main.py

from contextlib import asynccontextmanager
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel, field_validator
from typing import List
from fraud_model import FraudDetector
import uvicorn
import logging

# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Global detector instance
detector: FraudDetector = None


@asynccontextmanager
async def lifespan(app: FastAPI):
    global detector
    try:
        logger.info("Loading FraudDetector model...")
        detector = FraudDetector()
        logger.info("FraudDetector loaded successfully.")
    except Exception as e:
        logger.error(f"FATAL: Failed to initialize FraudDetector: {e}")
        raise RuntimeError(f"Model failed to load: {e}")
    yield
    detector = None
    logger.info("FraudDetector shut down.")


app = FastAPI(
    title="Bank Fraud Detection API",
    description="API for detecting fraudulent bank transactions using AI.",
    version="1.0.0",
    lifespan=lifespan
)


# --- Request / Response Models ---

class PredictionRequest(BaseModel):
    text: str

    @field_validator("text")
    @classmethod
    def text_must_not_be_empty(cls, v):
        if not v or not v.strip():
            raise ValueError("text must not be empty")
        return v.strip()


class BatchPredictionRequest(BaseModel):
    texts: List[str]

    @field_validator("texts")
    @classmethod
    def texts_must_not_be_empty(cls, v):
        if not v:
            raise ValueError("texts list must not be empty")
        cleaned = [t.strip() for t in v if t and t.strip()]
        if not cleaned:
            raise ValueError("texts list contains only empty strings")
        return cleaned


class PredictionResponse(BaseModel):
    text: str
    fraud_score: float
    risk_level: str


class AnalyzeResponse(BaseModel):
    text: str
    fraud_score: float
    risk_level: str
    is_fraud: bool
    detection: str


# --- Routes ---

@app.get("/health")
def health_check():
    if detector:
        return {"status": "healthy", "model": detector.model_name}
    return {"status": "unhealthy", "error": "Model not loaded"}


@app.post("/predict", response_model=PredictionResponse)
def predict_single(request: PredictionRequest):
    if not detector:
        raise HTTPException(status_code=503, detail="Model service unavailable")
    try:
        result = detector.predict(request.text)
        return result
    except Exception as e:
        logger.error(f"Prediction error: {e}")
        raise HTTPException(status_code=500, detail=str(e))


@app.post("/predict/batch", response_model=List[PredictionResponse])
def predict_batch(request: BatchPredictionRequest):
    if not detector:
        raise HTTPException(status_code=503, detail="Model service unavailable")
    try:
        results = detector.predict_batch(request.texts)
        return results
    except Exception as e:
        logger.error(f"Batch prediction error: {e}")
        raise HTTPException(status_code=500, detail=str(e))


@app.post("/analyze", response_model=AnalyzeResponse)
def analyze(request: PredictionRequest):
    if not detector:
        raise HTTPException(status_code=503, detail="Model service unavailable")
    try:
        result = detector.analyze(request.text)
        return result
    except Exception as e:
        logger.error(f"Analyze error: {e}")
        raise HTTPException(status_code=500, detail=str(e))


if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=7860)