# Copyright 2024, The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


import errno
import fcntl
import getpass
import hashlib
import logging
import multiprocessing
import os
import pathlib
import platform
import signal
import subprocess
import sys
import tempfile
import time

from atest.metrics import clearcut_client
from atest.proto import clientanalytics_pb2
from edit_monitor import utils
from proto import edit_event_pb2

DEFAULT_PROCESS_TERMINATION_TIMEOUT_SECONDS = 5
DEFAULT_MONITOR_INTERVAL_SECONDS = 5
DEFAULT_MEMORY_USAGE_THRESHOLD = 0.02  # 2% of total memory
DEFAULT_CPU_USAGE_THRESHOLD = 200
DEFAULT_REBOOT_TIMEOUT_SECONDS = 60 * 60 * 24
BLOCK_SIGN_FILE = "edit_monitor_block_sign"
# Enum of the Clearcut log source defined under
# /google3/wireless/android/play/playlog/proto/log_source_enum.proto
LOG_SOURCE = 2524


def default_daemon_target():
  """Place holder for the default daemon target."""
  print("default daemon target")


class DaemonManager:
  """Class to manage and monitor the daemon run as a subprocess."""

  def __init__(
      self,
      binary_path: str,
      daemon_target: callable = default_daemon_target,
      daemon_args: tuple = (),
      cclient: clearcut_client.Clearcut | None = None,
  ):
    self.binary_path = binary_path
    self.daemon_target = daemon_target
    self.daemon_args = daemon_args
    self.cclient = cclient or clearcut_client.Clearcut(LOG_SOURCE)

    self.user_name = getpass.getuser()
    self.host_name = platform.node()
    self.source_root = os.environ.get("ANDROID_BUILD_TOP", "")
    self.pid = os.getpid()
    self.daemon_process = None

    self.max_memory_usage = 0
    self.max_cpu_usage = 0
    self.total_memory_size = os.sysconf("SC_PAGE_SIZE") * os.sysconf(
        "SC_PHYS_PAGES"
    )

    pid_file_dir = pathlib.Path(tempfile.gettempdir()).joinpath("edit_monitor")
    pid_file_dir.mkdir(parents=True, exist_ok=True)
    self.pid_file_path = self._get_pid_file_path(pid_file_dir)
    self.block_sign = pathlib.Path(tempfile.gettempdir()).joinpath(
        BLOCK_SIGN_FILE
    )

  def start(self):
    """Writes the pidfile and starts the daemon proces."""
    if not utils.is_feature_enabled(
        "edit_monitor",
        self.user_name,
        "ENABLE_ANDROID_EDIT_MONITOR",
        100,
    ):
      logging.warning("Edit monitor is disabled, exiting...")
      return

    if self.block_sign.exists():
      logging.warning("Block sign found, exiting...")
      return

    if self.binary_path.startswith("/google/cog/"):
      logging.warning("Edit monitor for cog is not supported, exiting...")
      return

    setup_lock_file = pathlib.Path(tempfile.gettempdir()).joinpath(
        self.pid_file_path.name + ".setup"
    )
    logging.info("setup lock file: %s", setup_lock_file)
    with open(setup_lock_file, "w") as f:
      try:
        # Acquire an exclusive lock
        fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
        self._stop_any_existing_instance()
        self._write_pid_to_pidfile()
        self._start_daemon_process()
      except Exception as e:
        if (
            isinstance(e, IOError) and e.errno == errno.EAGAIN
        ):  # Failed to acquire the file lock.
          logging.warning("Another edit monitor is starting, exitinng...")
          return
        else:
          logging.exception("Failed to start daemon manager with error %s", e)
          self._send_error_event_to_clearcut(
              edit_event_pb2.EditEvent.FAILED_TO_START_EDIT_MONITOR
          )
          raise e
      finally:
        # Release the lock
        fcntl.flock(f, fcntl.LOCK_UN)

  def monitor_daemon(
      self,
      interval: int = DEFAULT_MONITOR_INTERVAL_SECONDS,
      memory_threshold: float = DEFAULT_MEMORY_USAGE_THRESHOLD,
      cpu_threshold: float = DEFAULT_CPU_USAGE_THRESHOLD,
      reboot_timeout: int = DEFAULT_REBOOT_TIMEOUT_SECONDS,
  ):
    """Monits the daemon process status.

