using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using IPA.Logging;
using IPA.Utilities;
using Newtonsoft.Json;
using Version = SemVer.Version;

namespace IPA.Loader
{
    /// <summary>
    /// A type to manage the loading of plugins.
    /// </summary>
    public class PluginLoader
    {
        /// <summary>
        /// The directory to load plugins from.
        /// </summary>
        public static string PluginsDirectory => Path.Combine(BeatSaber.InstallPath, "Plugins");

        internal static Task LoadTask() => Task.Run(() =>
        {
            LoadMetadata();
            Logger.log.Debug(string.Join(", ", PluginsMetadata));
            Resolve();
            Logger.log.Debug(string.Join(", ", PluginsMetadata));
            ComputeLoadOrder();
        });

        /// <summary>
        /// A class which describes
        /// </summary>
        public class PluginMetadata
        {
            // ReSharper disable once UnusedAutoPropertyAccessor.Global
            /// <summary>
            /// The assembly the plugin was loaded from.
            /// </summary>
            public Assembly Assembly { get; internal set; }
            /// <summary>
            /// The Type that is the main type for the plugin.
            /// </summary>
            public Type PluginType { get; internal set; }
            /// <summary>
            /// The human readable name of the plugin.
            /// </summary>
            public string Name { get; internal set; }
            /// <summary>
            /// The ModSaber ID of the plugin, or null if it doesn't have one.
            /// </summary>
            public string Id { get; internal set; }
            /// <summary>
            /// The version of the plugin.
            /// </summary>
            public Version Version { get; internal set; }
            /// <summary>
            /// The file the plugin was loaded from.
            /// </summary>
            public FileInfo File { get; internal set; }
            // ReSharper disable once UnusedAutoPropertyAccessor.Global
            /// <summary>
            /// The features this plugin requests.
            /// </summary>
            public string[] Features { get; internal set; }

            private PluginManifest manifest;
            internal PluginManifest Manifest
            {
                get => manifest;
                set
                {
                    manifest = value;
                    Name = value.Name;
                    Version = value.Version;
                    Id = value.Id;
                    Features = value.Features;
                }
            }

            /// <inheritdoc />
            public override string ToString() => $"{Name}({Id}@{Version})({PluginType?.AssemblyQualifiedName}) from '{File.Name}'";
        }

        /// <summary>
        /// A container object for all the data relating to a plugin.
        /// </summary>
        public class PluginInfo
        {
            internal IBeatSaberPlugin Plugin { get; set; }
            internal string Filename { get; set; }
            /// <summary>
            /// Metadata for the plugin.
            /// </summary>
            public PluginMetadata Metadata { get; internal set; } = new PluginMetadata();
        }

        internal static List<PluginMetadata> PluginsMetadata = new List<PluginMetadata>();

        internal static void LoadMetadata()
        {
            string[] plugins = Directory.GetFiles(PluginsDirectory, "*.dll");

            try
            {
                var selfmeta = new PluginMetadata
                {
                    Assembly = Assembly.ReflectionOnlyLoadFrom(Assembly.GetExecutingAssembly()
                        .Location), // load self as reflection only
                    File = new FileInfo(Path.Combine(BeatSaber.InstallPath, "IPA.exe")),
                    PluginType = null
                };

                string manifest;
                using (var manifestReader =
                    new StreamReader(
                        selfmeta.Assembly.GetManifestResourceStream(typeof(PluginLoader), "manifest.json") ??
                        throw new InvalidOperationException()))
                    manifest = manifestReader.ReadToEnd();

                selfmeta.Manifest = JsonConvert.DeserializeObject<PluginManifest>(manifest);

                PluginsMetadata.Add(selfmeta);
            }
            catch (Exception e)
            {
                Logger.loader.Critical("Error loading own manifest");
                Logger.loader.Critical(e);
            }

            foreach (var plugin in plugins)
            { // should probably do patching first /shrug
                try
                {
                    var metadata = new PluginMetadata();

                    var assembly = Assembly.ReflectionOnlyLoadFrom(plugin);
                    metadata.Assembly = assembly;
                    metadata.File = new FileInfo(plugin);

                    Type[] types;
                    try
                    {
                        types = assembly.GetTypes();
                    }
                    catch (ReflectionTypeLoadException e)
                    {
                        types = e.Types;
                    }
                    foreach (var type in types)
                    {
                        if (type == null) continue;

                        var iInterface = type.GetInterface(nameof(IBeatSaberPlugin));
                        if (iInterface == null) continue;
                        metadata.PluginType = type;
                        break;
                    }

                    if (metadata.PluginType == null)
                    {
                        Logger.loader.Warn($"Could not find plugin type for {Path.GetFileName(plugin)}");
                        continue;
                    }

