using System.Net.Http;
using System.Runtime.CompilerServices;
using System.IO;
using System.Text;
using System.Text.Json;
using AxCopilot.Models;
using AxCopilot.Services.Agent;

namespace AxCopilot.Services;

/// <summary>
/// LlmService의 Function Calling (tool_use) 확장.
/// Claude tool_use, Gemini function_calling 프로토콜을 지원합니다.
/// 기존 SendAsync/StreamAsync는 변경하지 않고, 에이전트 전용 메서드를 추가합니다.
/// </summary>
public partial class LlmService
{
    /// <summary>LLM 응답에서 파싱된 컨텐츠 블록.</summary>
    public class ContentBlock
    {
        public string Type { get; init; } = "text"; // "text" | "tool_use"
        public string Text { get; init; } = "";      // text 타입일 때
        public string ToolName { get; init; } = "";   // tool_use 타입일 때
        public string ToolId { get; init; } = "";     // tool_use ID
        public JsonElement? ToolInput { get; init; }   // tool_use 파라미터
        public string? ResolvedToolName { get; set; }
        public Task<ToolPrefetchResult?>? PrefetchedExecutionTask { get; set; }
    }

    public sealed record ToolPrefetchResult(
        Agent.ToolResult Result,
        long ElapsedMilliseconds,
        string? ResolvedToolName = null);

    public enum ToolStreamEventKind
    {
        TextDelta,
        ToolCallReady,
        Completed
    }

    public sealed record ToolStreamEvent(
        ToolStreamEventKind Kind,
        string Text = "",
        ContentBlock? ToolCall = null);

    /// <summary>도구 정의를 포함하여 LLM에 요청하고, 텍스트 + tool_use 블록을 파싱하여 반환합니다.</summary>
    /// <param name="forceToolCall">
    /// true이면 <c>tool_choice: "required"</c>를 요청에 추가하여 모델이 반드시 도구를 호출하도록 강제합니다.
    /// 아직 한 번도 도구를 호출하지 않은 첫 번째 요청에 사용하세요.
    /// Claude/Gemini는 지원하지 않으므로 vLLM/Ollama/OpenAI 계열에만 적용됩니다.
    /// </param>
    public async Task<List<ContentBlock>> SendWithToolsAsync(
        List<ChatMessage> messages,
        IReadOnlyCollection<IAgentTool> tools,
        CancellationToken ct = default,
        bool forceToolCall = false,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync = null)
    {
        var activeService = ResolveService();
        EnsureOperationModeAllowsLlmService(activeService);
        return NormalizeServiceName(activeService) switch
        {
            "sigmoid" => await SendSigmoidWithToolsAsync(messages, tools, ct),
            "gemini" => await SendGeminiWithToolsAsync(messages, tools, ct),
            "ollama" or "vllm" => await SendOpenAiWithToolsAsync(messages, tools, ct, forceToolCall, prefetchToolCallAsync),
            _ => throw new NotSupportedException($"서비스 '{activeService}'는 아직 Function Calling을 지원하지 않습니다.")
        };
    }

    public async IAsyncEnumerable<ToolStreamEvent> StreamWithToolsAsync(
        List<ChatMessage> messages,
        IReadOnlyCollection<IAgentTool> tools,
        bool forceToolCall = false,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync = null,
        [EnumeratorCancellation] CancellationToken ct = default)
    {
        var activeService = ResolveService();
        EnsureOperationModeAllowsLlmService(activeService);

        switch (NormalizeServiceName(activeService))
        {
            case "ollama":
            case "vllm":
                await foreach (var evt in StreamOpenAiToolEventsAsync(messages, tools, ct, forceToolCall, prefetchToolCallAsync).WithCancellation(ct))
                    yield return evt;
                yield break;

            case "sigmoid":
                foreach (var block in await SendSigmoidWithToolsAsync(messages, tools, ct))
                {
                    if (block.Type == "text" && !string.IsNullOrWhiteSpace(block.Text))
                        yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, block.Text);
                    else if (block.Type == "tool_use")
                        yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: block);
                }
                yield return new ToolStreamEvent(ToolStreamEventKind.Completed);
                yield break;

            case "gemini":
                foreach (var block in await SendGeminiWithToolsAsync(messages, tools, ct))
                {
                    if (block.Type == "text" && !string.IsNullOrWhiteSpace(block.Text))
                        yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, block.Text);
                    else if (block.Type == "tool_use")
                        yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: block);
                }
                yield return new ToolStreamEvent(ToolStreamEventKind.Completed);
                yield break;

            default:
                throw new NotSupportedException($"서비스 '{activeService}'는 아직 Function Calling 스트리밍을 지원하지 않습니다.");
        }
    }

    /// <summary>도구 실행 결과를 LLM에 피드백하기 위한 메시지를 생성합니다.</summary>
    public static ChatMessage CreateToolResultMessage(string toolId, string toolName, string result)
    {
        // Claude: role=user, content=[{type:"tool_result", tool_use_id, content}]
        // 내부적으로는 JSON으로 인코딩하여 Content에 저장
        var payload = JsonSerializer.Serialize(new
        {
            type = "tool_result",
            tool_use_id = toolId,
            tool_name = toolName,
            content = result
        });
        return new ChatMessage
        {
            Role = "user",
            Content = payload,
            Timestamp = DateTime.Now,
        };
    }

    // ─── Claude Function Calling ──────────────────────────────────────

    private async Task<List<ContentBlock>> SendSigmoidWithToolsAsync(
        List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools, CancellationToken ct)
    {
        var apiKey = ResolveApiKeyForService("sigmoid");
        if (string.IsNullOrEmpty(apiKey))
            throw new InvalidOperationException("Claude API 키가 설정되지 않았습니다.");

        var body = BuildSigmoidToolBody(messages, tools);
        var json = JsonSerializer.Serialize(body);

        using var req = new HttpRequestMessage(HttpMethod.Post, $"https://{SigmoidApiHost}/v1/messages");
        req.Content = new StringContent(json, Encoding.UTF8, "application/json");
        req.Headers.Add("x-api-key", apiKey);
        req.Headers.Add(SigmoidApiVersionHeader, SigmoidApiVersion);

        using var resp = await _http.SendAsync(req, ct);
        if (!resp.IsSuccessStatusCode)
        {
            var errBody = await resp.Content.ReadAsStringAsync(ct);
            throw new HttpRequestException(ClassifyHttpError(resp, errBody));
        }

        var respJson = await resp.Content.ReadAsStringAsync(ct);
        using var doc = JsonDocument.Parse(respJson);
        var root = doc.RootElement;

