using System;
using System.Collections.Generic;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Gott.Models;
using Microsoft.AspNetCore.Http;

namespace Gott.Services;

public class AnthropicService
{
    private readonly IHttpClientFactory _httpFactory;
    private readonly string _token;
    private readonly ToolService _toolService;
    private readonly DatabaseService _db;

    public AnthropicService(IHttpClientFactory httpFactory, string token, ToolService toolService, DatabaseService db)
    {
        _httpFactory = httpFactory;
        _token = token;
        _toolService = toolService;
        _db = db;
    }

    public async Task StreamChat(
        HttpResponse response,
        string modelId,
        List<object> systemPrompt,
        List<object> messages,
        string chainId,
        string workspace,
        string sessionId = null,
        int maxIterations = 100,
        string toolChoice = "any",
        CancellationToken cancellationToken = default)
    {
        var sw = System.Diagnostics.Stopwatch.StartNew();
        var usage = new TokenUsage();
        int iterations = 0;
        string lastStopReason = "";

        var chain = new ChainRecord
        {
            ChainId = chainId,
            SessionId = sessionId,
            Model = modelId
        };

        try
        {
            while (iterations < maxIterations)
            {
                iterations++;

                var payload = new Dictionary<string, object>
                {
                    ["model"] = modelId,
                    ["max_tokens"] = 16384,
                    ["cache_control"] = new { type = "ephemeral" },
                    ["system"] = systemPrompt,
                    ["messages"] = messages,
                    ["stream"] = true
                };

                if (!string.IsNullOrEmpty(workspace))
                {
                    payload["tools"] = _toolService.GetToolDefinitions();
                    // "any" erzwingt Tool-Nutzung, aber nur in der ersten Iteration,
                    // damit Claude nicht endlos Tools aufruft wenn die Aufgabe erledigt ist.
                    var effectiveChoice = (toolChoice == "any" && iterations == 1) ? "any" : "auto";
                    payload["tool_choice"] = new { type = effectiveChoice };
                }

                var client = CreateClient();
                var json = JsonSerializer.Serialize(payload);
                var httpContent = new StringContent(json, Encoding.UTF8, "application/json");

                var httpResp = await client.SendAsync(
                    new HttpRequestMessage(HttpMethod.Post, "https://api.anthropic.com/v1/messages") { Content = httpContent },
                    HttpCompletionOption.ResponseHeadersRead,
                    cancellationToken
                );

                if (!httpResp.IsSuccessStatusCode)
                {
                    var errBody = await httpResp.Content.ReadAsStringAsync(cancellationToken);
                    var errMsg = $"API {(int)httpResp.StatusCode}: {errBody}";
                    await _db.SaveMessage(new MessageRecord
                    {
                        ChainId = chainId, Iteration = iterations,
                        Role = "system", Type = "error",
                        Content = errMsg, IsError = true
                    });
                    await TryWriteSse(response, "error", new { error = errMsg }, cancellationToken);
                    await FinalizeChain(chain, usage, iterations, "error", sw);
                    await TryWriteSse(response, "done", new { chainId = chain.ChainId }, cancellationToken);
                    return;
                }

                var (stopReason, assistantContent, executedTools) = await ProcessStream(response, httpResp, usage, workspace, cancellationToken);
                lastStopReason = stopReason;

                messages.Add(new { role = "assistant", content = assistantContent });

                // Assistant-Blöcke persistieren
                foreach (var block in assistantContent)
                {
                    var blockJson = JsonSerializer.Serialize(block);
                    var el = JsonSerializer.Deserialize<JsonElement>(blockJson);
                    var blockType = el.GetProperty("type").GetString() ?? "";

                    if (blockType == "text")
                    {
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "text",
                            Content = el.GetProperty("text").GetString()
                        });
                    }
                    else if (blockType == "tool_use")
                    {
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "tool_use",
                            ToolName = el.GetProperty("name").GetString(),
                            ToolCallId = el.GetProperty("id").GetString(),
                            Content = el.GetProperty("input").ToString()
                        });
                    }
                }

                // Tool Results persistieren
                foreach (var tr in executedTools)
                {
                    await _db.SaveMessage(new MessageRecord
                    {
                        ChainId = chainId, Iteration = iterations,
                        Role = "user", Type = "tool_result",
                        ToolCallId = tr.Id,
                        Content = tr.Result,
                        IsError = tr.IsError
                    });
                }

                if (stopReason != "tool_use")
                {
                    var finalStopReason = string.IsNullOrEmpty(stopReason) ? "unexpected_end" : stopReason;
                    await FinalizeChain(chain, usage, iterations, finalStopReason, sw);
                    await TryWriteSse(response, "done", new
                    {
                        model = modelId,
                        inputTokens = usage.InputTokens,
                        outputTokens = usage.OutputTokens,
                        cacheCreationTokens = usage.CacheCreationTokens,
                        cacheReadTokens = usage.CacheReadTokens,
                        iterations,
                        chainId,
                        durationMs = sw.ElapsedMilliseconds,
                        stopReason = finalStopReason
                    }, cancellationToken);
                    return;
                }

