using Microsoft.Extensions.Logging;
using StellaOps.Plugin.Abstractions;
using StellaOps.Plugin.Abstractions.Attributes;
using StellaOps.Plugin.Abstractions.Manifest;
using System.Reflection;

namespace StellaOps.Plugin.Host.Discovery;

/// <summary>
/// Discovers plugins embedded in loaded assemblies.
/// </summary>
public sealed class EmbeddedPluginDiscovery : IPluginDiscovery
{
    private readonly ILogger<EmbeddedPluginDiscovery> _logger;
    private readonly IReadOnlyList<Assembly> _assemblies;

    /// <summary>
    /// Creates a new embedded plugin discovery instance.
    /// </summary>
    /// <param name="logger">Logger instance.</param>
    /// <param name="assemblies">Optional list of assemblies to scan. If null, scans all loaded assemblies.</param>
    public EmbeddedPluginDiscovery(
        ILogger<EmbeddedPluginDiscovery> logger,
        IEnumerable<Assembly>? assemblies = null)
    {
        _logger = logger;
        _assemblies = assemblies?.ToList() ?? [];
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<PluginManifest>> DiscoverAsync(
        IEnumerable<string> searchPaths,
        CancellationToken ct)
    {
        // searchPaths are ignored for embedded discovery
        // We only scan the provided assemblies or the application assemblies
        var manifests = new List<PluginManifest>();

        var assembliesToScan = _assemblies.Count > 0
            ? _assemblies
            : GetApplicationAssemblies();

        foreach (var assembly in assembliesToScan)
        {
            ct.ThrowIfCancellationRequested();

            try
            {
                var pluginTypes = assembly.GetTypes()
                    .Where(t => t.IsClass && !t.IsAbstract && typeof(IPlugin).IsAssignableFrom(t))
                    .ToList();

                foreach (var pluginType in pluginTypes)
                {
                    try
                    {
                        var manifest = CreateManifestFromType(pluginType);
                        if (manifest != null)
                        {
                            manifests.Add(manifest);
                            _logger.LogDebug(
                                "Discovered embedded plugin {PluginId} in assembly {Assembly}",
                                manifest.Info.Id, assembly.GetName().Name);
                        }
                    }
                    catch (Exception ex)
                    {
                        _logger.LogWarning(ex,
                            "Failed to create manifest for type {Type} in assembly {Assembly}",
                            pluginType.FullName, assembly.GetName().Name);
                    }
                }
            }
            catch (ReflectionTypeLoadException ex)
            {
                _logger.LogWarning(ex, "Failed to load types from assembly {Assembly}",
                    assembly.GetName().Name);
            }
        }

        return Task.FromResult<IReadOnlyList<PluginManifest>>(manifests);
    }

    /// <inheritdoc />
    public Task<PluginManifest> DiscoverSingleAsync(PluginSource source, CancellationToken ct)
    {
        if (source.Type != PluginSourceType.Embedded)
            throw new ArgumentException($"Unsupported source type: {source.Type}", nameof(source));

        // Location should be the fully qualified type name
        var typeName = source.Location;

        foreach (var assembly in GetApplicationAssemblies())
        {
            var type = assembly.GetType(typeName);
            if (type != null && typeof(IPlugin).IsAssignableFrom(type))
            {
                var manifest = CreateManifestFromType(type);
                if (manifest != null)
                    return Task.FromResult(manifest);
            }
        }

        throw new InvalidOperationException($"Embedded plugin type not found: {typeName}");
    }

    private static IReadOnlyList<Assembly> GetApplicationAssemblies()
    {
        var entryAssembly = Assembly.GetEntryAssembly();
        if (entryAssembly == null)
            return AppDomain.CurrentDomain.GetAssemblies();

        var referencedNames = entryAssembly.GetReferencedAssemblies();
        var assemblies = new List<Assembly> { entryAssembly };

        foreach (var name in referencedNames)
        {
            try
            {
                assemblies.Add(Assembly.Load(name));
            }
            catch
            {
                // Skip assemblies that can't be loaded
            }
        }

        return assemblies;
    }

    private static PluginManifest? CreateManifestFromType(Type pluginType)
    {
        var attribute = pluginType.GetCustomAttribute<PluginAttribute>();
        if (attribute == null)
            return null;

        return new PluginManifest
        {
            Info = new PluginInfo(
                Id: attribute.Id,
                Name: attribute.Name ?? pluginType.Name,
                Version: attribute.Version ?? "1.0.0",
                Vendor: attribute.Vendor ?? "Unknown",
                Description: attribute.Description),
            EntryPoint = pluginType.FullName!,
            AssemblyPath = pluginType.Assembly.Location,
            Capabilities = [],
            Dependencies = [],
            Permissions = [],
            Tags = []
        };
    }
}