using System.Diagnostics;
using System.Text.Json;
using ClawdDotNet.Core.Api;
using ClawdDotNet.Core.Api.Models;
using ClawdDotNet.Core.Audit;
using ClawdDotNet.Core.Budget;
using ClawdDotNet.Core.Config;
using ClawdDotNet.Core.Memory;
using ClawdDotNet.Core.Security;
using ClawdDotNet.Core.Accounting;
using ClawdDotNet.Core.Tools;
using ClawdDotNet.Core.State;
using ClawdDotNet.Core.Storage;
using Microsoft.Extensions.Logging;

namespace ClawdDotNet.Core.Engine;

public sealed class AgentEngine : IAgentMessageRouter, Staging.IFrozenCallExecutor
{
    private readonly IChatCompletionClient _client;
    private readonly ToolRegistry _toolRegistry;
    private readonly PermissionGate _permissionGate;
    private readonly IStateStore _stateStore;
    private readonly IMemoryRepository? _memoryRepository;
    private readonly Tasks.ITaskRepository? _taskRepository;
    private readonly IAuditRepository? _auditRepository;
    private readonly Staging.StagingGate? _stagingGate;
    private readonly IUsageRepository? _usageRepository;
    private readonly BudgetGuard? _budgetGuard;
    private readonly ModelPricingCatalog? _pricing;
    private readonly ILoggerFactory _loggerFactory;

    /// <summary>Tagesgrenzen der Instanz. Wird vom Host gesetzt.</summary>
    public InstanceBudget InstanceBudget { get; set; } = InstanceBudget.Unlimited;
    private readonly ContextCompactor _compactor;

    private readonly Dictionary<string, List<ChatEntry>> _chatHistories = new();
    private readonly Dictionary<string, List<ChatMessage>> _chatContexts = new();
    private readonly Lock _lock = new();

    /// <summary>
    /// Alle aktiven Chat-Läufe je Agent — laufende wie wartende. Mehrere Quellen können
    /// denselben Agenten gleichzeitig ansprechen (WebView, ToolJob, AgentComm), deshalb
    /// eine Liste: AbortChat muss jeden davon erreichen.
    /// </summary>
    private readonly Dictionary<string, List<CancellationTokenSource>> _runningChats = new();

    /// <summary>
    /// Serialisiert ChatAsync pro Agent. Der Konversationskontext ist eine geteilte
    /// Liste — liefen zwei Chats desselben Agenten gleichzeitig, verschränkten sich ihre
    /// Nachrichten zu einer ungültigen Tool-Sequenz, die die API mit HTTP 400 ablehnt.
    /// Verschiedene Agenten bleiben unabhängig voneinander.
    /// </summary>
    private readonly Dictionary<string, SemaphoreSlim> _agentGates = new();

    private Func<IReadOnlyList<AgentConfig>>? _agentConfigProvider;
    private Func<string, string?>? _agentDirResolver;
    private string _instanceId = "";

    private static readonly JsonSerializerOptions _jsonOpts = new()
    {
        WriteIndented = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
    };

    public AgentEngine(
        IChatCompletionClient client,
        ToolRegistry toolRegistry,
        PermissionGate permissionGate,
        IStateStore stateStore,
        ILoggerFactory loggerFactory,
        IMemoryRepository? memoryRepository = null,
        IUsageRepository? usageRepository = null,
        ModelPricingCatalog? pricing = null,
        Tasks.ITaskRepository? taskRepository = null,
        IAuditRepository? auditRepository = null,
        Staging.StagingGate? stagingGate = null)
    {
        _client = client;
        _toolRegistry = toolRegistry;
        _permissionGate = permissionGate;
        _stateStore = stateStore;
        _loggerFactory = loggerFactory;
        _memoryRepository = memoryRepository;
        _taskRepository = taskRepository;
        _auditRepository = auditRepository;
        _stagingGate = stagingGate;
        _usageRepository = usageRepository;
        _pricing = pricing;
        _budgetGuard = usageRepository is null ? null : new BudgetGuard(usageRepository);
        _compactor = new ContextCompactor(client, loggerFactory);
    }

    public event Action<string, string>? OnStepCompleted;

    /// <summary>
    /// Wird ausgelöst wenn ein neuer ChatEntry hinzugefügt wird (agentId, role, content, source).
    /// Erlaubt der UI, Nachrichten aus Hintergrund-Runs (ToolJobs, AgentComm) live anzuzeigen.
    /// Source gibt an, woher die Nachricht kam (webview, telegram, agentcomm, job, null).
    /// </summary>
    public event Action<string, string, string, string?>? OnChatEntryAdded;

    /// <summary>
    /// Wird nach jedem abgeschlossenen Run/Chat ausgelöst (model, result).
    /// Erlaubt der UI, Token-Verbrauch und Kosten für ALLE Runs zu tracken.
    /// </summary>
    public event Action<string, AgentRunResult>? OnRunCompleted;

    public async Task<AgentRunResult> RunAsync(
        AgentConfig agentConfig,
        string userMessage,
        string instanceId,
        CancellationToken externalCt,
        string? source = null,
        string? taskId = null)
    {
        // Vor der ersten Anfrage prüfen — ein erschöpftes Budget soll gar nichts kosten.
        if (await CheckBudgetAsync(agentConfig, externalCt) is { } denied)
            return denied;

