# Copyright 2015 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

import logging
import os
import sys
import threading
from contextlib import contextmanager
from dataclasses import dataclass

from setproctitle import setproctitle as set_process_title

from pants.base.build_environment import get_buildroot
from pants.base.exception_sink import ExceptionSink, SignalHandler
from pants.base.exiter import Exiter
from pants.bin.daemon_pants_runner import DaemonPantsRunner
from pants.engine.native import Native
from pants.engine.rules import UnionMembership
from pants.init.engine_initializer import EngineInitializer
from pants.init.logging import init_rust_logger, setup_logging
from pants.init.options_initializer import BuildConfigInitializer, OptionsInitializer
from pants.option.options_bootstrapper import OptionsBootstrapper
from pants.option.options_fingerprinter import OptionsFingerprinter
from pants.option.scope import GLOBAL_SCOPE
from pants.pantsd.process_manager import FingerprintedProcessManager
from pants.pantsd.service.fs_event_service import FSEventService
from pants.pantsd.service.pailgun_service import PailgunService
from pants.pantsd.service.pants_service import PantsServices
from pants.pantsd.service.scheduler_service import SchedulerService
from pants.pantsd.service.store_gc_service import StoreGCService
from pants.pantsd.watchman_launcher import WatchmanLauncher
from pants.util.contextutil import stdio_as
from pants.util.memo import memoized_property
from pants.util.strutil import ensure_text


class _LoggerStream(object):
    """A sys.std{out,err} replacement that pipes output to a logger.

    N.B. `logging.Logger` expects unicode. However, most of our outstream logic, such as in
    `exiter.py`, will use `sys.std{out,err}.buffer` and thus a bytes interface. So, we must provide
    a `buffer` property, and change the semantics of the buffer to always convert the message to
    unicode. This is an unfortunate code smell, as `logging` does not expose a bytes interface so
    this is the best solution we could think of.
    """

    def __init__(self, logger, log_level, handler):
        """
        :param logging.Logger logger: The logger instance to emit writes to.
        :param int log_level: The log level to use for the given logger.
        :param Handler handler: The underlying log handler, for determining the fileno
                                to support faulthandler logging.
        """
        self._logger = logger
        self._log_level = log_level
        self._handler = handler

    def write(self, msg):
        msg = ensure_text(msg)
        for line in msg.rstrip().splitlines():
            # The log only accepts text, and will raise a decoding error if the default encoding is ascii
            # if provided a bytes input for unicode text.
            line = ensure_text(line)
            self._logger.log(self._log_level, line.rstrip())

    def flush(self):
        return

    def isatty(self):
        return False

    def fileno(self):
        return self._handler.stream.fileno()

    @property
    def buffer(self):
        return self


class PantsDaemonSignalHandler(SignalHandler):
    def __init__(self, daemon):
        super().__init__()
        self._daemon = daemon

    def handle_sigint(self, signum, _frame):
        self._daemon.terminate(include_watchman=False)


class PantsDaemon(FingerprintedProcessManager):
    """A daemon that manages PantsService instances."""

    JOIN_TIMEOUT_SECONDS = 1
    LOG_NAME = "pantsd.log"

    class StartupFailure(Exception):
        """Represents a failure to start pantsd."""

    class RuntimeFailure(Exception):
        """Represents a pantsd failure at runtime, usually from an underlying service failure."""

    @dataclass(frozen=True)
    class Handle:
        """A handle to a "probably running" pantsd instance.

        We attempt to verify that the pantsd instance is still running when we create a Handle, but
        after it has been created it is entirely process that the pantsd instance perishes.
        """

        pid: int
        port: int
        metadata_base_dir: str

    class Factory:
        @classmethod
        def maybe_launch(cls, options_bootstrapper):
            """Creates and launches a daemon instance if one does not already exist.

