From d804310586056b410080f3b5244b9fa7991ae55e Mon Sep 17 00:00:00 2001
From: Igor Chubin <igor@chub.in>
Date: Sun, 20 Nov 2022 17:45:06 +0100
Subject: [PATCH] Add cmd/logsuppress.go

---
 cmd/logsuppress.go | 69 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 cmd/logsuppress.go

diff --git a/cmd/logsuppress.go b/cmd/logsuppress.go
new file mode 100644
index 0000000..d8ca9e6
--- /dev/null
+++ b/cmd/logsuppress.go
@@ -0,0 +1,69 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"sync"
+)
+
+// LogSuppressor provides io.Writer interface for logging
+// with lines suppression. For usage with log.Logger.
+type LogSuppressor struct {
+	filename   string
+	suppress   []string
+	linePrefix string
+
+	logFile *os.File
+	m       sync.Mutex
+}
+
+// NewLogSuppressor creates a new LogSuppressor for specified
+// filename and lines to be suppressed.
+func NewLogSuppressor(filename string, suppress []string, linePrefix string) *LogSuppressor {
+	return &LogSuppressor{
+		filename:   filename,
+		suppress:   suppress,
+		linePrefix: linePrefix,
+	}
+}
+
+// Open opens log file.
+func (ls *LogSuppressor) Open() error {
+	var err error
+	ls.logFile, err = os.OpenFile(ls.filename, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
+	return err
+}
+
+// Close closes log file.
+func (ls *LogSuppressor) Close() error {
+	return ls.logFile.Close()
+}
+
+// Write writes p to log, and returns number f bytes written.
+// Implements io.Writer interface.
+func (ls *LogSuppressor) Write(p []byte) (n int, err error) {
+	var (
+		output string
+	)
+
+	ls.m.Lock()
+	defer ls.m.Unlock()
+
+	lines := strings.Split(string(p), ls.linePrefix)
+	for _, line := range lines {
+		if (func() bool {
+			for _, suppress := range ls.suppress {
+				if strings.Contains(line, suppress) {
+					return true
+				}
+			}
+			return false
+		})() {
+			continue
+		}
+		output += line
+	}
+
+	n, err = ls.logFile.Write([]byte(output))
+	return n, err
+}