// Copyright (C) Stichting Deltares 2019. All rights reserved.
//
// This file is part of the Delta Shell Light Library.
//
// The Delta Shell Light Library 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 NUnit.Framework;

namespace Deltares.Dam.Tests.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
    {
        [TearDown]
        public void TearDown()
        {
            objectLeakMonitor = null;
            directCompositeChildrenLeakMonitors = null;
        }

        private ObjectLeakMonitor objectLeakMonitor;
        private ObjectLeakMonitor[] directCompositeChildrenLeakMonitors;

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

        protected void MonitorMemoryLeakage<T>(Func<T> createMonitoredObject, Func<T, IEnumerable<object>> getMonitoredChildren) where T : class, IDisposable
        {
            PerformMemoryMeasurements(createMonitoredObject, getMonitoredChildren);

            string report;
            var isLeaking = CreateMemoryLeakReport(objectLeakMonitor, directCompositeChildrenLeakMonitors, out report);
            if (!isLeaking)
            {
                Console.WriteLine(report);
            }
            Assert.IsFalse(isLeaking, report);
        }

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

            string report;
            var isLeaking = CreateMemoryLeakReport(objectLeakMonitor, directCompositeChildrenLeakMonitors, out report);
            if (!isLeaking)
            {
                Console.WriteLine(report);
            }
            Assert.IsFalse(isLeaking, report);
        }

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

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

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