    Periodically check the CPU/Memory usage of the daemon process as long as the
    process is still running and kill the process if the resource usage is above
    given thresholds.
    """
    if not self.daemon_process:
      return

    logging.info("start monitoring daemon process %d.", self.daemon_process.pid)
    reboot_time = time.time() + reboot_timeout
    while self.daemon_process.is_alive():
      if time.time() > reboot_time:
        self.reboot()
      try:
        memory_usage = self._get_process_memory_percent(self.daemon_process.pid)
        self.max_memory_usage = max(self.max_memory_usage, memory_usage)

        cpu_usage = self._get_process_cpu_percent(self.daemon_process.pid)
        self.max_cpu_usage = max(self.max_cpu_usage, cpu_usage)

        time.sleep(interval)
      except Exception as e:
        # Logging the error and continue.
        logging.warning("Failed to monitor daemon process with error: %s", e)

      if self.max_memory_usage >= memory_threshold:
        self._send_error_event_to_clearcut(
            edit_event_pb2.EditEvent.KILLED_DUE_TO_EXCEEDED_MEMORY_USAGE
        )
        logging.error(
            "Daemon process is consuming too much memory, rebooting..."
        )
        self.reboot()

      if self.max_cpu_usage >= cpu_threshold:
        self._send_error_event_to_clearcut(
            edit_event_pb2.EditEvent.KILLED_DUE_TO_EXCEEDED_CPU_USAGE
        )
        logging.error("Daemon process is consuming too much cpu, killing...")
        self._terminate_process(self.daemon_process.pid)

    logging.info(
        "Daemon process %d terminated. Max memory usage: %f, Max cpu"
        " usage: %f.",
        self.daemon_process.pid,
        self.max_memory_usage,
        self.max_cpu_usage,
    )

  def stop(self):
    """Stops the daemon process and removes the pidfile."""

    logging.info("in daemon manager cleanup.")
    try:
      if self.daemon_process:
        # The daemon process might already in termination process,
        # wait some time before kill it explicitly.
        self._wait_for_process_terminate(self.daemon_process.pid, 1)
        if self.daemon_process.is_alive():
          self._terminate_process(self.daemon_process.pid)
      self._remove_pidfile(self.pid)
      logging.info("Successfully stopped daemon manager.")
    except Exception as e:
      logging.exception("Failed to stop daemon manager with error %s", e)
      self._send_error_event_to_clearcut(
          edit_event_pb2.EditEvent.FAILED_TO_STOP_EDIT_MONITOR
      )
      sys.exit(1)
    finally:
      self.cclient.flush_events()

  def reboot(self):
    """Reboots the current process.

    Stops the current daemon manager and reboots the entire process based on
    the binary file. Exits directly If the binary file no longer exists.
    """
    logging.info("Rebooting process based on binary %s.", self.binary_path)

    # Stop the current daemon manager first.
    self.stop()

    # If the binary no longer exists, exit directly.
    if not os.path.exists(self.binary_path):
      logging.info("binary %s no longer exists, exiting.", self.binary_path)
      sys.exit(0)

    try:
      os.execv(self.binary_path, sys.argv)
    except OSError as e:
      logging.exception("Failed to reboot process with error: %s.", e)
      self._send_error_event_to_clearcut(
          edit_event_pb2.EditEvent.FAILED_TO_REBOOT_EDIT_MONITOR
      )
      sys.exit(1)  # Indicate an error occurred

  def cleanup(self):
    """Wipes out all edit monitor instances in the system.

