#nullable enable
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Text.Json;
using MediaBrowser.Common;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Common.Json;
using MediaBrowser.Common.Plugins;
using MediaBrowser.Model.Configuration;
using MediaBrowser.Model.Plugins;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace Emby.Server.Implementations.Plugins
{
    /// <summary>
    /// Defines the <see cref="PluginManager" />.
    /// </summary>
    public class PluginManager : IPluginManager
    {
        private readonly string _pluginsPath;
        private readonly Version _appVersion;
        private readonly JsonSerializerOptions _jsonOptions;
        private readonly ILogger<PluginManager> _logger;
        private readonly IApplicationHost _appHost;
        private readonly ServerConfiguration _config;
        private readonly IList<LocalPlugin> _plugins;
        private readonly Version _minimumVersion;

        /// <summary>
        /// Initializes a new instance of the <see cref="PluginManager"/> class.
        /// </summary>
        /// <param name="logger">The <see cref="ILogger"/>.</param>
        /// <param name="appHost">The <see cref="IApplicationHost"/>.</param>
        /// <param name="config">The <see cref="ServerConfiguration"/>.</param>
        /// <param name="pluginsPath">The plugin path.</param>
        /// <param name="appVersion">The application version.</param>
        public PluginManager(
            ILogger<PluginManager> logger,
            IApplicationHost appHost,
            ServerConfiguration config,
            string pluginsPath,
            Version appVersion)
        {
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            _pluginsPath = pluginsPath;
            _appVersion = appVersion ?? throw new ArgumentNullException(nameof(appVersion));
            _jsonOptions = JsonDefaults.GetOptions();
            _config = config;
            _appHost = appHost;
            _minimumVersion = new Version(0, 0, 0, 1);
            _plugins = Directory.Exists(_pluginsPath) ? DiscoverPlugins().ToList() : new List<LocalPlugin>();
        }

        /// <summary>
        /// Gets the Plugins.
        /// </summary>
        public IList<LocalPlugin> Plugins => _plugins;

        /// <summary>
        /// Returns all the assemblies.
        /// </summary>
        /// <returns>An IEnumerable{Assembly}.</returns>
        public IEnumerable<Assembly> LoadAssemblies()
        {
            // Attempt to remove any deleted plugins and change any successors to be active.
            for (int a = _plugins.Count - 1; a >= 0; a--)
            {
                var plugin = _plugins[a];
                if (plugin.Manifest.Status == PluginStatus.Deleted && DeletePlugin(plugin))
                {
                    UpdateSuccessors(plugin);
                }
            }

            // Now load the assemblies..
            foreach (var plugin in _plugins)
            {
                CheckIfStillSuperceded(plugin);

                if (plugin.IsEnabledAndSupported == false)
                {
                    _logger.LogInformation("Skipping disabled plugin {Version} of {Name} ", plugin.Version, plugin.Name);
                    continue;
                }

                foreach (var file in plugin.DllFiles)
                {
                    Assembly assembly;
                    try
                    {
                        assembly = Assembly.LoadFrom(file);
                    }
                    catch (FileLoadException ex)
                    {
                        _logger.LogError(ex, "Failed to load assembly {Path}. Disabling plugin.", file);
                        ChangePluginState(plugin, PluginStatus.Malfunctioned);
                        continue;
                    }

                    _logger.LogInformation("Loaded assembly {Assembly} from {Path}", assembly.FullName, file);
                    yield return assembly;
                }
            }
        }

        /// <summary>
        /// Creates all the plugin instances.
        /// </summary>
        public void CreatePlugins()
        {
            _ = _appHost.GetExports<IPlugin>(CreatePluginInstance)
                .Where(i => i != null)
                .ToArray();
        }

        /// <summary>
        /// Registers the plugin's services with the DI.
        /// Note: DI is not yet instantiated yet.
        /// </summary>
        /// <param name="serviceCollection">A <see cref="ServiceCollection"/> instance.</param>
        public void RegisterServices(IServiceCollection serviceCollection)
        {
            foreach (var pluginServiceRegistrator in _appHost.GetExportTypes<IPluginServiceRegistrator>())
            {
                var plugin = GetPluginByType(pluginServiceRegistrator.Assembly.GetType());
                if (plugin == null)
                {
                    _logger.LogError("Unable to find plugin in assembly {Assembly}", pluginServiceRegistrator.Assembly.FullName);
                    continue;
                }

