package de.spiritscorp.datasync.controller;
   
   /*-
    * 		Data Sync
    *
    * 		Copyright ©   2022    The Spirit
    * 		@email                        thespirit@spiritscorp.network
    *
    * 		This program is free software; you can redistribute it and/or modify
   * 		it under the terms of the GNU General Public License as published by
   * 		the Free Software Foundation; either version 3 of the License, or
   * 		(at your option) any later version.
   *
   * 		This program is distributed in the hope that it will be useful,
   * 		but WITHOUT ANY WARRANTY; without even the implied warranty of
   * 		MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   * 		See the GNU General Public License for more details.
   *
   * 		You should have received a copy of the GNU General Public License
   * 		along with this program. If not, see <http://www.gnu.org/licenses/>.
   */
  
  import java.awt.AWTException;
  import java.awt.SystemTray;
  import java.awt.TrayIcon;
  import java.nio.file.Files;
  import java.nio.file.LinkOption;
  import java.nio.file.Path;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  
  import javafx.application.Platform;
  import javafx.collections.ObservableList;
  
  import de.spiritscorp.datasync.gui.BgView;
  import de.spiritscorp.datasync.gui.Gui;
  import de.spiritscorp.datasync.io.Debug;
  import de.spiritscorp.datasync.io.Logger;
  import de.spiritscorp.datasync.io.Preference;
  import de.spiritscorp.datasync.model.BgModel;
  import de.spiritscorp.datasync.model.Model;
  
  /**
   * Central orchestration engine handling asynchronous background file synchronization routines.
   * <p>
   * The {@code BgController} manages the application's daemon lifecycle. It leverages a dedicated
   * two-tier concurrent executor architecture to decouple continuous time-threshold monitoring from
   * high-overhead disk I/O operations. This design prevents resource starvation and avoids system
   * UI freezes by offloading execution workloads to isolated worker threads.
   * <p>
   * System state integration is maintained via an operating system {@link SystemTray} proxy interface,
   * allowing the core UI application framework to seamlessly minimize into background execution lanes.
   * <p>
   *
   * @author Tom Spirit
   * @version 2.1.0
   */
  public class BgController {
  
  	/** Default initial delay in milliseconds before the background scheduler activates. */
  	static final long INITIAL_DELAY = 15L * 1_000;
  	/** Extended delay in milliseconds applied during system boot execution to prevent early resource contention. */
  	static final long BOOT_START_DELAY = 10L * 60 * 1_000;
  
  	/** Operating system tray integration proxy for minimizing the application frame. */
  	private final SystemTray sysTray;
  	/** The core dataset of synchronization job contexts monitored and orchestrated by this engine. */
  	private final ObservableList<SyncJobContext> jobList;
  	/** The central logger instance for tracking daemon lifecycles and background routine states. */
  	private final Logger logger;
  	/** Primary view controller handling UI flow control and state transitions. */
  	private final ViewController controller;
  	/** The visual representation of the background menu and tray interface context. */
  	private BgView bgView;
  	/** Reference to the primary graphical user interface application framework. */
  	private final Gui gui;
  	/** Formatter utility responsible for converting raw sync metrics into human-readable UI logs. */
  	private final LogFormatter logFormatter;
  
  	/** First-tier executor dedicated solely to low-overhead, periodic time-threshold heartbeat monitoring. */
  	private ScheduledExecutorService scheduler;
  	/** Second-tier decoupled thread pool isolated for high-overhead file system and disk I/O execution workloads. */
  	private ExecutorService workerQueue;
  
  	/** Test interface: Allows accelerating intervals inside JUnit execution tasks */
  	private double timeMultiplier = 1.0;
  