        // 토큰 사용량
        if (root.TryGetProperty("usage", out var usage))
            TryParseSigmoidUsageFromElement(usage);

        // 컨텐츠 블록 파싱
        var blocks = new List<ContentBlock>();
        if (root.TryGetProperty("content", out var content))
        {
            foreach (var block in content.EnumerateArray())
            {
                var type = block.TryGetProperty("type", out var tp) ? tp.GetString() : "";
                if (type == "text")
                {
                    blocks.Add(new ContentBlock
                    {
                        Type = "text",
                        Text = block.TryGetProperty("text", out var txt) ? txt.GetString() ?? "" : ""
                    });
                }
                else if (type == "tool_use")
                {
                    blocks.Add(new ContentBlock
                    {
                        Type = "tool_use",
                        ToolName = block.TryGetProperty("name", out var nm) ? nm.GetString() ?? "" : "",
                        ToolId = block.TryGetProperty("id", out var bid) ? bid.GetString() ?? "" : "",
                        ToolInput = block.TryGetProperty("input", out var inp) ? inp.Clone() : null
                    });
                }
            }
        }

        return blocks;
    }

    private object BuildSigmoidToolBody(List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools)
    {
        var llm = _settings.Settings.Llm;
        var msgs = new List<object>();

        foreach (var m in messages)
        {
            if (m.Role == "system") continue;

            // tool_result 메시지인지 확인
            if (m.Role == "user" && m.Content.StartsWith("{\"type\":\"tool_result\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var root = doc.RootElement;
                    msgs.Add(new
                    {
                        role = "user",
                        content = new object[]
                        {
                            new
                            {
                                type = "tool_result",
                                tool_use_id = root.TryGetProperty("tool_use_id", out var tuid) ? tuid.GetString() : "",
                                content = root.TryGetProperty("content", out var tcont) ? tcont.GetString() : ""
                            }
                        }
                    });
                    continue;
                }
                catch { /* 파싱 실패시 일반 메시지로 처리 */ }
            }

            // assistant 메시지에 tool_use 블록이 포함된 경우 (에이전트 루프)
            if (m.Role == "assistant" && m.Content.StartsWith("{\"_tool_use_blocks\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    if (!doc.RootElement.TryGetProperty("_tool_use_blocks", out var blocksArr)) throw new Exception();
                    var contentList = new List<object>();
                    foreach (var b in blocksArr.EnumerateArray())
                    {
                        var bType = b.TryGetProperty("type", out var bt) ? bt.GetString() : "";
                        if (bType == "text")
                            contentList.Add(new { type = "text", text = b.TryGetProperty("text", out var tx) ? tx.GetString() ?? "" : "" });
                        else if (bType == "tool_use")
                            contentList.Add(new
                            {
                                type = "tool_use",
                                id = b.TryGetProperty("id", out var bid) ? bid.GetString() ?? "" : "",
                                name = b.TryGetProperty("name", out var nm) ? nm.GetString() ?? "" : "",
                                input = b.TryGetProperty("input", out var inp) ? (object)inp.Clone() : new { }
                            });
                    }
                    msgs.Add(new { role = "assistant", content = contentList });
                    continue;
                }
                catch { /* 파싱 실패시 일반 메시지로 처리 */ }
            }

            // Claude Vision: 이미지가 있으면 content를 배열로 변환
            if (m.Images?.Count > 0 && m.Role == "user")
            {
                var contentParts = new List<object>();
                foreach (var img in m.Images)
                    contentParts.Add(new { type = "image", source = new { type = "base64", media_type = img.MimeType, data = img.Base64 } });
                contentParts.Add(new { type = "text", text = m.Content });
                msgs.Add(new { role = m.Role, content = contentParts });
            }
            else
            {
                msgs.Add(new { role = m.Role, content = m.Content });
            }
        }

        // 도구 정의
        var toolDefs = tools.Select(t => new
        {
            name = t.Name,
            description = t.Description,
            input_schema = new
            {
                type = "object",
                properties = t.Parameters.Properties.ToDictionary(
                    kv => kv.Key,
                    kv => BuildPropertySchema(kv.Value, false)),
                required = t.Parameters.Required
            }
        }).ToArray();

        // 시스템 프롬프트
        var systemPrompt = messages.FirstOrDefault(m => m.Role == "system")?.Content ?? _systemPrompt;
        var activeModel = ResolveModel();

        if (!string.IsNullOrEmpty(systemPrompt))
        {
            return new
            {
                model = activeModel,
                max_tokens = ResolveOpenAiCompatibleMaxTokens(),
                temperature = llm.Temperature,
                system = systemPrompt,
                messages = msgs,
                tools = toolDefs,
                stream = false
            };
        }

        return new
        {
            model = activeModel,
            max_tokens = ResolveOpenAiCompatibleMaxTokens(),
            temperature = llm.Temperature,
            messages = msgs,
            tools = toolDefs,
            stream = false
        };
    }

    // ─── Gemini Function Calling ───────────────────────────────────────

    private async Task<List<ContentBlock>> SendGeminiWithToolsAsync(
        List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools, CancellationToken ct)
    {
        var llm = _settings.Settings.Llm;
        var apiKey = ResolveApiKeyForService("gemini");
        if (string.IsNullOrEmpty(apiKey))
            throw new InvalidOperationException("Gemini API 키가 설정되지 않았습니다.");

        var activeModel = ResolveModel();
        var body = BuildGeminiToolBody(messages, tools);
        var url = $"https://generativelanguage.googleapis.com/v1beta/models/{activeModel}:generateContent?key={apiKey}";
        var json = JsonSerializer.Serialize(body);

        using var content = new StringContent(json, Encoding.UTF8, "application/json");
        using var resp = await _http.PostAsync(url, content, ct);
        if (!resp.IsSuccessStatusCode)
        {
            var errBody = await resp.Content.ReadAsStringAsync(ct);
            throw new HttpRequestException($"Gemini API 오류 ({resp.StatusCode}): {errBody}");
        }

        var respJson = await resp.Content.ReadAsStringAsync(ct);
        using var doc = JsonDocument.Parse(respJson);
        var root = doc.RootElement;