        var runId = Guid.NewGuid().ToString("N");
        var result = await RunCoreAsync(agentConfig, userMessage, instanceId, externalCt, runId, source);
        await RecordUsageAsync(agentConfig, result);
        await RecordReceiptAsync(runId, agentConfig, result, source ?? AuditSource.Direct, taskId);
        return result;
    }

    private async Task<AgentRunResult> RunCoreAsync(
        AgentConfig agentConfig,
        string userMessage,
        string instanceId,
        CancellationToken externalCt,
        string runId,
        string? source)
    {
        var logger = _loggerFactory.CreateLogger($"ClawdDotNet.Core.Engine.{agentConfig.AgentId}");
        var loopGuard = new LoopGuard(agentConfig.LoopGuard);
        var sw = Stopwatch.StartNew();

        using var timeoutCts = new CancellationTokenSource(agentConfig.LoopGuard.Timeout);
        using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(externalCt, timeoutCts.Token);
        var ct = linkedCts.Token;

        logger.LogInformation("Agent run started: {AgentId}, model={Model}",
            agentConfig.AgentId, agentConfig.Model);

        try
        {
            var tools = _toolRegistry.GetForAgent(agentConfig);
            var toolDefinitions = BuildToolDefinitions(tools);

            var messages = new List<ChatMessage>();

            var systemPrompt = agentConfig.FullSystemPrompt;
            if (!string.IsNullOrWhiteSpace(systemPrompt))
                messages.Add(ChatMessage.System(systemPrompt));

            messages.Add(ChatMessage.User(userMessage));

            string? finalMessage = null;
            var tally = new TokenTally();
            var cachingEnabled = PromptCache.IsEnabledFor(agentConfig.PromptCaching, agentConfig.Model);

            while (true)
            {
                ct.ThrowIfCancellationRequested();
                loopGuard.RecordStep();

                if (cachingEnabled)
                    PromptCache.ApplyBreakpoints(messages);

                var request = new ChatRequest
                {
                    Model = agentConfig.Model,
                    Messages = messages,
                    Tools = toolDefinitions.Count > 0 ? toolDefinitions : null,
                    // B11/T8: Ausgabe deckeln — die teuerste Token-Art gegen Ausreißer schützen.
                    MaxTokens = agentConfig.LoopGuard.MaxResponseTokens > 0
                        ? agentConfig.LoopGuard.MaxResponseTokens
                        : null
                };

                var response = await _client.CompleteAsync(request, ct);

                var promptTokens = 0;
                if (response.Usage is not null)
                {
                    tally.Add(response.Usage);
                    promptTokens = response.Usage.PromptTokens;
                    loopGuard.RecordTokens(response.Usage.TotalTokens);
                }

                // Context-Compaction auch in RunAsync – verhindert Token-Explosion bei komplexen Analysen
                var compacted = await _compactor.CompactIfNeededAsync(
                    messages, promptTokens, agentConfig.LoopGuard, agentConfig.Model, ct);
                if (compacted)
                {
                    OnStepCompleted?.Invoke(agentConfig.AgentId, "Context kompaktiert (RunAsync)");
                }

                var choice = response.Choices.FirstOrDefault();
                if (choice is null)
                {
                    finalMessage = "[No response from model]";
                    break;
                }

                var assistantMessage = choice.Message;

                if (assistantMessage.ToolCalls is { Count: > 0 })
                {
                    messages.Add(ChatMessage.AssistantWithToolCalls(assistantMessage.ToolCalls));

                    foreach (var toolCall in assistantMessage.ToolCalls)
                    {
                        var toolResult = await ExecuteToolCallAsync(
                            toolCall, agentConfig, instanceId, tools, logger, ct, runId, source);

                        messages.Add(ChatMessage.ToolResponse(toolCall.Id, toolResult));
                    }

                    OnStepCompleted?.Invoke(agentConfig.AgentId,
                        $"Step {loopGuard.Steps}: {assistantMessage.ToolCalls.Count} tool call(s) executed");
                }
                else
                {
                    finalMessage = assistantMessage.Content ?? "";
                    break;
                }
            }

            sw.Stop();
            logger.LogInformation(
                "Agent run completed: {AgentId}, steps={Steps}, tokens={Tokens} (davon {Cached} aus Cache), duration={Duration}ms",
                agentConfig.AgentId, loopGuard.Steps, tally.Total, tally.Cached, sw.ElapsedMilliseconds);

            var result = new AgentRunResult(
                agentConfig.AgentId,
                AgentRunStatus.Completed,
                finalMessage,
                loopGuard.Steps,
                tally.Total,
                sw.Elapsed)
            {
                PromptTokens = tally.Prompt,
                CompletionTokens = tally.Completion,
                CachedTokens = tally.Cached
            };
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (OperationCanceledException) when (timeoutCts.IsCancellationRequested)
        {
            sw.Stop();
            logger.LogWarning("Agent run timed out: {AgentId} after {Duration}ms",
                agentConfig.AgentId, sw.ElapsedMilliseconds);

            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Cancelled, null,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (OperationCanceledException)
        {
            sw.Stop();
            logger.LogInformation("Agent run cancelled: {AgentId}", agentConfig.AgentId);

            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Cancelled, null,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (LoopLimitExceededException ex)
        {
            sw.Stop();
            logger.LogWarning("Agent run loop limit exceeded: {AgentId}: {Message}",
                agentConfig.AgentId, ex.Message);

            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.LoopLimitExceeded, null,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed, ex);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (Exception ex)
        {
            sw.Stop();
            logger.LogError(ex, "Agent run failed: {AgentId}", agentConfig.AgentId);

