app.py

import gradio as gr
import torch
import numpy as np
import json
import time
from transformers import AutoTokenizer
import os
import importlib
from huggingface_hub import hf_hub_download
from llama_diffusion_model import CustomTransformerModel, CustomTransformerConfig, disable_dropout
import spaces

hf_token = os.getenv("HF_TOKEN")


# --- Load tokenizer ---
tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-3.2-3B", use_fast=True, token=hf_token)
vocab_size = len(tokenizer)
eos_token_id = tokenizer.eos_token_id
mask_token_id = tokenizer.encode('MASK', add_special_tokens=False)[0]
assistant_marker_ids = tokenizer.encode("Assistant:", add_special_tokens=False)

# def load_model():
#     ckpt_path = hf_hub_download(
#         repo_id="ruurd/tini_bi_m",
#         filename="diffusion-model.pth",
#         token=os.getenv("HF_TOKEN")
#     )

#     device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
#     model = torch.load(ckpt_path, map_location=device)
#     model = disable_dropout(model)
#     model.to(device)
#     model.eval()
#     return model

def load_model():
    ckpt_path = hf_hub_download(
        repo_id="ruurd/tini_model",
        filename="diffusion-model.pth",
        token=os.getenv("HF_TOKEN"),
        # revision="xxx",
    )

    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    # Step 1: Create model from scratch
    model = CustomTransformerModel(CustomTransformerConfig())

    # Step 2: Load state_dict from full checkpoint
    full_model = torch.load(ckpt_path, map_location=device)

    # This handles both full model or just state_dict
    try:
        state_dict = full_model.state_dict()
    except AttributeError:
        state_dict = full_model  # already a state_dict

    # Step 3: Load weights (might print mismatches)
    missing, unexpected = model.load_state_dict(state_dict, strict=False)
    print("Missing keys:", missing)
    print("Unexpected keys:", unexpected)

    model = disable_dropout(model)
    model.to(device)
    model.eval()
    return model

rng = np.random.default_rng()

# --- Utility Functions ---
def decode_tokens_safe(token_ids):
    return tokenizer.decode(token_ids, skip_special_tokens=True).replace("\n", " ")

def find_answer_start(input_ids, marker_ids):
    for i in range(len(input_ids) - len(marker_ids) + 1):
        if input_ids[i:i + len(marker_ids)] == marker_ids:
            return i + len(marker_ids)
    return None

def get_noising_schedule(i, max_it, sharpness=5.0):
    x = i / max_it
    return (np.exp(-sharpness * x) - np.exp(-sharpness)) / (1 - np.exp(-sharpness))

def noisify_answer(input_ids, answer_start, threshold=1.0, clustering=0.5, noise_start = 1.0):
    noised = input_ids.copy()
    answer_len = len(noised) - answer_start
    num_to_noise = int(threshold * answer_len * noise_start)
    mask_token_id = tokenizer.encode('MASK', add_special_tokens = False)[0]

    if num_to_noise == 0:
        return noised, []

    num_clusters = max(1, int((1 - clustering) * num_to_noise))
    cluster_size = max(1, int(num_to_noise / num_clusters))

    noised_indices = set()
    for _ in range(num_clusters):
        center = rng.integers(answer_start, len(noised))
        span_start = max(answer_start, center - cluster_size // 2)
        span_end = min(len(noised), span_start + cluster_size)
        noised_indices.update(range(span_start, span_end))

    noised_indices = sorted(list(noised_indices))[:num_to_noise]

    for idx in noised_indices:
        noised[idx] = mask_token_id

    return noised, noised_indices


# Add new noising function
def confidence_guided_noising(input_ids, answer_start, confidences, noise_clipping, threshold=1.0, noise_start=1.0):
    noised = input_ids.copy()
    answer_len = len(input_ids) - answer_start
    num_to_noise = int(threshold * answer_len * noise_start)
    if num_to_noise == 0:
        return noised, []

    all_indices = np.arange(answer_start, len(input_ids))
    eos_indices = [i for i in all_indices if input_ids[i] == eos_token_id]
    non_eos_indices = [i for i in all_indices if input_ids[i] != eos_token_id]

    # Proportionally split how many to noise
    num_non_eos_to_noise = int(num_to_noise * len(non_eos_indices) / (len(non_eos_indices) + len(eos_indices) + 1e-5))
    num_eos_to_noise = num_to_noise - num_non_eos_to_noise

    noised_indices = []