        TryParseGeminiUsage(root);

        var blocks = new List<ContentBlock>();
        if (root.TryGetProperty("candidates", out var candidates) && candidates.GetArrayLength() > 0)
        {
            var firstCandidate = candidates[0];
            if (firstCandidate.TryGetProperty("content", out var contentObj) &&
                contentObj.TryGetProperty("parts", out var parts))
            {
                foreach (var part in parts.EnumerateArray())
                {
                    if (part.TryGetProperty("text", out var text))
                    {
                        blocks.Add(new ContentBlock { Type = "text", Text = text.GetString() ?? "" });
                    }
                    else if (part.TryGetProperty("functionCall", out var fc))
                    {
                        blocks.Add(new ContentBlock
                        {
                            Type = "tool_use",
                            ToolName = fc.TryGetProperty("name", out var fcName) ? fcName.GetString() ?? "" : "",
                            ToolId = Guid.NewGuid().ToString("N")[..12],
                            ToolInput = fc.TryGetProperty("args", out var a) ? a.Clone() : null
                        });
                    }
                }
            }
        }

        return blocks;
    }

    private object BuildGeminiToolBody(List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools)
    {
        var contents = new List<object>();
        foreach (var m in messages)
        {
            if (m.Role == "system") continue;
            var role = m.Role == "assistant" ? "model" : "user";

            // tool_result 메시지 처리
            if (m.Role == "user" && m.Content.StartsWith("{\"type\":\"tool_result\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var root = doc.RootElement;
                    var toolName = root.TryGetProperty("tool_name", out var tn) ? tn.GetString() ?? "" : "";
                    var toolContent = root.TryGetProperty("content", out var tc) ? tc.GetString() ?? "" : "";
                    contents.Add(new
                    {
                        role = "function",
                        parts = new object[]
                        {
                            new
                            {
                                functionResponse = new
                                {
                                    name = toolName,
                                    response = new { result = toolContent }
                                }
                            }
                        }
                    });
                    continue;
                }
                catch { }
            }

            // assistant 메시지에 tool_use 블록이 포함된 경우 (에이전트 루프)
            if (m.Role == "assistant" && m.Content.StartsWith("{\"_tool_use_blocks\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    if (doc.RootElement.TryGetProperty("_tool_use_blocks", out var blocksArr))
                    {
                        var parts = new List<object>();
                        foreach (var b in blocksArr.EnumerateArray())
                        {
                            var bType = b.TryGetProperty("type", out var bt) ? bt.GetString() : "";
                            if (bType == "text")
                                parts.Add(new { text = b.TryGetProperty("text", out var tx) ? tx.GetString() ?? "" : "" });
                            else if (bType == "tool_use")
                                parts.Add(new
                                {
                                    functionCall = new
                                    {
                                        name = b.TryGetProperty("name", out var nm) ? nm.GetString() ?? "" : "",
                                        args = b.TryGetProperty("input", out var inp) ? (object)inp.Clone() : new { }
                                    }
                                });
                        }
                        contents.Add(new { role = "model", parts });
                        continue;
                    }
                }
                catch { }
            }

            // Gemini Vision: 이미지가 있으면 parts에 inlineData 추가
            if (m.Images?.Count > 0 && m.Role == "user")
            {
                var imgParts = new List<object> { new { text = m.Content } };
                foreach (var img in m.Images)
                    imgParts.Add(new { inlineData = new { mimeType = img.MimeType, data = img.Base64 } });
                contents.Add(new { role, parts = imgParts });
            }
            else
            {
                contents.Add(new { role, parts = new[] { new { text = m.Content } } });
            }
        }

        // 도구 정의 (Gemini function_declarations 형식)
        var funcDecls = tools.Select(t => new
        {
            name = t.Name,
            description = t.Description,
            parameters = new
            {
                type = "OBJECT",
                properties = t.Parameters.Properties.ToDictionary(
                    kv => kv.Key,
                    kv => BuildPropertySchema(kv.Value, true)),
                required = t.Parameters.Required
            }
        }).ToArray();

        var systemInstruction = messages.FirstOrDefault(m => m.Role == "system");

        var body = new Dictionary<string, object>
        {
            ["contents"] = contents,
            ["tools"] = new[] { new { function_declarations = funcDecls } },
            ["generationConfig"] = new
            {
                temperature = ResolveTemperature(),
                maxOutputTokens = _settings.Settings.Llm.MaxContextTokens,
            }
        };

        if (systemInstruction != null)
        {
            body["systemInstruction"] = new
            {
                parts = new[] { new { text = systemInstruction.Content } }
            };
        }

        return body;
    }

    // ─── OpenAI Compatible (Ollama / vLLM) Function Calling ──────────

    private async Task<List<ContentBlock>> SendOpenAiWithToolsAsync(
        List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools, CancellationToken ct,
        bool forceToolCall = false,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync = null)
    {
        var activeService = ResolveService();

        // 등록 모델의 커스텀 엔드포인트 우선 사용 (ResolveServerInfo)
        var (resolvedEp, _, allowInsecureTls) = ResolveServerInfo();
        var endpoint = string.IsNullOrEmpty(resolvedEp)
            ? ResolveEndpointForService(activeService)
            : resolvedEp;
        var registered = GetActiveRegisteredModel();
        var isIbmDeployment = UsesIbmDeploymentChatApi(activeService, registered, endpoint);

        var body = isIbmDeployment
            ? BuildIbmToolBody(messages, tools, forceToolCall)
            : BuildOpenAiToolBody(messages, tools, forceToolCall);

        string url;
        if (isIbmDeployment)
            url = BuildIbmDeploymentChatUrl(endpoint, stream: true);
        else if (activeService.ToLowerInvariant() == "ollama")
            url = endpoint.TrimEnd('/') + "/api/chat";
        else
            url = endpoint.TrimEnd('/') + "/v1/chat/completions";
        var json = JsonSerializer.Serialize(body);

        using var req = new HttpRequestMessage(HttpMethod.Post, url)
        {
            Content = new StringContent(json, Encoding.UTF8, "application/json")
        };
        // CP4D 또는 Bearer 인증 적용
        await ApplyAuthHeaderAsync(req, ct);

        using var resp = await SendWithTlsAsync(req, allowInsecureTls, ct, HttpCompletionOption.ResponseHeadersRead);
        if (!resp.IsSuccessStatusCode)
        {
            var errBody = await resp.Content.ReadAsStringAsync(ct);
            var detail = ExtractErrorDetail(errBody);
            LogService.Warn($"[ToolUse] {activeService} API 오류 ({resp.StatusCode}): {errBody}");

            if (isIbmDeployment && forceToolCall && (int)resp.StatusCode == 400)
            {
                LogService.Warn("[ToolUse] IBM 배포형 경로에서 tool_choice가 거부되어 대체 강제 전략으로 재시도합니다.");
                var fallbackBody = BuildIbmToolBody(messages, tools, forceToolCall: true, useToolChoice: false);
                var fallbackJson = JsonSerializer.Serialize(fallbackBody);
                using var retryReq = new HttpRequestMessage(HttpMethod.Post, url)
                {
                    Content = new StringContent(fallbackJson, Encoding.UTF8, "application/json")
                };
                await ApplyAuthHeaderAsync(retryReq, ct);
                using var retryResp = await SendWithTlsAsync(retryReq, allowInsecureTls, ct, HttpCompletionOption.ResponseHeadersRead);
                if (retryResp.IsSuccessStatusCode)
                    return await ReadOpenAiToolBlocksFromStreamAsync(retryResp, true, prefetchToolCallAsync, ct);
            }

