// Copyright (c) .NET Foundation and contributors. 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 System.Diagnostics;
using System.IO;
using System.Xml;

namespace Mono.Linker
{
    /// <summary>
    /// Class which implements IDependencyRecorder and writes the dependencies into an DGML file.
    /// </summary>
    public class DgmlDependencyRecorder : IDependencyRecorder, IDisposable
    {
        public const string DefaultDependenciesFileName = "linker-dependencies.dgml";
        public Dictionary<string, int> nodeList = new();
        public HashSet<(string dependent, string dependee, string reason)> linkList = new(); // first element is source, second is target (dependent --> dependee), third is reason

        private readonly LinkContext context;
        private XmlWriter? writer;
        private Stream? stream;

        public DgmlDependencyRecorder(LinkContext context, string? fileName = null)
        {
            this.context = context;

            XmlWriterSettings settings = new XmlWriterSettings
            {
                Indent = true,
                IndentChars = " "
            };

            fileName ??= DefaultDependenciesFileName;

            if (string.IsNullOrEmpty(Path.GetDirectoryName(fileName)) && !string.IsNullOrEmpty(context.OutputDirectory))
            {
                fileName = Path.Combine(context.OutputDirectory, fileName);
                Directory.CreateDirectory(context.OutputDirectory);
            }

            var depsFile = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None);
            stream = depsFile;

            writer = XmlWriter.Create(stream, settings);
            writer.WriteStartDocument();
            writer.WriteStartElement("DirectedGraph", "http://schemas.microsoft.com/vs/2009/dgml");
        }

        public void FinishRecording()
        {
            Debug.Assert(writer != null);

            writer.WriteStartElement("Nodes");
            {
                foreach (var pair in nodeList)
                {
                    writer.WriteStartElement("Node");
                    writer.WriteAttributeString("Id", pair.Value.ToString());
                    writer.WriteAttributeString("Label", pair.Key);
                    writer.WriteEndElement();
                }
            }
            writer.WriteEndElement();

            writer.WriteStartElement("Links");
            {
                foreach (var tup in linkList)
                {
                    writer.WriteStartElement("Link");
                    writer.WriteAttributeString("Source", nodeList[tup.dependent].ToString());
                    writer.WriteAttributeString("Target", nodeList[tup.dependee].ToString());
                    writer.WriteAttributeString("Reason", tup.reason);
                    writer.WriteEndElement();
                }
            }
            writer.WriteEndElement();

            writer.WriteStartElement("Properties");
            {
                writer.WriteStartElement("Property");
                writer.WriteAttributeString("Id", "Label");
                writer.WriteAttributeString("Label", "Label");
                writer.WriteAttributeString("DataType", "String");
                writer.WriteEndElement();

                writer.WriteStartElement("Property");
                writer.WriteAttributeString("Id", "Reason");
                writer.WriteAttributeString("Label", "Reason");
                writer.WriteAttributeString("DataType", "String");
                writer.WriteEndElement();
            }
            writer.WriteEndElement();

            writer.WriteEndElement();
            writer.WriteEndDocument();

            writer.Flush();
        }

        public void Dispose()
        {
            if (writer == null)
                return;

            writer.Dispose();
            stream?.Dispose();
            writer = null;
            stream = null;
        }

        public void RecordDependency(object target, in DependencyInfo reason, bool marked)
        {
            if (writer == null)
                throw new InvalidOperationException();

            if (reason.Kind == DependencyKind.Unspecified)
                return;

            // For now, just report a dependency from source to target without noting the DependencyKind.
            RecordDependency(reason.Source, target, reason.Kind);
        }

        public void RecordDependency(object? source, object target, object? reason)
        {
            if (writer == null)
                throw new InvalidOperationException();

            if (!DependencyRecorderHelper.ShouldRecord(context, source, target))
                return;

            string dependent = DependencyRecorderHelper.TokenString(context, source);
            string dependee = DependencyRecorderHelper.TokenString(context, target);

            // figure out why nodes are sometimes null, are we missing some information in the graph?
            if (!nodeList.ContainsKey(dependent)) AddNode(dependent);
            if (!nodeList.ContainsKey(dependee)) AddNode(dependee);
            if (source != target)
            {
                AddLink(dependent, dependee, reason);
            }
        }

        private int _nodeIndex;

        void AddNode(string node)
        {
            nodeList.Add(node, _nodeIndex);
            _nodeIndex++;
        }

        void AddLink(string source, string target, object? kind)
        {
            linkList.Add((source, target, DependencyRecorderHelper.TokenString(context, kind)));
        }

        public void RecordDependency(object source, object target, bool marked)
        {
            throw new NotImplementedException();
        }
    }
}