            :param OptionsBootstrapper options_bootstrapper: The bootstrap options.
            :returns: A Handle for the running pantsd instance.
            :rtype: PantsDaemon.Handle
            """
            stub_pantsd = cls.create(options_bootstrapper, full_init=False)
            with stub_pantsd._services.lifecycle_lock:
                if stub_pantsd.needs_restart(stub_pantsd.options_fingerprint):
                    # Once we determine we actually need to launch, recreate with full initialization.
                    pantsd = cls.create(options_bootstrapper)
                    return pantsd.launch()
                else:
                    # We're already launched.
                    return PantsDaemon.Handle(
                        stub_pantsd.await_pid(10),
                        stub_pantsd.read_named_socket("pailgun", int),
                        stub_pantsd._metadata_base_dir,
                    )

        @classmethod
        def restart(cls, options_bootstrapper):
            """Restarts a running daemon instance.

            :param OptionsBootstrapper options_bootstrapper: The bootstrap options.
            :returns: A Handle for the pantsd instance.
            :rtype: PantsDaemon.Handle
            """
            pantsd = cls.create(options_bootstrapper)
            with pantsd._services.lifecycle_lock:
                # N.B. This will call `pantsd.terminate()` before starting.
                return pantsd.launch()

        @classmethod
        def create(cls, options_bootstrapper, full_init=True):
            """
            :param OptionsBootstrapper options_bootstrapper: The bootstrap options.
            :param bool full_init: Whether or not to fully initialize an engine et al for the purposes
                                   of spawning a new daemon. `full_init=False` is intended primarily
                                   for lightweight lifecycle checks (since there is a ~1s overhead to
                                   initialize the engine). See the impl of `maybe_launch` for an example
                                   of the intended usage.
            """
            bootstrap_options = options_bootstrapper.bootstrap_options
            bootstrap_options_values = bootstrap_options.for_global_scope()
            # TODO: https://github.com/pantsbuild/pants/issues/3479
            watchman = WatchmanLauncher.create(bootstrap_options_values).watchman

            if full_init:
                build_root = get_buildroot()
                native = Native()
                build_config = BuildConfigInitializer.get(options_bootstrapper)
                legacy_graph_scheduler = EngineInitializer.setup_legacy_graph(
                    native, options_bootstrapper, build_config
                )
                services = cls._setup_services(
                    build_root,
                    bootstrap_options_values,
                    legacy_graph_scheduler,
                    watchman,
                    union_membership=UnionMembership(build_config.union_rules()),
                )
            else:
                build_root = None
                native = None
                services = PantsServices()

            return PantsDaemon(
                native=native,
                build_root=build_root,
                work_dir=bootstrap_options_values.pants_workdir,
                log_level=bootstrap_options_values.level.upper(),
                services=services,
                metadata_base_dir=bootstrap_options_values.pants_subprocessdir,
                bootstrap_options=bootstrap_options,
            )

        @staticmethod
        def _setup_services(
            build_root,
            bootstrap_options,
            legacy_graph_scheduler,
            watchman,
            union_membership: UnionMembership,
        ):
            """Initialize pantsd services.

            :returns: A PantsServices instance.
            """
            should_shutdown_after_run = bootstrap_options.shutdown_pantsd_after_run
            fs_event_service = (
                FSEventService(
                    watchman, scheduler=legacy_graph_scheduler.scheduler, build_root=build_root
                )
                if bootstrap_options.watchman_enable
                else None
            )

            invalidation_globs = OptionsInitializer.compute_pantsd_invalidation_globs(
                build_root, bootstrap_options
            )

            scheduler_service = SchedulerService(
                fs_event_service=fs_event_service,
                legacy_graph_scheduler=legacy_graph_scheduler,
                build_root=build_root,
                invalidation_globs=invalidation_globs,
                union_membership=union_membership,
            )

            pailgun_service = PailgunService(
                (bootstrap_options.pantsd_pailgun_host, bootstrap_options.pantsd_pailgun_port),
                DaemonPantsRunner,
                scheduler_service,
                should_shutdown_after_run,
            )

            store_gc_service = StoreGCService(legacy_graph_scheduler.scheduler)

            return PantsServices(
                services=tuple(
                    service
                    for service in (
                        fs_event_service,
                        scheduler_service,
                        pailgun_service,
                        store_gc_service,
                    )
                    if service is not None
                ),
                port_map=dict(pailgun=pailgun_service.pailgun_port),
            )