            // 400 BadRequest → 도구 없이 일반 응답으로 폴백 시도
            if ((int)resp.StatusCode == 400)
                throw new ToolCallNotSupportedException(
                    $"{activeService} API 오류 ({resp.StatusCode}): {detail}");

            throw new HttpRequestException($"{activeService} API 오류 ({resp.StatusCode}): {detail}");
        }

        return await ReadOpenAiToolBlocksFromStreamAsync(resp, isIbmDeployment, prefetchToolCallAsync, ct);
    }

    /// <summary>
    /// Qwen/vLLM 등이 tool_calls 대신 텍스트로 도구 호출을 출력하는 경우를 파싱합니다.
    /// 지원 패턴:
    /// 1. &lt;tool_call&gt;{"name":"...", "arguments":{...}}&lt;/tool_call&gt;
    /// 2. Qwen3 &lt;tool_call&gt;\n{"name":"...", "arguments":{...}}\n&lt;/tool_call&gt;
    /// 3. 여러 건의 연속 tool_call 태그
    /// </summary>
    private static List<ContentBlock> TryExtractToolCallsFromText(string text)
    {
        var results = new List<ContentBlock>();
        if (string.IsNullOrWhiteSpace(text)) return results;

        // 패턴 1: <tool_call>...</tool_call> 태그 (Qwen 계열 기본 출력)
        var tagPattern = new System.Text.RegularExpressions.Regex(
            @"<\s*tool_call\s*>\s*(\{[\s\S]*?\})\s*<\s*/\s*tool_call\s*>",
            System.Text.RegularExpressions.RegexOptions.IgnoreCase);

        foreach (System.Text.RegularExpressions.Match m in tagPattern.Matches(text))
        {
            var block = TryParseToolCallJson(m.Groups[1].Value);
            if (block != null) results.Add(block);
        }

        // 패턴 2: ✿FUNCTION✿ 또는 <|tool_call|> (일부 Qwen 변형)
        if (results.Count == 0)
        {
            var fnPattern = new System.Text.RegularExpressions.Regex(
                @"✿FUNCTION✿\s*(\w+)\s*\n\s*(\{[\s\S]*?\})\s*(?:✿|$)",
                System.Text.RegularExpressions.RegexOptions.IgnoreCase);
            foreach (System.Text.RegularExpressions.Match m in fnPattern.Matches(text))
            {
                var block = TryParseToolCallJsonWithName(m.Groups[1].Value, m.Groups[2].Value);
                if (block != null) results.Add(block);
            }
        }

        // 패턴 3: JSON 객체가 직접 출력된 경우 ({"name":"tool_name","arguments":{...}})
        if (results.Count == 0)
        {
            var jsonPattern = new System.Text.RegularExpressions.Regex(
                @"\{\s*""name""\s*:\s*""(\w+)""\s*,\s*""arguments""\s*:\s*(\{[\s\S]*?\})\s*\}");
            foreach (System.Text.RegularExpressions.Match m in jsonPattern.Matches(text))
            {
                var block = TryParseToolCallJsonWithName(m.Groups[1].Value, m.Groups[2].Value);
                if (block != null) results.Add(block);
            }
        }

        return results;
    }

    /// <summary>{"name":"...", "arguments":{...}} 형식 JSON을 ContentBlock으로 변환.</summary>
    private static ContentBlock? TryParseToolCallJson(string json)
    {
        try
        {
            using var doc = JsonDocument.Parse(json);
            var root = doc.RootElement;
            var name = root.TryGetProperty("name", out var n) ? n.GetString() ?? "" : "";
            if (string.IsNullOrEmpty(name)) return null;

            JsonElement? args = null;
            if (root.TryGetProperty("arguments", out var a))
                args = a.Clone();
            else if (root.TryGetProperty("parameters", out var p))
                args = p.Clone();

            return new ContentBlock
            {
                Type = "tool_use",
                ToolName = name,
                ToolId = $"text_fc_{Guid.NewGuid():N}"[..16],
                ToolInput = args,
            };
        }
        catch { return null; }
    }

    /// <summary>이름과 arguments JSON이 별도로 주어진 경우.</summary>
    private static ContentBlock? TryParseToolCallJsonWithName(string name, string argsJson)
    {
        if (string.IsNullOrWhiteSpace(name)) return null;
        try
        {
            using var doc = JsonDocument.Parse(argsJson);
            return new ContentBlock
            {
                Type = "tool_use",
                ToolName = name.Trim(),
                ToolId = $"text_fc_{Guid.NewGuid():N}"[..16],
                ToolInput = doc.RootElement.Clone(),
            };
        }
        catch { return null; }
    }

    private object BuildOpenAiToolBody(List<ChatMessage> messages, IReadOnlyCollection<IAgentTool> tools, bool forceToolCall = false)
    {
        var llm = _settings.Settings.Llm;
        var msgs = new List<object>();

        foreach (var m in messages)
        {
            // tool_result 메시지 → OpenAI tool 응답 형식
            if (m.Role == "user" && m.Content.StartsWith("{\"type\":\"tool_result\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var root = doc.RootElement;
                    msgs.Add(new
                    {
                        role = "tool",
                        tool_call_id = root.GetProperty("tool_use_id").GetString(),
                        content = root.GetProperty("content").GetString(),
                    });
                    continue;
                }
                catch { }
            }

