# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
#
# Copyright (C) 2019-2020 Canonical Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import logging
import os
import subprocess
import sys
import urllib.parse
import warnings
from textwrap import dedent
from time import sleep
from typing import Dict, Optional, Sequence

from snapcraft.internal import repo
from snapcraft.internal.errors import SnapcraftEnvironmentError

from .._base_provider import Provider, errors
from ._images import get_image_source

# LXD is only supported on Linux and causes issues when imported on Windows.
# We conditionally import it and rely on ensure_provider() to check OS before
# using pylxd.
if sys.platform == "linux":
    import pylxd

logger = logging.getLogger(__name__)
# Filter out attribute setting warnings for properties that exist in LXD operations
# but are unhandled in pylxd.
warnings.filterwarnings("ignore", module="pylxd.models.operation")


class LXD(Provider):
    """A LXD provider for snapcraft to execute its lifecycle."""

    _PROJECT_DEVICE_NAME = "snapcraft-project"
    _PROJECT_EXPORTED_PRIME_NAME = "snapcraft-project-prime"

    # Given that we are running snapcraft from the snapcraft snap, which has
    # classic confinement and require using the lxd snap, the lxd and lxc
    # binaries should be found in /snap/bin
    _LXD_BIN = os.path.join(os.path.sep, "snap", "bin", "lxd")
    _LXC_BIN = os.path.join(os.path.sep, "snap", "bin", "lxc")

    @classmethod
    def ensure_provider(cls):
        error_message = None  # type: Optional[str]
        prompt_installable = False

        if sys.platform != "linux":
            error_message = "LXD is not supported on this platform"
        else:
            try:
                if not repo.snaps.SnapPackage.is_snap_installed("lxd"):
                    error_message = (
                        "The LXD snap is required to continue: snap install lxd"
                    )
                    prompt_installable = True
            except repo.errors.SnapdConnectionError:
                error_message = (
                    "snap support is required to continue: "
                    "https://docs.snapcraft.io/installing-snapd/6735"
                )

        if error_message is not None:
            raise errors.ProviderNotFound(
                provider=cls._get_provider_name(),
                prompt_installable=prompt_installable,
                error_message=error_message,
            )

        # If we reach this point, it means the lxd snap is properly setup.
        # Now is the time for additional sanity checks to ensure the provider
        # will work.
        try:
            # TODO: add support for more distributions. Maybe refactor a bit so that Repo behaves
            # similar to a build provider.
            if repo.Repo.is_package_installed("lxd") or repo.Repo.is_package_installed(
                "lxd-client"
            ):
                raise SnapcraftEnvironmentError(
                    (
                        "The {!r} provider does not support having the 'lxd' or "
                        "'lxd-client' deb packages installed. To completely migrate "
                        "to the LXD snap run 'lxd.migrate' and try again."
                    ).format(cls._get_provider_name())
                )
        except repo.errors.NoNativeBackendError:
            pass

    @classmethod
    def setup_provider(cls, *, echoer) -> None:
        repo.snaps.install_snaps(["lxd/latest/stable"])

        try:
            subprocess.check_output([cls._LXD_BIN, "waitready", "--timeout=30"])
        except subprocess.CalledProcessError as call_error:
            raise SnapcraftEnvironmentError(
                "Timeout reached waiting for LXD to start."
            ) from call_error

        try:
            subprocess.check_output([cls._LXD_BIN, "init", "--auto"])
        except subprocess.CalledProcessError as call_error:
            raise SnapcraftEnvironmentError(
                "Failed to initialize LXD. "
                "Try manually initializing before trying again: lxd init --auto."
            ) from call_error

    @classmethod
    def _get_provider_name(cls):
        return "LXD"

    @classmethod
    def _get_is_snap_injection_capable(cls) -> bool:
        return True

    def __init__(
        self,
        *,
        project,
        echoer,
        is_ephemeral: bool = False,
        build_provider_flags: Dict[str, str] = None,
    ) -> None:
        super().__init__(
            project=project,
            echoer=echoer,
            is_ephemeral=is_ephemeral,
            build_provider_flags=build_provider_flags,
        )
        # This endpoint is hardcoded everywhere lxc/lxd-pkg-snap#33
        lxd_socket_path = "/var/snap/lxd/common/lxd/unix.socket"
        endpoint = "http+unix://{}".format(urllib.parse.quote(lxd_socket_path, safe=""))
        try:
            self._lxd_client: pylxd.Client = pylxd.Client(endpoint=endpoint)
        except pylxd.client.exceptions.ClientConnectionFailed:
            raise errors.ProviderCommunicationError(
                provider_name=self._get_provider_name(),
                message="cannot connect to the LXD socket ({!r}).".format(
                    lxd_socket_path
                ),
            )

        self._container: Optional[pylxd.models.container.Container] = None

    def _run(
        self, command: Sequence[str], hide_output: bool = False
    ) -> Optional[bytes]:
        self._ensure_container_running()

        env_command = super()._get_env_command()

