import datetime
import hashlib
import logging
import time
import urllib.parse
import urllib.request
from pathlib import Path
from shutil import which
from typing import List, NoReturn

from pipx import constants
from pipx.commands.common import package_name_from_spec
from pipx.constants import TEMP_VENV_EXPIRATION_THRESHOLD_DAYS, WINDOWS
from pipx.emojis import hazard
from pipx.util import (
    PipxError,
    exec_app,
    get_pypackage_bin_path,
    pipx_wrap,
    rmdir,
    run_pypackage_bin,
)
from pipx.venv import Venv

logger = logging.getLogger(__name__)


VENV_EXPIRED_FILENAME = "pipx_expired_venv"


def run(
    app: str,
    package_or_url: str,
    app_args: List[str],
    python: str,
    pip_args: List[str],
    venv_args: List[str],
    pypackages: bool,
    verbose: bool,
    use_cache: bool,
) -> NoReturn:
    """Installs venv to temporary dir (or reuses cache), then runs app from
    package
    """

    if urllib.parse.urlparse(app).scheme:
        if not app.endswith(".py"):
            raise PipxError(
                """
                pipx will only execute apps from the internet directly if they
                end with '.py'. To run from an SVN, try pipx --spec URL BINARY
                """
            )
        logger.info("Detected url. Downloading and executing as a Python file.")

        content = _http_get_request(app)
        exec_app([str(python), "-c", content])

    elif which(app):
        logger.warning(
            pipx_wrap(
                f"""
                {hazard}  {app} is already on your PATH and installed at
                {which(app)}. Downloading and running anyway.
                """,
                subsequent_indent=" " * 4,
            )
        )

    if WINDOWS:
        app_filename = f"{app}.exe"
        logger.info(f"Assuming app is {app_filename!r} (Windows only)")
    else:
        app_filename = app

    pypackage_bin_path = get_pypackage_bin_path(app)
    if pypackage_bin_path.exists():
        logger.info(
            f"Using app in local __pypackages__ directory at {str(pypackage_bin_path)}"
        )
        run_pypackage_bin(pypackage_bin_path, app_args)
    if pypackages:
        raise PipxError(
            f"""
            '--pypackages' flag was passed, but {str(pypackage_bin_path)!r} was
            not found. See https://github.com/cs01/pythonloc to learn how to
            install here, or omit the flag.
            """
        )

    venv_dir = _get_temporary_venv_path(package_or_url, python, pip_args, venv_args)

    venv = Venv(venv_dir)
    bin_path = venv.bin_path / app_filename
    _prepare_venv_cache(venv, bin_path, use_cache)

    if venv.has_app(app, app_filename):
        logger.info(f"Reusing cached venv {venv_dir}")
        venv.run_app(app, app_filename, app_args)
    else:
        logger.info(f"venv location is {venv_dir}")
        _download_and_run(
            Path(venv_dir),
            package_or_url,
            app,
            app_filename,
            app_args,
            python,
            pip_args,
            venv_args,
            use_cache,
            verbose,
        )


def _download_and_run(
    venv_dir: Path,
    package_or_url: str,
    app: str,
    app_filename: str,
    app_args: List[str],
    python: str,
    pip_args: List[str],
    venv_args: List[str],
    use_cache: bool,
    verbose: bool,
) -> NoReturn:
    venv = Venv(venv_dir, python=python, verbose=verbose)
    venv.create_venv(venv_args, pip_args)

    if venv.pipx_metadata.main_package.package is not None:
        package_name = venv.pipx_metadata.main_package.package
    else:
        package_name = package_name_from_spec(
            package_or_url, python, pip_args=pip_args, verbose=verbose
        )

    venv.install_package(
        package_name=package_name,
        package_or_url=package_or_url,
        pip_args=pip_args,
        include_dependencies=False,
        include_apps=True,
        is_main_package=True,
    )

    if not venv.has_app(app, app_filename):
        apps = venv.pipx_metadata.main_package.apps
        raise PipxError(
            f"""
            '{app}' executable script not found in package '{package_or_url}'.
            Available executable scripts: {', '.join(b for b in apps)}
            """
        )

    if not use_cache:
        # Let future _remove_all_expired_venvs know to remove this
        (venv_dir / VENV_EXPIRED_FILENAME).touch()

    venv.run_app(app, app_filename, app_args)


def _get_temporary_venv_path(
    package_or_url: str, python: str, pip_args: List[str], venv_args: List[str]
) -> Path:
    """Computes deterministic path using hashing function on arguments relevant
    to virtual environment's end state. Arguments used should result in idempotent
    virtual environment. (i.e. args passed to app aren't relevant, but args
    passed to venv creation are.)
    """
    m = hashlib.sha256()
    m.update(package_or_url.encode())
    m.update(python.encode())
    m.update("".join(pip_args).encode())
    m.update("".join(venv_args).encode())
    venv_folder_name = m.hexdigest()[0:15]  # 15 chosen arbitrarily
    return Path(constants.PIPX_VENV_CACHEDIR) / venv_folder_name


def _is_temporary_venv_expired(venv_dir: Path) -> bool:
    created_time_sec = venv_dir.stat().st_ctime
    current_time_sec = time.mktime(datetime.datetime.now().timetuple())
    age = current_time_sec - created_time_sec
    expiration_threshold_sec = 60 * 60 * 24 * TEMP_VENV_EXPIRATION_THRESHOLD_DAYS
    return age > expiration_threshold_sec or (venv_dir / VENV_EXPIRED_FILENAME).exists()


def _prepare_venv_cache(venv: Venv, bin_path: Path, use_cache: bool) -> None:
    venv_dir = venv.root
    if not use_cache and bin_path.exists():
        logger.info(f"Removing cached venv {str(venv_dir)}")
        rmdir(venv_dir)
    _remove_all_expired_venvs()


def _remove_all_expired_venvs() -> None:
    for venv_dir in Path(constants.PIPX_VENV_CACHEDIR).iterdir():
        if _is_temporary_venv_expired(venv_dir):
            logger.info(f"Removing expired venv {str(venv_dir)}")
            rmdir(venv_dir)


def _http_get_request(url: str) -> str:
    try:
        res = urllib.request.urlopen(url)
        charset = res.headers.get_content_charset() or "utf-8"
        return res.read().decode(charset)
    except Exception as e:
        logger.debug("Uncaught Exception:", exc_info=True)
        raise PipxError(str(e))