                    Stream metadataStream;
                    try
                    {
                        metadataStream = assembly.GetManifestResourceStream(metadata.PluginType, "manifest.json");
                        if (metadataStream == null)
                        {
                            Logger.loader.Error($"manifest.json not found in plugin {Path.GetFileName(plugin)}");
                            continue;
                        }
                    }
                    catch (FileNotFoundException)
                    {
                        Logger.loader.Error($"manifest.json not found in plugin {Path.GetFileName(plugin)}");
                        continue;
                    }

                    string manifest;
                    using (var manifestReader = new StreamReader(metadataStream))
                        manifest = manifestReader.ReadToEnd();

                    metadata.Manifest = JsonConvert.DeserializeObject<PluginManifest>(manifest);

                    PluginsMetadata.Add(metadata);
                }
                catch (Exception e)
                {
                    Logger.loader.Error($"Could not load data for plugin {Path.GetFileName(plugin)}");
                    Logger.loader.Error(e);
                }
            }
        }

        internal static void Resolve()
        { // resolves duplicates and conflicts, etc
            PluginsMetadata.Sort((a, b) => a.Version.CompareTo(b.Version));
            
            var ids = new HashSet<string>();
            var ignore = new HashSet<PluginMetadata>();
            var resolved = new List<PluginMetadata>(PluginsMetadata.Count);
            foreach (var meta in PluginsMetadata)
            {
                if (meta.Id != null)
                {
                    if (ids.Contains(meta.Id))
                    {
                        Logger.loader.Warn($"Found duplicates of {meta.Id}, using newest");
                        ignore.Add(meta);
                        continue; // because of sorted order, hightest order will always be the first one
                    }

                    bool processedLater = false;
                    foreach (var meta2 in PluginsMetadata)
                    {
                        if (ignore.Contains(meta2)) continue;
                        if (meta == meta2)
                        {
                            processedLater = true;
                            continue;
                        }

                        if (!meta2.Manifest.Conflicts.ContainsKey(meta.Id)) continue;

                        var range = meta2.Manifest.Conflicts[meta.Id];
                        if (!range.IsSatisfied(meta.Version)) continue;

                        Logger.loader.Warn($"{meta.Id}@{meta.Version} conflicts with {meta2.Name}");

                        if (processedLater)
                        {
                            Logger.loader.Warn($"Ignoring {meta2.Name}");
                            ignore.Add(meta2);
                        }
                        else
                        {
                            Logger.loader.Warn($"Ignoring {meta.Name}");
                            ignore.Add(meta);
                            break;
                        }
                    }
                }

                if (ignore.Contains(meta)) continue;
                if (meta.Id != null) ids.Add(meta.Id);

                resolved.Add(meta);
            }

            PluginsMetadata = resolved;
        }

        internal static void ComputeLoadOrder()
        {
            PluginsMetadata.Sort((a, b) =>
            {
                if (a.Id == b.Id) return 0;
                if (a.Id != null)
                {
                    if (b.Manifest.Dependencies.ContainsKey(a.Id) || b.Manifest.LoadAfter.Contains(a.Id)) return -1;
                    if (b.Manifest.LoadBefore.Contains(a.Id)) return 1;
                }
                if (b.Id != null)
                {
                    if (a.Manifest.Dependencies.ContainsKey(b.Id) || a.Manifest.LoadAfter.Contains(b.Id)) return 1;
                    if (a.Manifest.LoadBefore.Contains(b.Id)) return -1;
                }

                return 0;
            });
            Logger.log.Debug(string.Join(", ", PluginsMetadata));

            var metadata = new List<PluginMetadata>();
            var pluginsToLoad = new Dictionary<string, Version>();
            foreach (var meta in PluginsMetadata)
            {
                bool load = true;
                foreach (var dep in meta.Manifest.Dependencies)
                {
                    if (pluginsToLoad.ContainsKey(dep.Key) && dep.Value.IsSatisfied(pluginsToLoad[dep.Key])) continue;

                    load = false;
                    Logger.loader.Warn($"{meta.Name} is missing dependency {dep.Key}@{dep.Value}");
                }

                if (load)
                {
                    metadata.Add(meta);
                    if (meta.Id != null)
                        pluginsToLoad.Add(meta.Id, meta.Version);
                }
            }

            PluginsMetadata = metadata;
        }

        internal static void LoadPlugins()
        {

        }
    }
}