        # TODO: use pylxd
        cmd = [self._LXC_BIN, "exec", self.instance_name, "--"]
        cmd.extend(env_command)
        cmd.extend(command)
        self._log_run(cmd)

        output = None
        try:
            if hide_output:
                output = subprocess.check_output(cmd)
            else:
                subprocess.check_call(cmd)
        except subprocess.CalledProcessError as process_error:
            raise errors.ProviderExecError(
                provider_name=self._get_provider_name(),
                command=command,
                exit_code=process_error.returncode,
                output=process_error.output,
            ) from process_error

        return output

    def _launch(self) -> None:
        build_base = self.project._get_build_base()
        try:
            source = get_image_source(base=build_base)
        except KeyError:
            raise errors.ProviderInvalidBaseError(
                provider_name=self._get_provider_name(), build_base=build_base
            )

        config = {"name": self.instance_name, "source": source}

        try:
            container = self._lxd_client.containers.create(config, wait=True)
        except pylxd.exceptions.LXDAPIException as lxd_api_error:
            raise errors.ProviderLaunchError(
                provider_name=self._get_provider_name(), error_message=lxd_api_error
            ) from lxd_api_error
        container.save(wait=True)
        self._container = container

        self._start()

    def _supports_syscall_interception(self) -> bool:
        # syscall interception relies on the seccomp_listener kernel feature
        environment = self._lxd_client.host_info.get("environment", {})
        kernel_features = environment.get("kernel_features", {})
        return kernel_features.get("seccomp_listener", "false") == "true"

    def _start(self):
        if not self._lxd_client.containers.exists(self.instance_name):
            raise errors.ProviderInstanceNotFoundError(instance_name=self.instance_name)

        if self._container is None:
            self._container = self._lxd_client.containers.get(self.instance_name)

        self._container.sync()

        # map to the owner of the directory we are eventually going to write the
        # snap to.
        self._container.config["raw.idmap"] = "both {!s} 0".format(
            os.stat(self.project._project_dir).st_uid
        )
        # If possible, allow container to make safe mknod calls. Documented at
        # https://linuxcontainers.org/lxd/docs/master/syscall-interception
        if self._supports_syscall_interception():
            self._container.config["security.syscalls.intercept.mknod"] = "true"
        self._container.save(wait=True)

        if self._container.status.lower() != "running":
            try:
                self._container.start(wait=True)
            except pylxd.exceptions.LXDAPIException as lxd_api_error:
                print(self._container.status)
                raise errors.ProviderStartError(
                    provider_name=self._get_provider_name(), error_message=lxd_api_error
                ) from lxd_api_error

        self.echoer.wrapped("Waiting for container to be ready")

    def _stop(self):
        # If _container is still None here it means creation/starting was not
        # successful.
        if self._container is None:
            return

        self._container.sync()

        if self._container.status.lower() != "stopped":
            try:
                self._container.stop(wait=True)
            except pylxd.exceptions.LXDAPIException as lxd_api_error:
                raise errors.ProviderStopError(
                    provider_name=self._get_provider_name(), error_message=lxd_api_error
                ) from lxd_api_error

    def _push_file(self, *, source: str, destination: str) -> None:
        # Sanity check - developer error if container not initialized.
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        self._ensure_container_running()

        # TODO: better handling of larger files.
        with open(source, "rb") as source_data:
            source_contents = source_data.read()

        try:
            self._container.files.put(destination, source_contents)
        except pylxd.exceptions.LXDAPIException as lxd_api_error:
            raise errors.ProviderFileCopyError(
                provider_name=self._get_provider_name(), error_message=lxd_api_error
            )

    def create(self) -> None:
        """Create the LXD instance and setup the build environment."""
        self.echoer.info("Launching a container.")
        self.launch_instance()
        self._mount_project()

    def destroy(self) -> None:
        """Destroy the instance, trying to stop it first."""
        self._stop()

    def _get_mount_name(self, target: str) -> str:
        """Provide a formatted name for target mount point."""
        home_dir = self._get_home_directory().as_posix()

        # Special cases for compatibility.
        if target == os.path.join(home_dir, "project"):
            return self._PROJECT_DEVICE_NAME
        elif target == os.path.join(home_dir, "prime"):
            return self._PROJECT_EXPORTED_PRIME_NAME

