import json
import os
import re
import signal
import subprocess
import sys
import tempfile
import threading
import traceback
from collections.abc import Callable, Generator, Iterator
from contextlib import AbstractContextManager, contextmanager
from dataclasses import dataclass
from pathlib import Path
from typing import Any
from unittest import TestCase

from colorama import Style
from pydantic import BaseModel

from test_driver.debug import DebugAbstract, DebugNop
from test_driver.errors import MachineError, RequestedAssertionFailed
from test_driver.logger import AbstractLogger
from test_driver.machine import (
    BaseMachine,
    MachineDeprecationWrapper,
    NspawnMachine,
    QemuMachine,
    retry,
)
from test_driver.polling_condition import PollingCondition
from test_driver.vlan import VLan


class NodeConfiguration(BaseModel):
    name: str
    start_script: Path


class DriverConfiguration(BaseModel):
    vms: dict[str, NodeConfiguration]
    containers: dict[str, NodeConfiguration]
    vlans: list[int]
    global_timeout: int
    enable_ssh_backdoor: bool
    test_script: Path


def load_driver_configuration(file_path: str) -> DriverConfiguration:
    with open(file_path) as f:
        data = json.load(f)
    return DriverConfiguration.model_validate(data)


class AssertionTester(TestCase):
    """
    Subclass of `unittest.TestCase` which is used in the
    `testScript` to perform assertions.

    It throws a custom exception whose parent class
    gets special treatment in the logs.
    """

    failureException = RequestedAssertionFailed


def get_tmp_dir() -> Path:
    """Returns a temporary directory that is defined by TMPDIR, TEMP, TMP or CWD
    Raises an exception in case the retrieved temporary directory is not writeable
    See https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir
    """
    tmp_dir = Path(os.environ.get("XDG_RUNTIME_DIR", tempfile.gettempdir()))
    tmp_dir.mkdir(mode=0o700, exist_ok=True)
    if not tmp_dir.is_dir():
        raise NotADirectoryError(
            f"The directory defined by XDG_RUNTIME_DIR, TMPDIR, TEMP, TMP or CWD: {tmp_dir} is not a directory"
        )
    if not os.access(tmp_dir, os.W_OK):
        raise PermissionError(
            f"The directory defined by XDG_RUNTIME_DIR, TMPDIR, TEMP, TMP, or CWD: {tmp_dir} is not writeable"
        )
    return tmp_dir


def pythonize_name(name: str) -> str:
    return re.sub(r"^[^A-Za-z_]|[^A-Za-z0-9_]", "_", name)


def in_nix_sandbox() -> bool:
    # There seems to be no better method at the time
    typical_nix_env_vars = "NIX_BUILD_TOP" in os.environ
    nix_shell_marker = "IN_NIX_SHELL" in os.environ

    return typical_nix_env_vars and not nix_shell_marker


@dataclass
class VsockPair:
    guest: Path
    host: Path
    cid: int


class VHostDeviceVsock:
    def __init__(self, tmp_dir: Path, machines: list[str]):
        self.temp_dir_handle = tempfile.TemporaryDirectory(dir=tmp_dir)
        self.temp_dir = Path(self.temp_dir_handle.name)
        self.sockets = {
            machine: VsockPair(
                self.temp_dir / f"{machine}_guest.socket",
                self.temp_dir / f"{machine}_host.socket",
                cid,
            )
            for cid, machine in enumerate(machines, start=3)
        }

        self.vhost_proc = subprocess.Popen(
            [
                "vhost-device-vsock",
                *(
                    arg
                    for vsock_pair in self.sockets.values()
                    for arg in (
                        "--vm",
                        f"guest-cid={vsock_pair.cid},socket={vsock_pair.guest},uds-path={vsock_pair.host}",
                    )
                ),
            ]
        )

    def __del__(self) -> None:
        self.vhost_proc.kill()
        self.temp_dir_handle.cleanup()


class Driver:
    """A handle to the driver that sets up the environment
    and runs the tests"""

    config: DriverConfiguration
    tests: str
    vlans: list[VLan] = []
    machines_qemu: list[QemuMachine] = []
    machines_nspawn: list[NspawnMachine] = []
    polling_conditions: list[PollingCondition]
    race_timer: threading.Timer
    keep_machine_state: bool
    logger: AbstractLogger
    debug: DebugAbstract
    vhost_vsock: VHostDeviceVsock | None = None