            // assistant 메시지에 tool_use 블록이 포함된 경우
            if (m.Role == "assistant" && m.Content.StartsWith("{\"_tool_use_blocks\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var blocksArr = doc.RootElement.GetProperty("_tool_use_blocks");
                    var textContent = "";
                    var toolCallsList = new List<object>();
                    foreach (var b in blocksArr.EnumerateArray())
                    {
                        var bType = b.GetProperty("type").GetString();
                        if (bType == "text")
                            textContent = b.GetProperty("text").GetString() ?? "";
                        else if (bType == "tool_use")
                        {
                            var argsJson = b.TryGetProperty("input", out var inp) ? inp.GetRawText() : "{}";
                            toolCallsList.Add(new
                            {
                                id = b.GetProperty("id").GetString() ?? "",
                                type = "function",
                                function = new
                                {
                                    name = b.GetProperty("name").GetString() ?? "",
                                    arguments = argsJson,
                                }
                            });
                        }
                    }
                    msgs.Add(new
                    {
                        role = "assistant",
                        content = string.IsNullOrEmpty(textContent) ? (string?)null : textContent,
                        tool_calls = toolCallsList,
                    });
                    continue;
                }
                catch { }
            }

            // ── 이미지 첨부 (Vision) ──
            if (m.Role == "user" && m.Images?.Count > 0)
            {
                var contentParts = new List<object>();
                foreach (var img in m.Images)
                    contentParts.Add(new { type = "image_url", image_url = new { url = $"data:{img.MimeType};base64,{img.Base64}" } });
                contentParts.Add(new { type = "text", text = m.Content });
                msgs.Add(new { role = m.Role, content = contentParts });
            }
            else
            {
                msgs.Add(new { role = m.Role, content = m.Content });
            }
        }

        // OpenAI 도구 정의
        var toolDefs = tools.Select(t =>
        {
            // parameters 객체: required가 비어있으면 생략 (일부 Ollama 버전 호환)
            var paramDict = new Dictionary<string, object>
            {
                ["type"] = "object",
                ["properties"] = t.Parameters.Properties.ToDictionary(
                    kv => kv.Key,
                    kv => BuildPropertySchema(kv.Value, false)),
            };
            if (t.Parameters.Required is { Count: > 0 })
                paramDict["required"] = t.Parameters.Required;

            return new
            {
                type = "function",
                function = new
                {
                    name = t.Name,
                    description = t.Description,
                    parameters = paramDict,
                }
            };
        }).ToArray();

        var activeService = ResolveService();
        var activeModel = ResolveModel();
        var executionPolicy = GetActiveExecutionPolicy();
        var isOllama = activeService.Equals("ollama", StringComparison.OrdinalIgnoreCase);
        if (isOllama)
        {
            return new
            {
                model = activeModel,
                messages = msgs,
                tools = toolDefs,
                stream = false,
                options = new { temperature = ResolveToolTemperature() }
            };
        }

        var body = new Dictionary<string, object?>
        {
            ["model"] = activeModel,
            ["messages"] = msgs,
            ["tools"] = toolDefs,
            ["stream"] = true,
            ["temperature"] = ResolveToolTemperature(),
            ["max_tokens"] = ResolveOpenAiCompatibleMaxTokens(),
            ["parallel_tool_calls"] = executionPolicy.EnableParallelReadBatch,
        };
        // tool_choice: "required" — 모델이 반드시 도구를 호출하도록 강제
        // 아직 한 번도 도구를 호출하지 않은 첫 번째 요청에서만 사용 (chatty 모델 대응)
        if (forceToolCall)
            body["tool_choice"] = "required";
        var effort = ResolveReasoningEffort();
        if (!string.IsNullOrWhiteSpace(effort))
            body["reasoning_effort"] = effort;
        return body;
    }

    /// <summary>IBM 배포형 /text/chat 전용 도구 바디. parameters 래퍼 사용, model 필드 없음.</summary>
    private object BuildIbmToolBody(
        List<ChatMessage> messages,
        IReadOnlyCollection<IAgentTool> tools,
        bool forceToolCall = false,
        bool useToolChoice = true)
    {
        var executionPolicy = GetActiveExecutionPolicy();
        var strictToolOnlyDirective =
            forceToolCall &&
            string.Equals(executionPolicy.Key, "tool_call_strict", StringComparison.OrdinalIgnoreCase);
        var msgs = new List<object>();

        // 시스템 프롬프트
        var systemPrompt = messages.FirstOrDefault(m => m.Role == "system")?.Content ?? _systemPrompt;
        if (!string.IsNullOrWhiteSpace(systemPrompt))
            msgs.Add(new { role = "system", content = systemPrompt });

        foreach (var m in messages)
        {
            if (m.Role == "system") continue;

            // tool_result → OpenAI role:"tool" 형식 (watsonx /text/chat 지원)
            if (m.Role == "user" && m.Content.StartsWith("{\"type\":\"tool_result\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var root = doc.RootElement;
                    msgs.Add(new
                    {
                        role = "tool",
                        tool_call_id = root.GetProperty("tool_use_id").GetString(),
                        content = root.GetProperty("content").GetString(),
                    });
                    continue;
                }
                catch { }
            }

            // _tool_use_blocks → OpenAI tool_calls 형식
            if (m.Role == "assistant" && m.Content.StartsWith("{\"_tool_use_blocks\""))
            {
                try
                {
                    using var doc = JsonDocument.Parse(m.Content);
                    var blocksArr = doc.RootElement.GetProperty("_tool_use_blocks");
                    var textContent = "";
                    var toolCallsList = new List<object>();
                    foreach (var b in blocksArr.EnumerateArray())
                    {
                        var bType = b.GetProperty("type").GetString();
                        if (bType == "text")
                            textContent = b.GetProperty("text").GetString() ?? "";
                        else if (bType == "tool_use")
                        {
                            var argsJson = b.TryGetProperty("input", out var inp) ? inp.GetRawText() : "{}";
                            toolCallsList.Add(new
                            {
                                id = b.GetProperty("id").GetString() ?? "",
                                type = "function",
                                function = new
                                {
                                    name = b.GetProperty("name").GetString() ?? "",
                                    arguments = argsJson,
                                }
                            });
                        }
                    }
                    msgs.Add(new
                    {
                        role = "assistant",
                        content = string.IsNullOrEmpty(textContent) ? (string?)null : textContent,
                        tool_calls = toolCallsList,
                    });
                    continue;
                }
                catch { }
            }

            msgs.Add(new { role = m.Role == "assistant" ? "assistant" : "user", content = m.Content });
        }

        if (strictToolOnlyDirective)
        {
            msgs.Add(new
            {
                role = "user",
                content = "[TOOL_ONLY] 설명하지 말고 지금 즉시 tools 중 하나 이상을 호출하세요. 평문 응답 금지. 도구 호출만 하세요."
            });
        }