            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Failed, null,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed, ex);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
    }

    public async Task<AgentRunResult> ChatAsync(
        AgentConfig agentConfig,
        string userMessage,
        string instanceId,
        CancellationToken externalCt,
        string? source = null,
        string? taskId = null)
    {
        if (await CheckBudgetAsync(agentConfig, externalCt) is { } denied)
            return denied;

        var runId = Guid.NewGuid().ToString("N");

        // Abbrechbar sein, schon bevor der Lauf an der Reihe ist — sonst hängt eine
        // wartende Nachricht auch dann noch, wenn der Benutzer längst abgebrochen hat.
        using var runCts = CancellationTokenSource.CreateLinkedTokenSource(externalCt);
        RegisterRun(agentConfig.AgentId, runCts);

        var gate = GetAgentGate(agentConfig.AgentId);
        try
        {
            await gate.WaitAsync(runCts.Token);
        }
        catch (OperationCanceledException)
        {
            UnregisterRun(agentConfig.AgentId, runCts);
            return new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Cancelled, "[Chat abgebrochen]",
                0, 0, TimeSpan.Zero);
        }

        try
        {
            var result = await ChatCoreAsync(agentConfig, userMessage, instanceId, runCts.Token, source, runId);
            await RecordUsageAsync(agentConfig, result);
            await RecordReceiptAsync(runId, agentConfig, result, source, taskId);
            return result;
        }
        finally
        {
            UnregisterRun(agentConfig.AgentId, runCts);
            gate.Release();
        }
    }

    private async Task<AgentRunResult> ChatCoreAsync(
        AgentConfig agentConfig,
        string userMessage,
        string instanceId,
        CancellationToken runCt,
        string? source,
        string runId)
    {
        var logger = _loggerFactory.CreateLogger($"ClawdDotNet.Core.Engine.Chat.{agentConfig.AgentId}");
        var loopGuard = new LoopGuard(agentConfig.LoopGuard);
        var sw = Stopwatch.StartNew();

        // Die Timeout-Uhr läuft erst ab hier — Wartezeit in der Warteschlange
        // darf den Lauf nicht aufzehren.
        using var timeoutCts = new CancellationTokenSource(agentConfig.LoopGuard.Timeout);
        using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(runCt, timeoutCts.Token);
        var ct = linkedCts.Token;

        try
        {
            var tools = _toolRegistry.GetForAgent(agentConfig);
            var toolDefinitions = BuildToolDefinitions(tools);

            List<ChatMessage> messages;
            lock (_lock)
            {
                if (!_chatContexts.TryGetValue(agentConfig.AgentId, out messages!))
                {
                    messages = new List<ChatMessage>();
                    var systemPrompt = agentConfig.FullSystemPrompt;
                    if (!string.IsNullOrWhiteSpace(systemPrompt))
                        messages.Add(ChatMessage.System(systemPrompt));
                    _chatContexts[agentConfig.AgentId] = messages;
                }
            }

            // Routing-Hinweis: Dem Agenten mitteilen, woher die Nachricht kommt
            var routedMessage = source switch
            {
                ChatSource.WebView => $"[WebView Chat – antworte als normaler Text, NICHT über Telegram senden]\n{userMessage}",
                ChatSource.Telegram => userMessage, // Telegram-Nachrichten kommen bereits mit [Telegram] Prefix vom Job
                _ => userMessage
            };

            messages.Add(ChatMessage.User(routedMessage));
            AddChatEntry(agentConfig.AgentId, "user", userMessage, source);

            string? finalMessage = null;
            var tally = new TokenTally();
            var cachingEnabled = PromptCache.IsEnabledFor(agentConfig.PromptCaching, agentConfig.Model);

            while (true)
            {
                ct.ThrowIfCancellationRequested();
                loopGuard.RecordStep();

                if (cachingEnabled)
                    PromptCache.ApplyBreakpoints(messages);

                var request = new ChatRequest
                {
                    Model = agentConfig.Model,
                    Messages = messages,
                    Tools = toolDefinitions.Count > 0 ? toolDefinitions : null,
                    // B11/T8: Ausgabe deckeln — die teuerste Token-Art gegen Ausreißer schützen.
                    MaxTokens = agentConfig.LoopGuard.MaxResponseTokens > 0
                        ? agentConfig.LoopGuard.MaxResponseTokens
                        : null
                };

                var response = await _client.CompleteAsync(request, ct);

                var promptTokens = 0;
                if (response.Usage is not null)
                {
                    tally.Add(response.Usage);
                    promptTokens = response.Usage.PromptTokens;
                    loopGuard.RecordTokens(response.Usage.TotalTokens);
                }

                // Context-Compaction nach API-Response prüfen
                var compacted = await _compactor.CompactIfNeededAsync(
                    messages, promptTokens, agentConfig.LoopGuard, agentConfig.Model, ct);
                if (compacted)
                {
                    PersistChatState(agentConfig.AgentId);
                    OnStepCompleted?.Invoke(agentConfig.AgentId, "Context kompaktiert");
                }

                var choice = response.Choices.FirstOrDefault();
                if (choice is null)
                {
                    finalMessage = "[No response from model]";
                    break;
                }

                var assistantMessage = choice.Message;

                if (assistantMessage.ToolCalls is { Count: > 0 })
                {
                    messages.Add(ChatMessage.AssistantWithToolCalls(assistantMessage.ToolCalls));

                    foreach (var toolCall in assistantMessage.ToolCalls)
                    {
                        var toolResult = await ExecuteToolCallAsync(
                            toolCall, agentConfig, instanceId, tools, logger, ct, runId, source);
                        messages.Add(ChatMessage.ToolResponse(toolCall.Id, toolResult));
                    }

