// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Collections.Generic;

using Microsoft.VisualStudio.TestPlatform.ObjectModel;
using Microsoft.VisualStudio.TestPlatform.ObjectModel.DataCollection;
using Microsoft.VisualStudio.TestPlatform.Utilities;

namespace Microsoft.VisualStudio.TestPlatform.Common.DataCollector;

/// <summary>
/// The test platform data collection events.
/// </summary>
internal sealed class TestPlatformDataCollectionEvents : DataCollectionEvents
{
    /// <summary>
    /// Maps the type of event args to the multi cast delegate for that event
    /// </summary>
    private readonly Dictionary<Type, EventInvoker> _eventArgsToEventInvokerMap;

    /// <summary>
    /// Initializes a new instance of the <see cref="TestPlatformDataCollectionEvents"/> class by mapping the types of expected event args to the multi cast
    /// delegate that invokes the event on registered targets
    /// </summary>
    internal TestPlatformDataCollectionEvents()
    {
        _eventArgsToEventInvokerMap = new Dictionary<Type, EventInvoker>(4)
        {
            [typeof(TestHostLaunchedEventArgs)] = OnTestHostLaunched,
            [typeof(SessionStartEventArgs)] = OnSessionStart,
            [typeof(SessionEndEventArgs)] = OnSessionEnd,
            [typeof(TestCaseStartEventArgs)] = OnTestCaseStart,
            [typeof(TestCaseEndEventArgs)] = OnTestCaseEnd
        };
    }

    /// <summary>
    /// Delegate for the event invoker methods (OnSessionStart, OnTestCaseResume, etc.)
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private delegate void EventInvoker(DataCollectionEventArgs e);

    /// <summary>
    /// Raised when test host process has initialized
    /// </summary>
    public override event EventHandler<TestHostLaunchedEventArgs>? TestHostLaunched;

    /// <summary>
    /// Raised when a session is starting
    /// </summary>
    public override event EventHandler<SessionStartEventArgs>? SessionStart;

    /// <summary>
    /// Raised when a session is ending
    /// </summary>
    public override event EventHandler<SessionEndEventArgs>? SessionEnd;

    /// <summary>
    /// Raised when a test case is starting
    /// </summary>
    public override event EventHandler<TestCaseStartEventArgs>? TestCaseStart;

    /// <summary>
    /// Raised when a test case is ending
    /// </summary>
    public override event EventHandler<TestCaseEndEventArgs>? TestCaseEnd;

    /// <summary>
    /// Raises the event corresponding to the event arguments to all registered handlers
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    internal void RaiseEvent(DataCollectionEventArgs e)
    {
        ValidateArg.NotNull(e, nameof(e));

        if (_eventArgsToEventInvokerMap.TryGetValue(e.GetType(), out var onEvent))
        {
            onEvent(e);
        }
        else
        {
            EqtTrace.Fail("TestPlatformDataCollectionEvents.RaiseEvent: Unrecognized data collection event of type {0}.", e.GetType().FullName);
        }
    }

    /// <summary>
    /// Checks whether any data collector has subscribed for test case events.
    /// </summary>
    internal bool AreTestCaseEventsSubscribed()
    {
        bool valueOnFailure = false;
        return (HasEventListener(TestCaseStart, valueOnFailure) || HasEventListener(TestCaseEnd, valueOnFailure));
    }

    private static bool HasEventListener(MulticastDelegate? eventToCheck, bool valueOnFailure)
    {
        try
        {
            if (eventToCheck == null)
            {
                return false;
            }

            Delegate[] listeners = eventToCheck.GetInvocationList();
            return listeners != null && listeners.Length != 0;
        }
        catch (Exception ex)
        {
            EqtTrace.Error("TestPlatformDataCollectionEvents.AreTestCaseLevelEventsRequired: Exception occurred while checking whether event {0} has any listeners or not. {1}", eventToCheck, ex);
            return valueOnFailure;
        }
    }

    /// <summary>
    /// Raises the TestHostLaunched event
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private void OnTestHostLaunched(DataCollectionEventArgs e)
    {
        TestHostLaunched.SafeInvoke(this, e, "DataCollectionEvents.TestHostLaunched");
    }

    /// <summary>
    /// Raises the SessionStart event
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private void OnSessionStart(DataCollectionEventArgs e)
    {
        SessionStart.SafeInvoke(this, e, "DataCollectionEvents.SessionStart");
    }

    /// <summary>
    /// Raises the SessionEnd event
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private void OnSessionEnd(DataCollectionEventArgs e)
    {
        SessionEnd.SafeInvoke(this, e, "DataCollectionEvents.SessionEnd");
    }

    /// <summary>
    /// Raises the TestCaseStart event
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private void OnTestCaseStart(DataCollectionEventArgs e)
    {
        TestCaseStart.SafeInvoke(this, e, "DataCollectionEvents.TestCaseStart");
    }

    /// <summary>
    /// Raises the TestCaseEnd event
    /// </summary>
    /// <param name="e">
    /// Contains the event data
    /// </param>
    private void OnTestCaseEnd(DataCollectionEventArgs e)
    {
        TestCaseEnd.SafeInvoke(this, e, "DataCollectionEvents.TestCaseEnd");
    }
}