# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import errno
import os
import subprocess
import sys
import tempfile

import buildconfig
from mozfile import which


def preprocess(out, asm_file):
    cxx = buildconfig.substs["CXX"]
    if not os.path.exists(cxx[0]):
        tool = cxx[0]
        cxx[0] = which(tool)
        if not cxx[0]:
            raise OSError(errno.ENOENT, f"Could not find {tool} on PATH.")

    cppflags = buildconfig.substs["OS_CPPFLAGS"]

    # subprocess.Popen(stdout=) only accepts actual file objects, which `out`,
    # above, is not.  So fake a temporary file to write to.
    (outhandle, tmpout) = tempfile.mkstemp(suffix=".cpp")

    # #line directives will confuse armasm64, and /EP is the only way to
    # preprocess without emitting #line directives.
    command = cxx + ["/EP"] + cppflags + ["/TP", asm_file]
    with open(tmpout, "wb") as t:
        result = subprocess.Popen(command, stdout=t).wait()
        if result != 0:
            sys.exit(result)

    with open(tmpout, "rb") as t:
        out.write(t.read())

    os.close(outhandle)
    os.remove(tmpout)
