app/app.py

import torch
from transformers import AutoTokenizer, AutoModelForCausalLM
import gradio as gr
import pandas as pd
from functools import lru_cache

# ----------------------------------------------------------------------
# IMPORTANT: This version uses the PatchscopesRetriever implementation
# from the Tokens2Words paper (https://github.com/schwartz-lab-NLP/Tokens2Words)
# ----------------------------------------------------------------------
try:
    from .word_retriever import PatchscopesRetriever  # pip install tokens2words
except ImportError:
    PatchscopesRetriever = None

DEFAULT_MODEL = "meta-llama/Llama-3.1-8B"  # light default so the demo boots everywhere
DEVICE = (
    "cuda" if torch.cuda.is_available() else 'cpu'
)

@lru_cache(maxsize=4)
def get_model_and_tokenizer(model_name: str):
    tokenizer = AutoTokenizer.from_pretrained(model_name)
    model = AutoModelForCausalLM.from_pretrained(
        model_name,
        torch_dtype=torch.bfloat16 ,
        output_hidden_states=True,
    ).to(DEVICE)
    model.eval()
    return model, tokenizer


def find_last_token_index(full_ids, word_ids):
    """Locate end position of word_ids inside full_ids (first match)."""
    for i in range(len(full_ids) - len(word_ids) + 1):
        if full_ids[i : i + len(word_ids)] == word_ids:
            return i + len(word_ids) - 1
    return None


def analyse_word(model_name: str, extraction_template: str, word: str, patchscopes_template: str):
    if PatchscopesRetriever is None:
        return (
            "<p style='color:red'>❌ Patchscopes library not found. Run:<br/>"
            "<code>pip install git+https://github.com/schwartz-lab-NLP/Tokens2Words</code></p>"
        )

    model, tokenizer = get_model_and_tokenizer(model_name)

    # Build extraction prompt (where hidden states will be collected)
    extraction_prompt ="X"

    # Identify last token position of the *word* inside the prompt IDs
    word_token_ids = tokenizer.encode(word, add_special_tokens=False)

    # Instantiate Patchscopes retriever
    patch_retriever = PatchscopesRetriever(
        model,
        tokenizer,
        extraction_prompt,
        patchscopes_template,
        prompt_target_placeholder="X",
    )

    # Run retrieval for the word across all layers (one pass)
    retrieved_words  = patch_retriever.get_hidden_states_and_retrieve_word(
        word,
        num_tokens_to_generate=len(tokenizer.tokenize(word)),
    )[0]

    # Build a table summarising which layers match
    records = []
    matches = 0
    for layer_idx, ret_word in enumerate(retrieved_words):
        match = ret_word.strip(" ") == word.strip(" ")
        if match:
            matches += 1
        records.append({"Layer": layer_idx, "Retrieved": ret_word, "Match?": "✓" if match else ""})

    df = pd.DataFrame(records)

    def _style(row):
        color = "background-color: lightgreen" if row["Match?"] else ""
        return [color] * len(row)

    html_table = df.style.apply(_style, axis=1).hide(axis="index").to_html(escape=False)

    sub_tokens = tokenizer.convert_ids_to_tokens(word_token_ids)
    top = (
        f"<p><b>Sub‑word tokens:</b> {' , '.join(sub_tokens)}</p>"
        f"<p><b>Total matched layers:</b> {matches} / {len(retrieved_words)}</p>"
    )
    return top + html_table


# ----------------------------- GRADIO UI -------------------------------
with gr.Blocks(theme="soft") as demo:
    gr.Markdown(
        """# Tokens→Words Viewer\nInteractively inspect how hidden‑state patching (Patchscopes) reveals a word's detokenised representation across model layers."""
    )

    with gr.Row():
        model_name = gr.Dropdown(
            label="🤖 Model",
            choices=[DEFAULT_MODEL, "mistralai/Mistral-7B-v0.1", "meta-llama/Llama-2-7b", "Qwen/Qwen2-7B"],
            value=DEFAULT_MODEL,
        )
        extraction_template = gr.Textbox(
            label="Extraction prompt (use X as placeholder)",
            value="repeat the following word X twice: 1)X 2)",
        )
    patchscopes_template = gr.Textbox(
        label="Patchscopes prompt (use X as placeholder)",
        value="repeat the following word X twice: 1)X 2)",
    )
    word_box = gr.Textbox(label="Word to test", value="interpretable")
    run_btn = gr.Button("Analyse")
    out_html = gr.HTML()

    run_btn.click(
        analyse_word,
        inputs=[model_name, extraction_template, word_box, patchscopes_template],
        outputs=out_html,
    )

if __name__ == "__main__":
    demo.launch()