目录重构完成，但是Preview通道尚未可用

internal/frp/log.go

@@ -0,0 +1,81 @@
+package frp
+
+import (
+	"io"
+	"os"
+	"strings"
+)
+
+// ReadTailLog 读取文件末尾 n 行
+func ReadTailLog(filePath string, n int) ([]string, error) {
+	file, err := os.Open(filePath)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	info, err := file.Stat()
+	if err != nil {
+		return nil, err
+	}
+	fileSize := info.Size()
+	if fileSize == 0 {
+		return []string{}, nil
+	}
+
+	const chunkSize = 4096
+	var lines []string
+	var leftover []byte
+	offset := fileSize
+
+	for len(lines) < n && offset > 0 {
+		readSize := chunkSize
+		if offset < int64(chunkSize) {
+			readSize = int(offset)
+		}
+		offset -= int64(readSize)
+
+		buf := make([]byte, readSize)
+		_, err := file.ReadAt(buf, offset)
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+
+		data := append(buf, leftover...)
+		leftover = nil
+
+		start := 0
+		for i := len(data) - 1; i >= 0; i-- {
+			if data[i] == '\n' {
+				if i+1 < len(data) {
+					line := string(data[i+1:])
+					if line != "" {
+						lines = append([]string{line}, lines...)
+						if len(lines) >= n {
+							break
+						}
+					}
+				}
+				start = i
+			}
+		}
+
+		if len(lines) < n && start > 0 {
+			leftover = data[:start]
+		}
+	}
+
+	if len(lines) < n && len(leftover) > 0 {
+		parts := strings.Split(string(leftover), "\n")
+		for i := len(parts) - 1; i >= 0; i-- {
+			if parts[i] != "" {
+				lines = append([]string{parts[i]}, lines...)
+				if len(lines) >= n {
+					break
+				}
+			}
+		}
+	}
+
+	return lines, nil
+}