                    OnStepCompleted?.Invoke(agentConfig.AgentId,
                        $"Chat step {loopGuard.Steps}: {assistantMessage.ToolCalls.Count} tool call(s)");
                }
                else
                {
                    finalMessage = assistantMessage.Content ?? "";
                    messages.Add(ChatMessage.Assistant(finalMessage));
                    AddChatEntry(agentConfig.AgentId, "assistant", finalMessage, source);
                    break;
                }
            }

            sw.Stop();
            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Completed, finalMessage,
                loopGuard.Steps, tally.Total, sw.Elapsed)
            {
                PromptTokens = tally.Prompt,
                CompletionTokens = tally.Completion,
                CachedTokens = tally.Cached
            };
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (OperationCanceledException)
        {
            sw.Stop();
            var cancelMsg = "[Chat abgebrochen]";
            AddChatEntry(agentConfig.AgentId, "assistant", cancelMsg, source);
            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Cancelled, cancelMsg,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (LoopLimitExceededException ex)
        {
            sw.Stop();
            var limitMsg = $"[Loop-Limit erreicht: {ex.Message}]";
            logger.LogWarning("Chat loop limit: {AgentId}: {Message}", agentConfig.AgentId, ex.Message);
            AddChatEntry(agentConfig.AgentId, "assistant", limitMsg, source);
            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.LoopLimitExceeded, limitMsg,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed, ex);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
        catch (Exception ex)
        {
            sw.Stop();
            var errorMsg = $"[Fehler: {ex.Message}]";
            logger.LogError(ex, "Chat failed: {AgentId}", agentConfig.AgentId);
            AddChatEntry(agentConfig.AgentId, "assistant", errorMsg, source);
            var result = new AgentRunResult(
                agentConfig.AgentId, AgentRunStatus.Failed, errorMsg,
                loopGuard.Steps, loopGuard.Tokens, sw.Elapsed, ex);
            OnRunCompleted?.Invoke(agentConfig.Model, result);
            return result;
        }
    }

    // ─── Nebenläufigkeits-Helfer ───

    private SemaphoreSlim GetAgentGate(string agentId)
    {
        lock (_lock)
        {
            if (!_agentGates.TryGetValue(agentId, out var gate))
            {
                gate = new SemaphoreSlim(1, 1);
                _agentGates[agentId] = gate;
            }
            return gate;
        }
    }

    private void RegisterRun(string agentId, CancellationTokenSource cts)
    {
        lock (_lock)
        {
            if (!_runningChats.TryGetValue(agentId, out var list))
            {
                list = new List<CancellationTokenSource>();
                _runningChats[agentId] = list;
            }
            list.Add(cts);
        }
    }

    private void UnregisterRun(string agentId, CancellationTokenSource cts)
    {
        lock (_lock)
        {
            if (!_runningChats.TryGetValue(agentId, out var list))
                return;

            list.Remove(cts);
            if (list.Count == 0)
                _runningChats.Remove(agentId);
        }
    }

    public IReadOnlyList<ChatEntry> GetChatHistory(string agentId)
    {
        lock (_lock)
            return _chatHistories.TryGetValue(agentId, out var history)
                ? history.ToList().AsReadOnly()
                : [];
    }

    public bool IsRunning(string agentId)
    {
        lock (_lock)
            return _runningChats.ContainsKey(agentId);
    }

    /// <summary>Anzahl Agenten mit mindestens einem aktiven Chat-Lauf — für Diagnose/Heartbeat.</summary>
    public int RunningChatCount
    {
        get { lock (_lock) return _runningChats.Count; }
    }

    /// <summary>
    /// Momentaufnahme des Konversationskontexts eines Agenten — also der Nachrichten,
    /// die beim nächsten Schritt tatsächlich an das Modell gehen.
    /// Nützlich für Diagnose und Kontextgrößen-Anzeige.
    /// </summary>
    public IReadOnlyList<ChatMessage> GetChatContext(string agentId)
    {
        lock (_lock)
            return _chatContexts.TryGetValue(agentId, out var ctx)
                ? ctx.ToList()
                : [];
    }

    /// <summary>
    /// Bricht ALLE Chat-Läufe des Agenten ab — laufende wie wartende.
    /// </summary>
    public void AbortChat(string agentId)
    {
        List<CancellationTokenSource> toCancel;
        lock (_lock)
        {
            if (!_runningChats.TryGetValue(agentId, out var list))
                return;
            toCancel = list.ToList();
        }