        // OpenAI 호환 도구 정의 (형식 동일, watsonx에서 tools 필드 지원)
        var toolDefs = tools.Select(t =>
        {
            var paramDict = new Dictionary<string, object>
            {
                ["type"] = "object",
                ["properties"] = t.Parameters.Properties.ToDictionary(
                    kv => kv.Key,
                    kv => BuildPropertySchema(kv.Value, false)),
            };
            if (t.Parameters.Required is { Count: > 0 })
                paramDict["required"] = t.Parameters.Required;

            return new
            {
                type = "function",
                function = new
                {
                    name = t.Name,
                    description = t.Description,
                    parameters = paramDict,
                }
            };
        }).ToArray();

        // IBM watsonx: parameters 래퍼 사용, model 필드 없음
        // tool_choice: "required" 지원 여부는 배포 버전마다 다를 수 있으므로
        // forceToolCall=true일 때 추가하되, 오류 시 상위에서 ToolCallNotSupportedException으로 폴백됨
        if (forceToolCall && useToolChoice)
        {
            return new
            {
                messages = msgs,
                tools = toolDefs,
                tool_choice = "required",
                parameters = new
                {
                    temperature = ResolveToolTemperature(),
                    max_new_tokens = ResolveOpenAiCompatibleMaxTokens()
                }
            };
        }

        return new
        {
            messages = msgs,
            tools = toolDefs,
            parameters = new
            {
                temperature = ResolveToolTemperature(),
                max_new_tokens = ResolveOpenAiCompatibleMaxTokens()
            }
        };
    }

    private sealed class ToolCallAccumulator
    {
        public int Index { get; init; }
        public string Id { get; set; } = "";
        public string Name { get; set; } = "";
        public StringBuilder Arguments { get; } = new();
        public bool Emitted { get; set; }
    }

    private async Task<List<ContentBlock>> ReadOpenAiToolBlocksFromStreamAsync(
        HttpResponseMessage resp,
        bool usesIbmDeploymentApi,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync,
        CancellationToken ct)
    {
        var blocks = new List<ContentBlock>();
        var textBuilder = new StringBuilder();

        await foreach (var evt in StreamOpenAiToolEventsAsync(resp, usesIbmDeploymentApi, prefetchToolCallAsync, ct).WithCancellation(ct))
        {
            if (evt.Kind == ToolStreamEventKind.TextDelta && !string.IsNullOrWhiteSpace(evt.Text))
            {
                textBuilder.Append(evt.Text);
            }
            else if (evt.Kind == ToolStreamEventKind.ToolCallReady && evt.ToolCall != null)
            {
                blocks.Add(evt.ToolCall);
            }
        }

        var text = textBuilder.ToString().Trim();
        var result = new List<ContentBlock>();
        if (!string.IsNullOrWhiteSpace(text))
            result.Add(new ContentBlock { Type = "text", Text = text });
        result.AddRange(blocks);

        if (!result.Any(b => b.Type == "tool_use"))
        {
            var textBlock = result.FirstOrDefault(b => b.Type == "text" && !string.IsNullOrWhiteSpace(b.Text));
            if (textBlock != null)
            {
                var extracted = TryExtractToolCallsFromText(textBlock.Text);
                if (extracted.Count > 0)
                {
                    foreach (var block in extracted)
                    {
                        if (prefetchToolCallAsync != null)
                            block.PrefetchedExecutionTask = prefetchToolCallAsync(block);
                    }
                    result.AddRange(extracted);
                    LogService.Debug($"[ToolUse] 텍스트에서 도구 호출 {extracted.Count}건 추출 (SSE 폴백 파싱)");
                }
            }
        }

        return result;
    }

    private async IAsyncEnumerable<ToolStreamEvent> StreamOpenAiToolEventsAsync(
        List<ChatMessage> messages,
        IReadOnlyCollection<IAgentTool> tools,
        [EnumeratorCancellation] CancellationToken ct,
        bool forceToolCall = false,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync = null)
    {
        var activeService = ResolveService();
        var (resolvedEp, _, allowInsecureTls) = ResolveServerInfo();
        var endpoint = string.IsNullOrEmpty(resolvedEp)
            ? ResolveEndpointForService(activeService)
            : resolvedEp;
        var registered = GetActiveRegisteredModel();
        var isIbmDeployment = UsesIbmDeploymentChatApi(activeService, registered, endpoint);

        var body = isIbmDeployment
            ? BuildIbmToolBody(messages, tools, forceToolCall)
            : BuildOpenAiToolBody(messages, tools, forceToolCall);

        string url;
        if (isIbmDeployment)
            url = BuildIbmDeploymentChatUrl(endpoint, stream: true);
        else if (activeService.Equals("ollama", StringComparison.OrdinalIgnoreCase))
            url = endpoint.TrimEnd('/') + "/api/chat";
        else
            url = endpoint.TrimEnd('/') + "/v1/chat/completions";
        var json = JsonSerializer.Serialize(body);

        using var req = new HttpRequestMessage(HttpMethod.Post, url)
        {
            Content = new StringContent(json, Encoding.UTF8, "application/json")
        };
        await ApplyAuthHeaderAsync(req, ct);
        using var resp = await SendWithTlsAsync(req, allowInsecureTls, ct, HttpCompletionOption.ResponseHeadersRead);
        if (!resp.IsSuccessStatusCode)
        {
            var errBody = await resp.Content.ReadAsStringAsync(ct);
            var detail = ExtractErrorDetail(errBody);
            if (isIbmDeployment && forceToolCall && (int)resp.StatusCode == 400)
            {
                var fallbackBody = BuildIbmToolBody(messages, tools, forceToolCall: true, useToolChoice: false);
                var fallbackJson = JsonSerializer.Serialize(fallbackBody);
                using var retryReq = new HttpRequestMessage(HttpMethod.Post, url)
                {
                    Content = new StringContent(fallbackJson, Encoding.UTF8, "application/json")
                };
                await ApplyAuthHeaderAsync(retryReq, ct);
                using var retryResp = await SendWithTlsAsync(retryReq, allowInsecureTls, ct, HttpCompletionOption.ResponseHeadersRead);
                if (!retryResp.IsSuccessStatusCode)
                    throw new ToolCallNotSupportedException($"{activeService} API 오류 ({retryResp.StatusCode}): {detail}");

                await foreach (var evt in StreamOpenAiToolEventsAsync(retryResp, true, prefetchToolCallAsync, ct).WithCancellation(ct))
                    yield return evt;
                yield break;
            }

            if ((int)resp.StatusCode == 400)
                throw new ToolCallNotSupportedException($"{activeService} API 오류 ({resp.StatusCode}): {detail}");