    def __init__(
        self,
        native,
        build_root,
        work_dir,
        log_level,
        services,
        metadata_base_dir,
        bootstrap_options=None,
    ):
        """
        :param Native native: A `Native` instance.
        :param string build_root: The pants build root.
        :param string work_dir: The pants work directory.
        :param string log_level: The log level to use for daemon logging.
        :param PantsServices services: A registry of services to use in this run.
        :param string metadata_base_dir: The ProcessManager metadata base dir.
        :param Options bootstrap_options: The bootstrap options, if available.
        """
        super().__init__(name="pantsd", metadata_base_dir=metadata_base_dir)
        self._native = native
        self._build_root = build_root
        self._work_dir = work_dir
        self._log_level = log_level
        self._services = services
        self._bootstrap_options = bootstrap_options
        self._log_show_rust_3rdparty = (
            bootstrap_options.for_global_scope().log_show_rust_3rdparty
            if bootstrap_options
            else True
        )

        self._log_dir = os.path.join(work_dir, self.name)
        self._logger = logging.getLogger(__name__)
        # N.B. This Event is used as nothing more than a convenient atomic flag - nothing waits on it.
        self._kill_switch = threading.Event()

    @memoized_property
    def watchman_launcher(self):
        return WatchmanLauncher.create(self._bootstrap_options.for_global_scope())

    @property
    def is_killed(self):
        return self._kill_switch.is_set()

    @property
    def options_fingerprint(self):
        return OptionsFingerprinter.combined_options_fingerprint_for_scope(
            GLOBAL_SCOPE, self._bootstrap_options, fingerprint_key="daemon", invert=True
        )

    def shutdown(self, service_thread_map):
        """Gracefully terminate all services and kill the main PantsDaemon loop."""
        with self._services.lifecycle_lock:
            for service, service_thread in service_thread_map.items():
                self._logger.info(f"terminating pantsd service: {service}")
                service.terminate()
                service_thread.join(self.JOIN_TIMEOUT_SECONDS)
            self._logger.info("terminating pantsd")
            self._kill_switch.set()

    @staticmethod
    def _close_stdio():
        """Close stdio streams to avoid output in the tty that launched pantsd."""
        for fd in (sys.stdin, sys.stdout, sys.stderr):
            file_no = fd.fileno()
            fd.flush()
            fd.close()
            os.close(file_no)

    @contextmanager
    def _pantsd_logging(self):
        """A context manager that runs with pantsd logging.

        Asserts that stdio (represented by file handles 0, 1, 2) is closed to ensure that we can
        safely reuse those fd numbers.
        """

        # Ensure that stdio is closed so that we can safely reuse those file descriptors.
        for fd in (0, 1, 2):
            try:
                os.fdopen(fd)
                raise AssertionError(f"pantsd logging cannot initialize while stdio is open: {fd}")
            except OSError:
                pass

        # Redirect stdio to /dev/null for the rest of the run, to reserve those file descriptors
        # for further forks.
        with stdio_as(stdin_fd=-1, stdout_fd=-1, stderr_fd=-1):
            # Reinitialize logging for the daemon context.
            init_rust_logger(self._log_level, self._log_show_rust_3rdparty)
            result = setup_logging(
                self._log_level,
                log_dir=self._log_dir,
                log_name=self.LOG_NAME,
                native=self._native,
                warnings_filter_regexes=self._bootstrap_options.for_global_scope(),
            )
            self._native.override_thread_logging_destination_to_just_pantsd()

            # Do a python-level redirect of stdout/stderr, which will not disturb `0,1,2`.
            # TODO: Consider giving these pipes/actual fds, in order to make them "deep" replacements
            # for `1,2`, and allow them to be used via `stdio_as`.
            sys.stdout = _LoggerStream(logging.getLogger(), logging.INFO, result.log_handler)
            sys.stderr = _LoggerStream(logging.getLogger(), logging.WARN, result.log_handler)

            self._logger.debug("logging initialized")
            yield (result.log_handler.stream, result.log_handler.native_filename)

    def _setup_services(self, pants_services):
        for service in pants_services.services:
            self._logger.info(f"setting up service {service}")
            service.setup(self._services)