                CheckIfStillSuperceded(plugin);
                if (!plugin.IsEnabledAndSupported)
                {
                    continue;
                }

                try
                {
                    var instance = (IPluginServiceRegistrator?)Activator.CreateInstance(pluginServiceRegistrator);
                    instance?.RegisterServices(serviceCollection);
                }
#pragma warning disable CA1031 // Do not catch general exception types
                catch (Exception ex)
#pragma warning restore CA1031 // Do not catch general exception types
                {
                    _logger.LogError(ex, "Error registering plugin services from {Assembly}.", pluginServiceRegistrator.Assembly.FullName);
                    if (ChangePluginState(plugin, PluginStatus.Malfunctioned))
                    {
                        _logger.LogInformation("Disabling plugin {Path}", plugin.Path);
                    }
                }
            }
        }

        /// <summary>
        /// Imports a plugin manifest from <paramref name="folder"/>.
        /// </summary>
        /// <param name="folder">Folder of the plugin.</param>
        public void ImportPluginFrom(string folder)
        {
            if (string.IsNullOrEmpty(folder))
            {
                throw new ArgumentNullException(nameof(folder));
            }

            // Load the plugin.
            var plugin = LoadManifest(folder);
            // Make sure we haven't already loaded this.
            if (plugin == null || _plugins.Any(p => p.Manifest.Equals(plugin.Manifest)))
            {
                return;
            }

            _plugins.Add(plugin);
            EnablePlugin(plugin);
        }

        /// <summary>
        /// Removes the plugin reference '<paramref name="plugin"/>.
        /// </summary>
        /// <param name="plugin">The plugin.</param>
        /// <returns>Outcome of the operation.</returns>
        public bool RemovePlugin(LocalPlugin plugin)
        {
            if (plugin == null)
            {
                throw new ArgumentNullException(nameof(plugin));
            }

            if (DeletePlugin(plugin))
            {
                return true;
            }

            _logger.LogWarning("Unable to delete {Path}, so marking as deleteOnStartup.", plugin.Path);
            // Unable to delete, so disable.
            return ChangePluginState(plugin, PluginStatus.Deleted);
        }

        /// <summary>
        /// Attempts to find the plugin with and id of <paramref name="id"/>.
        /// </summary>
        /// <param name="id">The <see cref="Guid"/> of plugin.</param>
        /// <param name="version">Optional <see cref="Version"/> of the plugin to locate.</param>
        /// <returns>A <see cref="LocalPlugin"/> if located, or null if not.</returns>
        public LocalPlugin? GetPlugin(Guid id, Version? version = null)
        {
            LocalPlugin? plugin;

            if (version == null)
            {
                // If no version is given, return the current instance.
                var plugins = _plugins.Where(p => p.Id.Equals(id));

                plugin = plugins.FirstOrDefault(p => p.Instance != null);
                if (plugin == null)
                {
                    plugin = plugins.OrderByDescending(p => p.Version).FirstOrDefault();
                }
            }
            else
            {
                // Match id and version number.
                plugin = _plugins.FirstOrDefault(p => p.Id.Equals(id) && p.Version.Equals(version));
            }

            return plugin;
        }

        /// <summary>
        /// Enables the plugin, disabling all other versions.
        /// </summary>
        /// <param name="plugin">The <see cref="LocalPlugin"/> of the plug to disable.</param>
        public void EnablePlugin(LocalPlugin plugin)
        {
            if (plugin == null)
            {
                throw new ArgumentNullException(nameof(plugin));
            }

            if (ChangePluginState(plugin, PluginStatus.Active))
            {
                UpdateSuccessors(plugin);
            }
        }

        /// <summary>
        /// Disable the plugin.
        /// </summary>
        /// <param name="plugin">The <see cref="LocalPlugin"/> of the plug to disable.</param>
        public void DisablePlugin(LocalPlugin plugin)
        {
            if (plugin == null)
            {
                throw new ArgumentNullException(nameof(plugin));
            }