    Stops all the existing edit monitor instances and place a block sign
    to prevent any edit monitor process to start. This method is only used
    in emergency case when there's something goes wrong with the edit monitor
    that requires immediate cleanup to prevent damanger to the system.
    """
    logging.debug("Start cleaning up all existing instances.")
    self._send_error_event_to_clearcut(edit_event_pb2.EditEvent.FORCE_CLEANUP)

    try:
      # First places a block sign to prevent any edit monitor process to start.
      self.block_sign.touch()
    except (FileNotFoundError, PermissionError, OSError):
      logging.exception("Failed to place the block sign")

    # Finds and kills all the existing instances of edit monitor.
    existing_instances_pids = self._find_all_instances_pids()
    for pid in existing_instances_pids:
      logging.info(
          "Found existing edit monitor instance with pid %d, killing...", pid
      )
      try:
        self._terminate_process(pid)
      except Exception:
        logging.exception("Failed to terminate process %d", pid)

  def _stop_any_existing_instance(self):
    if not self.pid_file_path.exists():
      logging.debug("No existing instances.")
      return

    ex_pid = self._read_pid_from_pidfile()

    if ex_pid:
      logging.info("Found another instance with pid %d.", ex_pid)
      self._terminate_process(ex_pid)
      self._remove_pidfile(ex_pid)

  def _read_pid_from_pidfile(self) -> int | None:
    try:
      with open(self.pid_file_path, "r") as f:
        return int(f.read().strip())
    except FileNotFoundError as e:
      logging.warning("pidfile %s does not exist.", self.pid_file_path)
      return None

  def _write_pid_to_pidfile(self):
    """Creates a pidfile and writes the current pid to the file.

    Raise FileExistsError if the pidfile already exists.
    """
    try:
      # Use the 'x' mode to open the file for exclusive creation
      with open(self.pid_file_path, "x") as f:
        f.write(f"{self.pid}")
    except FileExistsError as e:
      # This could be caused due to race condition that a user is trying
      # to start two edit monitors at the same time. Or because there is
      # already an existing edit monitor running and we can not kill it
      # for some reason.
      logging.exception("pidfile %s already exists.", self.pid_file_path)
      raise e

  def _start_daemon_process(self):
    """Starts a subprocess to run the daemon."""
    p = multiprocessing.Process(
        target=self.daemon_target, args=self.daemon_args
    )
    p.daemon = True
    p.start()

    logging.info("Start subprocess with PID %d", p.pid)
    self.daemon_process = p

  def _terminate_process(
      self, pid: int, timeout: int = DEFAULT_PROCESS_TERMINATION_TIMEOUT_SECONDS
  ):
    """Terminates a process with given pid.

    It first sends a SIGTERM to the process to allow it for proper
    termination with a timeout. If the process is not terminated within
    the timeout, kills it forcefully.
    """
    try:
      os.kill(pid, signal.SIGTERM)
      if not self._wait_for_process_terminate(pid, timeout):
        logging.warning(
            "Process %d not terminated within timeout, try force kill", pid
        )
        os.kill(pid, signal.SIGKILL)
    except ProcessLookupError:
      logging.info("Process with PID %d not found (already terminated)", pid)

  def _wait_for_process_terminate(self, pid: int, timeout: int) -> bool:
    start_time = time.time()

    while time.time() < start_time + timeout:
      if not self._is_process_alive(pid):
        return True
      time.sleep(1)

    logging.error("Process %d not terminated within %d seconds.", pid, timeout)
    return False

  def _is_process_alive(self, pid: int) -> bool:
    try:
      output = subprocess.check_output(
          ["ps", "-p", str(pid), "-o", "state="], text=True
      ).strip()
      state = output.split()[0]
      return state != "Z"  # Check if the state is not 'Z' (zombie)
    except subprocess.CalledProcessError:
      # Process not found (already dead).
      return False
    except (FileNotFoundError, OSError, ValueError) as e:
      logging.warning(
          "Unable to check the status for process %d with error: %s.", pid, e
      )
      return True

