// Copyright (C) Stichting Deltares 2025. All rights reserved.
// 
// This file is part of the application DAM - UI.
// 
// DAM - UI 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/>.
// 
// All names, logos, and references to "Deltares" are registered trademarks of
// Stichting Deltares and remain full property of Stichting Deltares at all times.
// All rights reserved.

using System;
using System.Collections.Generic;
using System.Linq;
using Deltares.Dam.Tests.TestUtils;
using NUnit.Framework;

namespace Deltares.Dam.TestHelper.TestUtils;

/// <summary>
///     A base class providing template methods to be used for performing
///     memory leak tests.
/// </summary>
/// <remarks>This class is working purely on non-GUI level.</remarks>
[TestFixture]
public abstract class MemoryLeakTestBase
{
    private ObjectLeakMonitor objectLeakMonitor;
    private ObjectLeakMonitor[] directCompositeChildrenLeakMonitors;

    [TearDown]
    public void TearDown()
    {
        objectLeakMonitor = null;
        directCompositeChildrenLeakMonitors = null;
    }

    /// <summary>
    ///     Clear all static caches that should be cleared at end of application
    /// </summary>
    private void ClearStaticCaches()
    {
        // Clear all static, non-GUI caches here
    }

    protected bool MonitorMemoryLeakage<T>(Func<T, IEnumerable<object>> getMonitoredChildren, out string report) where T : class, IDisposable, new()
    {
        PerformMemoryMeasurements(() => new T(), getMonitoredChildren);

        bool isLeaking = CreateMemoryLeakReport(objectLeakMonitor, directCompositeChildrenLeakMonitors, out string memoryLeakReport);
        if (!isLeaking)
        {
            Console.WriteLine(memoryLeakReport);
        }

        report = memoryLeakReport;
        return isLeaking;
    }

    /// <summary>
    ///     Performs the memory measurements.
    /// </summary>
    /// <typeparam name="T">The object type to be monitored. It's default constructor will be used.</typeparam>
    /// <param name="createMonitoredObject">The object creation method.</param>
    /// <param name="getMonitoredChildren">The get monitored children.</param>
    /// <remarks>
    ///     <p>
    ///         The creation is performed in a separate method than where the <see cref="ObjectLeakMonitor" /> are checked to
    ///         ensure the objects will be garbage collected.
    ///     </p>
    /// </remarks>
    private void PerformMemoryMeasurements<T>(Func<T> createMonitoredObject, Func<T, IEnumerable<object>> getMonitoredChildren) where T : class, IDisposable
    {
        using (T objectToMonitor = createMonitoredObject())
        {
            objectLeakMonitor = new ObjectLeakMonitor(objectToMonitor);
            directCompositeChildrenLeakMonitors = getMonitoredChildren != null
                                                      ? getMonitoredChildren(objectToMonitor)
                                                        .Select(mc => new ObjectLeakMonitor(mc))
                                                        .ToArray()
                                                      : null;
        }

        ClearStaticCaches();
    }

    /// <summary>
    ///     Creates the memory leak report.
    /// </summary>
    /// <param name="monitor">The monitor for the object under test.</param>
    /// <param name="compositeChildrenLeakMonitors">The composite children leak monitors.</param>
    /// <param name="report">Output: The memory leak report.</param>
    /// <returns>True if a memory or object leak has been detected; False otherwise.</returns>
    private bool CreateMemoryLeakReport(ObjectLeakMonitor monitor, ObjectLeakMonitor[] compositeChildrenLeakMonitors, out string report)
    {
        report = Environment.NewLine + "=================================================================" + Environment.NewLine;
        report += "Memory leak report for " + monitor.MonitoredObjectType + Environment.NewLine;
        report += "Object garbage collected: " + !monitor.ObjectIsAlive() + Environment.NewLine;

        if ((compositeChildrenLeakMonitors != null) && compositeChildrenLeakMonitors.Any())
        {
            report += "All monitored composite children garbage collected: " + compositeChildrenLeakMonitors.All(c => !c.ObjectIsAlive()) + Environment.NewLine;

            foreach (ObjectLeakMonitor compositeChildrenLeakMonitor in compositeChildrenLeakMonitors)
            {
                report += "\tChild (" + compositeChildrenLeakMonitor.MonitoredObjectType + ") garbage collected: " + !compositeChildrenLeakMonitor.ObjectIsAlive() + Environment.NewLine;
            }
        }

        report += "=================================================================";

        return monitor.ObjectIsAlive() || ((compositeChildrenLeakMonitors != null) && compositeChildrenLeakMonitors.Any(c => c.ObjectIsAlive()));
    }
}