using System;
using System.Collections.Generic;
using System.Reflection;
using UnityEngine;

namespace ShrinkModFramework
{
    internal static class ShrinkHarmonyPatchService
    {
        private sealed class EmptyLease : IDisposable
        {
            public static readonly EmptyLease Instance = new();
            public void Dispose() { }
        }

        private sealed class HarmonyLease : IDisposable
        {
            private readonly Type _harmonyType;
            private readonly object _harmony;
            private readonly string _harmonyId;
            private readonly bool _verboseLogging;
            private bool _disposed;

            public HarmonyLease(Type harmonyType, object harmony, string harmonyId, bool verboseLogging)
            {
                _harmonyType = harmonyType;
                _harmony = harmony;
                _harmonyId = harmonyId;
                _verboseLogging = verboseLogging;
            }

            public void Dispose()
            {
                if (_disposed)
                    return;
                _disposed = true;

                try
                {
                    var unpatchSelf = _harmonyType.GetMethod("UnpatchSelf",
                        BindingFlags.Public | BindingFlags.Instance,
                        null,
                        Type.EmptyTypes,
                        null);
                    if (unpatchSelf != null)
                    {
                        unpatchSelf.Invoke(_harmony, null);
                    }
                    else
                    {
                        var unpatchAll = _harmonyType.GetMethod("UnpatchAll",
                            BindingFlags.Public | BindingFlags.Static,
                            null,
                            new[] { typeof(string) },
                            null);
                        if (unpatchAll == null)
                            throw new MissingMethodException("Harmony.UnpatchSelf()/UnpatchAll(string) 不存在。");
                        unpatchAll.Invoke(null, new object[] { _harmonyId });
                    }

                    if (_verboseLogging)
                        Debug.Log($"[ShrinkModFramework] 已撤回 Harmony 补丁：{_harmonyId}");
                }
                catch (Exception ex)
                {
                    Debug.LogError($"[ShrinkModFramework] 撤回 Harmony 补丁失败：{_harmonyId}\n{ex.Message}");
                }
                finally
                {
                    AppliedHarmonyIds.Remove(_harmonyId);
                }
            }
        }

        private static readonly HashSet<string> AppliedHarmonyIds = new(StringComparer.Ordinal);

        public static void ApplyPatchesIfNeeded(ShrinkModInfo modInfo, bool enableHarmonyPatching, bool verboseLogging)
        {
            _ = ApplyPatchesCore(modInfo, enableHarmonyPatching, verboseLogging, reversible: false);
        }

        public static IDisposable AcquirePatchesIfNeeded(ShrinkModInfo modInfo, bool enableHarmonyPatching,
            bool verboseLogging)
        {
            return ApplyPatchesCore(modInfo, enableHarmonyPatching, verboseLogging, reversible: true);
        }

        private static IDisposable ApplyPatchesCore(ShrinkModInfo modInfo, bool enableHarmonyPatching,
            bool verboseLogging, bool reversible)
        {
            if (!enableHarmonyPatching || !modInfo.AutoApplyHarmonyPatches)
                return EmptyLease.Instance;

            var harmonyType = Type.GetType("HarmonyLib.Harmony, 0Harmony");
            if (harmonyType == null)
            {
                if (verboseLogging)
                    Debug.Log($"[ShrinkModFramework] 未检测到 Harmony，跳过模组 {modInfo.ModId} 的补丁自动应用。");
                return EmptyLease.Instance;
            }

            var harmonyId = $"shrink.mod.{modInfo.ModId}";
            if (!AppliedHarmonyIds.Add(harmonyId))
                return EmptyLease.Instance;

            try
            {
                var harmony = Activator.CreateInstance(harmonyType, harmonyId);
                var patchAll = harmonyType.GetMethod("PatchAll", new[] { typeof(Assembly) });
                if (patchAll == null)
                    throw new MissingMethodException("Harmony.PatchAll(Assembly) 不存在。");

                patchAll.Invoke(harmony, new object[] { modInfo.EntryType.Assembly });

                if (verboseLogging)
                    Debug.Log($"[ShrinkModFramework] 已应用 Harmony 补丁：{modInfo.ModId}");

                return reversible
                    ? new HarmonyLease(harmonyType, harmony, harmonyId, verboseLogging)
                    : EmptyLease.Instance;
            }
            catch (Exception ex)
            {
                AppliedHarmonyIds.Remove(harmonyId);
                throw new InvalidOperationException($"模组 {modInfo.ModId} 应用 Harmony 补丁失败：{ex.Message}", ex);
            }
        }

        internal static void ResetForTesting() => AppliedHarmonyIds.Clear();
    }
}