                var toolResults = new List<object>();
                foreach (var tr in executedTools)
                {
                    // Tool-Results in der History auf 20.000 Zeichen kürzen.
                    // Das vollständige Ergebnis wurde bereits in der DB gespeichert.
                    // 20k Zeichen ≈ ~5k Tokens – verhindert Token-Explosion bei großen
                    // read_file / execute-Outputs die sich über alle weiteren Iterationen schleppen.
                    const int MaxToolResultChars = 20_000;
                    var content = tr.Result.Length > MaxToolResultChars
                        ? tr.Result[..MaxToolResultChars] + $"\n\n[... gekürzt, {tr.Result.Length - MaxToolResultChars} weitere Zeichen ...]"
                        : tr.Result;

                    toolResults.Add(new
                    {
                        type = "tool_result",
                        tool_use_id = tr.Id,
                        content,
                        is_error = tr.IsError
                    });
                }

                messages.Add(new { role = "user", content = toolResults });
            }

            await FinalizeChain(chain, usage, iterations, "max_iterations", sw);
            await TryWriteSse(response, "error", new { error = "Max iterations erreicht" }, cancellationToken);
            await TryWriteSse(response, "done", new { chainId = chain.ChainId }, cancellationToken);
        }
        catch (OperationCanceledException)
        {
            // Client hat die Verbindung getrennt (z.B. Browser-Refresh)
            await FinalizeChain(chain, usage, iterations, "client_disconnected", sw);
        }
        catch (Exception ex)
        {
            // Unerwarteter Fehler – in DB speichern und versuchen an Client zu senden
            var errMsg = $"Stream-Fehler: {ex.Message}";
            await _db.SaveMessage(new MessageRecord
            {
                ChainId = chainId, Iteration = iterations,
                Role = "system", Type = "error",
                Content = errMsg, IsError = true
            });
            await FinalizeChain(chain, usage, iterations, "error", sw);
            await TryWriteSse(response, "error", new { error = errMsg }, cancellationToken);
            await TryWriteSse(response, "done", new { chainId = chain.ChainId }, cancellationToken);
        }
    }

    private async Task FinalizeChain(ChainRecord chain, TokenUsage usage, int iterations, string stopReason, System.Diagnostics.Stopwatch sw)
    {
        chain.InputTokens = usage.InputTokens;
        chain.OutputTokens = usage.OutputTokens;
        chain.CacheCreationTokens = usage.CacheCreationTokens;
        chain.CacheReadTokens = usage.CacheReadTokens;
        chain.Iterations = iterations;
        chain.StopReason = stopReason;
        chain.DurationMs = sw.ElapsedMilliseconds;
        await _db.UpdateChain(chain);
    }

    private async Task<(string StopReason, List<object> Content, List<ToolResult> Tools)> ProcessStream(
        HttpResponse response,
        HttpResponseMessage httpResp,
        TokenUsage usage,
        string workspace,
        CancellationToken cancellationToken = default)
    {
        var stream = await httpResp.Content.ReadAsStreamAsync(cancellationToken);
        using var reader = new StreamReader(stream);

        var stopReason = "";
        var assistantContent = new List<object>();
        var currentToolId = "";
        var currentToolName = "";
        var currentToolInputJson = new StringBuilder();
        var currentTextBlock = new StringBuilder();

        var blockTypes = new Dictionary<int, string>();
        var executedTools = new List<ToolResult>();

        string line;
        while ((line = await reader.ReadLineAsync(cancellationToken)) != null)
        {
            if (!line.StartsWith("data: ")) continue;
            var data = line["data: ".Length..];
            if (string.IsNullOrWhiteSpace(data)) continue;

            JsonElement evt;
            try { evt = JsonSerializer.Deserialize<JsonElement>(data); }
            catch { continue; }

            var evtType = evt.TryGetProperty("type", out var t) ? t.GetString() ?? "" : "";

            switch (evtType)
            {
                case "message_start":
                {
                    if (evt.TryGetProperty("message", out var msg) &&
                        msg.TryGetProperty("usage", out var u))
                    {
                        if (u.TryGetProperty("input_tokens", out var it))
                            usage.InputTokens += it.GetInt64();
                        if (u.TryGetProperty("cache_creation_input_tokens", out var cc))
                            usage.CacheCreationTokens += cc.GetInt64();
                        if (u.TryGetProperty("cache_read_input_tokens", out var cr))
                            usage.CacheReadTokens += cr.GetInt64();
                    }
                    break;
                }

                case "content_block_start":
                {
                    var idx = evt.GetProperty("index").GetInt32();
                    var cb = evt.GetProperty("content_block");
                    var cbType = cb.GetProperty("type").GetString() ?? "";
                    blockTypes[idx] = cbType;

