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

from colorama import Style

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 Machine, NixStartScript, retry
from test_driver.polling_condition import PollingCondition
from test_driver.vlan import VLan

SENTINEL = object()


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)


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

    tests: str
    vlans: list[VLan]
    machines: list[Machine]
    polling_conditions: list[PollingCondition]
    global_timeout: int
    race_timer: threading.Timer
    logger: AbstractLogger
    debug: DebugAbstract

    def __init__(
        self,
        start_scripts: list[str],
        vlans: list[int],
        tests: str,
        out_dir: Path,
        logger: AbstractLogger,
        keep_vm_state: bool = False,
        global_timeout: int = 24 * 60 * 60 * 7,
        debug: DebugAbstract = DebugNop(),
    ):
        self.tests = tests
        self.out_dir = out_dir
        self.global_timeout = global_timeout
        self.race_timer = threading.Timer(global_timeout, self.terminate_test)
        self.logger = logger
        self.debug = debug

        tmp_dir = get_tmp_dir()

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

        def cmd(scripts: list[str]) -> Iterator[NixStartScript]:
            for s in scripts:
                yield NixStartScript(s)

        self.polling_conditions = []

        self.machines = [
            Machine(
                start_command=cmd,
                keep_vm_state=keep_vm_state,
                name=cmd.machine_name,
                tmp_dir=tmp_dir,
                callbacks=[self.check_polling_conditions],
                out_dir=self.out_dir,
                logger=self.logger,
            )
            for cmd in cmd(start_scripts)
        ]

    def __enter__(self) -> "Driver":
        return self

    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}")

    def subtest(self, name: str) -> Iterator[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,
            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,
            Machine=Machine,  # for typing
            t=AssertionTester(),
            debug=self.debug,
        )
        machine_symbols = {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:
            (machine_symbols["machine"],) = self.machines
        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, offset: int) -> None:
        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)."
        )
        names = [machine.name for machine in self.machines]
        longest_name = len(max(names, key=len))
        for num, name in enumerate(names, start=offset + 1):
            spaces = " " * (longest_name - len(name) + 2)
            print(
                f"    {name}:{spaces}{Style.BRIGHT}ssh -o User=root vsock/{num}{Style.RESET_ALL}"
            )

    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.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"):
            for machine in self.machines:
                machine.start()

    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_vm_state: bool = False,
    ) -> Machine:
        tmp_dir = get_tmp_dir()

        cmd = NixStartScript(start_command)
        name = name or cmd.machine_name

        return Machine(
            tmp_dir=tmp_dir,
            out_dir=self.out_dir,
            start_command=cmd,
            name=name,
            keep_vm_state=keep_vm_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:  # type: ignore
                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=timeout)

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