    # --- Non-EOS ---
    if non_eos_indices:
        raw_weights = 1.0 - np.array([confidences[i - answer_start] for i in non_eos_indices])
        raw_weights = np.clip(raw_weights, a_min=noise_clipping, a_max=None)
        weights = raw_weights / raw_weights.sum()

        chosen = rng.choice(non_eos_indices, size=min(num_non_eos_to_noise, len(non_eos_indices)), replace=False, p=weights)
        noised_indices.extend(chosen.tolist())

    # --- EOS ---
    if eos_indices and num_eos_to_noise > 0:
        raw_weights = 1.0 - np.array([confidences[i - answer_start] for i in eos_indices])
        raw_weights = np.clip(raw_weights, a_min=noise_clipping, a_max=None)
        weights = raw_weights / raw_weights.sum()

        chosen = rng.choice(eos_indices, size=min(num_eos_to_noise, len(eos_indices)), replace=False, p=weights)
        noised_indices.extend(chosen.tolist())

    for idx in noised_indices:
        noised[idx] = mask_token_id

    noised_indices = sorted(noised_indices)
    return noised, noised_indices

def filter_logits(logits, top_k=0, top_p=0.0):
    """Filter logits per position for top-k / nucleus (top-p) sampling."""
    logits = logits.clone()  # don't modify in-place
    batch_size, seq_len, vocab_size = logits.shape

    for i in range(seq_len):
        token_logits = logits[0, i]

        if top_k > 0:
            top_values, _ = torch.topk(token_logits, top_k)
            threshold = top_values[-1]
            token_logits[token_logits < threshold] = float("-inf")

        if top_p > 0.0:
            sorted_logits, sorted_indices = torch.sort(token_logits, descending=True)
            cumulative_probs = torch.softmax(sorted_logits, dim=-1).cumsum(dim=-1)

            sorted_indices_to_remove = cumulative_probs > top_p
            sorted_indices_to_remove[1:] = sorted_indices_to_remove[:-1].clone()
            sorted_indices_to_remove[0] = 0  # always keep at least 1 token

            token_logits[sorted_indices[sorted_indices_to_remove]] = float("-inf")

        logits[0, i] = token_logits

    return logits

@spaces.GPU
def generate_diffusion_text(input_ids):
    with torch.no_grad():
        input_tensor = torch.tensor([input_ids], dtype=torch.long).to(model.device)
        logits = model(input_ids=input_tensor)["logits"]
        logits = filter_logits(logits, top_k=top_k, top_p=top_p) 
        logits = logits.clamp(min=-1e8, max=1e4)
        probs = torch.nn.functional.softmax(logits, dim=-1)[0]
        probs = torch.clamp(probs, min=1e-8, max=1.0)
        assert torch.all(torch.isfinite(probs)), "Non-finite values in probs!"
        assert (probs >= 0).all(), "Negative probs!"
        sampled = torch.multinomial(probs, num_samples=1).squeeze(-1).tolist()

        # Extract confidence of selected tokens
        conf = probs[range(len(sampled)), sampled].cpu().numpy()
    return sampled, conf 

# --- Inference Wrapper ---
def diffusion_chat(question, max_it, pause_length, sharpness, clustering, noise_start, use_confidence_noising, noise_clipping):
    placeholder = "What do you know about the city of Amsterdam?"
    if question.strip() == "":
        question = placeholder

    print('started generation')
    prompt = f"User: {question}\nAssistant:"
    input_ids = tokenizer.encode(prompt, add_special_tokens=False)
    answer_start = find_answer_start(input_ids, assistant_marker_ids)
    if answer_start is None:
        yield "Error: Could not find Assistant marker in input."
        return
    
    if len(input_ids) < 256:
        input_ids += [mask_token_id] * (256 - len(input_ids))
    else:
        input_ids = input_ids[:256]

    ori_input_tokens = input_ids
    current_tokens, just_noised_indices = noisify_answer(
                input_ids, answer_start, threshold=1.0, clustering=clustering, noise_start = 1.0,
            )
    yield f"<b>Iteration 0 (initial noise):</b><br>" + tokenizer.decode(current_tokens[answer_start:], skip_special_tokens=True).replace('\n', '<br>')
    time.sleep(pause_length)
    last_tokens = []
    prev_decoded_tokens = []

    for i in range(max_it):
        print('Generating output')

        # Model step
        generated_tokens, confidences = generate_diffusion_text(current_tokens)

        # Save full output for noising step
        current_tokens = ori_input_tokens[:answer_start] + generated_tokens[answer_start:]

