// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using Microsoft.Build.Execution;

#nullable disable

namespace Microsoft.Build.BackEnd
{
    /// <summary>
    /// The NodeManager class is responsible for marshalling data to/from the NodeProviders and organizing the
    /// creation of new nodes on request.
    /// </summary>
    internal class TaskHostNodeManager : INodeManager
    {
        /// <summary>
        /// The node provider for task hosts.
        /// </summary>
        private INodeProvider _outOfProcTaskHostNodeProvider;

        /// <summary>
        /// The build component host.
        /// </summary>
        private IBuildComponentHost _componentHost;

        /// <summary>
        /// Tracks whether ShutdownComponent has been called.
        /// </summary>
        private bool _componentShutdown;

        /// <summary>
        /// Constructor.
        /// </summary>
        private TaskHostNodeManager()
        {
            // do nothing
        }

        #region INodeManager Members

        /// <summary>
        /// Creates a node on an available NodeProvider, if any..
        /// Not used - base class <see cref="NodeProviderOutOfProcBase"/> implementation is reused instead.
        /// </summary>
        public IList<NodeInfo> CreateNodes(NodeConfiguration configuration, NodeAffinity affinity, int numberOfNodesToCreate)
            => throw new NotSupportedException("not used");

        /// <summary>
        /// Sends data to the specified node.
        /// </summary>
        /// <param name="node">The node.</param>
        /// <param name="packet">The packet to send.</param>
        public void SendData(int node, INodePacket packet)
        {
            throw new NotSupportedException("not used");
        }

        /// <summary>
        /// Shuts down all of the connected managed nodes.
        /// </summary>
        /// <param name="enableReuse">Flag indicating if nodes should prepare for reuse.</param>
        public void ShutdownConnectedNodes(bool enableReuse)
        {
            Assumed.False(_componentShutdown, "We should never be calling ShutdownNodes after ShutdownComponent has been called");
            _outOfProcTaskHostNodeProvider?.ShutdownConnectedNodes(enableReuse);
        }

        /// <summary>
        /// Shuts down all of the managed nodes permanently.
        /// </summary>
        public void ShutdownAllNodes()
        {
            _outOfProcTaskHostNodeProvider?.ShutdownAllNodes();
        }
        #endregion

        #region IBuildComponent Members

        /// <summary>
        /// Initializes the component
        /// </summary>
        /// <param name="host">The component host</param>
        public void InitializeComponent(IBuildComponentHost host)
        {
            Assumed.Null(_componentHost, "TaskHostNodeManager already initialized.");
            Assumed.NotNull(host, "We can't create a TaskHostNodeManager with a null componentHost");

            _componentHost = host;
            _outOfProcTaskHostNodeProvider = _componentHost.GetComponent(BuildComponentType.OutOfProcTaskHostNodeProvider) as INodeProvider;
            _componentShutdown = false;
        }

        /// <summary>
        /// Shuts down the component.
        /// </summary>
        public void ShutdownComponent()
        {
            _outOfProcTaskHostNodeProvider = null;
            _componentHost = null;
            _componentShutdown = true;

            ClearPerBuildState();
        }

        /// <summary>
        /// Reset the state of objects in the node manager which need to be reset between builds.
        /// </summary>
        public void ClearPerBuildState()
        {
            // do nothing
        }

        #endregion

        #region INodePacketFactory Members

        /// <summary>
        /// Registers the specified handler for a particular packet type.
        /// </summary>
        /// <param name="packetType">The packet type.</param>
        /// <param name="factory">The factory for packets of the specified type.</param>
        /// <param name="handler">The handler to be called when packets of the specified type are received.</param>
        public void RegisterPacketHandler(NodePacketType packetType, NodePacketFactoryMethod factory, INodePacketHandler handler)
        {
            throw new NotSupportedException("not used");
        }

        /// <summary>
        /// Unregisters a packet handler.
        /// </summary>
        /// <param name="packetType">The packet type.</param>
        public void UnregisterPacketHandler(NodePacketType packetType)
        {
            throw new NotSupportedException("not used");
        }

        /// <summary>
        /// Takes a serializer, deserializes the packet and routes it to the appropriate handler.
        /// </summary>
        /// <param name="nodeId">The node from which the packet was received.</param>
        /// <param name="packetType">The packet type.</param>
        /// <param name="translator">The translator containing the data from which the packet should be reconstructed.</param>
        public void DeserializeAndRoutePacket(int nodeId, NodePacketType packetType, ITranslator translator)
        {
            throw new NotSupportedException("not used");
        }

        /// <summary>
        /// Takes a serializer, deserializes the packet and routes it to the appropriate handler.
        /// </summary>
        /// <param name="packetType">The packet type.</param>
        /// <param name="translator">The translator containing the data from which the packet should be reconstructed.</param>
        public INodePacket DeserializePacket(NodePacketType packetType, ITranslator translator)
        {
            throw new NotSupportedException("not used");
        }

        /// <summary>
        /// Routes the specified packet. This is called by the Inproc node directly since it does not have to do any deserialization
        /// </summary>
        /// <param name="nodeId">The node from which the packet was received.</param>
        /// <param name="packet">The packet to route.</param>
        public void RoutePacket(int nodeId, INodePacket packet)
        {
            throw new NotSupportedException("not used");
        }

        #endregion

        /// <summary>
        /// Factory for component creation.
        /// </summary>
        internal static IBuildComponent CreateComponent(BuildComponentType type)
        {
            Assumed.Equal(type, BuildComponentType.TaskHostNodeManager, $"Cannot create component of type {type}");
            return new TaskHostNodeManager();
        }

        IEnumerable<Process> INodeManager.GetProcesses()
        {
            return _outOfProcTaskHostNodeProvider.GetProcesses();
        }
    }
}