#!/usr/bin/env python3
# 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 os
import platform
import sys
import subprocess
from textwrap import dedent

MIN_PYTHON_VERSION = (3, 7)
MAX_PYTHON_VERSION_TO_CONSIDER = (3, 11)


def load_mach(dir_path, mach_path):
    # Defer import of "importlib.util" until after Python version check has happened
    # so that Python 2 usages fail gracefully.
    import importlib.util
    spec = importlib.util.spec_from_file_location('mach_initialize', mach_path)
    mach_initialize = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(mach_initialize)
    return mach_initialize.initialize(dir_path)


def check_and_get_mach(dir_path):
    initialize_paths = (
        # Run Thunderbird's mach_initialize.py if it exists
        'comm/build/mach_initialize.py',
        'build/mach_initialize.py',
        # test package initialize
        'tools/mach_initialize.py',
    )
    for initialize_path in initialize_paths:
        mach_path = os.path.join(dir_path, initialize_path)
        if os.path.isfile(mach_path):
            return load_mach(dir_path, mach_path)
    return None


def try_alternate_python3_executables(args):
    for i in range(MIN_PYTHON_VERSION[1], MAX_PYTHON_VERSION_TO_CONSIDER[1] + 1):
        try:
            potential_python_binary = f"python3.{i}"
            if os.name == 'nt':
                potential_python_binary += ".exe"

            out = subprocess.run(
                [potential_python_binary, "--version"],
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
                encoding="UTF-8")

            binary_minor_version = int(out.stdout[9:11].strip("."))

            if binary_minor_version >= MIN_PYTHON_VERSION[1]:
                print(f"We found '{potential_python_binary}' and will attempt to re-run Mach with it.")
                os.execvp(potential_python_binary, [potential_python_binary] + ["mach"] + args)

        except Exception:
            # We don't really care what goes wrong, just don't let it bubble up
            # If we can't successfully launch with a different python3 binary
            # we will just print the normal help messages.
            pass


def main(args):
    # Ensure we are running Python 3.7+. We run this check as soon as
    # possible to avoid a cryptic import/usage error.
    if sys.version_info < MIN_PYTHON_VERSION:
        print(f"Python {MIN_PYTHON_VERSION[0]}.{MIN_PYTHON_VERSION[1]}+ is required to run mach.")
        print("You are running Mach with Python {0}".format(platform.python_version()))
        try_alternate_python3_executables(args)
        if sys.platform.startswith("linux"):
            print(dedent("""
            See https://firefox-source-docs.mozilla.org/setup/linux_build.html#installingpython
            for guidance on how to install Python on your system.
            """).strip())
        elif sys.platform.startswith("darwin"):
            print(dedent("""
            See https://firefox-source-docs.mozilla.org/setup/macos_build.html
            for guidance on how to prepare your system to build Firefox. Perhaps
            you need to update Xcode, or install Python using brew?
            """).strip())
        elif "MOZILLABUILD" in os.environ and os.environ.get("TERM"):
            print(dedent("""
            Python is provided by MozillaBuild; ensure your MozillaBuild installation is
            up to date. See https://firefox-source-docs.mozilla.org/setup/windows_build.html#install-mozillabuild
            for details.
            """).strip())
        elif sys.platform.startswith("win"):
            print(dedent("""
            You probably want to be interacting with Mach from within MozillaBuild, see
            https://firefox-source-docs.mozilla.org/setup/windows_build.html for details.
            
            If you are deliberately using Mach from outside MozillaBuild, then see
            https://firefox-source-docs.mozilla.org/mach/windows-usage-outside-mozillabuild.html#install-python
            for guidance on installing native Python on your system.
            """).strip())
        else:
            print(dedent("""
            We do not have specific instructions for your platform on how to
            install Python. You may find Pyenv (https://github.com/pyenv/pyenv)
            helpful, if your system package manager does not provide a way to
            install a recent enough Python 3.
            """).strip())
        sys.exit(1)

    # XCode python sets __PYVENV_LAUNCHER__, which overrides the executable
    # used when a python subprocess is created. This is an issue when we want
    # to run using our virtualenv python executables.
    # In future Python relases, __PYVENV_LAUNCHER__ will be cleared before
    # application code (mach) is started.
    # https://github.com/python/cpython/pull/9516
    os.environ.pop("__PYVENV_LAUNCHER__", None)

    mach = check_and_get_mach(os.path.dirname(os.path.realpath(__file__)))
    if not mach:
        print('Could not run mach: No mach source directory found.')
        sys.exit(1)
    sys.exit(mach.run(args))


if __name__ == '__main__':
    main(sys.argv[1:])