init: 1.0.0

pkg/logger/read.go

@@ -0,0 +1,98 @@
+package logger
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+)
+
+func ReadLastNLines(path string, n int) ([]string, error) {
+	// Open the file
+	file, err := os.Open(fmt.Sprintf("%s/%s", path, accessFilename))
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	// Get file size
+	fileInfo, err := file.Stat()
+	if err != nil {
+		return nil, err
+	}
+	fileSize := fileInfo.Size()
+
+	// If file is empty, return empty slice
+	if fileSize == 0 {
+		return []string{}, nil
+	}
+
+	// Buffer for reading
+	bufferSize := int64(4096)
+	if bufferSize > fileSize {
+		bufferSize = fileSize
+	}
+	buffer := make([]byte, bufferSize)
+
+	// Start reading from the end
+	position := fileSize
+	lines := make([]string, 0, n)
+	lineCount := 0
+
+	for lineCount < n && position > 0 {
+		// How much to read
+		readSize := bufferSize
+		if position < bufferSize {
+			readSize = position
+		}
+		position -= readSize
+
+		// Read chunk from position
+		_, err := file.Seek(position, io.SeekStart)
+		if err != nil {
+			return nil, err
+		}
+
+		_, err = file.Read(buffer[:readSize])
+		if err != nil {
+			return nil, err
+		}
+
+		// Count newlines in reverse
+		for i := readSize - 1; i >= 0; i-- {
+			if buffer[i] == '\n' {
+				lineCount++
+				if lineCount > n {
+					// We found more than n lines
+					// Need to adjust position to read only last n lines
+					position += int64(i) + 1
+					break
+				}
+			}
+		}
+	}
+
+	// If we couldn't find n lines, start from beginning
+	if position < 0 {
+		position = 0
+	}
+
+	// Seek to the position where we want to start reading
+	_, err = file.Seek(position, io.SeekStart)
+	if err != nil {
+		return nil, err
+	}
+
+	// Read lines from position to end
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		lines = append(lines, scanner.Text())
+	}
+
+	// Check if we need to trim
+	if len(lines) > n {
+		lines = lines[len(lines)-n:]
+	}
+
+	return lines, scanner.Err()
+}