# <<*>> -^v- SNOWARE APPLICATION
# usage: Automatic operator implementation.
# author: S.A.
# time: 2026-06-07
# Copyright (c) [2026] [S.A. SNOWARE-SCU]
# [MineSentinel] is licensed under Mulan PubL v2.
# You can use this software according to the terms and conditions of the Mulan PubL v2.
# You may obtain a copy of Mulan PubL v2 at:
#          http://license.coscl.org.cn/MulanPubL-2.0
# THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
# EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
# MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
# See the Mulan PubL v2 for more details.

# frozen_string_literal: true

PERSISTENCE_PERIOD = 30 # Wait for systemctl to take the order.

require 'logger'
require_relative 'server_status_detector'

# rubocop:disable Style/ClassVars
class MethodExecutor
  RST_COUNTS_LIMIT = 10
  @@rst_counter = 0
  # Initialize the standard log system.
  @@logger = Logger.new($stdout) # This script will be launched as a systemd server.
  $stdout.sync = true
  $stderr.sync = true
  # Fetch the environmental variable and convert it into log level.
  @@logger.level = case ENV.fetch('LOG_LEVEL', nil) # @为单个实例（半生不熟的概念，貌似是在不同的空间独立创建），@@为共享同一个
                   when nil, 'debug' # Default config.
                     Logger::Severity::DEBUG
                   when 'info'
                     Logger::Severity::INFO
                   when 'warn'
                     Logger::Severity::WARN
                   when 'error'
                     Logger::Severity::ERROR
                   else
                     raise ArgumentError
                   end
  @@logger.progname = 'MineSentinel'

  # rubocop:disable Metrics/MethodLength

  # @param level [String] "info" | "warn" | "error" | "debug"
  # @param module_name [String]
  # @param message [String]
  # @return [void]
  def self.record(level, module_name, message)
    case level
    when 'info'
      @@logger.info("#{module_name}: #{message}")
    when 'warn'
      @@logger.warn("#{module_name}: #{message}")
    when 'error'
      @@logger.error("#{module_name}: #{message}")
    when 'debug'
      @@logger.debug("#{module_name}: #{message}")
    else
      raise ArgumentError
    end
  end

  # rubocop:enable Metrics/MethodLength
  # rubocop:disable Metrics/MethodLength, Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity

  # @return [void]
  def self.reset_minecraft_server
    record('info', 'reset', "Attempt ##{@@rst_counter + 1} to reset Minecraft server.")

    if @@rst_counter >= RST_COUNTS_LIMIT
      record('error', 'reset',
             "Tried #{RST_COUNTS_LIMIT} times and failed, now I'll idle until server is manually restarted.")
      loop do
        sleep 10
        SystemdNotifier.notify('WATCHDOG=1') if defined?(SystemdNotifier)
        next unless ServerStatusDetector::MinecraftServer.self_diag[:type] == true

        record('info', 'reset', 'Server recovered! Resuming normal monitoring.')
        @@rst_counter = 0
        return
      end
    end

    @@rst_counter += 1

    unless Process.euid.zero?
      record('error', 'reset', 'Permission denied: root required to manage systemd services.')
      raise Errno::EPERM
    end

    record('info', 'reset', "Spawning 'systemctl restart minecraft' (PID will be captured)...")
    pid = spawn 'systemctl restart minecraft'
    record('debug', 'reset', "systemctl restart spawned with PID #{pid}.")
    tick_beg = Time.now

    # rubocop:disable Metrics/BlockLength
    loop do
      sleep 0.5
      SystemdNotifier.notify('WATCHDOG=1')
      proc_status = Process.waitpid2(pid, Process::WNOHANG)
      if proc_status # 子进程已退出，返回 [pid, status]
        _, status = proc_status
        elapsed = (Time.now - tick_beg).round(2)
        if status.success?
          record('info', 'reset', "'systemctl restart' succeeded in #{elapsed}s.")
          @@rst_counter = 0 # 成功时重置计数器
        else
          record('error', 'reset',
                 "'systemctl restart' failed with exitcode #{status.exitstatus} after #{elapsed}s.")
        end
        break
      else # 子进程仍在运行 (WNOHANG 返回 nil)
        if Time.now - tick_beg > PERSISTENCE_PERIOD
          record('warn', 'reset',
                 "'systemctl restart' timed out after #{PERSISTENCE_PERIOD}s. Force-killing PID #{pid}...")
          system "kill -9 #{pid}"
          record('warn', 'reset', "Running 'systemctl kill minecraft' (last resort)...")
          system 'systemctl kill minecraft' # 没招了，毁灭吧
          sleep 0.5
          record('info', 'reset', "Running 'systemctl start minecraft' (rebirth)...")
          system 'systemctl start minecraft' # 重生
          record('info', 'reset', 'Force-reset sequence completed.')
          break
        end
      end
      # rubocop:enable Metrics/BlockLength
    end
  end
  # rubocop:enable Metrics/MethodLength, Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
  # rubocop:enable Style/ClassVars
end