    def __init__(
        self,
        config: DriverConfiguration,
        out_dir: Path,
        logger: AbstractLogger,
        keep_machine_state: bool = False,
        debug: DebugAbstract = DebugNop(),
    ):
        self.config = config
        self.tests = config.test_script.read_text()
        self.out_dir = out_dir
        self.logger = logger
        self.debug = debug
        self.polling_conditions = []
        self.keep_machine_state = keep_machine_state

    def __enter__(self) -> "Driver":
        self.race_timer = threading.Timer(
            self.config.global_timeout, self.terminate_test
        )
        tmp_dir = get_tmp_dir()

        with self.logger.nested("start all VLans"):
            self.vlans = [VLan(nr, tmp_dir, self.logger) for nr in self.config.vlans]

        self.polling_conditions = []

        if self.config.enable_ssh_backdoor and self.config.vms:
            with self.logger.nested("start vhost-device-vsock"):
                self.vhost_vsock = VHostDeviceVsock(
                    tmp_dir, list(self.config.vms.keys())
                )

        self.machines_qemu = [
            QemuMachine(
                name=name,
                start_command=vm_config.start_script.as_posix(),
                keep_machine_state=self.keep_machine_state,
                tmp_dir=tmp_dir,
                callbacks=[self.check_polling_conditions],
                out_dir=self.out_dir,
                logger=self.logger,
                vsock_host=(
                    self.vhost_vsock.sockets[name].host
                    if self.vhost_vsock is not None
                    else None
                ),
                vsock_guest=(
                    self.vhost_vsock.sockets[name].guest
                    if self.vhost_vsock is not None
                    else None
                ),
            )
            for name, vm_config in self.config.vms.items()
        ]

        if self.config.containers and in_nix_sandbox():
            self._init_nspawn_environment()

        self.machines_nspawn = [
            NspawnMachine(
                name=name,
                start_command=container_config.start_script.as_posix(),
                tmp_dir=tmp_dir,
                logger=self.logger,
                keep_machine_state=self.keep_machine_state,
                callbacks=[self.check_polling_conditions],
                out_dir=self.out_dir,
            )
            for name, container_config in self.config.containers.items()
        ]

        return self

    def _init_nspawn_environment(self) -> None:
        assert os.geteuid() == 0, (
            f"systemd-nspawn requires root to work. You are {os.geteuid()}"
        )

        # set up prerequisites for systemd-nspawn containers.
        # these are not guaranteed to be set up in the Nix sandbox.
        # if running interactively as root, these will already be set up.

        # check if /run is writable by root
        if not os.access("/run", os.W_OK):
            Path("/run").mkdir(parents=True, exist_ok=True)
            subprocess.run(["mount", "-t", "tmpfs", "none", "/run"], check=True)
            Path("/run/netns").mkdir(parents=True, exist_ok=True)

        # check if /var/run is a symlink to /run
        if not (os.path.exists("/var/run") and os.path.samefile("/var/run", "/run")):
            Path("/var").mkdir(parents=True, exist_ok=True)
            subprocess.run(["ln", "-s", "/run", "/var/run"], check=True)

        # check if /sys/fs/cgroup is mounted as cgroup2
        with open("/proc/mounts", encoding="utf-8") as mounts:
            for line in mounts:
                parts = line.split()
                if len(parts) >= 3 and parts[1] == "/sys/fs/cgroup":
                    if parts[2] == "cgroup2":
                        break
            else:
                Path("/sys/fs/cgroup").mkdir(parents=True, exist_ok=True)
                subprocess.run(
                    ["mount", "-t", "cgroup2", "none", "/sys/fs/cgroup"], check=True
                )

        # systemd-nspawn requires that /etc/os-release exists
        # It supports SYSTEMD_NSPAWN_CHECK_OS_RELEASE=0, but that
        # would try to "fix" it by bind mounting, which is worse.
        if not os.path.isfile("/etc/os-release"):
            subprocess.run(["touch", "/etc/os-release"], check=True)

        # ensure /etc/machine-id exists and is non-empty
        if (
            not os.path.isfile("/etc/machine-id")
            or os.path.getsize("/etc/machine-id") == 0
        ):
            subprocess.run(
                ["systemd-machine-id-setup"], check=True
            )  # set up /etc/machine-id