  def _remove_pidfile(self, expected_pid: int):
    recorded_pid = self._read_pid_from_pidfile()

    if recorded_pid is None:
      logging.info("pid file %s already removed.", self.pid_file_path)
      return

    if recorded_pid != expected_pid:
      logging.warning(
          "pid file contains pid from a different process, expected pid: %d,"
          " actual pid: %d.",
          expected_pid,
          recorded_pid,
      )
      return

    logging.debug("removing pidfile written by process %s", expected_pid)
    try:
      os.remove(self.pid_file_path)
    except FileNotFoundError:
      logging.info("pid file %s already removed.", self.pid_file_path)

  def _get_pid_file_path(self, pid_file_dir: pathlib.Path) -> pathlib.Path:
    """Generates the path to store the pidfile.

    The file path should have the format of "/tmp/edit_monitor/xxxx.lock"
    where xxxx is a hashed value based on the binary path that starts the
    process.
    """
    hash_object = hashlib.sha256()
    hash_object.update(self.binary_path.encode("utf-8"))
    pid_file_path = pid_file_dir.joinpath(hash_object.hexdigest() + ".lock")
    logging.info("pid_file_path: %s", pid_file_path)

    return pid_file_path

  def _get_process_memory_percent(self, pid: int) -> float:
    with open(f"/proc/{pid}/stat", "r") as f:
      stat_data = f.readline().split()
      # RSS is the 24th field in /proc/[pid]/stat
      rss_pages = int(stat_data[23])
      process_memory = rss_pages * 4 * 1024  # Convert to bytes

    return (
        process_memory / self.total_memory_size
        if self.total_memory_size
        else 0.0
    )

  def _get_process_cpu_percent(self, pid: int, interval: int = 1) -> float:
    total_start_time = self._get_total_cpu_time(pid)
    with open("/proc/uptime", "r") as f:
      uptime_start = float(f.readline().split()[0])

    time.sleep(interval)

    total_end_time = self._get_total_cpu_time(pid)
    with open("/proc/uptime", "r") as f:
      uptime_end = float(f.readline().split()[0])

    return (
        (total_end_time - total_start_time) / (uptime_end - uptime_start) * 100
    )

  def _get_total_cpu_time(self, pid: int) -> float:
    with open(f"/proc/{str(pid)}/stat", "r") as f:
      stats = f.readline().split()
      # utime is the 14th field in /proc/[pid]/stat measured in clock ticks.
      utime = int(stats[13])
      # stime is the 15th field in /proc/[pid]/stat measured in clock ticks.
      stime = int(stats[14])
      return (utime + stime) / os.sysconf(os.sysconf_names["SC_CLK_TCK"])

  def _find_all_instances_pids(self) -> list[int]:
    pids = []

    try:
      output = subprocess.check_output(["ps", "-ef", "--no-headers"], text=True)
      for line in output.splitlines():
        parts = line.split()
        process_path = parts[7]
        if pathlib.Path(process_path).name == "edit_monitor":
          pid = int(parts[1])
          if pid != self.pid:  # exclude the current process
            pids.append(pid)
    except Exception:
      logging.exception(
          "Failed to get pids of existing edit monitors from ps command."
      )

    return pids

  def _send_error_event_to_clearcut(self, error_type):
    edit_monitor_error_event_proto = edit_event_pb2.EditEvent(
        user_name=self.user_name,
        host_name=self.host_name,
        source_root=self.source_root,
    )
    edit_monitor_error_event_proto.edit_monitor_error_event.CopyFrom(
        edit_event_pb2.EditEvent.EditMonitorErrorEvent(error_type=error_type)
    )
    log_event = clientanalytics_pb2.LogEvent(
        event_time_ms=int(time.time() * 1000),
        source_extension=edit_monitor_error_event_proto.SerializeToString(),
    )
    self.cclient.log(log_event)