    @staticmethod
    def _make_thread(service):
        name = f"{service.__class__.__name__}Thread"

        def target():
            Native().override_thread_logging_destination_to_just_pantsd()
            service.run()

        t = threading.Thread(target=target, name=name)
        t.daemon = True
        return t

    def _run_services(self, pants_services):
        """Service runner main loop."""
        if not pants_services.services:
            self._logger.critical("no services to run, bailing!")
            return

        service_thread_map = {
            service: self._make_thread(service) for service in pants_services.services
        }

        # Start services.
        for service, service_thread in service_thread_map.items():
            self._logger.info(f"starting service {service}")
            try:
                service_thread.start()
            except (RuntimeError, FSEventService.ServiceError):
                self.shutdown(service_thread_map)
                raise PantsDaemon.StartupFailure(
                    f"service {service} failed to start, shutting down!"
                )

        # Once all services are started, write our pid and notify the SchedulerService to start
        # watching it.
        self._initialize_pid()

        # Monitor services.
        while not self.is_killed:
            for service, service_thread in service_thread_map.items():
                if not service_thread.is_alive():
                    self.shutdown(service_thread_map)
                    raise PantsDaemon.RuntimeFailure(
                        f"service failure for {service}, shutting down!"
                    )
                else:
                    # Avoid excessive CPU utilization.
                    service_thread.join(self.JOIN_TIMEOUT_SECONDS)

    def _write_named_sockets(self, socket_map):
        """Write multiple named sockets using a socket mapping."""
        for socket_name, socket_info in socket_map.items():
            self.write_named_socket(socket_name, socket_info)

    def _initialize_pid(self):
        """Writes out our pid and metadata, and begin watching it for validity.

        Once written and watched, does a one-time read of the pid to confirm that we haven't raced
        another process starting.

        All services must already have been initialized before this is called.
        """

        # Write the pidfile.
        self.write_pid()
        self.write_metadata_by_name(
            "pantsd", self.FINGERPRINT_KEY, ensure_text(self.options_fingerprint)
        )

        # Add the pidfile to watching via the scheduler.
        pidfile_absolute = self._metadata_file_path("pantsd", "pid")
        if pidfile_absolute.startswith(self._build_root):
            scheduler_service = next(
                s for s in self._services.services if isinstance(s, SchedulerService)
            )
            scheduler_service.add_invalidation_glob(
                os.path.relpath(pidfile_absolute, self._build_root)
            )
        else:
            logging.getLogger(__name__).warning(
                "Not watching pantsd pidfile because subprocessdir is outside of buildroot. Having "
                "subprocessdir be a child of buildroot (as it is by default) may help avoid stray "
                "pantsd processes."
            )

        # Finally, once watched, confirm that we didn't race another process.
        try:
            with open(pidfile_absolute, "r") as f:
                pid_from_file = f.read()
        except IOError:
            raise Exception(f"Could not read pants pidfile at {pidfile_absolute}.")
        if int(pid_from_file) != os.getpid():
            raise Exception(f"Another instance of pantsd is running at {pid_from_file}")

    def run_sync(self):
        """Synchronously run pantsd."""
        os.environ.pop("PYTHONPATH")

        # Switch log output to the daemon's log stream from here forward.
        # Also, register an exiter using os._exit to ensure we only close stdio streams once.
        self._close_stdio()
        with self._pantsd_logging() as (log_stream, log_filename), ExceptionSink.exiter_as(
            lambda _: Exiter(exiter=os._exit)
        ):

            # We don't have any stdio streams to log to anymore, so we log to a file.
            # We don't override the faulthandler destination because the stream we get will proxy things
            # via the rust logging code, and faulthandler needs to be writing directly to a real file
            # descriptor. When pantsd logging was originally initialised, we already set up faulthandler
            # to log to the correct file descriptor, so don't override it.
            #
            # We can get tracebacks of the pantsd process by tailing the pantsd log and sending it
            # SIGUSR2.
            ExceptionSink.reset_interactive_output_stream(
                log_stream, override_faulthandler_destination=False,
            )