            // Update the manifest on disk
            if (ChangePluginState(plugin, PluginStatus.Disabled))
            {
                UpdateSuccessors(plugin);
            }
        }

        /// <summary>
        /// Disable the plugin.
        /// </summary>
        /// <param name="assembly">The <see cref="Assembly"/> of the plug to disable.</param>
        public void FailPlugin(Assembly assembly)
        {
            // Only save if disabled.
            if (assembly == null)
            {
                throw new ArgumentNullException(nameof(assembly));
            }

            var plugin = _plugins.FirstOrDefault(p => p.DllFiles.Contains(assembly.Location));
            if (plugin == null)
            {
                // A plugin's assembly didn't cause this issue, so ignore it.
                return;
            }

            ChangePluginState(plugin, PluginStatus.Malfunctioned);
        }

        /// <summary>
        /// Saves the manifest back to disk.
        /// </summary>
        /// <param name="manifest">The <see cref="PluginManifest"/> to save.</param>
        /// <param name="path">The path where to save the manifest.</param>
        /// <returns>True if successful.</returns>
        public bool SaveManifest(PluginManifest manifest, string path)
        {
            if (manifest == null)
            {
                return false;
            }

            try
            {
                var data = JsonSerializer.Serialize(manifest, _jsonOptions);
                File.WriteAllText(Path.Combine(path, "meta.json"), data, Encoding.UTF8);
                return true;
            }
#pragma warning disable CA1031 // Do not catch general exception types
            catch (Exception e)
#pragma warning restore CA1031 // Do not catch general exception types
            {
                _logger.LogWarning(e, "Unable to save plugin manifest. {Path}", path);
                return false;
            }
        }

        /// <summary>
        /// Changes a plugin's load status.
        /// </summary>
        /// <param name="plugin">The <see cref="LocalPlugin"/> instance.</param>
        /// <param name="state">The <see cref="PluginStatus"/> of the plugin.</param>
        /// <returns>Success of the task.</returns>
        private bool ChangePluginState(LocalPlugin plugin, PluginStatus state)
        {
            if (plugin.Manifest.Status == state || string.IsNullOrEmpty(plugin.Path))
            {
                // No need to save as the state hasn't changed.
                return true;
            }

            plugin.Manifest.Status = state;
            return SaveManifest(plugin.Manifest, plugin.Path);
        }

        /// <summary>
        /// Finds the plugin record using the type.
        /// </summary>
        /// <param name="type">The <see cref="Type"/> being sought.</param>
        /// <returns>The matching record, or null if not found.</returns>
        private LocalPlugin? GetPluginByType(Type type)
        {
            // Find which plugin it is by the path.
            return _plugins.FirstOrDefault(p => string.Equals(p.Path, Path.GetDirectoryName(type.Assembly.Location), StringComparison.Ordinal));
        }

        /// <summary>
        /// Creates the instance safe.
        /// </summary>
        /// <param name="type">The type.</param>
        /// <returns>System.Object.</returns>
        private IPlugin? CreatePluginInstance(Type type)
        {
            // Find the record for this plugin.
            var plugin = GetPluginByType(type);
            if (plugin?.Manifest.Status < PluginStatus.Active)
            {
                return null;
            }

            try
            {
                _logger.LogDebug("Creating instance of {Type}", type);
                var instance = (IPlugin)ActivatorUtilities.CreateInstance(_appHost.ServiceProvider, type);
                if (plugin == null)
                {
                    // Create a dummy record for the providers.
                    // TODO: remove this code, if all provided have been released as separate plugins.
                    plugin = new LocalPlugin(
                        instance.AssemblyFilePath,
                        true,
                        new PluginManifest
                        {
                            Id = instance.Id,
                            Status = PluginStatus.Active,
                            Name = instance.Name,
                            Version = instance.Version.ToString()
                        })
                    {
                        Instance = instance
                    };

