using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;

namespace OpenNest;

/// <summary>
/// Registry of whole-job INestingEngine implementations, parallel to NestEngineRegistry (which is for
/// the legacy single-plate NestEngineBase). The four production strategies are exposed here through
/// FixedStrategyNestingEngine so they compete on equal footing with model-submitted engines. Unlike
/// NestEngineRegistry, this has no ActiveEngineName/global-selection concept — callers choose an engine
/// explicitly from AvailableEngines.
/// </summary>
public static class NestingEngineRegistry
{
    private static readonly List<NestingEngineInfo> engines = new();

    static NestingEngineRegistry()
    {
        Register("Default", "Multi-phase nesting (Linear, Pairs, RectBestFit, Remainder)",
            () => new FixedStrategyNestingEngine("Default"));

        Register("Strip", "Strip-based nesting for mixed-drawing layouts",
            () => new FixedStrategyNestingEngine("Strip"));

        Register("Vertical Remnant", "Optimizes for largest right-side vertical drop",
            () => new FixedStrategyNestingEngine("Vertical Remnant"));

        Register("Horizontal Remnant", "Optimizes for largest top-side horizontal drop",
            () => new FixedStrategyNestingEngine("Horizontal Remnant"));
    }

    public static IReadOnlyList<NestingEngineInfo> AvailableEngines => engines;

    public static void Register(string name, string description, Func<INestingEngine> factory)
    {
        if (engines.Any(e => e.Name.Equals(name, StringComparison.OrdinalIgnoreCase)))
        {
            Debug.WriteLine($"[NestingEngineRegistry] Duplicate engine '{name}' skipped");
            return;
        }

        engines.Add(new NestingEngineInfo(name, description, factory));
    }

    /// <summary>Scans *.dll in directory for non-abstract INestingEngine types with a public
    /// parameterless constructor, registering each under its CLR type name. Mirrors
    /// NestEngineRegistry.LoadPlugins's per-assembly/per-type isolation: one bad plugin never
    /// prevents the rest from loading.</summary>
    public static void LoadPlugins(string directory)
    {
        if (!Directory.Exists(directory))
            return;

        foreach (var dll in Directory.GetFiles(directory, "*.dll"))
        {
            try
            {
                var assembly = Assembly.LoadFrom(dll);

                foreach (var type in assembly.GetTypes())
                {
                    if (type.IsAbstract || !typeof(INestingEngine).IsAssignableFrom(type))
                        continue;

                    var ctor = type.GetConstructor(Type.EmptyTypes);

                    if (ctor == null)
                    {
                        Debug.WriteLine($"[NestingEngineRegistry] Skipping {type.Name}: no parameterless constructor");
                        continue;
                    }

                    try
                    {
                        Register(type.Name, string.Empty, () => (INestingEngine)ctor.Invoke(null));
                        Debug.WriteLine($"[NestingEngineRegistry] Loaded plugin engine: {type.Name}");
                    }
                    catch (Exception ex)
                    {
                        Debug.WriteLine($"[NestingEngineRegistry] Failed to register {type.Name}: {ex.Message}");
                    }
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"[NestingEngineRegistry] Failed to load assembly {Path.GetFileName(dll)}: {ex.Message}");
            }
        }
    }
}