backend_service.py

from dotenv import load_dotenv
load_dotenv()
import os
import httpx

# Hugging Face Spaces: Only transformers backend is supported (no vLLM, no llama-cpp/gguf)

"""
FastAPI Backend AI Service using Gemma-3n-E4B-it
Provides OpenAI-compatible chat completion endpoints powered by google/gemma-3n-E4B-it
"""
import warnings

# Suppress warnings before any other imports
warnings.filterwarnings("ignore", category=FutureWarning, module="transformers")
warnings.filterwarnings("ignore", message=".*slow image processor.*")
warnings.filterwarnings("ignore", message=".*rope_scaling.*")

# Direct Hugging Face caches to a writable folder under /tmp (use only HF_HOME, TRANSFORMERS_CACHE is deprecated)
os.environ.setdefault("HF_HOME", "/tmp/.cache/huggingface")
# Suppress advisory warnings from transformers (including deprecation warnings)
os.environ["TRANSFORMERS_NO_ADVISORY_WARNINGS"] = "1"
hf_token = os.environ.get("HF_TOKEN")
import asyncio
import logging
import time
from contextlib import asynccontextmanager
from typing import List, Dict, Any, Optional, Union

from fastapi import FastAPI, HTTPException, Depends, Request
from fastapi.responses import StreamingResponse, JSONResponse
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel, Field, field_validator

import uvicorn
import requests
from PIL import Image



# Keep transformers imports as fallback
from transformers import AutoTokenizer, AutoModelForCausalLM

# Transformers imports (now fallback for non-GGUF models)
from transformers import pipeline, AutoTokenizer, AutoModelForCausalLM, AutoConfig  # type: ignore
from transformers import BitsAndBytesConfig  # type: ignore
# Gemma 3n specific imports
from transformers import Gemma3nForConditionalGeneration, AutoProcessor  # type: ignore
import torch
# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)



# Pydantic models for multimodal content
class TextContent(BaseModel):
    type: str = Field(default="text", description="Content type")
    text: str = Field(..., description="Text content")
    
    @field_validator('type')
    @classmethod
    def validate_type(cls, v: str) -> str:
        if v != "text":
            raise ValueError("Type must be 'text'")
        return v

class ImageContent(BaseModel):
    type: str = Field(default="image", description="Content type")
    url: str = Field(..., description="Image URL")
    
    @field_validator('type')
    @classmethod
    def validate_type(cls, v: str) -> str:
        if v != "image":
            raise ValueError("Type must be 'image'")
        return v

# Pydantic models for OpenAI-compatible API
class ChatMessage(BaseModel):
    role: str = Field(..., description="The role of the message author")
    content: Union[str, List[Union[TextContent, ImageContent]]] = Field(..., description="The content of the message - either string or list of content items")
    
    @field_validator('role')
    @classmethod
    def validate_role(cls, v: str) -> str:
        if v not in ["system", "user", "assistant"]:
            raise ValueError("Role must be one of: system, user, assistant")
        return v

class ChatCompletionRequest(BaseModel):
    model: str = Field(default_factory=lambda: os.environ.get("AI_MODEL", "google/gemma-3n-E4B-it"), description="The model to use for completion")
    messages: List[ChatMessage] = Field(..., description="List of messages in the conversation")
    max_tokens: Optional[int] = Field(default=512, ge=1, le=2048, description="Maximum tokens to generate")
    temperature: Optional[float] = Field(default=0.7, ge=0.0, le=2.0, description="Sampling temperature")
    stream: Optional[bool] = Field(default=False, description="Whether to stream responses")
    top_p: Optional[float] = Field(default=0.95, ge=0.0, le=1.0, description="Top-p sampling")

class ChatCompletionChoice(BaseModel):
    index: int
    message: ChatMessage
    finish_reason: str

class ChatCompletionResponse(BaseModel):
    id: str
    object: str = "chat.completion"
    created: int
    model: str
    choices: List[ChatCompletionChoice]

class ChatCompletionChunk(BaseModel):
    id: str
    object: str = "chat.completion.chunk"
    created: int
    model: str
    choices: List[Dict[str, Any]]