        // Außerhalb des Locks abbrechen: Cancel führt Continuations aus, die
        // ihrerseits wieder auf _lock zugreifen können.
        foreach (var cts in toCancel)
        {
            try { cts.Cancel(); }
            catch (ObjectDisposedException) { /* Lauf war bereits fertig */ }
        }
    }

    public void ClearChatHistory(string agentId)
    {
        lock (_lock)
        {
            _chatHistories.Remove(agentId);
            _chatContexts.Remove(agentId);
        }

        var dir = _agentDirResolver?.Invoke(agentId);
        if (dir is null) return;

        var historyPath = Path.Combine(dir, "ChatHistory.json");
        var contextPath = Path.Combine(dir, "ChatContext.json");
        if (File.Exists(historyPath)) File.Delete(historyPath);
        if (File.Exists(contextPath)) File.Delete(contextPath);
    }

    public void SetAgentConfigProvider(
        Func<IReadOnlyList<AgentConfig>> provider,
        string instanceId,
        Func<string, string?>? agentDirResolver = null)
    {
        _agentConfigProvider = provider;
        _instanceId = instanceId;
        _agentDirResolver = agentDirResolver;
    }

    public void LoadPersistedChats()
    {
        var configs = _agentConfigProvider?.Invoke() ?? [];
        foreach (var agent in configs)
        {
            var dir = _agentDirResolver?.Invoke(agent.AgentId);
            if (dir is null || !Directory.Exists(dir)) continue;

            try
            {
                var historyPath = Path.Combine(dir, "ChatHistory.json");
                if (File.Exists(historyPath))
                {
                    var history = JsonSerializer.Deserialize<List<ChatEntry>>(
                        AtomicFile.ReadAllText(historyPath), _jsonOpts);
                    if (history is { Count: > 0 })
                    {
                        lock (_lock)
                            _chatHistories[agent.AgentId] = history;
                    }
                }

                var contextPath = Path.Combine(dir, "ChatContext.json");
                if (File.Exists(contextPath))
                {
                    var raw = AtomicFile.ReadAllText(contextPath);
                    List<ChatMessage>? context = null;

                    // Versuche zuerst als Array (direktes List<ChatMessage>)
                    // Dann als Wrapper-Objekt {"messages":[...]}
                    try
                    {
                        context = JsonSerializer.Deserialize<List<ChatMessage>>(raw, _jsonOpts);
                    }
                    catch (JsonException)
                    {
                        try
                        {
                            using var doc = JsonDocument.Parse(raw);
                            if (doc.RootElement.TryGetProperty("messages", out var msgs))
                            {
                                context = JsonSerializer.Deserialize<List<ChatMessage>>(
                                    msgs.GetRawText(), _jsonOpts);
                            }
                        }
                        catch { /* Beide Formate fehlgeschlagen — ignorieren */ }
                    }

                    if (context is { Count: > 0 })
                    {
                        lock (_lock)
                            _chatContexts[agent.AgentId] = context;
                    }
                }
            }
            catch (Exception ex)
            {
                _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Persistence")
                    .LogWarning(ex, "Failed to load chat state for agent {AgentId}", agent.AgentId);
            }
        }
    }

    // ─── IAgentMessageRouter ───

    public IReadOnlyList<AgentInfo> ListAgents(string callerAgentId)
    {
        var configs = _agentConfigProvider?.Invoke() ?? [];
        return configs
            .Where(a => a.AgentId != callerAgentId)
            .Select(a => new AgentInfo(a.AgentId, a.DisplayName, a.Description, a.Model, IsRunning(a.AgentId)))
            .ToList();
    }

    public async Task<AgentMessageResult> SendMessageAsync(
        string fromAgentId, string toAgentId, string message, CancellationToken ct)
    {
        var configs = _agentConfigProvider?.Invoke();
        if (configs is null)
            return new AgentMessageResult(false, null, "Agent config provider not set.");

        // Selbstadressierung würde am Agent-Gate hängen bleiben: Der laufende Chat
        // hält es bereits und würde auf sich selbst warten.
        if (fromAgentId == toAgentId)
            return new AgentMessageResult(false, null,
                "Ein Agent kann sich keine Nachricht an sich selbst schicken.");

        var targetConfig = configs.FirstOrDefault(a => a.AgentId == toAgentId);
        if (targetConfig is null)
            return new AgentMessageResult(false, null, $"Agent '{toAgentId}' not found.");

        var fromConfig = configs.FirstOrDefault(a => a.AgentId == fromAgentId);
        var fromName = fromConfig?.DisplayName ?? fromAgentId;

        var wrappedMessage = $"[Nachricht von Agent \"{fromName}\" ({fromAgentId})]\n\n{message}";

        try
        {
            var result = await ChatAsync(targetConfig, wrappedMessage, _instanceId, ct, source: ChatSource.AgentComm);

            return result.Status switch
            {
                AgentRunStatus.Completed => new AgentMessageResult(true, result.FinalMessage),
                AgentRunStatus.LoopLimitExceeded => new AgentMessageResult(true, result.FinalMessage,
                    "Agent hat das Step-Limit erreicht, die Nachricht wurde aber zugestellt."),
                _ => new AgentMessageResult(false, null, $"Agent run status: {result.Status}")
            };
        }
        catch (Exception ex)
        {
            return new AgentMessageResult(false, null, $"Failed to reach agent: {ex.Message}");
        }
    }

    public async Task<AgentSpawnResult> SpawnAgentAsync(
        string fromAgentId, string targetAgentId, string taskMessage, CancellationToken ct)
    {
        var configs = _agentConfigProvider?.Invoke();
        if (configs is null)
            return new AgentSpawnResult(false, targetAgentId, null, "Agent config provider not set.");

        var targetConfig = configs.FirstOrDefault(a => a.AgentId == targetAgentId);
        if (targetConfig is null)
            return new AgentSpawnResult(false, targetAgentId, null, $"Agent '{targetAgentId}' not found.");

        if (IsRunning(targetAgentId))
            return new AgentSpawnResult(false, targetAgentId, null,
                $"Agent '{targetConfig.DisplayName}' läuft bereits. Verwende send_message statt spawn.");

