using System.Text;

using Lua;
using Lua.Standard;

namespace AIStudio.Tools.PluginSystem;

public static partial class PluginFactory
{
    private static readonly List<IAvailablePlugin> AVAILABLE_PLUGINS = [];
    private static readonly SemaphoreSlim PLUGIN_LOAD_SEMAPHORE = new(1, 1);
    
    /// <summary>
    /// A list of all available plugins.
    /// </summary>
    public static IReadOnlyCollection<IPluginMetadata> AvailablePlugins => AVAILABLE_PLUGINS;
    
    /// <summary>
    /// Try to load all plugins from the plugins directory.
    /// </summary>
    /// <remarks>
    /// Loading plugins means:<br/>
    /// - Parsing and checking the plugin code<br/>
    /// - Check for forbidden plugins<br/>
    /// - Creating a new instance of the allowed plugin<br/>
    /// - Read the plugin metadata<br/>
    /// <br/>
    /// Loading a plugin does not mean to start the plugin, though.
    /// </remarks>
    public static async Task LoadAll(CancellationToken cancellationToken = default)
    {
        if (!IS_INITIALIZED)
        {
            LOG.LogError("PluginFactory is not initialized. Please call Setup() before using it.");
            return;
        }
        
        if (!await PLUGIN_LOAD_SEMAPHORE.WaitAsync(0, cancellationToken))
            return;

        try
        {
            LOG.LogInformation("Start loading plugins.");
            if (!Directory.Exists(PLUGINS_ROOT))
            {
                LOG.LogInformation("No plugins found.");
                return;
            }
        
            AVAILABLE_PLUGINS.Clear();
        
            //
            // The easiest way to load all plugins is to find all `plugin.lua` files and load them.
            // By convention, each plugin is enforced to have a `plugin.lua` file.
            //
            var pluginMainFiles = Directory.EnumerateFiles(PLUGINS_ROOT, "plugin.lua", SearchOption.AllDirectories);
            foreach (var pluginMainFile in pluginMainFiles)
            {
                if (cancellationToken.IsCancellationRequested)
                    break;
            
                LOG.LogInformation($"Try to load plugin: {pluginMainFile}");
                var code = await File.ReadAllTextAsync(pluginMainFile, Encoding.UTF8, cancellationToken);
                var pluginPath = Path.GetDirectoryName(pluginMainFile)!;
                var plugin = await Load(pluginPath, code, cancellationToken);
            
                switch (plugin)
                {
                    case NoPlugin noPlugin when noPlugin.Issues.Any():
                        LOG.LogError($"Was not able to load plugin: '{pluginMainFile}'. Reason: {noPlugin.Issues.First()}");
                        continue;
                
                    case NoPlugin:
                        LOG.LogError($"Was not able to load plugin: '{pluginMainFile}'. Reason: Unknown.");
                        continue;
                
                    case { IsValid: false }:
                        LOG.LogError($"Was not able to load plugin '{pluginMainFile}', because the Lua code is not a valid AI Studio plugin. There are {plugin.Issues.Count()} issues to fix. First issue is: {plugin.Issues.FirstOrDefault()}");
                        #if DEBUG
                        foreach (var pluginIssue in plugin.Issues)
                            LOG.LogError($"Plugin issue: {pluginIssue}");
                        #endif
                        continue;

                    case { IsMaintained: false }:
                        LOG.LogWarning($"The plugin '{pluginMainFile}' is not maintained anymore. Please consider to disable it.");
                        break;
                }
            
                LOG.LogInformation($"Successfully loaded plugin: '{pluginMainFile}' (Id='{plugin.Id}', Type='{plugin.Type}', Name='{plugin.Name}', Version='{plugin.Version}', Authors='{string.Join(", ", plugin.Authors)}')");
                AVAILABLE_PLUGINS.Add(new PluginMetadata(plugin, pluginPath));
            }
        
            // Start or restart all plugins:
            await RestartAllPlugins(cancellationToken);
        }
        finally
        {
            PLUGIN_LOAD_SEMAPHORE.Release();
            LOG.LogInformation("Finished loading plugins.");
        }
    }

    public static async Task<PluginBase> Load(string? pluginPath, string code, CancellationToken cancellationToken = default)
    {
        if(ForbiddenPlugins.Check(code) is { IsForbidden: true } forbiddenState)
            return new NoPlugin($"This plugin is forbidden: {forbiddenState.Message}");
        
        var state = LuaState.Create();
        if (!string.IsNullOrWhiteSpace(pluginPath))
        {
            // Add the module loader so that the plugin can load other Lua modules:
            state.ModuleLoader = new PluginLoader(pluginPath);
        }

        // Add some useful libraries:
        state.OpenModuleLibrary();
        state.OpenStringLibrary();
        state.OpenTableLibrary();
        state.OpenMathLibrary();
        state.OpenBitwiseLibrary();
        state.OpenCoroutineLibrary();

        try
        {
            await state.DoStringAsync(code, cancellationToken: cancellationToken);
        }
        catch (LuaParseException e)
        {
            return new NoPlugin($"Was not able to parse the plugin: {e.Message}");
        }
        catch (LuaRuntimeException e)
        {
            return new NoPlugin($"Was not able to run the plugin: {e.Message}");
        }
        
        if (!state.Environment["TYPE"].TryRead<string>(out var typeText))
            return new NoPlugin("TYPE does not exist or is not a valid string.");
        
        if (!Enum.TryParse<PluginType>(typeText, out var type))
            return new NoPlugin($"TYPE is not a valid plugin type. Valid types are: {CommonTools.GetAllEnumValues<PluginType>()}");
        
        if(type is PluginType.NONE)
            return new NoPlugin($"TYPE is not a valid plugin type. Valid types are: {CommonTools.GetAllEnumValues<PluginType>()}");
        
        var isInternal = !string.IsNullOrWhiteSpace(pluginPath) && pluginPath.StartsWith(INTERNAL_PLUGINS_ROOT, StringComparison.OrdinalIgnoreCase);
        return type switch
        {
            PluginType.LANGUAGE => new PluginLanguage(isInternal, state, type),
            
            _ => new NoPlugin("This plugin type is not supported yet. Please try again with a future version of AI Studio.")
        };
    }
}