Yi.Admin/Yi.Abp.Net8/module/ai-hub/Yi.Framework.AiHub.Domain.Shared/Dtos/Gemini/GeminiGenerateContentAcquirer.cs

using System.Text.Json;
using Yi.Framework.AiHub.Domain.Shared.Dtos.OpenAi;
using Yi.Framework.AiHub.Domain.Shared.Extensions;

namespace Yi.Framework.AiHub.Domain.Shared.Dtos.Gemini;

public static class GeminiGenerateContentAcquirer
{
    /// <summary>
    /// 从请求体中提取用户最后一条消息内容
    /// 路径: contents[last].parts[last].text
    /// </summary>
    public static string GetLastUserContent(JsonElement request)
    {
        var contents = request.GetPath("contents");
        if (!contents.HasValue || contents.Value.ValueKind != JsonValueKind.Array)
        {
            return string.Empty;
        }

        var contentsArray = contents.Value.EnumerateArray().ToList();
        if (contentsArray.Count == 0)
        {
            return string.Empty;
        }

        var lastContent = contentsArray[^1];
        var parts = lastContent.GetPath("parts");
        if (!parts.HasValue || parts.Value.ValueKind != JsonValueKind.Array)
        {
            return string.Empty;
        }

        var partsArray = parts.Value.EnumerateArray().ToList();
        if (partsArray.Count == 0)
        {
            return string.Empty;
        }

        // 获取最后一个 part 的 text
        var lastPart = partsArray[^1];
        return lastPart.GetPath("text").GetString() ?? string.Empty;
    }

    /// <summary>
    /// 从响应中提取文本内容（非 thought 类型）
    /// 路径: candidates[0].content.parts[].text (where thought != true)
    /// </summary>
    public static string GetTextContent(JsonElement response)
    {
        var candidates = response.GetPath("candidates");
        if (!candidates.HasValue || candidates.Value.ValueKind != JsonValueKind.Array)
        {
            return string.Empty;
        }

        var candidatesArray = candidates.Value.EnumerateArray().ToList();
        if (candidatesArray.Count == 0)
        {
            return string.Empty;
        }

        var parts = candidatesArray[0].GetPath("content", "parts");
        if (!parts.HasValue || parts.Value.ValueKind != JsonValueKind.Array)
        {
            return string.Empty;
        }

        // 遍历所有 parts，只取非 thought 的 text
        foreach (var part in parts.Value.EnumerateArray())
        {
            var isThought = part.GetPath("thought").GetBool();
            if (!isThought)
            {
                var text = part.GetPath("text").GetString();
                if (!string.IsNullOrEmpty(text))
                {
                    return text;
                }
            }
        }

        return string.Empty;
    }

    public static ThorUsageResponse? GetUsage(JsonElement response)
    {
        var usage = response.GetPath("usageMetadata");
        if (!usage.HasValue)
        {
            return null;
        }

        var inputTokens = usage.Value.GetPath("promptTokenCount").GetInt();
        var outputTokens = usage.Value.GetPath("candidatesTokenCount").GetInt()
                           + usage.Value.GetPath("cachedContentTokenCount").GetInt()
                           + usage.Value.GetPath("thoughtsTokenCount").GetInt()
                           + usage.Value.GetPath("toolUsePromptTokenCount").GetInt();

        return new ThorUsageResponse
        {
            PromptTokens = inputTokens,
            InputTokens = inputTokens,
            OutputTokens = outputTokens,
            CompletionTokens = outputTokens,
            TotalTokens = inputTokens + outputTokens,
        };
    }

    /// <summary>
    /// 获取图片 base64（包含 data:image 前缀）
    /// 从最后一个 part 开始查找 inlineData，找不到再从最后一个 part 开始查找 text
    /// </summary>
    public static string GetImagePrefixBase64(JsonElement response)
    {
        var parts = response.GetPath("candidates", 0, "content", "parts");
        if (!parts.HasValue || parts.Value.ValueKind != JsonValueKind.Array)
        {
            return string.Empty;
        }

        var partsArray = parts.Value.EnumerateArray().ToList();
        if (partsArray.Count == 0)
        {
            return string.Empty;
        }

        // Step 1: 从最后一个 part 开始查找 inlineData
        for (int i = partsArray.Count - 1; i >= 0; i--)
        {
            var inlineBase64 = partsArray[i].GetPath("inlineData", "data").GetString();
            if (!string.IsNullOrEmpty(inlineBase64))
            {
                var mimeType = partsArray[i].GetPath("inlineData", "mimeType").GetString() ?? "image/png";
                return $"data:{mimeType};base64,{inlineBase64}";
            }
        }

        // Step 2: 从最后一个 part 开始查找 text 中的 markdown 图片
        for (int i = partsArray.Count - 1; i >= 0; i--)
        {
            var text = partsArray[i].GetPath("text").GetString();
            if (string.IsNullOrEmpty(text))
            {
                continue;
            }

            // markdown 图片格式: ![image](data:image/png;base64,xxx)
            var startMarker = "(data:image/";
            var startIndex = text.IndexOf(startMarker, StringComparison.Ordinal);
            if (startIndex < 0)
            {
                continue;
            }

            startIndex += 1; // 跳过 "("
            var endIndex = text.IndexOf(')', startIndex);
            if (endIndex > startIndex)
            {
                return text.Substring(startIndex, endIndex - startIndex);
            }
        }

        return string.Empty;
    }
}