        var fromConfig = configs.FirstOrDefault(a => a.AgentId == fromAgentId);
        var fromName = fromConfig?.DisplayName ?? fromAgentId;

        var wrappedMessage = $"[Spawn-Auftrag von Agent \"{fromName}\" ({fromAgentId})]\n\n{taskMessage}";

        try
        {
            var result = await RunAsync(targetConfig, wrappedMessage, _instanceId, ct);

            return result.Status == AgentRunStatus.Completed
                ? new AgentSpawnResult(true, targetAgentId, result.FinalMessage)
                : new AgentSpawnResult(false, targetAgentId, null, $"Agent run status: {result.Status}");
        }
        catch (Exception ex)
        {
            return new AgentSpawnResult(false, targetAgentId, null, $"Spawn failed: {ex.Message}");
        }
    }

    private void AddChatEntry(string agentId, string role, string content, string? source = null)
    {
        lock (_lock)
        {
            if (!_chatHistories.TryGetValue(agentId, out var history))
            {
                history = new List<ChatEntry>();
                _chatHistories[agentId] = history;
            }
            history.Add(new ChatEntry(role, content, DateTime.Now, source));
        }
        PersistChatState(agentId);
        OnChatEntryAdded?.Invoke(agentId, role, content, source);
    }

    private void PersistChatState(string agentId)
    {
        var dir = _agentDirResolver?.Invoke(agentId);
        if (dir is null) return;

        try
        {
            Directory.CreateDirectory(dir);

            List<ChatEntry>? history;
            List<ChatMessage>? context;
            lock (_lock)
            {
                _chatHistories.TryGetValue(agentId, out history);
                _chatContexts.TryGetValue(agentId, out context);
            }

            // Atomar schreiben: Ein Absturz mitten im Vorgang würde sonst den
            // bisherigen Verlauf löschen und einen halben zurücklassen.
            if (history is not null)
                AtomicFile.WriteAllText(
                    Path.Combine(dir, "ChatHistory.json"),
                    JsonSerializer.Serialize(history, _jsonOpts));

            if (context is not null)
                AtomicFile.WriteAllText(
                    Path.Combine(dir, "ChatContext.json"),
                    JsonSerializer.Serialize(context, _jsonOpts));
        }
        catch (Exception ex)
        {
            _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Persistence")
                .LogWarning(ex, "Failed to persist chat state for agent {AgentId}", agentId);
        }
    }

    private async Task<string> ExecuteToolCallAsync(
        ToolCall toolCall,
        AgentConfig agentConfig,
        string instanceId,
        IReadOnlyList<IAgentTool> availableTools,
        ILogger logger,
        CancellationToken ct,
        string runId,
        string? source)
    {
        var toolName = toolCall.Function.Name;
        var arguments = toolCall.Function.Arguments ?? "";
        var sw = Stopwatch.StartNew();

        // Das Audit wird von der Engine gestempelt (A3) — Herkunft aus dem Wissen der
        // Engine, nie aus dem Tool-Ergebnis. Best effort: ein Audit-Fehler darf den Lauf
        // nicht scheitern lassen.
        Task Audit(AuditStatus status, string summary)
            => RecordAuditAsync(runId, agentConfig, source, toolName, arguments, status, summary, sw.ElapsedMilliseconds);

        try
        {
            _permissionGate.Enforce(agentConfig.AgentId, toolName, agentConfig);

            var tool = availableTools.FirstOrDefault(t => t.Name == toolName);
            if (tool is null)
            {
                await Audit(AuditStatus.NotFound, $"Tool '{toolName}' nicht zugewiesen/unbekannt");
                return JsonSerializer.Serialize(ToolResult.Fail($"Tool '{toolName}' not found."));
            }

            // Staging-Durchsetzung (A2): irreversible Aktionen werden vorgeschlagen statt
            // ausgeführt. Eine Prompt-Injection kann so nur einen Vorschlag erzeugen.
            if (_stagingGate is not null)
            {
                var intercept = await _stagingGate.InterceptAsync(
                    agentConfig.AgentId, instanceId, runId, toolName, arguments, ct);

                if (intercept.Outcome == Staging.StagingOutcome.Denied)
                {
                    await Audit(AuditStatus.Denied, intercept.Message);
                    return JsonSerializer.Serialize(new { error = intercept.Message });
                }

                if (intercept.Outcome == Staging.StagingOutcome.Staged)
                {
                    await Audit(AuditStatus.Staged, intercept.Message);
                    return intercept.Message; // dem Agenten als reguläres Tool-Ergebnis
                }
            }

            var input = string.IsNullOrWhiteSpace(toolCall.Function.Arguments)
                ? default
                : JsonDocument.Parse(toolCall.Function.Arguments).RootElement;

            var context = BuildToolContext(agentConfig, instanceId, toolName, ct);

            logger.LogDebug("Executing tool {Tool} for agent {AgentId}", toolName, agentConfig.AgentId);

            var result = await tool.ExecuteAsync(input, context, ct);

            logger.LogDebug("Tool {Tool} completed: success={Success}", toolName, result.Success);

            if (!result.Success)
            {
                await Audit(AuditStatus.Error, result.ErrorMessage ?? "");
                return JsonSerializer.Serialize(new { error = result.ErrorMessage });
            }

            var content = TruncateToolResult(result.Content, agentConfig.MaxToolResultChars);
            if (content.Length != result.Content.Length)
            {
                logger.LogInformation(
                    "Tool-Ergebnis von {Tool} gekürzt: {Original} → {Limit} Zeichen",
                    toolName, result.Content.Length, agentConfig.MaxToolResultChars);
            }