class HealthResponse(BaseModel):
    status: str
    model: str
    version: str

class ModelInfo(BaseModel):
    id: str
    object: str = "model"
    created: int
    owned_by: str = "huggingface"

class ModelsResponse(BaseModel):
    object: str = "list"
    data: List[ModelInfo]

class CompletionRequest(BaseModel):
    prompt: str = Field(..., description="The prompt to complete")
    max_tokens: Optional[int] = Field(default=512, ge=1, le=2048)
    temperature: Optional[float] = Field(default=0.7, ge=0.0, le=2.0)



# Model can be configured via environment variable - defaults to Gemma 3n (transformers format)
current_model = os.environ.get("AI_MODEL", "google/gemma-3n-E4B-it")
vision_model = os.environ.get("VISION_MODEL", "Salesforce/blip-image-captioning-base")

# Transformers model support
processor = None  # For Gemma 3n we use AutoProcessor instead of just tokenizer
model = None
image_text_pipeline = None  # type: ignore



# Image processing utilities
async def download_image(url: str) -> Image.Image:
    """Download and process image from URL"""
    try:
        response = requests.get(url, timeout=10)
        response.raise_for_status()
        image = Image.open(requests.compat.BytesIO(response.content))  # type: ignore
        return image
    except Exception as e:
        logger.error(f"Failed to download image from {url}: {e}")
        raise HTTPException(status_code=400, detail=f"Failed to download image: {str(e)}")

def extract_text_and_images(content: Union[str, List[Any]]) -> tuple[str, List[str]]:
    """Extract text and image URLs from message content"""
    if isinstance(content, str):
        return content, []
    
    text_parts: List[str] = []
    image_urls: List[str] = []
    
    for item in content:
        if hasattr(item, 'type'):
            if item.type == "text" and hasattr(item, 'text'):
                text_parts.append(str(item.text))
            elif item.type == "image" and hasattr(item, 'url'):
                image_urls.append(str(item.url))
    
    return " ".join(text_parts), image_urls

def has_images(messages: List[ChatMessage]) -> bool:
    """Check if any messages contain images"""
    for message in messages:
        if isinstance(message.content, list):
            for item in message.content:
                if hasattr(item, 'type') and item.type == "image":
                    return True
    return False



@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan manager for startup and shutdown events"""
    global processor, model, image_text_pipeline, current_model
    logger.info("🚀 Starting AI Backend Service (Hugging Face Spaces mode)...")
    try:
        logger.info(f"📥 Loading model with transformers: {current_model}")
        
        # For Gemma 3n models, use the specific classes
        if "gemma-3n" in current_model.lower():
            processor = AutoProcessor.from_pretrained(current_model)
            model = Gemma3nForConditionalGeneration.from_pretrained(
                current_model,
                low_cpu_mem_usage=True,
                trust_remote_code=True,
                torch_dtype=torch.bfloat16 if torch.cuda.is_available() else torch.float32,
            ).eval()
        else:
            # Fallback for other models
            processor = AutoTokenizer.from_pretrained(current_model)
            model = AutoModelForCausalLM.from_pretrained(
                current_model,
                low_cpu_mem_usage=True,
                trust_remote_code=True,
            )
        
        logger.info(f"✅ Successfully loaded model and processor: {current_model}")
        
        # Gemma 3n is multimodal, so we don't need a separate image pipeline
        if "gemma-3n" not in current_model.lower():
            # Load image pipeline for multimodal support (only for non-Gemma-3n models)
            try:
                logger.info(f"🖼️ Initializing image captioning pipeline with model: {vision_model}")
                image_text_pipeline = pipeline("image-to-text", model=vision_model)
                logger.info("✅ Image captioning pipeline loaded successfully")
            except Exception as e:
                logger.warning(f"⚠️ Could not load image captioning pipeline: {e}")
                image_text_pipeline = None
        else:
            logger.info("✅ Gemma 3n has built-in multimodal support")
            image_text_pipeline = None
            
    except Exception as e:
        logger.error(f"❌ Failed to initialize model: {e}")
        raise RuntimeError(f"Service initialization failed: {e}")
    yield
    logger.info("🔄 Shutting down AI Backend Service...")
    processor = None
    model = None
    image_text_pipeline = None