    @property
    def machines(self) -> list[QemuMachine | NspawnMachine]:
        machines = self.machines_qemu + self.machines_nspawn
        # Sort the machines by name for consistency with `nodesAndContainers` in <nixos/lib/testing/network.nix>.
        machines.sort(key=lambda machine: machine.name)
        return machines

    def __exit__(self, *_: Any) -> None:
        with self.logger.nested("cleanup"):
            self.race_timer.cancel()
            for machine in self.machines:
                try:
                    machine.release()
                except Exception as e:
                    self.logger.error(f"Error during cleanup of {machine.name}: {e}")

            for vlan in self.vlans:
                try:
                    vlan.stop()
                except Exception as e:
                    self.logger.error(f"Error during cleanup of vlan{vlan.nr}: {e}")

            if self.config.enable_ssh_backdoor:
                try:
                    del self.vhost_vsock
                except Exception as e:
                    self.logger.error(
                        f"Error during cleanup of vhost-device-vsock process: {e}"
                    )

    def subtest(self, name: str) -> Generator[None]:
        """Group logs under a given test name"""
        with self.logger.subtest(name):
            try:
                yield
            except Exception as e:
                self.logger.log_test_error(f'Test "{name}" failed with error: "{e}"')
                raise e

    def test_symbols(self) -> dict[str, Any]:
        @contextmanager
        def subtest(name: str) -> Iterator[None]:
            return self.subtest(name)

        general_symbols = dict(
            start_all=self.start_all,
            test_script=self.test_script,
            machines=self.machines,
            machines_qemu=self.machines_qemu,
            machines_nspawn=self.machines_nspawn,
            vlans=self.vlans,
            driver=self,
            log=self.logger,
            os=os,
            create_machine=self.create_machine,
            subtest=subtest,
            run_tests=self.run_tests,
            join_all=self.join_all,
            retry=retry,
            serial_stdout_off=self.serial_stdout_off,
            serial_stdout_on=self.serial_stdout_on,
            polling_condition=self.polling_condition,
            BaseMachine=BaseMachine,  # for typing
            QemuMachine=QemuMachine,  # for typing
            NspawnMachine=NspawnMachine,  # for typing
            t=AssertionTester(),
            debug=self.debug,
            dump_machine_ssh=self.dump_machine_ssh,
        )
        machine_symbols: dict[
            str, QemuMachine | NspawnMachine | MachineDeprecationWrapper
        ] = {pythonize_name(m.name): m for m in self.machines}
        # If there's exactly one machine, make it available under the name
        # "machine", even if it's not called that.
        if len(self.machines) == 1 and "machine" not in machine_symbols:
            only_machine_name = next(iter(machine_symbols))
            machine_symbols["machine"] = MachineDeprecationWrapper(
                f"It's deprecated to use the `machine` variable when the only machine is called {only_machine_name}. This behavior will no longer work in NixOS 27.05.",
                self.machines[0],
            )
        vlan_symbols = {
            f"vlan{v.nr}": self.vlans[idx] for idx, v in enumerate(self.vlans)
        }
        print(
            "additionally exposed symbols:\n    "
            + ", ".join(map(lambda m: m.name, self.machines))
            + ",\n    "
            + ", ".join(map(lambda v: f"vlan{v.nr}", self.vlans))
            + ",\n    "
            + ", ".join(list(general_symbols.keys()))
        )
        return {**general_symbols, **machine_symbols, **vlan_symbols}

    def dump_machine_ssh(self) -> None:
        if not self.config.enable_ssh_backdoor:
            return

        if self.machines:
            print("SSH backdoor enabled, the machines can be accessed like this:")
            print(
                f"{Style.BRIGHT}Note:{Style.RESET_ALL} this requires {Style.BRIGHT}systemd-ssh-proxy(1){Style.RESET_ALL} to be enabled (default on NixOS 25.05 and newer)."
            )
            longest_name = len(
                max((machine.name for machine in self.machines), key=len)
            )
            for index, machine in enumerate(self.machines):
                name = machine.name
                spaces = " " * (longest_name - len(name) + 2)
                print(
                    f"    {name}:{spaces}{Style.BRIGHT}{machine.ssh_backdoor_command()}{Style.RESET_ALL}"
                )
        else:
            print("SSH backdoor enabled, but no machines defined")

    def test_script(self) -> None:
        """Run the test script"""
        with self.logger.nested("run the VM test script"):
            symbols = self.test_symbols()  # call eagerly
            try:
                exec(self.tests, symbols, None)
            except MachineError:
                for line in traceback.format_exc().splitlines():
                    self.logger.log_test_error(line)
                sys.exit(1)
            except RequestedAssertionFailed:
                exc_type, exc, tb = sys.exc_info()
                # We manually print the stack frames, keeping only the ones from the test script
                # (note: because the script is not a real file, the frame filename is `<string>`)
                filtered = [
                    frame
                    for frame in traceback.extract_tb(tb)
                    if frame.filename == "<string>"
                ]

                self.logger.log_test_error("Traceback (most recent call last):")