  	/**
  	 * Constructs a fully operational background engine attached to the primary interface layers.
  	 * <p>
  	 * The initialization phase maps structural JavaFX core properties, bindings, and multi-job tracking
  	 * contexts. It automatically registers native {@link SystemTray} hardware capacity parameters to bind
  	 * the decoupled visual notification framework shell.
  	 * <p>
  	 *
  	 * @param gui        The visual primary graphical user interface facade wrapper
  	 * @param controller The central master view controller orchestrating active window transitions
 	 * @param jobList    The reactive data backing list containing operational task metrics and execution state tokens
 	 * @param logger     The standardized system logging framework interface
 	 */
 	BgController( final Gui gui, final ViewController controller, final ObservableList<SyncJobContext> jobList, final Logger logger ) {
 		this.gui = gui;
 		this.controller = controller;
 		this.jobList = jobList;
 		this.logger = logger;
 		this.logFormatter = new LogFormatter();
 		this.sysTray = SystemTray.isSupported() ? SystemTray.getSystemTray() : null;
 		setEnvironment( timeMultiplier, new BgView( this ), Executors.newSingleThreadScheduledExecutor(), Executors.newSingleThreadExecutor() );
 	}
 
 	/**
 	 * Initiates a global application termination sequence triggered from the background context.
 	 * <p>
 	 * This method acts as the bridge for the {@code BgView} (SystemTray) to command a full system exit.
 	 * It systematically deallocates and dismantles internal concurrent tracking structures using a
 	 * standardized background grace period before delegating downstream lifecycle teardown protocols
 	 * to the central application controller.
 	 * <p>
 	 *
 	 * @see #shutdownExecutors(long)
 	 */
 	public void requestApplicationShutdown() {
 		// Disassemble concurrent tracking frameworks before global window exit procedures trigger
 		shutdownExecutors( MainViewController.BG_TIMEOUT );
 		controller.handleApplicationShutdown();
 	}
 
 	/**
 	 * Interrupts the active background execution cycle and restores the primary user interface.
 	 * <p>
 	 * This dual-purpose lifecycle hook is invoked by both the primary workspace ({@code MainView})
 	 * and the system notification shell ({@code BgView}). It enforces an immediate visibility state
 	 * transition on the main window stage and guarantees a deterministic, timed collapse of all
 	 * active thread pool frames.
 	 * <p>
 	 *
 	 * @param timeout The maximum allocation window in milliseconds granted to active
 	 *                worker threads to complete processing cycles before a hard
 	 *                interruption signal is enforced.
 	 * @see #shutdownExecutors(long)
 	 */
 	public void interruptBgJob( final long timeout ) {
 		if( Platform.isFxApplicationThread() ) {
 			gui.getWindowStage().show();
 		}
 		shutdownExecutors( timeout );
 		Debug.printDebug( "[Bg Controller] Background routine interrupted" );
 	}
 
 	/**
 	 * Initiates the continuous background daemon monitoring pipeline and minimizes the user interface.
 	 * <p>
 	 * Activating this boot phase suppresses the primary desktop window frame and binds the visual notifications
 	 * infrastructure into the native operating system taskbar environment. It dynamically analyzes user scheduling
 	 * rules to compute an optimal, non-blocking check frequency tick rate.
 	 * <p>
 	 * Once configurations are parsed, an initial delay configuration is selected—differentiating between fresh
 	 * application boots ({@code BOOT_START_DELAY}) and quick UI toggle states ({@code INITIAL_DELAY}). The continuous
 	 * tracking routine is then permanently registered inside the internal {@link ScheduledExecutorService} core thread framework.
 	 * <p>
 	 *
 	 * @param bootDelay Enforces an extended cold-boot initialization timeout buffer if set to {@code true};
 	 *                  allocates a standard near-instant scheduling offset if set to {@code false}.
 	 */
 	void startBgJob( final boolean bootDelay ) {
 		gui.getWindowStage().hide();
 		if( sysTray != null && bgView.getTrayIcon() != null ) {
 			try {
 				sysTray.add( bgView.getTrayIcon() );
 			}catch( final AWTException exception ) {
 				Debug.printError( "[Bg Controller] Failed to register TrayIcon context." );
 				Debug.printException( getClass(), exception );
 				gui.getWindowStage().show();
 				return;
 			}
 		}
 
 		Debug.printDebug( "[Bg Controller] Multi-Job Background-Daemon initialization started." );
 