        # Replace home directory with "snapcraft".
        name = target.replace(home_dir, "snapcraft", 1)

        # Replace path separators with dashes.
        name = name.replace("/", "-")
        return name

    def _is_mounted(self, target: str) -> bool:
        """Query if there is a mount at target mount point."""
        # Sanity check - developer error if container not initialized.
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        name = self._get_mount_name(target)
        return name in self._container.devices

    def _mount(self, host_source: str, target: str) -> None:
        """Mount host source directory to target mount point."""
        # Sanity check - developer error if container not initialized.
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        if self._is_mounted(target):
            # Nothing to do if already mounted.
            return

        name = self._get_mount_name(target)
        self._container.sync()
        self._container.devices[name] = {
            "type": "disk",
            "source": host_source,
            "path": target,
        }

        try:
            self._container.save(wait=True)
        except pylxd.exceptions.LXDAPIException as lxd_api_error:
            raise errors.ProviderMountError(
                provider_name=self._get_provider_name(), error_message=lxd_api_error
            ) from lxd_api_error

    def clean_project(self) -> bool:
        was_cleaned = super().clean_project()
        if was_cleaned:
            if self._container is None:
                try:
                    self._container = self._lxd_client.containers.get(
                        self.instance_name
                    )
                except pylxd.exceptions.NotFound:
                    # If no container found, nothing to delete.
                    return was_cleaned
            self._stop()
            self._container.delete(wait=True)
        return was_cleaned

    def pull_file(self, name: str, destination: str, delete: bool = False) -> None:
        # Sanity check - developer error if container not initialized.
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        self._ensure_container_running()

        # TODO: better handling of larger files.
        try:
            source_data = self._container.files.get(name)
        except pylxd.exceptions.LXDAPIException as lxd_api_error:
            raise errors.ProviderFileCopyError(
                provider_name=self._get_provider_name(), error_message=lxd_api_error
            )
        else:
            with open(destination, "wb") as destination_data:
                destination_data.write(source_data)
        if delete and self._container.files.delete_available:
            self._container.files.delete(name)
        if delete and not self._container.files.delete_available:
            logger.warning("File deletion not supported by this LXD version.")

    def shell(self) -> None:
        self._run(command=["/bin/bash"])

    def _wait_for_systemd(self) -> None:
        # systemctl states we care about here are:
        # - running: The system is fully operational. Process returncode: 0
        # - degraded: The system is operational but one or more units failed.
        #             Process returncode: 1
        for i in range(40):
            try:
                self._run(["systemctl", "is-system-running"], hide_output=True)
                break
            except errors.ProviderExecError as exec_error:
                if exec_error.output is not None:
                    running_state = exec_error.output.decode().strip()
                    if running_state == "degraded":
                        break
                    logger.debug(f"systemctl is-system-running: {running_state!r}")
                sleep(0.5)
        else:
            self.echoer.warning("Timed out waiting for systemd to be ready...")

    def _wait_for_network(self) -> None:
        self.echoer.wrapped("Waiting for network to be ready...")
        for i in range(40):
            try:
                self._run(["getent", "hosts", "snapcraft.io"], hide_output=True)
                break
            except errors.ProviderExecError:
                sleep(0.5)
        else:
            self.echoer.warning("Failed to setup networking.")

    def _setup_environment(self) -> None:
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        super()._setup_environment()

        self._install_file(
            path="/etc/systemd/network/10-eth0.network",
            content=dedent(
                """
                [Match]
                Name=eth0

                [Network]
                DHCP=ipv4
                LinkLocalAddressing=ipv6

                [DHCP]
                RouteMetric=100
                UseMTU=true
                """
            ),
            permissions="0644",
        )

        self._install_file(
            path="/etc/hostname", content=self.instance_name, permissions="0644"
        )

        self._wait_for_systemd()

        # Use resolv.conf managed by systemd-resolved.
        self._run(
            ["ln", "-sf", "/run/systemd/resolve/resolv.conf", "/etc/resolv.conf"],
            hide_output=True,
        )

        self._run(["systemctl", "enable", "systemd-resolved"], hide_output=True)
        self._run(["systemctl", "enable", "systemd-networkd"], hide_output=True)

        self._run(["systemctl", "restart", "systemd-resolved"], hide_output=True)
        self._run(["systemctl", "restart", "systemd-networkd"], hide_output=True)

        self._wait_for_network()

        # Setup snapd to bootstrap.
        self._run(["apt-get", "update"])

        # First install fuse and udev, snapd requires them.
        # Snapcraft requires dirmngr
        self._run(["apt-get", "install", "dirmngr", "udev", "fuse", "--yes"])

        # the system needs networking
        self._run(["systemctl", "enable", "systemd-udevd"], hide_output=True)
        self._run(["systemctl", "start", "systemd-udevd"], hide_output=True)

        # And only then install snapd.
        self._run(["apt-get", "install", "snapd", "sudo", "--yes"])
        self._run(["systemctl", "start", "snapd"], hide_output=True)

    def _setup_snapcraft(self):
        self._wait_for_network()
        super()._setup_snapcraft()

    def _ensure_container_running(self) -> None:
        # Sanity check - developer error if container not initialized.
        if self._container is None:
            raise RuntimeError("Attempted to use container before starting.")

        self._container.sync()
        if self._container.status.lower() != "running":
            raise errors.ProviderFileCopyError(
                provider_name=self._get_provider_name(),
                error_message=(
                    "Container is not running, the current state is: {!r}. "
                    "Ensure it has not been modified by external factors and try again"
                ).format(self._container.status),
            )
