src/streamlit_app.py

import io
import os
import tempfile
from pathlib import Path
from pylatex import Document
import streamlit as st

def compile_latex(source: str) -> bytes:
    """
    Compile LaTeX source into a PDF and return its raw bytes.

    Parameters:
    ----------
    source : str
        A complete LaTeX document body (e.g. including \\begin{document}…).
    
    Returns:
    -------
    bytes
        The compiled PDF file contents.
    """
    with tempfile.TemporaryDirectory() as tmpdir:
        # ドキュメントを初期化
        doc = Document("document", documentclass="article", font_size="10pt")
        doc.append(source)

        base_path = os.path.join(tmpdir, "document")
        # compiler 引数で pdflatex を指定。latexmk があれば省略可。
        _ = doc.generate_pdf(
            filepath=base_path,
            compiler="pdflatex",
            clean=True,
            clean_tex=True,
            silent=True,
        )

        return Path(base_path + ".pdf").read_bytes()

def main():
    st.title("LaTeX Compiler")
    prompt = st.text_area(
        "Enter full LaTeX source",
        value=(
            r"\documentclass{article}"
            "\n" r"\begin{document}"
            "\n" r"Hello, world!"
            "\n" r"\end{document}"
        ),
        height=200,
    )

    if st.button("Compile to PDF"):
        with st.spinner("Compiling…"):
            pdf_bytes = compile_latex(prompt)
        st.success("Compilation succeeded")
        st.download_button(
            "Download PDF",
            data=pdf_bytes,
            file_name="output.pdf",
            mime="application/pdf",
        )

if __name__ == "__main__":
    main()