 		// Dynamically determine the optimal check interval based on active jobs
 		final long calculatedTick = determineOptimalCheckTime();
 		final long tickInterval = (long) ( calculatedTick * timeMultiplier );
 		final long initialDelay = (long) ( ( bootDelay ? BOOT_START_DELAY : INITIAL_DELAY ) * timeMultiplier );
 		Debug.printDebug( "[Bg Controller] Heartbeat configured to tick every %d ms based on job preferences.", calculatedTick );
 		jobList.stream()
 				.filter( job -> job.getPreference()
 						.isBgSync() )
 				.forEach( job -> Debug.printDebug( "[Bg Controller] Executing background routine is activated for task: %s", job.getJobName() ) );
 		// Begin tracking task list rules loops
 		this.scheduler.scheduleAtFixedRate( this::checkAndQueueJobs, initialDelay, tickInterval, TimeUnit.MILLISECONDS );
 	}
 
 	/**
 	 * Determines the smallest defined checkTime among all active background jobs.
 	 * Falls back to a default interval (10 sec) if no matching jobs are active.
 	 */
 	private long determineOptimalCheckTime() {
 		long minCheckTime = 10_000; // Default fallback: 10 seconds
 		boolean foundActiveJob = false;
 
 		for( final SyncJobContext job : jobList ) {
 			final Preference pref = job.getPreference();
 			if( pref != null && pref.isBgSync() && pref.getBgTime() != null ) {
 				final long currentCheck = pref.getBgTime().getCheckTime();
 				if( !foundActiveJob || currentCheck < minCheckTime ) {
 					minCheckTime = currentCheck;
 					foundActiveJob = true;
 				}
 			}
 		}
 		return minCheckTime;
 	}
 
 	/**
 	 * Evaluates temporal boundaries across registered task configurations to schedule overdue synchronization pipelines.
 	 * <p>
 	 * This core evaluation loop acts as the engine's processing heartbeat. It scans all configured
 	 * synchronization definitions, applies an accelerated time scaling calculation using the {@code timeMultiplier},
 	 * and determines if an individual task context has surpassed its requested execution interval threshold.
 	 * <p>
 	 * Overdue jobs are safely flag-locked to guarantee execution idempotency. The payload runnable is subsequently
 	 * dispatched into a dedicated single-threaded sequential worker pool ({@code workerQueue}). This strict serialization
 	 * strategy isolates concurrent I/O access and actively prevents multiple background tasks from triggering destructive
 	 * physical disk drive thrashing.
 	 * <p>
 	 * To ensure resilient remote cancellation capabilities, the executing worker thread frame is explicitly mapped
 	 * directly back to the target {@link SyncJobContext} token inside the processing boundary.
 	 * <p>
 	 */
 	private void checkAndQueueJobs() {
 		for( final SyncJobContext job : jobList ) {
 			// Skip tasks if they are actively running or already waiting inside the execution queue lane
 			if( job.isRunning() ) continue;
 
 			final Preference pref = job.getPreference();
 			// Only process if background execution is explicitly requested for this task context
 			if( pref != null && pref.isBgSync() ) {
 				final long timeDelta = System.currentTimeMillis() - pref.getLastScanTime();
 				final long targetInterval = (long) ( pref.getBgTime().getTime() * timeMultiplier );
 				Debug.printDebug( "[Bg Controller] time since last check (%s): %s", job.getJobName(),
 						logFormatter.getTimeFormatted( ( System.currentTimeMillis() - pref.getLastScanTime() ) * 1_000_000 ) );
 				Path destPath = pref.getDestPaths().getFirst();
 				if( !Files.exists( destPath, LinkOption.NOFOLLOW_LINKS ) ) {
 					Debug.printDebug( "[Bg Controller] Destination Path is offline: %s", destPath.toString() );
 				}else if( timeDelta > targetInterval ) {
 					Debug.printDebug( "[Bg Controller] Polling threshold triggered for task: %s. Queueing worker task.", job.getJobName() );
 					job.setRunning( true );
 					// Dispatch into the dedicated loop queue lane (prevents hardware disk I/O thrashing)
 					workerQueue.execute( () -> {
 						try {
 							final BgModel bgModel = new BgModel( pref, logger, Model.createMap(), Model.createMap() );
 