            throw new HttpRequestException($"{activeService} API 오류 ({resp.StatusCode}): {detail}");
        }

        await foreach (var evt in StreamOpenAiToolEventsAsync(resp, isIbmDeployment, prefetchToolCallAsync, ct).WithCancellation(ct))
            yield return evt;
    }

    private async IAsyncEnumerable<ToolStreamEvent> StreamOpenAiToolEventsAsync(
        HttpResponseMessage resp,
        bool usesIbmDeploymentApi,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync,
        [EnumeratorCancellation] CancellationToken ct)
    {
        using var stream = await resp.Content.ReadAsStreamAsync(ct);
        using var reader = new StreamReader(stream);

        var firstChunkReceived = false;
        var toolAccumulators = new Dictionary<int, ToolCallAccumulator>();
        var lastIbmGeneratedText = "";

        while (!reader.EndOfStream && !ct.IsCancellationRequested)
        {
            var timeout = firstChunkReceived ? SubsequentChunkTimeout : FirstChunkTimeout;
            var line = await ReadLineWithTimeoutAsync(reader, ct, timeout);
            if (line == null)
            {
                if (!firstChunkReceived)
                    throw new TimeoutException("도구 호출 응답 첫 청크를 받지 못했습니다.");
                break;
            }

            if (string.IsNullOrWhiteSpace(line) || !line.StartsWith("data: ", StringComparison.Ordinal))
                continue;

            firstChunkReceived = true;
            var data = line["data: ".Length..].Trim();
            if (string.Equals(data, "[DONE]", StringComparison.OrdinalIgnoreCase))
                break;

            using var doc = JsonDocument.Parse(data);
            var root = doc.RootElement;
            TryParseOpenAiUsage(root);

            if (usesIbmDeploymentApi &&
                root.TryGetProperty("status", out var statusEl) &&
                string.Equals(statusEl.GetString(), "error", StringComparison.OrdinalIgnoreCase))
            {
                var detail = root.TryGetProperty("message", out var msgEl)
                    ? msgEl.GetString()
                    : "IBM vLLM 도구 호출 응답 오류";
                throw new ToolCallNotSupportedException(detail ?? "IBM vLLM 도구 호출 응답 오류");
            }

            if (TryExtractMessageToolBlocks(root, out var messageText, out var directToolBlocks))
            {
                if (!string.IsNullOrWhiteSpace(messageText))
                    yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, messageText);
                if (directToolBlocks.Count > 0)
                {
                    foreach (var toolBlock in directToolBlocks)
                    {
                        if (prefetchToolCallAsync != null)
                            toolBlock.PrefetchedExecutionTask = prefetchToolCallAsync(toolBlock);
                        yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: toolBlock);
                    }
                }
                continue;
            }

            if (usesIbmDeploymentApi &&
                root.TryGetProperty("results", out var resultsEl) &&
                resultsEl.ValueKind == JsonValueKind.Array &&
                resultsEl.GetArrayLength() > 0)
            {
                var first = resultsEl[0];
                var generatedText = first.TryGetProperty("generated_text", out var generatedTextEl)
                    ? generatedTextEl.GetString()
                    : first.TryGetProperty("output_text", out var outputTextEl)
                        ? outputTextEl.GetString()
                        : null;
                if (!string.IsNullOrEmpty(generatedText))
                {
                    if (generatedText.StartsWith(lastIbmGeneratedText, StringComparison.Ordinal))
                    {
                        var delta = generatedText[lastIbmGeneratedText.Length..];
                        if (!string.IsNullOrEmpty(delta))
                            yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, delta);
                        lastIbmGeneratedText = generatedText;
                    }
                    else
                    {
                        if (!string.IsNullOrEmpty(generatedText))
                            yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, generatedText);
                        lastIbmGeneratedText = generatedText;
                    }
                }
            }

            if (root.TryGetProperty("choices", out var choicesEl) &&
                choicesEl.ValueKind == JsonValueKind.Array &&
                choicesEl.GetArrayLength() > 0)
            {
                var firstChoice = choicesEl[0];
                if (firstChoice.TryGetProperty("delta", out var deltaEl))
                {
                    if (deltaEl.TryGetProperty("content", out var contentEl) &&
                        contentEl.ValueKind == JsonValueKind.String)
                    {
                        var chunk = contentEl.GetString();
                        if (!string.IsNullOrEmpty(chunk))
                            yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, chunk);
                    }

                    if (deltaEl.TryGetProperty("tool_calls", out var toolCallsEl) &&
                        toolCallsEl.ValueKind == JsonValueKind.Array)
                    {
                        foreach (var toolCallEl in toolCallsEl.EnumerateArray())
                        {
                            var index = toolCallEl.TryGetProperty("index", out var indexEl) &&
                                        indexEl.TryGetInt32(out var parsedIndex)
                                ? parsedIndex
                                : toolAccumulators.Count;

                            if (!toolAccumulators.TryGetValue(index, out var acc))
                            {
                                acc = new ToolCallAccumulator { Index = index };
                                toolAccumulators[index] = acc;
                            }

                            if (toolCallEl.TryGetProperty("id", out var idEl) && idEl.ValueKind == JsonValueKind.String)
                                acc.Id = idEl.GetString() ?? acc.Id;

                            if (toolCallEl.TryGetProperty("function", out var functionEl))
                            {
                                if (functionEl.TryGetProperty("name", out var nameEl) && nameEl.ValueKind == JsonValueKind.String)
                                    acc.Name = nameEl.GetString() ?? acc.Name;

                                if (functionEl.TryGetProperty("arguments", out var argumentsEl))
                                {
                                    if (argumentsEl.ValueKind == JsonValueKind.String)
                                        acc.Arguments.Append(argumentsEl.GetString());
                                    else if (argumentsEl.ValueKind is JsonValueKind.Object or JsonValueKind.Array)
                                        acc.Arguments.Append(argumentsEl.GetRawText());
                                }
                            }

