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"""Helper code for running isolated versions of NodeJS."""

import functools
import os
import platform
import sys

THIS_DIR = os.path.dirname(__file__)
DAWN_ROOT = os.path.realpath(os.path.join(THIS_DIR, '..', '..'))


@functools.cache
def get_node_dir() -> str:
    """Retrieves the directory that NodeJS should be available in."""
    cipd_os = get_cipd_compatible_current_os()
    cipd_arch = get_cipd_compatible_current_arch()
    cipd_platform = f'{cipd_os}-{cipd_arch}'
    return os.path.join(DAWN_ROOT, 'third_party', 'node', cipd_platform)


@functools.cache
def get_cipd_compatible_current_os() -> str:
    """Retrieves the current OS name.

    The returned string is compatible with CIPD's package naming scheme.
    """
    current_platform = sys.platform
    if current_platform in ('linux', 'cygwin'):
        return 'linux'
    if current_platform == 'win32':
        return 'windows'
    if current_platform == 'darwin':
        return 'mac'
    raise ValueError(f'Unknown platform {current_platform}')


@functools.cache
def get_cipd_compatible_current_arch() -> str:
    """Retrieves the current architecture.

    The returned string is compatible with CIPD's package naming scheme.
    """
    native_arm = platform.machine().lower() in ('arm', 'arm64')
    # This is necessary for the case of running x86 Python on arm devices via
    # an emulator. In this case, platform.machine() will show up as an x86
    # processor.
    emulated_x86 = 'armv8' in platform.processor().lower()
    if native_arm or emulated_x86:
        return 'arm64'

    native_x86 = platform.machine().lower() in ('x86', 'x86_64', 'amd64')
    if native_x86:
        return 'amd64'
    raise ValueError('Unable to determine architecture')


@functools.cache
def get_node_path() -> str:
    """Retrieves the path to the node executable.

    Returns:
        A filepath to the standalone node executable.
    """
    path = os.path.join(get_node_dir(), 'bin', 'node')
    if sys.platform == 'win32':
        path = os.path.join(get_node_dir(), 'node.exe')
    if not os.path.exists(path):
        raise RuntimeError(
            f'Unable to find the node binary under {get_node_dir()}. Is the '
            f'dawn_node gclient variable set?')
    return path


@functools.cache
def get_npm_command() -> list[str]:
    """Retrieves a command to run npm

    Returns:
        A list of strings that will run "npm" when run as a command for a
        subprocess.
    """
    path = os.path.join(get_node_dir(), 'lib', 'node_modules', 'npm', 'bin',
                        'npm-cli.js')
    if sys.platform == 'win32':
        path = os.path.join(get_node_dir(), 'node_modules', 'npm', 'bin',
                            'npm-cli.js')
    if not os.path.exists(path):
        raise RuntimeError(
            f'Unable to find the npm-cli.js file under {get_node_dir()}. Is the '
            f'dawn_node gclient variable set?')
    cmd = [
        get_node_path(),
        os.path.join(get_node_dir(), path),
    ]
    return cmd


@functools.cache
def get_npx_command() -> list[str]:
    """Retrieves a command to run npx.

    Returns:
        A list of strings that will run "npx" when run as a command for a
        subprocess.
    """
    # npx is normally an alias for "npm exec", so just use that instead of
    # looking for npx-cli.js.
    cmd = get_npm_command()
    cmd.append('exec')
    return cmd


def add_node_to_path() -> None:
    """Adds the directory for the standalone node binary to PATH."""
    node_install_dir = os.path.dirname(get_node_path())
    new_path = os.pathsep.join([node_install_dir, os.environ['PATH']])
    os.environ['PATH'] = new_path