app.py

# =============================================================
# Hugging Face Space – Lecture → Podcast Generator (User‑selectable Languages)
# =============================================================
# * **Text generation** – SmolAgents `HfApiModel` (Qwen/Qwen2.5‑Coder‑32B‑Instruct).
# * **Speech synthesis** – `huggingface_hub.InferenceClient.text_to_speech`.
# * Users pick which languages to generate (English, Bangla, Chinese,
#   Urdu, Nepali). Unselected languages are skipped.
# -----------------------------------------------------------------

import os
import tempfile
import textwrap
from pathlib import Path
from typing import List, Dict, Tuple, Optional

import gradio as gr
from huggingface_hub import InferenceClient
from PyPDF2 import PdfReader
from smolagents import HfApiModel

# ------------------------------------------------------------------
# LLM: Qwen 32‑B via SmolAgents
# ------------------------------------------------------------------
llm = HfApiModel(
    model_id="Qwen/Qwen2.5-Coder-32B-Instruct",
    max_tokens=2096,
    temperature=0.5,
    custom_role_conversions=None,
)

# ------------------------------------------------------------------
# HF Inference API client (reads HF_TOKEN secret if set)
# ------------------------------------------------------------------
client = InferenceClient(token=os.getenv("HF_TOKEN", None))

# ------------------------------------------------------------------
# Language metadata and matching TTS model IDs
# ------------------------------------------------------------------
LANG_INFO: Dict[str, Dict[str, str]] = {
    "en": {"name": "English", "tts_model": "facebook/mms-tts-eng"},
    "bn": {"name": "Bangla",  "tts_model": "facebook/mms-tts-ben"},
    "zh": {"name": "Chinese", "tts_model": "myshell-ai/MeloTTS-Chinese"},
    "ur": {"name": "Urdu",    "tts_model": "facebook/mms-tts-urd-script_arabic"},
    "ne": {"name": "Nepali",  "tts_model": "facebook/mms-tts-npi"},
}

# Helper map: name ➜ code
LANG_CODE_BY_NAME = {info["name"]: code for code, info in LANG_INFO.items()}

PROMPT_TEMPLATE = textwrap.dedent(
    """
    You are producing a lively two‑host educational podcast in {lang_name}.
    Summarize the following lecture content into a dialogue of ≈1200 words.
    Make it engaging: hosts ask questions, clarify ideas with analogies, and
    wrap up with a concise recap. Preserve technical accuracy.

    ### Lecture Content
    {content}
    """
)

# ------------------------------------------------------------------
# Helpers: extract and truncate PDF text
# ------------------------------------------------------------------

def extract_pdf_text(pdf_path: str) -> str:
    reader = PdfReader(pdf_path)
    return "\n".join(page.extract_text() or "" for page in reader.pages)

TOKEN_LIMIT = 6000  # rough word‑level cap before hitting context limit

def truncate_text(text: str, limit: int = TOKEN_LIMIT) -> str:
    words = text.split()
    return " ".join(words[:limit])

# ------------------------------------------------------------------
# Main pipeline
# ------------------------------------------------------------------

def generate_podcast(pdf: gr.File, selected_lang_names: List[str]) -> List[Optional[Tuple[str, None]]]:
    """Generate podcast audio files for chosen languages. Returns a list
    aligned with LANG_INFO order; unselected languages yield None."""
    # Ensure at least one language selected
    if not selected_lang_names:
        return [None] * len(LANG_INFO)

    selected_codes = [LANG_CODE_BY_NAME[name] for name in selected_lang_names]

    with tempfile.TemporaryDirectory() as tmpdir:
        raw_text = extract_pdf_text(pdf.name)
        lecture_text = truncate_text(raw_text)
        outputs: List[Optional[Tuple[str, None]]] = []

        for code, info in LANG_INFO.items():
            if code not in selected_codes:
                outputs.append(None)
                continue

            # 1️⃣ Draft dialogue in the target language
            prompt = PROMPT_TEMPLATE.format(lang_name=info["name"], content=lecture_text)
            dialogue: str = llm(prompt)

            # 2️⃣ Synthesize speech via HF Inference API
            audio_bytes: bytes = client.text_to_speech(dialogue, model=info["tts_model"])
            flac_path = Path(tmpdir) / f"podcast_{code}.flac"
            flac_path.write_bytes(audio_bytes)

            outputs.append((str(flac_path), None))  # (filepath, label)

        return outputs

# ------------------------------------------------------------------
# Gradio interface
# ------------------------------------------------------------------

language_choices = [info["name"] for info in LANG_INFO.values()]

inputs = [
    gr.File(label="Upload Lecture PDF", file_types=[".pdf"]),
    gr.CheckboxGroup(
        choices=language_choices,
        value=["English"],
        label="Select podcast language(s) to generate",
    ),
]

audio_components = [
    gr.Audio(label=f"{info['name']} Podcast", type="filepath") for info in LANG_INFO.values()
]

iface = gr.Interface(
    fn=generate_podcast,
    inputs=inputs,
    outputs=audio_components,
    title="Lecture → Podcast Generator (Choose Languages)",
    description=(
        "Upload a lecture PDF, choose your desired languages, and receive a "
        "two‑host audio podcast. Dialogue is crafted by Qwen‑32B; speech is "
        "synthesized on‑the‑fly using the Hugging Face Inference API — "
        "no heavy downloads or GPUs required."
    ),
)

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