                code = self.tests.splitlines()
                for frame, line in zip(filtered, traceback.format_list(filtered)):
                    self.logger.log_test_error(line.rstrip())
                    if lineno := frame.lineno:
                        self.logger.log_test_error(f"    {code[lineno - 1].strip()}")

                self.logger.log_test_error("")  # blank line for readability
                exc_prefix = exc_type.__name__ if exc_type is not None else "Error"
                for line in f"{exc_prefix}: {exc}".splitlines():
                    self.logger.log_test_error(line)

                self.debug.breakpoint()

                sys.exit(1)

            except Exception:
                self.debug.breakpoint()
                raise

    def run_tests(self) -> None:
        """Run the test script (for non-interactive test runs)"""
        self.logger.info(
            f"Test will time out and terminate in {self.config.global_timeout} seconds"
        )
        self.race_timer.start()
        self.test_script()
        # TODO: Collect coverage data
        for machine in self.machines:
            if machine.is_up():
                machine.execute("sync")

    def start_all(self) -> None:
        """Start all machines"""
        with self.logger.nested("start all VMs"):
            errors: list[tuple[str, BaseException]] = []

            def start_machine(machine: BaseMachine) -> None:
                try:
                    machine.start()
                except Exception as e:
                    errors.append((machine.name, e))

            threads = []
            for machine in self.machines:
                # Create a thread for each machine's start method
                t = threading.Thread(
                    target=start_machine,
                    args=(machine,),
                    name=f"start-{machine.name}",
                )
                threads.append(t)
                t.start()

            # Wait for all startup threads to complete before proceeding
            for t in threads:
                t.join()

            if errors:
                messages = [f"{name}: {e}" for name, e in errors]
                raise MachineError(
                    "Failed to start the following machines:\n" + "\n".join(messages)
                )

    def join_all(self) -> None:
        """Wait for all machines to shut down"""
        with self.logger.nested("wait for all VMs to finish"):
            for machine in self.machines:
                machine.wait_for_shutdown()
            self.race_timer.cancel()

    def terminate_test(self) -> None:
        # This will be usually running in another thread than
        # the thread actually executing the test script.
        with self.logger.nested("timeout reached; test terminating..."):
            for machine in self.machines:
                machine.release()
            # As we cannot `sys.exit` from another thread
            # We can at least force the main thread to get SIGTERM'ed.
            # This will prevent any user who caught all the exceptions
            # to swallow them and prevent itself from terminating.
            os.kill(os.getpid(), signal.SIGTERM)

    def create_machine(
        self,
        start_command: str,
        *,
        name: str | None = None,
        keep_machine_state: bool = False,
    ) -> QemuMachine:
        """
        Create a `QemuMachine`. This currently only supports qemu "nodes", not containers.
        """
        tmp_dir = get_tmp_dir()

        if self.config.enable_ssh_backdoor:
            self.logger.warning(
                f"create_machine({name}): not enabling SSH backdoor, this is not supported for VMs created with create_machine!"
            )
        return QemuMachine(
            tmp_dir=tmp_dir,
            out_dir=self.out_dir,
            start_command=start_command,
            name=name,
            keep_machine_state=keep_machine_state,
            logger=self.logger,
        )

    def serial_stdout_on(self) -> None:
        self.logger.print_serial_logs(True)

    def serial_stdout_off(self) -> None:
        self.logger.print_serial_logs(False)

    def check_polling_conditions(self) -> None:
        for condition in self.polling_conditions:
            condition.maybe_raise()

    def polling_condition(
        self,
        fun_: Callable | None = None,
        *,
        seconds_interval: float = 2.0,
        description: str | None = None,
    ) -> Callable[[Callable], AbstractContextManager] | AbstractContextManager:
        driver = self

        class Poll:
            def __init__(self, fun: Callable):
                self.condition = PollingCondition(
                    fun,
                    driver.logger,
                    seconds_interval,
                    description,
                )

            def __enter__(self) -> None:
                driver.polling_conditions.append(self.condition)

            def __exit__(self, a, b, c) -> None:
                res = driver.polling_conditions.pop()
                assert res is self.condition

            def wait(self, timeout: int = 900) -> None:
                def condition(last: bool) -> bool:
                    if last:
                        driver.logger.info(
                            f"Last chance for {self.condition.description}"
                        )
                    ret = self.condition.check(force=True)
                    if not ret and not last:
                        driver.logger.info(
                            f"({self.condition.description} failure not fatal yet)"
                        )
                    return ret

                with driver.logger.nested(f"waiting for {self.condition.description}"):
                    retry(condition, timeout_seconds=timeout)

        if fun_ is None:
            return Poll
        else:
            return Poll(fun_)
