app.py

import torch
import torch.nn as nn
import json
import gradio as gr

# --- Step 1: Load the vocabularies ---
# These files are in your Hugging Face Space repository, so we can load them directly.
with open('char_to_int.json', 'r') as f:
    char_to_int = json.load(f)
with open('int_to_lang.json', 'r') as f:
    int_to_lang = json.load(f)

# --- Step 2: Re-define the Model Architecture ---
# This MUST be the exact same architecture as the one you trained.
# All the hyperparameters (embedding_dim, hidden_dim, etc.) must match.
class CodeClassifierRNN(nn.Module):
    def __init__(self, vocab_size, embedding_dim, hidden_dim, output_dim, n_layers, bidirectional, dropout, pad_idx):
        super().__init__()
        self.embedding = nn.Embedding(vocab_size, embedding_dim, padding_idx=pad_idx)
        self.lstm = nn.LSTM(embedding_dim, hidden_dim, num_layers=n_layers, bidirectional=bidirectional, dropout=dropout if n_layers > 1 else 0, batch_first=True)
        self.dropout = nn.Dropout(dropout)
        self.fc = nn.Linear(hidden_dim * 2, output_dim) # * 2 for bidirectional
    def forward(self, text):
        embedded = self.embedding(text)
        _, (hidden, _) = self.lstm(embedded)
        hidden = torch.cat((hidden[-2,:,:], hidden[-1,:,:]), dim=1)
        hidden = self.dropout(hidden)
        output = self.fc(hidden)
        return output

# --- Step 3: Instantiate the model and load the trained weights ---
# Set hyperparameters to match your training script
PAD_IDX = char_to_int['<PAD>']
VOCAB_SIZE = len(char_to_int)
EMBEDDING_DIM = 128
HIDDEN_DIM = 192  # Must match the final trained model
OUTPUT_DIM = len(int_to_lang)
N_LAYERS = 2
BIDIRECTIONAL = True
DROPOUT = 0.5

# Create an instance of the model
model = CodeClassifierRNN(VOCAB_SIZE, EMBEDDING_DIM, HIDDEN_DIM, OUTPUT_DIM, N_LAYERS, BIDIRECTIONAL, DROPOUT, PAD_IDX)

# Load the saved state dictionary.
# We use map_location='cpu' because the Space runs on a CPU.
model.load_state_dict(torch.load('polyglot_classifier.pt', map_location='cpu'))
model.eval() # Set the model to evaluation mode

# --- Step 4: Create the prediction function ---
def classify_code(code_snippet):
    if not code_snippet:
        return {}
        
    # 1. Convert snippet to tensor of indices
    indexed = [char_to_int.get(c, char_to_int['<UNK>']) for c in code_snippet]
    tensor = torch.LongTensor(indexed).unsqueeze(0) # Add batch dimension
    
    # 2. Make prediction
    with torch.no_grad():
        prediction = model(tensor)
    
    # 3. Get probabilities using softmax
    probabilities = torch.softmax(prediction, dim=1)
    
    # 4. Get top 5 predictions
    top5_probs, top5_indices = torch.topk(probabilities, 5)

    # 5. Format for Gradio output
    confidences = {int_to_lang[str(idx.item())]: prob.item() for idx, prob in zip(top5_indices[0], top5_probs[0])}
    
    return confidences

# --- Step 5: Create and launch the Gradio Interface ---
iface = gr.Interface(
    fn=classify_code,
    inputs=gr.Code(language=None, label="Code Snippet"),
    outputs=gr.Label(num_top_classes=5, label="Predicted Language"),
    title="Polyglot Code Classifier",
    description="Enter a code snippet to see which programming language the AI thinks it is. This model was trained from scratch on a custom dataset.",
    examples=[
        ["def hello_world():\n    print('Hello from Python!')"],
        ["function greet() {\n    console.log('Hello from JavaScript!');\n}"],
        ["public class Main {\n    public static void main(String[] args) {\n        System.out.println(\"Hello, Java!\");\n    }\n}"]
    ]
)

iface.launch()