                    _plugins.Add(plugin);

                    plugin.Manifest.Status = PluginStatus.Active;
                }
                else
                {
                    plugin.Instance = instance;
                    var manifest = plugin.Manifest;
                    var pluginStr = plugin.Instance.Version.ToString();
                    bool changed = false;
                    if (string.Equals(manifest.Version, pluginStr, StringComparison.Ordinal))
                    {
                        // If a plugin without a manifest failed to load due to an external issue (eg config),
                        // this updates the manifest to the actual plugin values.
                        manifest.Version = pluginStr;
                        manifest.Name = plugin.Instance.Name;
                        manifest.Description = plugin.Instance.Description;
                        changed = true;
                    }

                    changed = changed || manifest.Status != PluginStatus.Active;
                    manifest.Status = PluginStatus.Active;

                    if (changed)
                    {
                        SaveManifest(manifest, plugin.Path);
                    }
                }

                _logger.LogInformation("Loaded plugin: {PluginName} {PluginVersion}", plugin.Name, plugin.Version);

                return instance;
            }
#pragma warning disable CA1031 // Do not catch general exception types
            catch (Exception ex)
#pragma warning restore CA1031 // Do not catch general exception types
            {
                _logger.LogError(ex, "Error creating {Type}", type.FullName);
                if (plugin != null)
                {
                    if (ChangePluginState(plugin, PluginStatus.Malfunctioned))
                    {
                        _logger.LogInformation("Plugin {Path} has been disabled.", plugin.Path);
                        return null;
                    }
                }

                _logger.LogDebug("Unable to auto-disable.");
                return null;
            }
        }

        private void CheckIfStillSuperceded(LocalPlugin plugin)
        {
            if (plugin.Manifest.Status != PluginStatus.Superceded)
            {
                return;
            }

            var predecessor = _plugins.OrderByDescending(p => p.Version)
                .FirstOrDefault(p => p.Id.Equals(plugin.Id) && p.IsEnabledAndSupported && p.Version != plugin.Version);
            if (predecessor != null)
            {
                return;
            }

            plugin.Manifest.Status = PluginStatus.Active;
        }

        /// <summary>
        /// Attempts to delete a plugin.
        /// </summary>
        /// <param name="plugin">A <see cref="LocalPlugin"/> instance to delete.</param>
        /// <returns>True if successful.</returns>
        private bool DeletePlugin(LocalPlugin plugin)
        {
            // Attempt a cleanup of old folders.
            try
            {
                Directory.Delete(plugin.Path, true);
                _logger.LogDebug("Deleted {Path}", plugin.Path);
                _plugins.Remove(plugin);
            }
#pragma warning disable CA1031 // Do not catch general exception types
            catch
#pragma warning restore CA1031 // Do not catch general exception types
            {
                return false;
            }

            return _plugins.Remove(plugin);
        }

        private LocalPlugin? LoadManifest(string dir)
        {
            try
            {
                Version? version;
                PluginManifest? manifest = null;
                var metafile = Path.Combine(dir, "meta.json");
                if (File.Exists(metafile))
                {
                    try
                    {
                        var data = File.ReadAllText(metafile, Encoding.UTF8);
                        manifest = JsonSerializer.Deserialize<PluginManifest>(data, _jsonOptions);
                    }
#pragma warning disable CA1031 // Do not catch general exception types
                    catch (Exception ex)
#pragma warning restore CA1031 // Do not catch general exception types
                    {
                        _logger.LogError(ex, "Error deserializing {Path}.", dir);
                    }
                }

                if (manifest != null)
                {
                    if (!Version.TryParse(manifest.TargetAbi, out var targetAbi))
                    {
                        targetAbi = _minimumVersion;
                    }

                    if (!Version.TryParse(manifest.Version, out version))
                    {
                        manifest.Version = _minimumVersion.ToString();
                    }

                    return new LocalPlugin(dir, _appVersion >= targetAbi, manifest);
                }

                // No metafile, so lets see if the folder is versioned.
                // TODO: Phase this support out in future versions.
                metafile = dir.Split(Path.DirectorySeparatorChar, StringSplitOptions.RemoveEmptyEntries)[^1];
                int versionIndex = dir.LastIndexOf('_');
                if (versionIndex != -1)
                {
                    // Get the version number from the filename if possible.
                    metafile = Path.GetFileName(dir[..versionIndex]) ?? dir[..versionIndex];
                    version = Version.TryParse(dir.AsSpan()[(versionIndex + 1)..], out Version? parsedVersion) ? parsedVersion : _appVersion;
                }
                else
                {
                    // Un-versioned folder - Add it under the path name and version it suitable for this instance.
                    version = _appVersion;
                }