                            var emittedBlock = await TryCreateCompletedToolCallAsync(acc, prefetchToolCallAsync).ConfigureAwait(false);
                            if (emittedBlock != null)
                                yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: emittedBlock);
                        }
                    }
                }

                if (firstChoice.TryGetProperty("message", out var messageEl))
                {
                    if (TryExtractMessageToolBlocks(messageEl, out var messageText2, out var directToolBlocks2))
                    {
                        if (!string.IsNullOrWhiteSpace(messageText2))
                            yield return new ToolStreamEvent(ToolStreamEventKind.TextDelta, messageText2);
                        if (directToolBlocks2.Count > 0)
                        {
                            foreach (var toolBlock in directToolBlocks2)
                            {
                                if (prefetchToolCallAsync != null)
                                    toolBlock.PrefetchedExecutionTask = prefetchToolCallAsync(toolBlock);
                                yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: toolBlock);
                            }
                        }
                    }
                }
            }
        }

        foreach (var acc in toolAccumulators.Values.OrderBy(a => a.Index))
        {
            var emittedBlock = await TryCreateCompletedToolCallAsync(acc, prefetchToolCallAsync, forceEmit: true).ConfigureAwait(false);
            if (emittedBlock != null)
                yield return new ToolStreamEvent(ToolStreamEventKind.ToolCallReady, ToolCall: emittedBlock);
        }

        yield return new ToolStreamEvent(ToolStreamEventKind.Completed);
    }

    private static bool TryExtractMessageToolBlocks(
        JsonElement messageOrRoot,
        out string text,
        out List<ContentBlock> toolBlocks)
    {
        text = "";
        toolBlocks = new List<ContentBlock>();
        JsonElement message = messageOrRoot;
        if (messageOrRoot.TryGetProperty("message", out var nestedMessage))
            message = nestedMessage;

        var consumed = false;
        if (message.TryGetProperty("content", out var contentEl) &&
            contentEl.ValueKind == JsonValueKind.String)
        {
            var parsedText = contentEl.GetString();
            if (!string.IsNullOrWhiteSpace(parsedText))
            {
                text = parsedText;
                consumed = true;
            }
        }

        if (message.TryGetProperty("tool_calls", out var toolCallsEl) &&
            toolCallsEl.ValueKind == JsonValueKind.Array)
        {
            foreach (var tc in toolCallsEl.EnumerateArray())
            {
                if (!tc.TryGetProperty("function", out var functionEl))
                    continue;

                JsonElement? parsedArgs = null;
                if (functionEl.TryGetProperty("arguments", out var argsEl))
                {
                    if (argsEl.ValueKind == JsonValueKind.String)
                    {
                        try
                        {
                            using var argsDoc = JsonDocument.Parse(argsEl.GetString() ?? "{}");
                            parsedArgs = argsDoc.RootElement.Clone();
                        }
                        catch { parsedArgs = null; }
                    }
                    else if (argsEl.ValueKind is JsonValueKind.Object or JsonValueKind.Array)
                    {
                        parsedArgs = argsEl.Clone();
                    }
                }

                toolBlocks.Add(new ContentBlock
                {
                    Type = "tool_use",
                    ToolName = functionEl.TryGetProperty("name", out var nameEl) ? nameEl.GetString() ?? "" : "",
                    ToolId = tc.TryGetProperty("id", out var idEl) ? idEl.GetString() ?? Guid.NewGuid().ToString("N")[..12] : Guid.NewGuid().ToString("N")[..12],
                    ToolInput = parsedArgs,
                });
            }

            consumed = true;
        }

        return consumed;
    }

    private static bool LooksLikeCompleteJson(string json)
    {
        if (string.IsNullOrWhiteSpace(json))
            return false;

        json = json.Trim();
        if (!(json.StartsWith('{') || json.StartsWith('[')))
            return false;

        try
        {
            using var _ = JsonDocument.Parse(json);
            return true;
        }
        catch
        {
            return false;
        }
    }

    private static async Task<ContentBlock?> TryCreateCompletedToolCallAsync(
        ToolCallAccumulator acc,
        Func<ContentBlock, Task<ToolPrefetchResult?>>? prefetchToolCallAsync,
        bool forceEmit = false)
    {
        if (acc.Emitted || string.IsNullOrWhiteSpace(acc.Name))
            return null;

        var argsJson = acc.Arguments.ToString().Trim();
        JsonElement? parsedArgs = null;
        if (!string.IsNullOrEmpty(argsJson))
        {
            if (!forceEmit && !LooksLikeCompleteJson(argsJson))
                return null;

            try
            {
                using var argsDoc = JsonDocument.Parse(argsJson);
                parsedArgs = argsDoc.RootElement.Clone();
            }
            catch
            {
                if (!forceEmit)
                    return null;
            }
        }

        var block = new ContentBlock
        {
            Type = "tool_use",
            ToolName = acc.Name,
            ToolId = string.IsNullOrWhiteSpace(acc.Id) ? Guid.NewGuid().ToString("N")[..12] : acc.Id,
            ToolInput = parsedArgs,
        };

        if (prefetchToolCallAsync != null)
            block.PrefetchedExecutionTask = prefetchToolCallAsync(block);

        acc.Emitted = true;
        return block;
    }

    // ─── 공통 헬퍼 ─────────────────────────────────────────────────────

    /// <summary>ToolProperty를 LLM API용 스키마 객체로 변환. array/enum/items 포함.</summary>
    private static object BuildPropertySchema(Agent.ToolProperty prop, bool upperCaseType)
    {
        var typeName = upperCaseType ? prop.Type.ToUpperInvariant() : prop.Type;

        if (prop.Type.Equals("array", StringComparison.OrdinalIgnoreCase) && prop.Items != null)
        {
            return new
            {
                type = typeName,
                description = prop.Description,
                items = BuildPropertySchema(prop.Items, upperCaseType)
            };
        }

        // enum 값이 있으면 포함
        if (prop.Enum is { Count: > 0 })
            return new { type = typeName, description = prop.Description, @enum = prop.Enum };

        return new { type = typeName, description = prop.Description };
    }

    /// <summary>에러 응답 본문에서 핵심 메시지를 추출합니다.</summary>
    private static string ExtractErrorDetail(string errBody)
    {
        if (string.IsNullOrWhiteSpace(errBody)) return "응답 없음";
        try
        {
            using var doc = JsonDocument.Parse(errBody);
            // Ollama: {"error":"..."}
            if (doc.RootElement.TryGetProperty("error", out var err))
            {
                if (err.ValueKind == JsonValueKind.String)
                    return err.GetString() ?? errBody;
                if (err.ValueKind == JsonValueKind.Object && err.TryGetProperty("message", out var m))
                    return m.GetString() ?? errBody;
            }
        }
        catch { }
        // JSON 아니면 원본 (최대 500자)
        return errBody.Length > 500 ? errBody[..500] + "…" : errBody;
    }
}

/// <summary>도구 호출 자체가 서버에서 거부된 경우 (400). 일반 텍스트 응답으로 폴백 시도 가능.</summary>
public class ToolCallNotSupportedException : Exception
{
    public ToolCallNotSupportedException(string message) : base(message) { }
}