,
    investment insights, and a one-paragraph human story of the month.
    """
    uid = get_user_id_fallback(db, user_id)
    cache_key = f"ai:narrative:monthly:{uid}"
    cached = cache.get(cache_key)
    if cached:
        return cached
    result = generate_spending_narrative(db, uid)
    cache.set(cache_key, result, ttl=1800)  # cache 30 min
    return result