            await Audit(AuditStatus.Ok, "");
            return content;
        }
        catch (ToolAccessDeniedException ex)
        {
            logger.LogWarning("Tool access denied: {Message}", ex.Message);
            await Audit(AuditStatus.Denied, ex.Message);
            return JsonSerializer.Serialize(new { error = ex.Message });
        }
        catch (OperationCanceledException) when (ct.IsCancellationRequested)
        {
            // Nicht als Tool-Fehler zurückgeben: Sonst läuft die Schleife noch einen
            // Schritt weiter und der Abbruch greift erst verzögert. Auch kein Audit —
            // der Aufruf kam nicht zum Abschluss.
            throw;
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "Tool {Tool} threw an exception", toolName);
            await Audit(AuditStatus.Error, ex.Message);
            return JsonSerializer.Serialize(new { error = $"Tool execution failed: {ex.Message}" });
        }
    }

    private AgentToolContext BuildToolContext(
        AgentConfig agentConfig, string instanceId, string toolName, CancellationToken ct)
    {
        var toolConfig = agentConfig.Tools.TryGetValue(toolName, out var cfg)
            ? cfg.AsReadOnly()
            : new Dictionary<string, object?>().AsReadOnly();

        var toolLogger = _loggerFactory.CreateLogger($"ClawdDotNet.Tools.{toolName}.Execution");

        return new AgentToolContext(
            agentConfig.AgentId,
            instanceId,
            toolConfig,
            _stateStore,
            toolLogger,
            ct,
            agentConfig.WorkspacePath,
            agentConfig.SharedWorkspacePath,
            this,
            _memoryRepository,
            _taskRepository);
    }

    /// <summary>
    /// Führt einen freigegebenen, eingefrorenen Aufruf aus (A2) — mit gültigem Tool-Kontext,
    /// aber ohne LLM-Schleife und ohne erneute Staging-Prüfung. Genau der übergebene
    /// Argument-JSON wird ausgeführt (Plan-Freeze).
    /// </summary>
    public async Task<string> ExecuteApprovedCallAsync(
        string agentId, string tool, string argumentsJson, string runId, CancellationToken ct)
    {
        var config = _agentConfigProvider?.Invoke().FirstOrDefault(a => a.AgentId == agentId);
        if (config is null)
            return JsonSerializer.Serialize(new { error = $"Agent '{agentId}' nicht gefunden." });

        var agentTool = _toolRegistry.GetForAgent(config).FirstOrDefault(t => t.Name == tool)
                        ?? _toolRegistry.Get(tool);
        if (agentTool is null)
            return JsonSerializer.Serialize(new { error = $"Tool '{tool}' nicht gefunden." });

        var sw = Stopwatch.StartNew();
        try
        {
            var input = string.IsNullOrWhiteSpace(argumentsJson)
                ? default
                : JsonDocument.Parse(argumentsJson).RootElement;

            var context = BuildToolContext(config, _instanceId, tool, ct);
            var result = await agentTool.ExecuteAsync(input, context, ct);

            var status = result.Success ? AuditStatus.Ok : AuditStatus.Error;
            await RecordAuditAsync(runId, config, AuditSource.Approval, tool, argumentsJson,
                status, result.Success ? "Freigegeben ausgeführt" : (result.ErrorMessage ?? ""), sw.ElapsedMilliseconds);

            return result.Success
                ? TruncateToolResult(result.Content, config.MaxToolResultChars)
                : JsonSerializer.Serialize(new { error = result.ErrorMessage });
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            await RecordAuditAsync(runId, config, AuditSource.Approval, tool, argumentsJson,
                AuditStatus.Error, ex.Message, sw.ElapsedMilliseconds);
            return JsonSerializer.Serialize(new { error = $"Tool execution failed: {ex.Message}" });
        }
    }

    // ─── Budget und Verbrauchserfassung ───

    /// <summary>
    /// Prüft das Tagesbudget. Gibt ein Ergebnis zurück, wenn der Lauf nicht stattfinden
    /// darf — sonst null.
    /// </summary>
    private async Task<AgentRunResult?> CheckBudgetAsync(AgentConfig agentConfig, CancellationToken ct)
    {
        if (_budgetGuard is null)
            return null;

        var status = await _budgetGuard.CheckAsync(agentConfig, InstanceBudget, ct);
        if (status.IsAllowed)
            return null;

        var logger = _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Budget");
        logger.LogWarning("Lauf abgelehnt für {AgentId}: {Reason}", agentConfig.AgentId, status.Reason);

        var result = new AgentRunResult(
            agentConfig.AgentId, AgentRunStatus.BudgetExceeded,
            $"[Budget erschöpft] {status.Reason}", 0, 0, TimeSpan.Zero);