# Initialize FastAPI app
app = FastAPI(
    title="AI Backend Service - Gemma 3n",
    description="OpenAI-compatible chat completion API powered by google/gemma-3n-E4B-it",
    version="1.0.0",
    lifespan=lifespan
)

# Add CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # Configure appropriately for production
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


def ensure_model_ready():
    """Check if transformers model is loaded and ready"""
    if processor is None or model is None:
        raise HTTPException(status_code=503, detail="Service not ready - no model initialized (transformers)")

def convert_messages_to_prompt(messages: List[ChatMessage]) -> str:
    """Convert OpenAI messages format to a single prompt string"""
    prompt_parts: List[str] = []
    
    for message in messages:
        role = message.role
        
        # Extract text content (handle both string and list formats)
        if isinstance(message.content, str):
            content = message.content
        else:
            content, _ = extract_text_and_images(message.content)
        
        if role == "system":
            prompt_parts.append(f"System: {content}")
        elif role == "user":
            prompt_parts.append(f"Human: {content}")
        elif role == "assistant":
            prompt_parts.append(f"Assistant: {content}")
    
    # Add assistant prompt to continue
    prompt_parts.append("Assistant:")
    
    return "\n".join(prompt_parts)

async def generate_multimodal_response(
    messages: List[ChatMessage],
    request: ChatCompletionRequest
) -> str:
    """Generate response using image-text-to-text pipeline for multimodal content"""
    if not image_text_pipeline:
        raise HTTPException(status_code=503, detail="Image processing not available - pipeline not initialized")
    
    try:
        # Find the last user message with images
        last_user_message = None
        for message in reversed(messages):
            if message.role == "user" and isinstance(message.content, list):
                last_user_message = message
                break
        
        if not last_user_message:
            raise HTTPException(status_code=400, detail="No user message with images found")
        
        # Extract text and images from the message
        text_content, image_urls = extract_text_and_images(last_user_message.content)
        
        if not image_urls:
            raise HTTPException(status_code=400, detail="No images found in the message")
        
        # Use the first image for now (could be extended to handle multiple images)
        image_url = image_urls[0]
        
        # Generate response using the image-to-text pipeline
        logger.info(f"🖼️ Processing image: {image_url}")
        try:
            # Use the pipeline directly with the image URL (no messages format needed for image-to-text)
            result = await asyncio.to_thread(lambda: image_text_pipeline(image_url))  # type: ignore
            
            # Handle response format from image-to-text pipeline
            if result and hasattr(result, '__len__') and len(result) > 0:  # type: ignore
                first_result = result[0]  # type: ignore
                if hasattr(first_result, 'get'):
                    generated_text = first_result.get('generated_text', f'I can see an image at {image_url}.')  # type: ignore
                else:
                    generated_text = str(first_result)
                
                # Combine with user's text question if provided
                if text_content:
                    response = f"Looking at this image, I can see: {generated_text}. "
                    if "what" in text_content.lower() or "?" in text_content:
                        response += f"Regarding your question '{text_content}': Based on what I can see, this appears to be {generated_text.lower()}."
                    else:
                        response += f"You mentioned: {text_content}"
                    return response
                else:
                    return f"I can see: {generated_text}"
            else:
                return f"I can see there's an image at {image_url}, but cannot process it right now."
                
        except Exception as pipeline_error:
            logger.warning(f"Pipeline error: {pipeline_error}")
            return f"I can see there's an image at {image_url}. The image appears to contain visual content that I'm having trouble processing right now."
            
    except Exception as e:
        logger.error(f"Error in multimodal generation: {e}")
        return f"I'm having trouble processing the image. Error: {str(e)}"


def generate_response_local(messages: List[ChatMessage], max_tokens: int = 512, temperature: float = 0.7, top_p: float = 0.95) -> str:
    """Generate response using local transformers model with chat template."""
    ensure_model_ready()
    try:
        logger.info(" Generating response using transformers model")
        return generate_response_transformers(messages, max_tokens, temperature, top_p)
    except Exception as e:
        logger.error(f"Local generation failed: {e}")
        return "I apologize, but I'm having trouble generating a response right now. Please try again."

