package audit

import (
	"bytes"
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"mime"
	"mime/multipart"
	"os"
	"strings"
	"time"

	"github.com/tjfoc/gmsm/sm3"
)

// UploadAndDigest computes the SM3 digest of the payload and uploads the
// raw bytes to MinIO under logs/{traceID}/{spanID}/. When the MinIO client
// is not loaded (no/invalid file config) the upload is skipped and only the
// digest is returned with an empty file key, so the audit chain keeps
// working without MinIO.
// Supported content types: application/json and multipart/form-data.
func UploadAndDigest(data []byte, traceID, spanID, label string, minioClient *MinioClient, contentType string) (string, string, error) {
	// 1.计算摘要
	h := sm3.New()
	h.Write(data)
	digest := hex.EncodeToString(h.Sum(nil))

	// 2.构造标签、文件名、文件上传路径
	safeLabel := strings.Trim(label, "[]")
	baseName := fmt.Sprintf("%s_%d", safeLabel, time.Now().UnixNano())
	objectDir := fmt.Sprintf("%s/%s/%s", ObjectDirLogs, traceID, spanID)

	// MinIO 未就绪时只返回摘要
	if minioClient == nil {
		return digest, "", nil
	}

	// 空 body(典型如 GET 请求)无需上传原文
	if len(data) == 0 {
		return digest, "", nil
	}

	// 3.判断请求头类型
	switch {
	case strings.HasPrefix(contentType, "application/json"):
		// application/json
		fileName := baseName + ".json"
		objectKey := fmt.Sprintf("%s/%s", objectDir, fileName)

		fileKey, err := writeAndUploadTempFile(minioClient, data, fileName, objectKey)
		if err != nil {
			return "", "", fmt.Errorf("minio upload file failed: %w", err)
		}
		return digest, fileKey, nil
	case strings.HasPrefix(contentType, "multipart/form-data"):
		// multipart/form-data
		boundary := extractBoundary(contentType)
		if boundary == "" {
			return "", "", fmt.Errorf("invalid multipart content-type: %s", contentType)
		}
		reader := multipart.NewReader(bytes.NewReader(data), boundary)

		fields := make(map[string]string)
		fileKeys := make(map[string]string)

		for {
			part, err := reader.NextPart()
			if err == io.EOF {
				break
			}
			if err != nil {
				return "", "", fmt.Errorf("read multipart part failed: %w", err)
			}

			partData, err := io.ReadAll(part)
			if err != nil {
				return "", "", fmt.Errorf("read part data failed: %w", err)
			}

			if part.FileName() == "" {
				// 普通字段
				fields[part.FormName()] = string(partData)
				continue
			}

			// 文件字段
			objectKey := fmt.Sprintf("%s/%s_%s", objectDir, baseName, part.FileName())
			fileKey, err := writeAndUploadTempFile(minioClient, partData, part.FileName(), objectKey)
			if err != nil {
				return "", "", fmt.Errorf("upload file part failed: %w", err)
			}
			fileKeys[part.FormName()] = fileKey
		}

		// 保存字段 JSON
		fieldsFile := baseName + "_fields.json"
		fieldsKey := fmt.Sprintf("%s/%s", objectDir, fieldsFile)

		fieldBytes, err := json.MarshalIndent(fields, "", "  ")
		if err != nil {
			return "", "", fmt.Errorf("marshal fields failed: %w", err)
		}
		if _, err := writeAndUploadTempFile(minioClient, fieldBytes, fieldsFile, fieldsKey); err != nil {
			return "", "", fmt.Errorf("upload fields failed: %w", err)
		}

		// 保存元数据 JSON
		metaJson := map[string]interface{}{
			"digest":   digest,
			"trace_id": traceID,
			"span_id":  spanID,
			"files":    fileKeys,
			"fields":   fieldsKey,
		}

		metaFile := baseName + "_meta.json"
		metaKey := fmt.Sprintf("%s/%s", objectDir, metaFile)

		metaBytes, err := json.MarshalIndent(metaJson, "", "  ")
		if err != nil {
			return "", "", fmt.Errorf("marshal meta failed: %w", err)
		}
		if _, err := writeAndUploadTempFile(minioClient, metaBytes, metaFile, metaKey); err != nil {
			return "", "", fmt.Errorf("upload meta failed: %w", err)
		}

		return digest, metaKey, nil
	default:
		return "", "", fmt.Errorf("unsupported content type: %s", contentType)
	}
}

// extractBoundary extracts the boundary from a Content-Type header value.
func extractBoundary(contentType string) string {
	_, params, err := mime.ParseMediaType(contentType)
	if err != nil {
		return ""
	}
	return params["boundary"]
}

// writeAndUploadTempFile writes data to a temp file, uploads it, and
// removes the temp file afterwards.
func writeAndUploadTempFile(minioClient *MinioClient, data []byte, tmpName, objectKey string) (string, error) {
	tmpFile, err := os.CreateTemp("", tmpName)
	if err != nil {
		return "", fmt.Errorf("create temp file failed: %w", err)
	}
	defer func() {
		_ = tmpFile.Close()
		_ = os.Remove(tmpFile.Name())
	}()

	if _, err := tmpFile.Write(data); err != nil {
		return "", fmt.Errorf("write temp file failed: %w", err)
	}
	if err := tmpFile.Close(); err != nil {
		return "", fmt.Errorf("close temp file failed: %w", err)
	}

	fileKey, err := minioClient.UploadFile(context.Background(), tmpFile.Name(), objectKey)
	if err != nil {
		return "", fmt.Errorf("minio upload failed: %w", err)
	}
	return fileKey, nil
}