from fastapi import FastAPI
from fastapi.responses import JSONResponse, StreamingResponse
from pydantic import BaseModel
import types
import json
from pydantic import validator
from endpoint_handler import EndpointHandler  # your handler file
import base64

app = FastAPI()

handler = None

@app.on_event("startup")
async def load_handler():
    global handler
    handler = EndpointHandler()

class PredictInput(BaseModel):
    image: str       # base64-encoded image string
    question: str
    stream: bool = False

    @validator("question")
    def question_not_empty(cls, v):
        if not v.strip():
            raise ValueError("Question must not be empty")
        return v

    @validator("image")
    def valid_base64_and_size(cls, v):
        try:
            decoded = base64.b64decode(v, validate=True)
        except Exception:
            raise ValueError("`image` must be valid base64")
        if len(decoded) > 10 * 1024 * 1024:  # 10 MB limit
            raise ValueError("Image exceeds 10 MB after decoding")
        return v

class PredictRequest(BaseModel):
    inputs: PredictInput

@app.get("/")
async def root():
    return {"message": "FastAPI app is running on Hugging Face"}

@app.post("/predict")
async def predict_endpoint(payload: PredictRequest):
    print(f"[Request] Received question: {payload.inputs.question}")
    
    data = {
        "inputs": {
            "image": payload.inputs.image,
            "question": payload.inputs.question,
            "stream": payload.inputs.stream
        }
    }
    
    try:
        result = handler.predict(data)
    except ValueError as ve:
        return JSONResponse({"error": str(ve)}, status_code=400)
    except Exception as e:
        return JSONResponse({"error": "Internal server error"}, status_code=500)

    # ─── If it's a generator, return SSE/streaming ──────────────────────────
    if isinstance(result, types.GeneratorType):
        def event_stream():
            try:
                for chunk in result:
                    # Each chunk should already be a Python dict or
                    # a string containing JSON. We wrap it in "data: …\n\n"
                    yield f"data: {json.dumps(chunk)}\n\n"
                # Finally send an end‐of‐stream marker
                yield f"data: {json.dumps({'end': True})}\n\n"
            except Exception as e:
                yield f"data: {json.dumps({'error': str(e)})}\n\n"

        return StreamingResponse(event_stream(), media_type="text/event-stream")

    # ─── Otherwise (non‐streaming), return a single JSON response ──────────
    #    result is expected to be a JSON‐string or a dict
    try:
        # If handler.predict returned a JSON‐encoded str, parse it to dict
        if isinstance(result, str):
            parsed = json.loads(result)
        else:
            parsed = result  # assume it's already a dict
    except Exception:
        # Fall back to returning the raw result
        return JSONResponse({"error": "Invalid JSON from handler"}, status_code=500)

    return JSONResponse(parsed)