From 4ae52ef993bca643a8d5ed8b0ede6764e9400799 Mon Sep 17 00:00:00 2001
From: lucarin91 <lucarin@protonmail.com>
Date: Mon, 29 Dec 2025 17:04:35 +0100
Subject: [PATCH] feat: add callbackWriter utility

---
 io.go | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 io.go

diff --git a/io.go b/io.go
new file mode 100644
index 0000000..bfa2c09
--- /dev/null
+++ b/io.go
@@ -0,0 +1,36 @@
+package f
+
+import (
+	"bytes"
+)
+
+const BufferSize = 1024
+
+// CallbackWriter is a custom writer that processes each line calling the callback.
+type CallbackWriter struct {
+	callback func(line string)
+	buffer   []byte
+}
+
+// NewCallbackWriter creates a new CallbackWriter.
+func NewCallbackWriter(process func(line string)) *CallbackWriter {
+	return &CallbackWriter{
+		callback: process,
+		buffer:   make([]byte, 0, BufferSize),
+	}
+}
+
+// Write implements the io.Writer interface.
+func (p *CallbackWriter) Write(data []byte) (int, error) {
+	p.buffer = append(p.buffer, data...)
+	for {
+		idx := bytes.IndexByte(p.buffer, '\n')
+		if idx == -1 {
+			break
+		}
+		line := p.buffer[:idx] // Do not include \n
+		p.buffer = p.buffer[idx+1:]
+		p.callback(string(line))
+	}
+	return len(data), nil
+}