                    if (cbType == "text")
                    {
                        currentTextBlock.Clear();
                        await WriteSseEvent(response, "text_start", new { index = idx });
                    }
                    else if (cbType == "tool_use")
                    {
                        if (currentTextBlock.Length > 0)
                        {
                            assistantContent.Add(new { type = "text", text = currentTextBlock.ToString() });
                            currentTextBlock.Clear();
                        }
                        currentToolId = cb.GetProperty("id").GetString() ?? "";
                        currentToolName = cb.GetProperty("name").GetString() ?? "";
                        currentToolInputJson.Clear();
                        await WriteSseEvent(response, "tool_start", new { name = currentToolName, id = currentToolId });
                    }
                    break;
                }

                case "content_block_delta":
                {
                    var delta = evt.GetProperty("delta");
                    var deltaType = delta.GetProperty("type").GetString() ?? "";

                    if (deltaType == "text_delta")
                    {
                        var text = delta.GetProperty("text").GetString() ?? "";
                        currentTextBlock.Append(text);
                        await WriteSseEvent(response, "text_delta", new { text });
                    }
                    else if (deltaType == "input_json_delta")
                    {
                        var partial = delta.GetProperty("partial_json").GetString() ?? "";
                        currentToolInputJson.Append(partial);
                    }
                    break;
                }

                case "content_block_stop":
                {
                    var idx = evt.GetProperty("index").GetInt32();
                    if (blockTypes.TryGetValue(idx, out var bt))
                    {
                        if (bt == "text")
                        {
                            var text = currentTextBlock.ToString();
                            if (text.Length > 0)
                            {
                                assistantContent.Add(new { type = "text", text });
                                await WriteSseEvent(response, "text_end", new { });
                            }
                            currentTextBlock.Clear();
                        }
                        else if (bt == "tool_use")
                        {
                            JsonElement inputEl;
                            try { inputEl = JsonSerializer.Deserialize<JsonElement>(currentToolInputJson.ToString()); }
                            catch { inputEl = JsonSerializer.Deserialize<JsonElement>("{}"); }

                            assistantContent.Add(new
                            {
                                type = "tool_use",
                                id = currentToolId,
                                name = currentToolName,
                                input = inputEl
                            });

                            string toolResult;
                            bool isError = false;
                            try { toolResult = await _toolService.ExecuteTool(currentToolName, inputEl, workspace); }
                            catch (Exception ex) { toolResult = $"Fehler: {ex.Message}"; isError = true; }

                            executedTools.Add(new ToolResult(currentToolId, toolResult, isError));

                            await WriteSseEvent(response, "tool_end", new
                            {
                                name = currentToolName,
                                input = currentToolInputJson.ToString(),
                                result = toolResult.Length > 500 ? toolResult[..500] + "..." : toolResult,
                                isError
                            });
                        }
                    }
                    break;
                }

                case "message_delta":
                {
                    if (evt.TryGetProperty("delta", out var d) &&
                        d.TryGetProperty("stop_reason", out var sr))
                        stopReason = sr.GetString() ?? "";
                    if (evt.TryGetProperty("usage", out var u2) &&
                        u2.TryGetProperty("output_tokens", out var ot))
                        usage.OutputTokens += ot.GetInt64();
                    break;
                }
            }
        }

        if (currentTextBlock.Length > 0)
            assistantContent.Add(new { type = "text", text = currentTextBlock.ToString() });

        return (stopReason, assistantContent, executedTools);
    }

    private HttpClient CreateClient()
    {
        var client = _httpFactory.CreateClient();
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _token);
        client.DefaultRequestHeaders.Add("anthropic-version", "2023-06-01");
        client.DefaultRequestHeaders.Add("anthropic-beta", "claude-code-20250219,oauth-2025-04-20");
        client.DefaultRequestHeaders.Add("User-Agent", "claude-cli/2.1.2 (external, cli)");
        client.DefaultRequestHeaders.Add("x-app", "cli");
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.DefaultRequestHeaders.Add("anthropic-dangerous-direct-browser-access", "true");
        return client;
    }

    public static async Task WriteSseEvent(HttpResponse response, string eventType, object data)
    {
        var json = JsonSerializer.Serialize(data);
        await response.WriteAsync($"event: {eventType}\ndata: {json}\n\n");
        await response.Body.FlushAsync();
    }

    private static async Task TryWriteSse(HttpResponse response, string eventType, object data, CancellationToken ct)
    {
        try
        {
            if (!ct.IsCancellationRequested)
                await WriteSseEvent(response, eventType, data);
        }
        catch
        {
            // Client bereits disconnected – ignorieren
        }
    }
}

public record ToolResult(string Id, string Result, bool IsError);

public class TokenUsage
{
    public long InputTokens { get; set; }
    public long OutputTokens { get; set; }
    public long CacheCreationTokens { get; set; }
    public long CacheReadTokens { get; set; }
}