inference.py

import torch
from transformers import AutoTokenizer, AutoModelForSequenceClassification, ModernBertConfig
# models.py (containing ModernBertForSentiment) will be loaded from the Hub due to trust_remote_code=True
from typing import Dict, Any
import yaml

class SentimentInference:
    def __init__(self, config_path: str = "config.yaml"):
        """Load configuration and initialize model and tokenizer from Hugging Face Hub."""
        with open(config_path, 'r') as f:
            config_data = yaml.safe_load(f)
        
        model_yaml_cfg = config_data.get('model', {})
        inference_yaml_cfg = config_data.get('inference', {})
        
        model_hf_repo_id = model_yaml_cfg.get('name_or_path')
        if not model_hf_repo_id:
            raise ValueError("model.name_or_path must be specified in config.yaml (e.g., 'username/model_name')")

        tokenizer_hf_repo_id = model_yaml_cfg.get('tokenizer_name_or_path', model_hf_repo_id)

        self.max_length = inference_yaml_cfg.get('max_length', model_yaml_cfg.get('max_length', 512))

        print(f"Loading tokenizer from: {tokenizer_hf_repo_id}")
        self.tokenizer = AutoTokenizer.from_pretrained(tokenizer_hf_repo_id)
        
        print(f"Loading base ModernBertConfig from: {model_hf_repo_id}")
        # Load the config that was uploaded with the model (config.json in the HF repo)
        # This config should already have the correct architecture defined by ModernBertConfig.
        # We then augment it with any custom parameters needed by ModernBertForSentiment's __init__.
        loaded_config = ModernBertConfig.from_pretrained(model_hf_repo_id)
        
        # Augment loaded_config with parameters from model_yaml_cfg needed for ModernBertForSentiment initialization
        # These should reflect how the model was trained and its specific custom head.
        loaded_config.pooling_strategy = model_yaml_cfg.get('pooling_strategy', 'mean') # Default to 'mean' as per your models.py change
        loaded_config.num_weighted_layers = model_yaml_cfg.get('num_weighted_layers', 4)
        loaded_config.classifier_dropout = model_yaml_cfg.get('dropout') # Allow None if not in yaml
        # num_labels should ideally be in the config.json uploaded to HF, but can be set here if needed.
        # For binary sentiment with a single logit output, num_labels is 1.
        loaded_config.num_labels = model_yaml_cfg.get('num_labels', 1)
        # The loss_function might not be strictly needed for inference if the model doesn't use it in forward pass for eval,
        # but if ModernBertForSentiment.__init__ requires it, it must be provided.
        # Assuming it's not critical for basic inference here to simplify.
        # loaded_config.loss_function = model_yaml_cfg.get('loss_function', {'name': '...', 'params': {}})

        print(f"Instantiating and loading model weights for {model_hf_repo_id}...")
        # trust_remote_code=True allows loading models.py (containing ModernBertForSentiment)
        # from the Hugging Face model repository.
        self.model = AutoModelForSequenceClassification.from_pretrained(
            model_hf_repo_id,
            config=loaded_config, # Pass the augmented config
            trust_remote_code=True
        )
        self.model.eval()
        print(f"Model {model_hf_repo_id} loaded successfully from Hugging Face Hub.")
        
    def predict(self, text: str) -> Dict[str, Any]:
        inputs = self.tokenizer(text, return_tensors="pt", truncation=True, max_length=self.max_length, padding=True)
        with torch.no_grad():
            outputs = self.model(input_ids=inputs['input_ids'], attention_mask=inputs['attention_mask'])
        logits = outputs.get("logits") # Use .get for safety
        if logits is None:
            raise ValueError("Model output did not contain 'logits'. Check model's forward pass.")
        prob = torch.sigmoid(logits).item()
        return {"sentiment": "positive" if prob > 0.5 else "negative", "confidence": prob}