package handler

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	"silk-server-go/internal/middleware"
	"silk-server-go/internal/service"

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

// maxImageSize 知识库图片大小上限（5MB）
const maxImageSize = 5 << 20

// imageContentType 根据扩展名返回图片 Content-Type
func imageContentType(ext string) (string, bool) {
	switch strings.ToLower(ext) {
	case ".jpg", ".jpeg":
		return "image/jpeg", true
	case ".png":
		return "image/png", true
	case ".webp":
		return "image/webp", true
	}
	return "", false
}

// validateImageFile 校验图片文件名扩展名与大小
func validateImageFile(filename string, size int64) error {
	if size <= 0 || size > maxImageSize {
		return errors.New("图片大小需在 1B~5MB 之间")
	}
	ext := strings.ToLower(filepath.Ext(filename))
	if _, ok := imageContentType(ext); !ok {
		return errors.New("仅支持 jpg/jpeg/png/webp 图片")
	}
	return nil
}

// buildObjectKey 生成 <prefix>/<日期>/<随机>.ext 的对象键
func buildObjectKey(prefix, filename string) (string, string, error) {
	ext := strings.ToLower(filepath.Ext(filename))
	if _, ok := imageContentType(ext); !ok {
		return "", "", errors.New("仅支持 jpg/jpeg/png/webp 图片")
	}
	buf := make([]byte, 8)
	if _, err := rand.Read(buf); err != nil {
		return "", "", err
	}
	date := time.Now().Format("20060102")
	key := fmt.Sprintf("%s/%s/%s%s", prefix, date, hex.EncodeToString(buf), ext)
	return key, ext, nil
}

// buildImageKey 生成 knowledge/<日期>/<随机>.ext 的对象键
func buildImageKey(filename string) (string, string, error) {
	return buildObjectKey("knowledge", filename)
}

// buildDataKey 生成 <prefix>/<日期>/<随机><ext>（不校验扩展名，由调用方校验）
func buildDataKey(prefix, filename string) (string, string, error) {
	ext := strings.ToLower(filepath.Ext(filename))
	buf := make([]byte, 8)
	if _, err := rand.Read(buf); err != nil {
		return "", "", err
	}
	date := time.Now().Format("20060102")
	return fmt.Sprintf("%s/%s/%s%s", prefix, date, hex.EncodeToString(buf), ext), ext, nil
}

// uploadKnowledgeImage 上传知识库图片（multipart 字段名 file）
func uploadKnowledgeImage(s3 *service.S3Service, bucket string) gin.HandlerFunc {
	return func(c *gin.Context) {
		file, header, err := c.Request.FormFile("file")
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": "请选择图片文件（字段名 file）"})
			return
		}
		defer file.Close()

		if err := validateImageFile(header.Filename, header.Size); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		key, ext, err := buildImageKey(header.Filename)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		contentType, _ := imageContentType(ext)

		if err := s3.EnsureBucket(bucket); err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "图片存储不可用: " + err.Error()})
			return
		}
		if err := s3.UploadImage(bucket, key, file, contentType); err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "图片上传失败: " + err.Error()})
			return
		}

		url := fmt.Sprintf("%s/%s/%s", s3.Endpoint(), bucket, key)
		c.JSON(http.StatusOK, gin.H{"url": url, "name": header.Filename, "size": header.Size})
	}
}

// uploadImageRoute 在知识库路由组中注册图片上传（由 RegisterKnowledgeRoutes 调用）
func registerKnowledgeImageRoute(rg *gin.RouterGroup, db *gorm.DB, s3 *service.S3Service, bucket string) {
	rg.POST("/knowledge/images", middleware.RequirePermission(db, "knowledge:write"), uploadKnowledgeImage(s3, bucket))
}