import logging
import os
import shutil
import subprocess
from typing import List, Optional, Set, Tuple

from scripts.lib.hash_reqs import expand_reqs, python_version
from scripts.lib.zulip_tools import ENDC, WARNING, os_families, run, run_as_root

ZULIP_PATH = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
VENV_CACHE_PATH = "/srv/zulip-venv-cache"

VENV_DEPENDENCIES = [
    "build-essential",
    "libffi-dev",
    "libfreetype6-dev",  # Needed for image types with Pillow
    "zlib1g-dev",  # Needed to handle compressed PNGs with Pillow
    "libjpeg-dev",  # Needed to handle JPEGs with Pillow
    "libldap2-dev",
    "python3-dev",  # Needed to install typed-ast dependency of mypy
    "python3-pip",
    "virtualenv",
    "libxml2-dev",  # Used for installing talon-core and python-xmlsec
    "libxslt1-dev",  # Used for installing talon-core
    "libpq-dev",  # Needed by psycopg2
    "libssl-dev",  # Needed to build pycurl and other libraries
    "libmagic1",  # Used for install python-magic
    "libyaml-dev",  # For fast YAML parsing in PyYAML
    # Needed by python-xmlsec:
    "libxmlsec1-dev",
    "pkg-config",
    # This is technically a node dependency, but we add it here
    # because we don't have another place that we install apt packages
    # on upgrade of a production server, and it's not worth adding
    # another call to `apt install` for.
    "jq",  # Used by scripts/lib/install-yarn to check yarn version
    "libsasl2-dev",  # For building python-ldap from source
]

COMMON_YUM_VENV_DEPENDENCIES = [
    "libffi-devel",
    "freetype-devel",
    "zlib-devel",
    "libjpeg-turbo-devel",
    "openldap-devel",
    "libyaml-devel",
    # Needed by python-xmlsec:
    "gcc",
    "python3-devel",
    "libxml2-devel",
    "xmlsec1-devel",
    "xmlsec1-openssl-devel",
    "libtool-ltdl-devel",
    "libxslt-devel",
    "postgresql-libs",  # libpq-dev on apt
    "openssl-devel",
    "jq",
]

REDHAT_VENV_DEPENDENCIES = [
    *COMMON_YUM_VENV_DEPENDENCIES,
    "python36-devel",
    "python-virtualenv",
]

FEDORA_VENV_DEPENDENCIES = [
    *COMMON_YUM_VENV_DEPENDENCIES,
    "python3-pip",
    "virtualenv",  # see https://unix.stackexchange.com/questions/27877/install-virtualenv-on-fedora-16
]


def get_venv_dependencies(vendor: str, os_version: str) -> List[str]:
    if "debian" in os_families():
        return VENV_DEPENDENCIES
    elif "rhel" in os_families():
        return REDHAT_VENV_DEPENDENCIES
    elif "fedora" in os_families():
        return FEDORA_VENV_DEPENDENCIES
    else:
        raise AssertionError("Invalid vendor")


def install_venv_deps(pip: str, requirements_file: str) -> None:
    pip_requirements = os.path.join(ZULIP_PATH, "requirements", "pip.txt")
    run([pip, "install", "--force-reinstall", "--require-hashes", "-r", pip_requirements])
    run(
        [
            pip,
            "install",
            "--use-deprecated=legacy-resolver",  # https://github.com/pypa/pip/issues/5780
            "--no-deps",
            "--require-hashes",
            "-r",
            requirements_file,
        ]
    )


def get_index_filename(venv_path: str) -> str:
    return os.path.join(venv_path, "package_index")


def get_package_names(requirements_file: str) -> List[str]:
    packages = expand_reqs(requirements_file)
    cleaned = []
    operators = ["~=", "==", "!=", "<", ">"]
    for package in packages:
        if package.startswith("git+https://") and "#egg=" in package:
            split_package = package.split("#egg=")
            if len(split_package) != 2:
                raise Exception(f"Unexpected duplicate #egg in package {package}")
            # Extract the package name from Git requirements entries
            package = split_package[1]

        for operator in operators:
            if operator in package:
                package = package.split(operator)[0]

        package = package.strip()
        if package:
            cleaned.append(package.lower())

    return sorted(cleaned)