        # --- GREEN HIGHLIGHT ---
        decoded_tokens = tokenizer.convert_ids_to_tokens(current_tokens[answer_start:])
        highlighted = []
        for j, tok in enumerate(decoded_tokens):
            tok_id = tokenizer.convert_tokens_to_ids(tok)
            if tok_id == eos_token_id:
                continue
            token_str = tokenizer.convert_tokens_to_string([tok])
            if prev_decoded_tokens and j < len(prev_decoded_tokens) and tok != prev_decoded_tokens[j]:
                highlighted.append(f'<span style="color:green">{token_str}</span>')
            else:
                highlighted.append(token_str)

        prev_decoded_tokens = decoded_tokens
        yield f"<b>Iteration {i+1}/{max_it} (after generation):</b><br>" + "".join(highlighted).replace('\n', '<br>')
        time.sleep(pause_length)

        # --- Early stopping ---
        last_tokens.append(current_tokens)
        if len(last_tokens) > 3:
            last_tokens.pop(0)
        if len(last_tokens) == 3 and last_tokens[0] == last_tokens[1] == last_tokens[2]:
            yield f"<b>Stopped early after {i+1} iterations.</b>"
            break

        previous_tokens = current_tokens.copy()

        # --- NOISING STEP ---
        threshold = get_noising_schedule(i, max_it, sharpness=sharpness)
        if use_confidence_noising:
            noised_answer, just_noised_indices = confidence_guided_noising(
                current_tokens, answer_start, confidences, noise_clipping, threshold=threshold, noise_start=noise_start
            )
            just_noised_indices = []
        else:
            noised_answer, just_noised_indices = noisify_answer(
                current_tokens, answer_start, threshold=threshold, clustering=clustering, noise_start = noise_start,
            )

        # Compose full input again: prompt + noised answer
        current_tokens = ori_input_tokens[:answer_start] + noised_answer[answer_start:]

        # --- RED HIGHLIGHT ---
        decoded_tokens = tokenizer.convert_ids_to_tokens(current_tokens[answer_start:])
        highlighted = []
        for j, tok in enumerate(decoded_tokens):
            tok_id = tokenizer.convert_tokens_to_ids(tok)
            if tok_id == eos_token_id:
                continue
            token_str = tokenizer.convert_tokens_to_string([tok])
            abs_idx = answer_start + j
            if abs_idx in just_noised_indices:
                highlighted.append(f'<span style="color:red">{token_str}</span>')
            else:
                highlighted.append(token_str)

        yield f"<b>Iteration {i+1}/{max_it} (before noising):</b><br>" + "".join(highlighted).replace('\n', '<br>')
        time.sleep(pause_length)


    answer_ids = current_tokens[answer_start:]
    try:
        eos_index = answer_ids.index(eos_token_id)
        final_ids = answer_ids[:eos_index]
    except ValueError:
        final_ids = answer_ids
    
    num_tokens = len(final_ids)
    final_output = tokenizer.decode(final_ids, skip_special_tokens=True)
    
    print(final_output)
    yield f"<b>Final Output ({num_tokens} tokens after {i+1} iterations):</b><br>" + final_output.replace('\n', '<br>')


# --- Gradio Interface ---
print("Loading model...")
model = load_model()
print("✅ Model loaded.")

demo = gr.Interface(
    fn=diffusion_chat,
    inputs=[
        gr.Textbox(label="User Question", lines=2, placeholder="What do you know about the city of Amsterdam?"),
        gr.Slider(1, 512, value=64, step=1, label="↑ = more iterations"),
        gr.Slider(0.01, 5, value=0.01, step=0.01, label="↑ = longer pause (for visualization)"),
        gr.Slider(1.0, 20.0, value=1.0, step=0.5, label="↓ = more noising (sharpness)"),
        gr.Slider(0.0, 1.0, value=0.0, step=0.05, label="↑ = more clustered noising (fewer, larger edits)"),
        gr.Slider(0.0, 1.0, value=0.2, step=0.05, label="↑ = more noise (noise start)"),
        gr.Checkbox(value=False, label="Use confidence-guided noising"),
        gr.Slider(0.01, 1.0, value=0.01, step=0.01, label="↓ = more confidence guidance (noise clipping)"),
        
    ],
    outputs=[gr.HTML(label="Diffusion Output")],
    title="Diffusion Language Model Chat",
    theme="default",
    description="This interface runs a diffusion-based language model to generate answers progressively."
)

demo.launch(share=True, allowed_paths=["."], ssr_mode=False)