            # Reset the log location and the backtrace preference from the global bootstrap options.
            global_bootstrap_options = self._bootstrap_options.for_global_scope()
            ExceptionSink.reset_should_print_backtrace_to_terminal(
                global_bootstrap_options.print_exception_stacktrace
            )
            ExceptionSink.reset_log_location(global_bootstrap_options.pants_workdir)

            self._native.set_panic_handler()

            # Set the process name in ps output to 'pantsd' vs './pants compile src/etc:: -ldebug'.
            set_process_title(f"pantsd [{self._build_root}]")

            # Write service socket information to .pids.
            self._write_named_sockets(self._services.port_map)

            # Enter the main service runner loop.
            self._setup_services(self._services)
            self._run_services(self._services)

    def post_fork_child(self):
        """Post-fork() child callback for ProcessManager.daemon_spawn()."""
        spawn_control_env = dict(
            PANTS_ENTRYPOINT=f"{__name__}:launch",
            # The daemon should run under the same sys.path as us; so we ensure
            # this. NB: It will scrub PYTHONPATH once started to avoid infecting
            # its own unrelated subprocesses.
            PYTHONPATH=os.pathsep.join(sys.path),
        )
        exec_env = {**os.environ, **spawn_control_env}

        # Pass all of sys.argv so that we can proxy arg flags e.g. `-ldebug`.
        cmd = [sys.executable] + sys.argv

        spawn_control_env_vars = " ".join(f"{k}={v}" for k, v in spawn_control_env.items())
        cmd_line = " ".join(cmd)
        self._logger.debug(f"cmd is: {spawn_control_env_vars} {cmd_line}")

        # TODO: Improve error handling on launch failures.
        os.spawnve(os.P_NOWAIT, sys.executable, cmd, env=exec_env)

    def needs_launch(self):
        """Determines if pantsd needs to be launched.

        N.B. This should always be called under care of the `lifecycle_lock`.

        :returns: True if the daemon needs launching, False otherwise.
        :rtype: bool
        """
        new_fingerprint = self.options_fingerprint
        self._logger.debug(
            "pantsd: is_alive={self.is_alive()} new_fingerprint={new_fingerprint} current_fingerprint={self.fingerprint}"
        )
        return self.needs_restart(new_fingerprint)

    def launch(self):
        """Launches pantsd in a subprocess.

        N.B. This should always be called under care of the `lifecycle_lock`.

        :returns: A Handle for the pantsd instance.
        :rtype: PantsDaemon.Handle
        """
        self.terminate(include_watchman=False)
        self.watchman_launcher.maybe_launch()
        self._logger.debug("launching pantsd")
        self.daemon_spawn()
        # Wait up to 60 seconds for pantsd to write its pidfile.
        pantsd_pid = self.await_pid(60)
        listening_port = self.read_named_socket("pailgun", int)
        self._logger.debug(f"pantsd is running at pid {self.pid}, pailgun port is {listening_port}")
        return self.Handle(pantsd_pid, listening_port, self._metadata_base_dir)

    def terminate(self, include_watchman=True):
        """Terminates pantsd and watchman.

        N.B. This should always be called under care of the `lifecycle_lock`.
        """
        super().terminate()
        if include_watchman:
            self.watchman_launcher.terminate()

    def needs_restart(self, option_fingerprint):
        """Overrides ProcessManager.needs_restart, to account for the case where pantsd is running
        but we want to shutdown after this run.

        :param option_fingerprint: A fingeprint of the global bootstrap options.
        :return: True if the daemon needs to restart.
        """
        should_shutdown_after_run = (
            self._bootstrap_options.for_global_scope().shutdown_pantsd_after_run
        )
        return super().needs_restart(option_fingerprint) or (
            self.is_alive() and should_shutdown_after_run
        )


def launch():
    """An external entrypoint that spawns a new pantsd instance."""
    PantsDaemon.Factory.create(OptionsBootstrapper.create()).run_sync()