import os
import io
import tempfile
import subprocess
import logging
import zipfile
from contextlib import contextmanager

logger = logging.getLogger(__name__)

@contextmanager
def _setenv(**mapping):
    """
    ``with`` context to temporarily modify the environment variables

    Usage:
        def test_myapp_respects_this_envvar():
            with _setenv(MYAPP_PLUGINS_DIR='testsandbox/plugins'):
                myapp.plugins.register()
                [...]
    """
    backup = os.environ.copy()
    os.environ.update(mapping)
    try:
        yield
    finally:
        os.environ.clear()
        os.environ.update(backup)


@contextmanager
def _chdir(dirname):
    """
    ``with`` context to temporarily chdir to a directory
    """
    current = os.getcwd()
    os.chdir(dirname)
    try:
        yield
    finally:
        os.chdir(current)

def make_pdf_from_zip(src_zip):
    """
    Returns the bytes of the PDF
    """
    with tempfile.TemporaryDirectory() as tmpdirname:
        zipfile.ZipFile(io.BytesIO(src_zip)).extractall(path=tmpdirname)
        with _setenv(
            PATH=(os.environ["PATH"] + ":/opt/texlive/2017/bin/x86_64-linux/"),
            HOME=tmpdirname,
            PERL5LIB=(os.environ.get("PERL5LIB", "") + ":/opt/texlive/2017/tlpkg/TeXLive/"),
        ):
            with _chdir(tmpdirname):
                # Run pdflatex...
                r = subprocess.run(
                    [
                        "latexmk",
                        "-verbose",
                        "-interaction=batchmode",
                        "-pdf",
                        "-output-directory={}".format(tmpdirname),
                        "document.tex",
                    ],
                    stdout=subprocess.PIPE,
                    stderr=subprocess.STDOUT,
                )
                stdout = r.stdout.decode("utf-8")
                logger.info(stdout)
                with open("document.pdf", "rb") as f:
                    pdf = f.read()
                    return pdf


def make_pdf_from_tex(tex):
    """
    Make a PDF from contexts of a .tex file
    """
    buf = io.BytesIO()
    with zipfile.ZipFile(buf, "w") as zipf:
        zipf.writestr("document.tex", tex)
    return make_pdf_from_zip(buf.getvalue())