                // Auto-create a plugin manifest, so we can disable it, if it fails to load.
                manifest = new PluginManifest
                {
                    Status = PluginStatus.Restart,
                    Name = metafile,
                    AutoUpdate = false,
                    Id = metafile.GetMD5(),
                    TargetAbi = _appVersion.ToString(),
                    Version = version.ToString()
                };

                return new LocalPlugin(dir, true, manifest);
            }
#pragma warning disable CA1031 // Do not catch general exception types
            catch (Exception ex)
#pragma warning restore CA1031 // Do not catch general exception types
            {
                _logger.LogError(ex, "Something went wrong!");
                return null;
            }
        }

        /// <summary>
        /// Gets the list of local plugins.
        /// </summary>
        /// <returns>Enumerable of local plugins.</returns>
        private IEnumerable<LocalPlugin> DiscoverPlugins()
        {
            var versions = new List<LocalPlugin>();

            if (!Directory.Exists(_pluginsPath))
            {
                // Plugin path doesn't exist, don't try to enumerate sub-folders.
                return Enumerable.Empty<LocalPlugin>();
            }

            var directories = Directory.EnumerateDirectories(_pluginsPath, "*.*", SearchOption.TopDirectoryOnly);
            LocalPlugin? entry;
            foreach (var dir in directories)
            {
                entry = LoadManifest(dir);
                if (entry != null)
                {
                    versions.Add(entry);
                }
            }

            string lastName = string.Empty;
            versions.Sort(LocalPlugin.Compare);
            // Traverse backwards through the list.
            // The first item will be the latest version.
            for (int x = versions.Count - 1; x >= 0; x--)
            {
                entry = versions[x];
                if (!string.Equals(lastName, entry.Name, StringComparison.OrdinalIgnoreCase))
                {
                    entry.DllFiles.AddRange(Directory.EnumerateFiles(entry.Path, "*.dll", SearchOption.AllDirectories));
                    if (entry.IsEnabledAndSupported)
                    {
                        lastName = entry.Name;
                        continue;
                    }
                }

                if (string.IsNullOrEmpty(lastName))
                {
                    continue;
                }

                var manifest = entry.Manifest;
                var cleaned = false;
                var path = entry.Path;
                if (_config.RemoveOldPlugins)
                {
                    // Attempt a cleanup of old folders.
                    try
                    {
                        _logger.LogDebug("Deleting {Path}", path);
                        Directory.Delete(path, true);
                        cleaned = true;
                    }
#pragma warning disable CA1031 // Do not catch general exception types
                    catch (Exception e)
#pragma warning restore CA1031 // Do not catch general exception types
                    {
                        _logger.LogWarning(e, "Unable to delete {Path}", path);
                    }

                    if (cleaned)
                    {
                        versions.RemoveAt(x);
                    }
                    else
                    {
                        if (manifest == null)
                        {
                            _logger.LogWarning("Unable to disable plugin {Path}", entry.Path);
                            continue;
                        }

                        ChangePluginState(entry, PluginStatus.Deleted);
                    }
                }
            }

            // Only want plugin folders which have files.
            return versions.Where(p => p.DllFiles.Count != 0);
        }

        /// <summary>
        /// Changes the status of the other versions of the plugin to "Superceded".
        /// </summary>
        /// <param name="plugin">The <see cref="LocalPlugin"/> that's master.</param>
        private void UpdateSuccessors(LocalPlugin plugin)
        {
            // This value is memory only - so that the web will show restart required.
            plugin.Manifest.Status = PluginStatus.Restart;

            // Detect whether there is another version of this plugin that needs disabling.
            var predecessor = _plugins.OrderByDescending(p => p.Version)
                .FirstOrDefault(
                    p => p.Id.Equals(plugin.Id)
                    && p.IsEnabledAndSupported
                    && p.Version != plugin.Version);

            if (predecessor == null)
            {
                return;
            }

            if (predecessor.Manifest.Status == PluginStatus.Active && !ChangePluginState(predecessor, PluginStatus.Superceded))
            {
                _logger.LogError("Unable to disable version {Version} of {Name}", predecessor.Version, predecessor.Name);
            }
        }
    }
}