#nullable enable

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

namespace ReplacedPerson.Core
{
    public interface IReplacedPersonMod
    {
        string Id { get; }
        string Version { get; }
        void Register(IReplacedPersonRegistry registry);
    }

    public interface IReplacedPersonRegistry
    {
        void RegisterCard(ReplacedCardDefinition definition);
        void RegisterEndCard(ReplacedEndCardDefinition definition);
        void RegisterEnemy(ReplacedEnemyDefinition definition);
        void RegisterReward(string id, string displayName);
        void RegisterStory(string id, string title, string body);
        void RegisterEffectResolver(string effectId, IReplacedPersonEffectResolver resolver);
        void RegisterCommand(string path, Func<IReadOnlyList<string>, string> handler);
    }

    public interface IReplacedPersonEffectResolver
    {
        ReplacedEffectResult Resolve(ReplacedEffectContext context);
    }

    public sealed class ReplacedEffectContext
    {
        public string EffectId { get; set; } = string.Empty;
        public int OwnerIndex { get; set; }
        public int OpponentIndex => 1 - OwnerIndex;
        public int Value { get; set; }
        public ReplacedMatchState State { get; set; } = null!;
    }

    public sealed class ReplacedEffectResult
    {
        public int BonusDamage { get; set; }
        public int CostDelta { get; set; }
        public int DrawDelta { get; set; }
        public string Log { get; set; } = string.Empty;
    }

    [Serializable]
    public sealed class ReplacedPersonModFile
    {
        public string Path { get; set; } = string.Empty;
        public string Sha256 { get; set; } = string.Empty;
    }

    [Serializable]
    public sealed class ReplacedPersonModManifest
    {
        public string Id { get; set; } = string.Empty;
        public string Version { get; set; } = string.Empty;
        public List<ReplacedPersonModFile> Files { get; set; } = new();
    }

    public sealed class ReplacedModCompatibilityResult
    {
        public bool Compatible => Differences.Count == 0;
        public List<string> Differences { get; } = new();
    }

    public static class ReplacedModCompatibility
    {
        public static ReplacedModCompatibilityResult Compare(IEnumerable<ReplacedPersonModManifest> authority,
            IEnumerable<ReplacedPersonModManifest> client)
        {
            var result = new ReplacedModCompatibilityResult();
            var expected = authority.ToDictionary(value => value.Id, StringComparer.Ordinal);
            var actual = client.ToDictionary(value => value.Id, StringComparer.Ordinal);
            foreach (var id in expected.Keys.Union(actual.Keys, StringComparer.Ordinal).OrderBy(value => value, StringComparer.Ordinal))
            {
                if (!expected.TryGetValue(id, out var expectedMod)) { result.Differences.Add("unexpected-mod:" + id); continue; }
                if (!actual.TryGetValue(id, out var actualMod)) { result.Differences.Add("missing-mod:" + id); continue; }
                if (!string.Equals(expectedMod.Version, actualMod.Version, StringComparison.Ordinal))
                    result.Differences.Add($"version:{id}:{expectedMod.Version}!={actualMod.Version}");
                CompareFiles(id, expectedMod.Files, actualMod.Files, result.Differences);
            }
            return result;
        }

        public static string ComputeManifestSetHash(IEnumerable<ReplacedPersonModManifest> manifests)
        {
            var text = new StringBuilder();
            foreach (var manifest in manifests.OrderBy(value => value.Id, StringComparer.Ordinal))
            {
                text.Append(manifest.Id).Append('|').Append(manifest.Version).Append('\n');
                foreach (var file in manifest.Files.OrderBy(value => value.Path, StringComparer.Ordinal))
                    text.Append(file.Path).Append('|').Append(file.Sha256.ToLowerInvariant()).Append('\n');
            }
            using var sha = SHA256.Create();
            var bytes = sha.ComputeHash(Encoding.UTF8.GetBytes(text.ToString()));
            return string.Concat(bytes.Select(value => value.ToString("x2")));
        }

