package handlers

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
)

const (
	// uploadDir 上传文件保存目录
	uploadDir = "./static/uploads"
	// uploadURLPrefix 上传文件对外访问的 URL 前缀
	uploadURLPrefix = "/static/uploads/"
	// maxUploadSize 单个文件最大大小（5MB）
	maxUploadSize = 5 << 20
)

// allowedImageExts 允许上传的图片扩展名
var allowedImageExts = map[string]bool{
	".jpg":  true,
	".jpeg": true,
	".png":  true,
	".gif":  true,
	".webp": true,
}

// allowedImageMIMEs 允许上传的图片真实 MIME 类型
var allowedImageMIMEs = map[string]bool{
	"image/jpeg": true,
	"image/png":  true,
	"image/gif":  true,
	"image/webp": true,
}

// UploadedFile 上传文件信息
type UploadedFile struct {
	Name    string `json:"name"`
	URL     string `json:"url"`
	Size    int64  `json:"size"`
	ModTime string `json:"mod_time"`
}

// sanitizeBaseName 清理文件名（去除扩展名和不安全字符）
func sanitizeBaseName(filename string) string {
	base := strings.TrimSuffix(filepath.Base(filename), filepath.Ext(filename))
	base = strings.ReplaceAll(base, " ", "-")

	var b strings.Builder
	for _, r := range base {
		if r == '-' || r == '_' ||
			(r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') {
			b.WriteRune(r)
		}
	}

	res := b.String()
	if res == "" {
		res = "image"
	}
	if len(res) > 40 {
		res = res[:40]
	}
	return res
}

// UploadImage 上传图片（校验格式与大小）
func UploadImage(c *gin.Context) {
	file, err := c.FormFile("file")
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "请选择要上传的文件"})
		return
	}

	// 校验文件大小
	if file.Size > maxUploadSize {
		c.JSON(http.StatusBadRequest, gin.H{
			"error": fmt.Sprintf("文件大小超过限制（最大 %d MB）", maxUploadSize>>20),
		})
		return
	}

	// 校验扩展名
	ext := strings.ToLower(filepath.Ext(file.Filename))
	if !allowedImageExts[ext] {
		c.JSON(http.StatusBadRequest, gin.H{"error": "不支持的图片格式，仅支持 jpg/jpeg/png/gif/webp"})
		return
	}

	// 打开文件并检测真实 MIME 类型（防止伪造扩展名）
	src, err := file.Open()
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "读取文件失败"})
		return
	}
	defer src.Close()

	head := make([]byte, 512)
	n, _ := src.Read(head)
	contentType := http.DetectContentType(head[:n])
	if !allowedImageMIMEs[contentType] {
		c.JSON(http.StatusBadRequest, gin.H{"error": "文件内容不是有效的图片"})
		return
	}

	// 重置读取位置，准备写入
	if _, err := src.Seek(0, io.SeekStart); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "读取文件失败"})
		return
	}

	// 确保上传目录存在
	if err := os.MkdirAll(uploadDir, 0o755); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "创建上传目录失败"})
		return
	}

	// 生成唯一文件名：时间戳_原始名.扩展名
	filename := fmt.Sprintf("%d_%s%s", time.Now().UnixNano(), sanitizeBaseName(file.Filename), ext)
	dstPath := filepath.Join(uploadDir, filename)

	dst, err := os.Create(dstPath)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "保存文件失败"})
		return
	}
	defer dst.Close()

	if _, err := io.Copy(dst, src); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "保存文件失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"url":  uploadURLPrefix + filename,
		"name": filename,
		"size": file.Size,
	})
}

// ListUploads 列出已上传的图片
func ListUploads(c *gin.Context) {
	if err := os.MkdirAll(uploadDir, 0o755); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "读取上传目录失败"})
		return
	}

	entries, err := os.ReadDir(uploadDir)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "读取上传目录失败"})
		return
	}

	files := make([]UploadedFile, 0, len(entries))
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		ext := strings.ToLower(filepath.Ext(e.Name()))
		if !allowedImageExts[ext] {
			continue
		}
		info, err := e.Info()
		if err != nil {
			continue
		}
		files = append(files, UploadedFile{
			Name:    e.Name(),
			URL:     uploadURLPrefix + e.Name(),
			Size:    info.Size(),
			ModTime: info.ModTime().Format("2006-01-02 15:04:05"),
		})
	}

	// 按修改时间倒序（最新的在前）
	sort.Slice(files, func(i, j int) bool {
		return files[i].ModTime > files[j].ModTime
	})

	c.JSON(http.StatusOK, gin.H{"data": files})
}

// DeleteUpload 删除已上传的图片
func DeleteUpload(c *gin.Context) {
	name := c.Param("name")

	// 防止路径穿越
	if name == "" || strings.Contains(name, "..") || strings.ContainsAny(name, `/\`) {
		c.JSON(http.StatusBadRequest, gin.H{"error": "非法的文件名"})
		return
	}

	ext := strings.ToLower(filepath.Ext(name))
	if !allowedImageExts[ext] {
		c.JSON(http.StatusBadRequest, gin.H{"error": "非法的文件类型"})
		return
	}

	path := filepath.Join(uploadDir, name)
	if _, err := os.Stat(path); err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "文件不存在"})
		return
	}

	if err := os.Remove(path); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "删除文件失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "删除成功"})
}