package middleware

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"path/filepath"
	"strings"

	"github.com/gin-gonic/gin"
	"tss-rocks-be/internal/types"
)

const (
	defaultMaxMemory = 32 << 20 // 32 MB
	maxHeaderBytes   = 512      // 用于MIME类型检测的最大字节数
)

// ValidateUpload 创建文件上传验证中间件
func ValidateUpload(cfg *types.UploadConfig) gin.HandlerFunc {
	return func(c *gin.Context) {
		// 检查是否是multipart/form-data请求
		if !strings.HasPrefix(c.GetHeader("Content-Type"), "multipart/form-data") {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "Content-Type must be multipart/form-data",
			})
			c.Abort()
			return
		}

		// 解析multipart表单
		if err := c.Request.ParseMultipartForm(defaultMaxMemory); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": fmt.Sprintf("Failed to parse form: %v", err),
			})
			c.Abort()
			return
		}

		form := c.Request.MultipartForm
		if form == nil || form.File == nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "No file uploaded",
			})
			c.Abort()
			return
		}

		// 遍历所有上传的文件
		for _, files := range form.File {
			for _, file := range files {
				// 检查文件大小
				if file.Size > int64(cfg.MaxSize)<<20 { // 转换为字节
					c.JSON(http.StatusBadRequest, gin.H{
						"error": fmt.Sprintf("File %s exceeds maximum size of %d MB", file.Filename, cfg.MaxSize),
					})
					c.Abort()
					return
				}

				// 检查文件扩展名
				ext := strings.ToLower(filepath.Ext(file.Filename))
				if !contains(cfg.AllowedExtensions, ext) {
					c.JSON(http.StatusBadRequest, gin.H{
						"error": fmt.Sprintf("File extension %s is not allowed", ext),
					})
					c.Abort()
					return
				}

				// 打开文件
				src, err := file.Open()
				if err != nil {
					c.JSON(http.StatusInternalServerError, gin.H{
						"error": fmt.Sprintf("Failed to open file: %v", err),
					})
					c.Abort()
					return
				}
				defer src.Close()

				// 读取文件头部用于MIME类型检测
				header := make([]byte, maxHeaderBytes)
				n, err := src.Read(header)
				if err != nil && err != io.EOF {
					c.JSON(http.StatusInternalServerError, gin.H{
						"error": fmt.Sprintf("Failed to read file: %v", err),
					})
					c.Abort()
					return
				}
				header = header[:n]

				// 检测MIME类型
				contentType := http.DetectContentType(header)
				if !contains(cfg.AllowedTypes, contentType) {
					c.JSON(http.StatusBadRequest, gin.H{
						"error": fmt.Sprintf("File type %s is not allowed", contentType),
					})
					c.Abort()
					return
				}

				// 将文件指针重置到开始位置
				_, err = src.Seek(0, 0)
				if err != nil {
					c.JSON(http.StatusInternalServerError, gin.H{
						"error": fmt.Sprintf("Failed to read file: %v", err),
					})
					c.Abort()
					return
				}

				// 将文件内容读入缓冲区
				buf := &bytes.Buffer{}
				_, err = io.Copy(buf, src)
				if err != nil {
					c.JSON(http.StatusInternalServerError, gin.H{
						"error": fmt.Sprintf("Failed to read file: %v", err),
					})
					c.Abort()
					return
				}

				// 将验证过的文件内容和类型保存到上下文中
				c.Set("validated_file_"+file.Filename, buf)
				c.Set("validated_content_type_"+file.Filename, contentType)
			}
		}

		c.Next()
	}
}

// contains 检查切片中是否包含指定的字符串
func contains(slice []string, str string) bool {
	for _, s := range slice {
		if s == str {
			return true
		}
	}
	return false
}

// GetValidatedFile 从上下文中获取验证过的文件内容
func GetValidatedFile(c *gin.Context, filename string) (*bytes.Buffer, string, bool) {
	file, exists := c.Get("validated_file_" + filename)
	if !exists {
		return nil, "", false
	}

	contentType, exists := c.Get("validated_content_type_" + filename)
	if !exists {
		return nil, "", false
	}

	return file.(*bytes.Buffer), contentType.(string), true
}