 							// Map active thread to the context token to let external shutdown requests throw interrupts
 							job.setActiveWorkerThread( Thread.currentThread() );
 							Debug.printDebug( "[Bg Controller] Executing background routine for task: %s", job.getJobName() );
 							bgModel.runBgJob();
 						}catch( final RuntimeException exception ) {
 							Debug.printDebug( "[Bg Controller Error] Critical fault captured inside background thread execution pipeline for: %s", job.getJobName() );
 							Debug.printException( this.getClass(), exception );
 						}finally {
 							job.setRunning( false );
 							job.setActiveWorkerThread( null );
 							Debug.printDebug( "[Bg Controller] Finished executing background routine for task: %s", job.getJobName() );
 						}
 					} );
 				}
 			}
 		}
 	}
 
 	/**
 	 * Deallocates the dual-tier concurrent execution infrastructure and dissolves operational states.
 	 * <p>
 	 * This structural shutdown hook safely liquidates asynchronous runtimes by issuing immediate
 	 * cancellation signals via {@link ExecutorService#shutdownNow()} to both the high-frequency tick scheduler
 	 * and the sequential data transfer queue. Active backup threads executing file system operations
 	 * are granted a strict temporal grace window to cooperatively wind down file handles.
 	 * <p>
 	 * Upon pool expiration, all underlying job context data models are purged of volatile execution parameters
 	 * and the associated hardware {@link TrayIcon} is stripped from the operating system shell to ensure
 	 * zero resource leaks.
 	 * <p>
 	 *
 	 * @param timeout The maximum synchronization epoch in milliseconds granted to active
 	 *                I/O operations to complete task evaluation loops before
 	 *                the lifecycle boundary is forcibly closed.
 	 */
 	private void shutdownExecutors( final long timeout ) {
 		Debug.printDebug( "[Bg Controller] Dissolving executor pools and cleaning up task contexts." );
 
 		if( scheduler != null ) {
 			scheduler.shutdownNow();
 		}
 
 		if( workerQueue != null ) {
 			// Drops instant interrupt signals down to the thread executing the active copy sequence
 			workerQueue.shutdownNow();
 			try {
 				if( !workerQueue.awaitTermination( timeout, TimeUnit.MILLISECONDS ) ) {
 					Debug.printDebug( "[Bg Controller] Worker queue termination delayed. Enforcing lifecycle exit." );
 				}
 			}catch( InterruptedException _ ) {
 				Thread.currentThread().interrupt();
 			}
 		}
 
 		// Clean up framework tracking tokens across the execution stack
 		for( final SyncJobContext job : jobList ) {
 			job.setRunning( false );
 			job.setActiveWorkerThread( null );
 		}
 
 		// Remove indicator shell icons
 		if( sysTray != null && bgView != null && bgView.getTrayIcon() != null ) {
 			sysTray.remove( bgView.getTrayIcon() );
 		}
 
 		Debug.printDebug( "[Bg Controller] Background-Daemon terminated cleanly." );
 	}
 
 	/**
 	 * Configures the internal asynchronous execution environment for isolation testing.
 	 * <p>
 	 * This configuration interface swaps out production thread pools with deterministic
 	 * mock implementations and scales execution time windows. It guarantees atomic evaluation
 	 * boundaries without leaking OS threads during unit test runs.
 	 * </p>
 	 *
 	 * @param multiplier  The scaling factor applied to time calculations (e.g., fractional values)
 	 * @param bgView      The background view for ui interactions.
 	 * @param scheduler   The scheduled executor tracking the heartbeat loops
 	 * @param workerQueue The sequential worker queue processing pending sync transfers
 	 */
 	private void setEnvironment( final double multiplier, final BgView bgView, final ScheduledExecutorService scheduler, final ExecutorService workerQueue ) {
 		if( multiplier > 0.0 ) this.timeMultiplier = multiplier;
 		if( bgView != null ) this.bgView = bgView;
 		if( scheduler != null ) this.scheduler = scheduler;
 		if( workerQueue != null ) this.workerQueue = workerQueue;
 	}
 }