admin/src/Oms.Application/Shared/AiLlmClient.cs

using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using Fake.Application;
using Microsoft.Extensions.DependencyInjection;
using Oms.Application.Mcp;
using Oms.Domain.AiAggregate.Entities;

namespace Oms.Application.Shared;

public class LlmChatMessage
{
    public string Role { get; set; } = "user";
    public string? Content { get; set; }
    public List<LlmToolCall>? ToolCalls { get; set; }
    public string? ToolCallId { get; set; }
    public string? Name { get; set; }
}

public class LlmToolCall
{
    public string Id { get; set; } = string.Empty;
    public string Type { get; set; } = "function";
    public string FunctionName { get; set; } = string.Empty;
    public string ArgumentsJson { get; set; } = "{}";
}

public class LlmToolDefinition
{
    public string Name { get; set; } = string.Empty;
    public string Description { get; set; } = string.Empty;
    public JsonNode Parameters { get; set; } = new JsonObject();
}

public class LlmChatResult
{
    public string? Content { get; set; }
    public List<LlmToolCall> ToolCalls { get; set; } = [];
}

/// <summary>
/// OpenAI 兼容 Chat Completions 客户端（通义 / DeepSeek / 豆包等）。
/// </summary>
public class AiLlmClient
{
    public const string HttpClientName = nameof(AiLlmClient);

    private readonly IHttpClientFactory _httpClientFactory;

    public AiLlmClient(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public async Task<string> ChatCompletionAsync(
        AiProvider provider,
        IReadOnlyList<(string Role, string Content)> messages,
        string? modelOverride = null,
        CancellationToken cancellationToken = default)
    {
        var result = await ChatCompletionDetailedAsync(
            provider,
            messages.Select(m => new LlmChatMessage { Role = m.Role, Content = m.Content }).ToList(),
            tools: null,
            modelOverride,
            cancellationToken);
        return result.Content?.Trim() ?? string.Empty;
    }

    public async Task<LlmChatResult> ChatCompletionDetailedAsync(
        AiProvider provider,
        IReadOnlyList<LlmChatMessage> messages,
        IReadOnlyList<LlmToolDefinition>? tools = null,
        string? modelOverride = null,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(provider.ApiKeyEnc))
        {
            throw new BusinessException($"请先配置 {provider.DisplayName} 的 API Key");
        }

        var model = modelOverride ?? provider.ApiSecretEnc;
        if (string.IsNullOrWhiteSpace(model))
        {
            throw new BusinessException($"请先配置 {provider.DisplayName} 的模型名（ApiSecret 字段）或在请求中传入 model");
        }

        var url = BuildChatUrl(provider.BaseUrl);
        var payload = BuildPayload(model, messages, tools);

        var client = _httpClientFactory.CreateClient(HttpClientName);
        using var request = new HttpRequestMessage(HttpMethod.Post, url);
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", provider.ApiKeyEnc.Trim());
        request.Content = new StringContent(payload.ToJsonString(new JsonSerializerOptions
        {
            Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
        }), Encoding.UTF8, "application/json");

        using var response = await client.SendAsync(request, cancellationToken);
        var body = await response.Content.ReadAsStringAsync(cancellationToken);
        if (!response.IsSuccessStatusCode)
        {
            throw new BusinessException($"AI 请求失败 ({(int)response.StatusCode}): {TrimError(body)}");
        }

        using var doc = JsonDocument.Parse(body);
        var root = doc.RootElement;
        if (root.TryGetProperty("choices", out var choices) &&
            choices.GetArrayLength() > 0 &&
            choices[0].TryGetProperty("message", out var message))
        {
            var result = new LlmChatResult();
            if (message.TryGetProperty("content", out var content) && content.ValueKind != JsonValueKind.Null)
            {
                result.Content = content.GetString();
            }