## GGUF/llama-cpp support removed for Hugging Face Spaces

def convert_messages_to_gemma_prompt(messages: List[ChatMessage]) -> str:
    """Convert OpenAI messages format to Gemma 3n chat format."""
    # Gemma 3n uses specific format with <start_of_turn> and <end_of_turn>
    prompt_parts = ["<bos>"]
    
    for message in messages:
        role = message.role
        content = message.content
        
        if role == "system":
            prompt_parts.append(f"<start_of_turn>system\n{content}<end_of_turn>")
        elif role == "user":
            prompt_parts.append(f"<start_of_turn>user\n{content}<end_of_turn>")
        elif role == "assistant":
            prompt_parts.append(f"<start_of_turn>model\n{content}<end_of_turn>")
    
    # Add the start for model response
    prompt_parts.append("<start_of_turn>model\n")
    
    return "\n".join(prompt_parts)

def generate_response_transformers(messages: List[ChatMessage], max_tokens: int = 512, temperature: float = 0.7, top_p: float = 0.95) -> str:
    """Generate response using transformers model with chat template."""
    try:
        # Check if we're using Gemma 3n
        if "gemma-3n" in current_model.lower():
            # Gemma 3n specific handling
            # Convert messages to HuggingFace format for chat template
            chat_messages = []
            for m in messages:
                # Gemma 3n supports multimodal, but for now we'll handle text only
                if isinstance(m.content, str):
                    content = [{"type": "text", "text": m.content}]
                else:
                    # Extract text content for now (image support can be added later)
                    text_content, _ = extract_text_and_images(m.content)
                    content = [{"type": "text", "text": text_content}]
                
                chat_messages.append({"role": m.role, "content": content})
            
            # Apply chat template using processor
            inputs = processor.apply_chat_template(
                chat_messages,
                add_generation_prompt=True,
                tokenize=True,
                return_dict=True,
                return_tensors="pt",
            )
            
            # Generate with Gemma 3n
            input_len = inputs["input_ids"].shape[-1]
            with torch.inference_mode():
                generation = model.generate(
                    **inputs,
                    max_new_tokens=max_tokens,
                    temperature=temperature,
                    top_p=top_p,
                    do_sample=temperature > 0,
                )
                generation = generation[0][input_len:]
            
            # Decode the response
            generated_text = processor.decode(generation, skip_special_tokens=True)
            return generated_text.strip()
            
        else:
            # Fallback for other models
            # Convert messages to HuggingFace format for chat template
            chat_messages = []
            for m in messages:
                content_str = m.content if isinstance(m.content, str) else extract_text_and_images(m.content)[0]
                chat_messages.append({"role": m.role, "content": content_str})
            
            # Apply chat template and tokenize
            inputs = processor.apply_chat_template(
                chat_messages,
                add_generation_prompt=True,
                tokenize=True,
                return_dict=True,
                return_tensors="pt",
            )
            # Generate response
            outputs = model.generate(
                input_ids=inputs["input_ids"],
                attention_mask=inputs.get("attention_mask"),
                max_new_tokens=max_tokens,
                temperature=temperature,
                top_p=top_p,
                do_sample=temperature > 0,
            )
            # Decode only the newly generated tokens (exclude input)
            generated_text = processor.decode(outputs[0][inputs["input_ids"].shape[-1]:], skip_special_tokens=True)
            return generated_text.strip()
        
    except Exception as e:
        logger.error(f"Transformers generation failed: {e}")
        return "I apologize, but I'm having trouble generating a response right now. Please try again."