def create_requirements_index_file(venv_path: str, requirements_file: str) -> str:
    """
    Creates a file, called package_index, in the virtual environment
    directory that contains all the PIP packages installed in the
    virtual environment. This file is used to determine the packages
    that can be copied to a new virtual environment.
    """
    index_filename = get_index_filename(venv_path)
    packages = get_package_names(requirements_file)
    with open(index_filename, "w") as writer:
        writer.write("\n".join(packages))
        writer.write("\n")

    return index_filename


def get_venv_packages(venv_path: str) -> Set[str]:
    """
    Returns the packages installed in the virtual environment using the
    package index file.
    """
    with open(get_index_filename(venv_path)) as reader:
        return {p.strip() for p in reader.read().split("\n") if p.strip()}


def try_to_copy_venv(venv_path: str, new_packages: Set[str]) -> bool:
    """
    Tries to copy packages from an old virtual environment in the cache
    to the new virtual environment. The algorithm works as follows:
        1. Find a virtual environment, v, from the cache that has the
        highest overlap with the new requirements such that:
            a. The new requirements only add to the packages of v.
            b. The new requirements only upgrade packages of v.
        2. Copy the contents of v to the new virtual environment using
        virtualenv-clone.
        3. Delete all .pyc files in the new virtual environment.
    """
    if not os.path.exists(VENV_CACHE_PATH):
        return False

    desired_python_version = python_version()
    venv_name = os.path.basename(venv_path)

    overlaps = []  # type: List[Tuple[int, str, Set[str]]]
    old_packages = set()  # type: Set[str]
    for sha1sum in os.listdir(VENV_CACHE_PATH):
        curr_venv_path = os.path.join(VENV_CACHE_PATH, sha1sum, venv_name)
        if curr_venv_path == venv_path or not os.path.exists(get_index_filename(curr_venv_path)):
            continue

        # Check the Python version in the venv matches the version we want to use.
        venv_python3 = os.path.join(curr_venv_path, "bin", "python3")
        if not os.path.exists(venv_python3):
            continue
        venv_python_version = subprocess.check_output(
            [venv_python3, "-VV"], universal_newlines=True
        )
        if desired_python_version != venv_python_version:
            continue

        old_packages = get_venv_packages(curr_venv_path)
        # We only consider using using old virtualenvs that only
        # contain packages that we want in our new virtualenv.
        if not (old_packages - new_packages):
            overlap = new_packages & old_packages
            overlaps.append((len(overlap), curr_venv_path, overlap))

    target_log = get_logfile_name(venv_path)
    source_venv_path = None
    if overlaps:
        # Here, we select the old virtualenv with the largest overlap
        overlaps = sorted(overlaps)
        _, source_venv_path, copied_packages = overlaps[-1]
        print(f"Copying packages from {source_venv_path}")
        clone_ve = f"{source_venv_path}/bin/virtualenv-clone"
        cmd = [clone_ve, source_venv_path, venv_path]

        try:
            # TODO: We can probably remove this in a few months, now
            # that we can expect that virtualenv-clone is present in
            # all of our recent virtualenvs.
            run_as_root(cmd)
        except subprocess.CalledProcessError:
            # Virtualenv-clone is either not installed or threw an
            # error.  Just return False: making a new venv is safe.
            logging.warning("Error cloning virtualenv %s", source_venv_path)
            return False

        # virtualenv-clone, unfortunately, copies the success stamp,
        # which means if the upcoming `pip install` phase were to
        # fail, we'd end up with a broken half-provisioned virtualenv
        # that's incorrectly tagged as properly provisioned.  The
        # right fix is to use
        # https://github.com/edwardgeorge/virtualenv-clone/pull/38,
        # but this rm is almost as good.
        success_stamp_path = os.path.join(venv_path, "success-stamp")
        run_as_root(["rm", "-f", success_stamp_path])

        run_as_root(["chown", "-R", f"{os.getuid()}:{os.getgid()}", venv_path])
        source_log = get_logfile_name(source_venv_path)
        copy_parent_log(source_log, target_log)
        create_log_entry(
            target_log, source_venv_path, copied_packages, new_packages - copied_packages
        )
        return True

    return False


def get_logfile_name(venv_path: str) -> str:
    return f"{venv_path}/setup-venv.log"


def create_log_entry(
    target_log: str,
    parent: str,
    copied_packages: Set[str],
    new_packages: Set[str],
) -> None:

    venv_path = os.path.dirname(target_log)
    with open(target_log, "a") as writer:
        writer.write(f"{venv_path}\n")
        if copied_packages:
            writer.write(f"Copied from {parent}:\n")
            writer.write("\n".join(f"- {p}" for p in sorted(copied_packages)))
            writer.write("\n")

        writer.write("New packages:\n")
        writer.write("\n".join(f"- {p}" for p in sorted(new_packages)))
        writer.write("\n\n")


def copy_parent_log(source_log: str, target_log: str) -> None:
    if os.path.exists(source_log):
        shutil.copyfile(source_log, target_log)


def do_patch_activate_script(venv_path: str) -> None:
    """
    Patches the bin/activate script so that the value of the environment variable VIRTUAL_ENV
    is set to venv_path during the script's execution whenever it is sourced.
    """
    # venv_path should be what we want to have in VIRTUAL_ENV after patching
    script_path = os.path.join(venv_path, "bin", "activate")

    with open(script_path) as f:
        lines = f.readlines()
    for i, line in enumerate(lines):
        if line.startswith("VIRTUAL_ENV="):
            lines[i] = f'VIRTUAL_ENV="{venv_path}"\n'

    with open(script_path, "w") as f:
        f.write("".join(lines))


def generate_hash(requirements_file: str) -> str:
    path = os.path.join(ZULIP_PATH, "scripts", "lib", "hash_reqs.py")
    output = subprocess.check_output([path, requirements_file], universal_newlines=True)
    return output.split()[0]


def setup_virtualenv(
    target_venv_path: Optional[str],
    requirements_file: str,
    patch_activate_script: bool = False,
) -> str:

    sha1sum = generate_hash(requirements_file)
    # Check if a cached version already exists
    if target_venv_path is None:
        cached_venv_path = os.path.join(VENV_CACHE_PATH, sha1sum, "venv")
    else:
        cached_venv_path = os.path.join(
            VENV_CACHE_PATH, sha1sum, os.path.basename(target_venv_path)
        )
    success_stamp = os.path.join(cached_venv_path, "success-stamp")
    if not os.path.exists(success_stamp):
        do_setup_virtualenv(cached_venv_path, requirements_file)
        with open(success_stamp, "w") as f:
            f.close()

    print(f"Using cached Python venv from {cached_venv_path}")
    if target_venv_path is not None:
        run_as_root(["ln", "-nsf", cached_venv_path, target_venv_path])
        if patch_activate_script:
            do_patch_activate_script(target_venv_path)
    return cached_venv_path


def add_cert_to_pipconf() -> None:
    conffile = os.path.expanduser("~/.pip/pip.conf")
    confdir = os.path.expanduser("~/.pip/")
    os.makedirs(confdir, exist_ok=True)
    run(["crudini", "--set", conffile, "global", "cert", os.environ["CUSTOM_CA_CERTIFICATES"]])


def do_setup_virtualenv(venv_path: str, requirements_file: str) -> None:

    # Setup Python virtualenv
    new_packages = set(get_package_names(requirements_file))

    run_as_root(["rm", "-rf", venv_path])
    if not try_to_copy_venv(venv_path, new_packages):
        # Create new virtualenv.
        run_as_root(["mkdir", "-p", venv_path])
        run_as_root(["virtualenv", "-p", "python3", venv_path])
        run_as_root(["chown", "-R", f"{os.getuid()}:{os.getgid()}", venv_path])
        create_log_entry(get_logfile_name(venv_path), "", set(), new_packages)

    create_requirements_index_file(venv_path, requirements_file)

    pip = os.path.join(venv_path, "bin", "pip")

    # use custom certificate if needed
    if os.environ.get("CUSTOM_CA_CERTIFICATES"):
        print("Configuring pip to use custom CA certificates...")
        add_cert_to_pipconf()

    try:
        install_venv_deps(pip, requirements_file)
    except subprocess.CalledProcessError:
        try:
            # Might be a failure due to network connection issues. Retrying...
            print(WARNING + "`pip install` failed; retrying..." + ENDC)
            install_venv_deps(pip, requirements_file)
        except BaseException as e:
            # Suppress exception chaining
            raise e from None

    run_as_root(["chmod", "-R", "a+rX", venv_path])