            if (message.TryGetProperty("tool_calls", out var toolCalls) &&
                toolCalls.ValueKind == JsonValueKind.Array)
            {
                foreach (var call in toolCalls.EnumerateArray())
                {
                    var id = call.TryGetProperty("id", out var idEl) ? idEl.GetString() ?? "" : "";
                    var fn = call.TryGetProperty("function", out var fnEl) ? fnEl : default;
                    var name = fn.ValueKind == JsonValueKind.Object && fn.TryGetProperty("name", out var n)
                        ? n.GetString() ?? ""
                        : "";
                    var args = fn.ValueKind == JsonValueKind.Object && fn.TryGetProperty("arguments", out var a)
                        ? a.GetString() ?? "{}"
                        : "{}";
                    if (!string.IsNullOrWhiteSpace(name))
                    {
                        result.ToolCalls.Add(new LlmToolCall
                        {
                            Id = string.IsNullOrWhiteSpace(id) ? Guid.NewGuid().ToString("N") : id,
                            FunctionName = name,
                            ArgumentsJson = string.IsNullOrWhiteSpace(args) ? "{}" : args
                        });
                    }
                }
            }

            return result;
        }

        if (root.TryGetProperty("error", out var error) &&
            error.TryGetProperty("message", out var errorMessage))
        {
            throw new BusinessException(errorMessage.GetString() ?? "AI 返回错误");
        }

        throw new BusinessException("AI 响应格式无法解析");
    }

    private static JsonObject BuildPayload(
        string model,
        IReadOnlyList<LlmChatMessage> messages,
        IReadOnlyList<LlmToolDefinition>? tools)
    {
        var msgArr = new JsonArray();
        foreach (var m in messages)
        {
            var obj = new JsonObject { ["role"] = m.Role };
            if (m.Role == "tool")
            {
                obj["tool_call_id"] = m.ToolCallId ?? "";
                if (!string.IsNullOrWhiteSpace(m.Name)) obj["name"] = m.Name;
                obj["content"] = m.Content ?? "";
            }
            else if (m.ToolCalls is { Count: > 0 })
            {
                if (m.Content != null) obj["content"] = m.Content;
                var calls = new JsonArray();
                foreach (var c in m.ToolCalls)
                {
                    calls.Add(new JsonObject
                    {
                        ["id"] = c.Id,
                        ["type"] = "function",
                        ["function"] = new JsonObject
                        {
                            ["name"] = c.FunctionName,
                            ["arguments"] = c.ArgumentsJson
                        }
                    });
                }
                obj["tool_calls"] = calls;
            }
            else
            {
                obj["content"] = m.Content ?? "";
            }

            msgArr.Add(obj);
        }

        var payload = new JsonObject
        {
            ["model"] = model,
            ["messages"] = msgArr,
            ["temperature"] = 0.3
        };

        if (tools is { Count: > 0 })
        {
            var toolArr = new JsonArray();
            foreach (var t in tools)
            {
                toolArr.Add(new JsonObject
                {
                    ["type"] = "function",
                    ["function"] = new JsonObject
                    {
                        ["name"] = t.Name,
                        ["description"] = t.Description,
                        ["parameters"] = t.Parameters.DeepClone()
                    }
                });
            }
            payload["tools"] = toolArr;
            payload["tool_choice"] = "auto";
        }

        return payload;
    }

    private static string BuildChatUrl(string baseUrl)
    {
        var url = (baseUrl ?? string.Empty).Trim().TrimEnd('/');
        if (string.IsNullOrEmpty(url))
        {
            throw new BusinessException("AI 提供商 BaseUrl 未配置");
        }

        if (url.EndsWith("/chat/completions", StringComparison.OrdinalIgnoreCase))
        {
            return url;
        }

        if (url.EndsWith("/v1", StringComparison.OrdinalIgnoreCase) ||
            url.EndsWith("/v4", StringComparison.OrdinalIgnoreCase))
        {
            return url + "/chat/completions";
        }

        return url + "/v1/chat/completions";
    }

    private static string TrimError(string body)
    {
        if (string.IsNullOrWhiteSpace(body))
        {
            return "空响应";
        }

        return body.Length <= 300 ? body : body[..300];
    }
}

public static class AiLlmServiceExtensions
{
    public static IServiceCollection AddAiLlmClient(this IServiceCollection services)
    {
        services.AddHttpClient(AiLlmClient.HttpClientName, client =>
        {
            client.Timeout = TimeSpan.FromMinutes(3);
        });
        services.AddHttpClient(McpToolExecutor.TrackHttpClientName, client =>
        {
            client.Timeout = TimeSpan.FromSeconds(45);
        });
        services.AddTransient<AiLlmClient>();
        return services;
    }
}