@app.get("/", response_class=JSONResponse)
async def root() -> Dict[str, Any]:
    """Root endpoint with service information"""
    return {
        "message": "AI Backend Service is running with Mistral Nemo!",
        "model": current_model,
        "version": "1.0.0",
        "endpoints": {
            "health": "/health",
            "models": "/v1/models",
            "chat_completions": "/v1/chat/completions"
        }
    }

@app.get("/health", response_model=HealthResponse)
async def health_check():
    """Health check endpoint"""
    global current_model, tokenizer, model
    return HealthResponse(
        status="healthy" if (tokenizer is not None and model is not None) else "unhealthy",
        model=current_model,
        version="1.0.0"
    )

@app.get("/v1/models", response_model=ModelsResponse)
async def list_models():
    """List available models (OpenAI-compatible)"""
    
    models = [
        ModelInfo(
            id=current_model,
            created=int(time.time()),
            owned_by="huggingface"
        )
    ]
    
    # Add vision model if available
    if image_text_pipeline:
        models.append(
            ModelInfo(
                id=vision_model,
                created=int(time.time()),
                owned_by="huggingface"
            )
        )
    
    return ModelsResponse(data=models)

        
        # ...existing code...




# --- Hugging Face Spaces: Only transformers backend supported ---
@app.post("/v1/chat/completions", response_model=ChatCompletionResponse)
async def create_chat_completion(request: ChatCompletionRequest) -> ChatCompletionResponse:
    """Create a chat completion (OpenAI-compatible) with multimodal support. Hugging Face Spaces: Only transformers backend supported."""
    try:
        if not request.messages:
            raise HTTPException(status_code=400, detail="Messages cannot be empty")
        is_multimodal = has_images(request.messages)
        if is_multimodal:
            if not image_text_pipeline:
                raise HTTPException(status_code=503, detail="Image processing not available")
            response_text = await generate_multimodal_response(request.messages, request)
        else:
            logger.info(f"Generating local response for messages: {request.messages}")
            response_text = await asyncio.to_thread(
                generate_response_local,
                request.messages,
                request.max_tokens or 512,
                request.temperature or 0.7,
                request.top_p or 0.95
            )
        response_text = response_text.strip() if response_text else "No response generated."
        return ChatCompletionResponse(
            id=f"chatcmpl-{int(time.time())}",
            created=int(time.time()),
            model=request.model,
            choices=[ChatCompletionChoice(
                index=0,
                message=ChatMessage(role="assistant", content=response_text),
                finish_reason="stop"
            )]
        )
    except Exception as e:
        logger.error(f"Error in chat completion: {e}")
        raise HTTPException(status_code=500, detail=f"Internal server error: {str(e)}")



@app.post("/v1/completions")
async def create_completion(
    request: CompletionRequest
) -> Dict[str, Any]:
    """Create a text completion (OpenAI-compatible)"""
    try:
        if not request.prompt:
            raise HTTPException(status_code=400, detail="Prompt cannot be empty")
        ensure_model_ready()
        # Use the prompt as a single user message
        messages = [ChatMessage(role="user", content=request.prompt)]
        response_text = await asyncio.to_thread(
            generate_response_local,
            messages,
            request.max_tokens or 512,
            request.temperature or 0.7,
            0.95
        )
        return {
            "id": f"cmpl-{int(time.time())}",
            "object": "text_completion",
            "created": int(time.time()),
            "model": current_model,
            "choices": [{
                "text": response_text,
                "index": 0,
                "finish_reason": "stop"
            }]
        }
    except Exception as e:
        logger.error(f"Error in completion: {e}")
        raise HTTPException(status_code=500, detail=f"Internal server error: {str(e)}")

@app.post("/api/response")
async def api_response(request: Request) -> JSONResponse:
    """Endpoint to receive and send responses via API."""
    try:
        data = await request.json()
        message = data.get("message", "No message provided")
        return JSONResponse(content={
            "status": "success",
            "received_message": message,
            "response_message": f"You sent: {message}"
        })
    except Exception as e:
        logger.error(f"Error processing API response: {e}")
        raise HTTPException(status_code=500, detail="Internal server error")

# Main entry point moved to the end for proper initialization
if __name__ == "__main__":
    import uvicorn
    uvicorn.run("backend_service:app", host="0.0.0.0", port=8000, reload=True)