        private static void CompareFiles(string modId, IEnumerable<ReplacedPersonModFile> expected,
            IEnumerable<ReplacedPersonModFile> actual, ICollection<string> differences)
        {
            var expectedFiles = expected.ToDictionary(value => value.Path, StringComparer.Ordinal);
            var actualFiles = actual.ToDictionary(value => value.Path, StringComparer.Ordinal);
            foreach (var path in expectedFiles.Keys.Union(actualFiles.Keys, StringComparer.Ordinal).OrderBy(value => value, StringComparer.Ordinal))
            {
                if (!expectedFiles.TryGetValue(path, out var expectedFile)) { differences.Add($"unexpected-file:{modId}:{path}"); continue; }
                if (!actualFiles.TryGetValue(path, out var actualFile)) { differences.Add($"missing-file:{modId}:{path}"); continue; }
                if (!string.Equals(expectedFile.Sha256, actualFile.Sha256, StringComparison.OrdinalIgnoreCase))
                    differences.Add($"hash:{modId}:{path}");
            }
        }
    }

    public sealed class ReplacedPersonRegistry : IReplacedPersonRegistry
    {
        private readonly ReplacedContentCatalog _catalog;
        private readonly Dictionary<string, string> _rewards = new(StringComparer.Ordinal);
        private readonly Dictionary<string, (string title, string body)> _stories = new(StringComparer.Ordinal);
        private readonly Dictionary<string, IReplacedPersonEffectResolver> _effects = new(StringComparer.Ordinal);
        private readonly Dictionary<string, Func<IReadOnlyList<string>, string>> _commands = new(StringComparer.OrdinalIgnoreCase);

        public ReplacedPersonRegistry(ReplacedContentCatalog baseCatalog) => _catalog = baseCatalog.Clone();
        public ReplacedContentCatalog CreateSnapshot() => _catalog.Clone();
        public IReadOnlyDictionary<string, IReplacedPersonEffectResolver> Effects => _effects;
        public IReadOnlyDictionary<string, Func<IReadOnlyList<string>, string>> Commands => _commands;

        public void RegisterCard(ReplacedCardDefinition definition) => AddUnique(_catalog.Cards, definition.Id, definition);
        public void RegisterEndCard(ReplacedEndCardDefinition definition) => AddUnique(_catalog.EndCards, definition.Id, definition);
        public void RegisterEnemy(ReplacedEnemyDefinition definition) => AddUnique(_catalog.Enemies, definition.Id, definition);
        public void RegisterReward(string id, string displayName) => AddUnique(_rewards, id, displayName);
        public void RegisterStory(string id, string title, string body) => AddUnique(_stories, id, (title, body));
        public void RegisterEffectResolver(string effectId, IReplacedPersonEffectResolver resolver)
        {
            AddUnique(_effects, effectId, resolver);
            AddUnique(_catalog.EffectResolvers, effectId, resolver);
        }
        public void RegisterCommand(string path, Func<IReadOnlyList<string>, string> handler) => AddUnique(_commands, path, handler);

        private static void AddUnique<T>(IDictionary<string, T> target, string id, T value)
        {
            if (string.IsNullOrWhiteSpace(id)) throw new ArgumentException("Registry id must not be empty.", nameof(id));
            var key = id.Trim();
            if (target.ContainsKey(key)) throw new InvalidOperationException("Duplicate registry id: " + id);
            target.Add(key, value);
        }
    }

    public sealed class ReplacedHotReloadCatalog
    {
        public ReplacedContentCatalog Current { get; private set; }
        public ReplacedContentCatalog? Pending { get; private set; }
        public string CurrentHash => Current.ComputeHash();
        public string PendingHash => Pending?.ComputeHash() ?? string.Empty;

        public ReplacedHotReloadCatalog(ReplacedContentCatalog initial) => Current = initial.Clone();
        public void Stage(ReplacedContentCatalog next) => Pending = next.Clone();
        public ReplacedContentCatalog SnapshotForNewMatch()
        {
            if (Pending != null) { Current = Pending; Pending = null; }
            return Current.Clone();
        }
    }
}