        OnRunCompleted?.Invoke(agentConfig.Model, result);
        return result;
    }

    /// <summary>
    /// Schreibt den Verbrauch eines Laufs fort. Fehler hierbei dürfen den Lauf nicht
    /// nachträglich scheitern lassen — die eigentliche Arbeit ist bereits getan.
    /// </summary>
    private async Task RecordUsageAsync(AgentConfig agentConfig, AgentRunResult result)
    {
        if (_usageRepository is null)
            return;

        try
        {
            var estimate = _pricing?.Estimate(agentConfig.Model, result.PromptTokens, result.CompletionTokens);

            await _usageRepository.RecordAsync(new RunUsage
            {
                AgentId = agentConfig.AgentId,
                Model = agentConfig.Model,
                PromptTokens = result.PromptTokens,
                CompletionTokens = result.CompletionTokens,
                CachedTokens = result.CachedTokens,
                CostUsd = estimate?.Usd ?? 0m,
                CostIsKnown = estimate?.IsKnown ?? false,
                Status = result.Status.ToString(),
                StepCount = result.StepCount,
                DurationMs = (long)result.Duration.TotalMilliseconds,
                OccurredAt = DateTime.Now
            }, CancellationToken.None);
        }
        catch (Exception ex)
        {
            _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Usage")
                .LogWarning(ex, "Verbrauch konnte nicht festgehalten werden für {AgentId}",
                    agentConfig.AgentId);
        }
    }

    // ─── Audit-Log und Receipts (A3) ───

    /// <summary>
    /// Schreibt einen Tool-Aufruf ins Audit-Log. Best effort — ein Fehler hierbei darf den
    /// Lauf nicht scheitern lassen; die eigentliche Arbeit ist bereits getan.
    /// </summary>
    private async Task RecordAuditAsync(
        string runId, AgentConfig agentConfig, string? source, string tool,
        string arguments, AuditStatus status, string summary, long durationMs)
    {
        if (_auditRepository is null)
            return;

        try
        {
            await _auditRepository.AppendAsync(new AuditEntry
            {
                RunId = runId,
                AgentId = agentConfig.AgentId,
                Model = agentConfig.Model,
                Source = AuditSource.Normalize(source),
                Tool = tool,
                Arguments = Cap(arguments, 4_000),
                Status = status,
                Summary = Cap(summary, 500),
                DurationMs = durationMs,
                OccurredAt = DateTime.Now
            }, CancellationToken.None);
        }
        catch (Exception ex)
        {
            _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Audit")
                .LogWarning(ex, "Audit-Eintrag konnte nicht geschrieben werden ({Tool})", tool);
        }
    }

    /// <summary>
    /// Hält den Abschluss-Beleg eines Laufs fest (Receipt). Best effort, wie beim Audit.
    /// </summary>
    private async Task RecordReceiptAsync(
        string runId, AgentConfig agentConfig, AgentRunResult result, string? source, string? taskId)
    {
        if (_auditRepository is null)
            return;

        try
        {
            var estimate = _pricing?.Estimate(agentConfig.Model, result.PromptTokens, result.CompletionTokens);

            await _auditRepository.RecordReceiptAsync(new RunReceipt
            {
                RunId = runId,
                AgentId = agentConfig.AgentId,
                Model = agentConfig.Model,
                Source = AuditSource.Normalize(source),
                TaskId = taskId,
                Status = result.Status.ToString(),
                StepCount = result.StepCount,
                PromptTokens = result.PromptTokens,
                CompletionTokens = result.CompletionTokens,
                CachedTokens = result.CachedTokens,
                CostUsd = estimate?.Usd ?? 0m,
                CostIsKnown = estimate?.IsKnown ?? false,
                DurationMs = (long)result.Duration.TotalMilliseconds,
                ResultRef = Cap(result.FinalMessage ?? "", 500),
                OccurredAt = DateTime.Now
            }, CancellationToken.None);
        }
        catch (Exception ex)
        {
            _loggerFactory.CreateLogger("ClawdDotNet.Core.Engine.Receipt")
                .LogWarning(ex, "Receipt konnte nicht geschrieben werden für {AgentId}", agentConfig.AgentId);
        }
    }

    private static string Cap(string value, int max)
        => value.Length <= max ? value : value[..max] + "…";

    /// <summary>Sammelt die Token-Zahlen über alle Schritte eines Runs.</summary>
    private sealed class TokenTally
    {
        public int Total { get; private set; }
        public int Prompt { get; private set; }
        public int Completion { get; private set; }
        public int Cached { get; private set; }

        // Voll qualifiziert: "Usage" ist auch ein Namespace (ClawdDotNet.Core.Accounting).
        public void Add(Api.Models.Usage usage)
        {
            Total += usage.TotalTokens;
            Prompt += usage.PromptTokens;
            Completion += usage.CompletionTokens;
            Cached += usage.CachedTokens;
        }
    }

    /// <summary>
    /// Kürzt ein Tool-Ergebnis, bevor es in den Kontext wandert.
    ///
    /// Ohne diese Grenze kann ein einzelner Aufruf den Kontext sprengen — ein WebFetch
    /// mit dem Standardlimit von 512 KB entspricht rund 130.000 Tokens in EINER
    /// Tool-Antwort. Die Compaction greift erst danach, der teure Request ist zu dem
    /// Zeitpunkt längst bezahlt.
    /// </summary>
    internal static string TruncateToolResult(string result, int maxChars)
    {
        if (maxChars <= 0 || result.Length <= maxChars)
            return result;

        var omitted = result.Length - maxChars;
        return result[..maxChars] +
               $"\n\n[… {omitted:N0} Zeichen gekürzt. Das Ergebnis war zu groß für den Kontext. " +
               "Grenze die Abfrage ein, wenn du den Rest brauchst.]";
    }

    private static List<ToolDefinition> BuildToolDefinitions(IReadOnlyList<IAgentTool> tools)
    {
        return tools.Select(t => new ToolDefinition
        {
            Function = new FunctionDefinition
            {
                Name = t.Name,
                Description = t.Description,
                Parameters = t.InputSchema
            }
        }).ToList();
    }
}