refactor: use dependency injection in backend

backend/internal/middleware/file_size_limit.go

@@ -0,0 +1,46 @@
+package middleware
+
+import (
+	"fmt"
+	"github.com/gin-gonic/gin"
+	"github.com/stonith404/pocket-id/backend/internal/utils"
+	"net/http"
+)
+
+type FileSizeLimitMiddleware struct{}
+
+func NewFileSizeLimitMiddleware() *FileSizeLimitMiddleware {
+	return &FileSizeLimitMiddleware{}
+}
+
+func (m *FileSizeLimitMiddleware) Add(maxSize int64) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxSize)
+		if err := c.Request.ParseMultipartForm(maxSize); err != nil {
+			utils.HandlerError(c, http.StatusRequestEntityTooLarge, fmt.Sprintf("The file can't be larger than %s bytes", formatFileSize(maxSize)))
+			c.Abort()
+			return
+		}
+		c.Next()
+	}
+}
+
+// formatFileSize formats a file size in bytes to a human-readable string
+func formatFileSize(size int64) string {
+	const (
+		KB = 1 << (10 * 1)
+		MB = 1 << (10 * 2)
+		GB = 1 << (10 * 3)
+	)
+
+	switch {
+	case size >= GB:
+		return fmt.Sprintf("%.2f GB", float64(size)/GB)
+	case size >= MB:
+		return fmt.Sprintf("%.2f MB", float64(size)/MB)
+	case size >= KB:
+		return fmt.Sprintf("%.2f KB", float64(size)/KB)
+	default:
+		return fmt.Sprintf("%d bytes", size)
+	}
+}