Initial commit

logwriter.go

@@ -0,0 +1,147 @@
+package logwriter
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"time"
+)
+
+type LogWriter struct {
+	TimeFormat string
+	TimeZone   *time.Location
+	writer     io.Writer
+
+	newLine bool
+}
+
+// New created new LogWriter.
+func New(w io.Writer) *LogWriter {
+	lw := &LogWriter{
+		TimeFormat: defaultTimeFormat,
+		TimeZone:   defaultTimeZone,
+		writer:     w,
+		newLine:    true}
+
+	return lw
+}
+
+// Println formats using the default formats for its operands and writes to writer.
+// Spaces are always added between operands and a newline is appended.
+// It returns the number of bytes written and any write error encountered.
+func (lw *LogWriter) Println(a ...any) (n int, err error) {
+	s := fmt.Sprintln(a...)
+
+	n, err = lw.Write([]byte(s))
+	if err != nil {
+		return n, err
+	}
+
+	lw.newLine = true
+
+	return n, nil
+}
+
+// Print formats using the default formats for its operands and writes to writer.
+// Spaces are added between operands when neither is a string.
+// It returns the number of bytes written and any write error encountered.
+func (lw *LogWriter) Print(a ...any) (n int, err error) {
+	s := fmt.Sprint(a...)
+
+	n, err = lw.Write([]byte(s))
+	if err != nil {
+		return n, err
+	}
+
+	if s[len(s)-1] == '\n' {
+		lw.newLine = true
+	} else {
+		lw.newLine = false
+	}
+
+	return n, nil
+}
+
+// Printf formats according to a format specifier and writes to writer.
+// It returns the number of bytes written and any write error encountered.
+func (lw *LogWriter) Printf(format string, a ...any) (n int, err error) {
+	s := fmt.Sprintf(format, a...)
+
+	n, err = lw.Write([]byte(s))
+	if err != nil {
+		return n, err
+	}
+
+	if s[len(s)-1] == '\n' {
+		lw.newLine = true
+	} else {
+		lw.newLine = false
+	}
+
+	return n, nil
+}
+
+// Write writes len(p) bytes from p to the writer.
+// It returns the number of bytes written from p (0 <= n <= len(p))
+// and any error encountered that caused the write to stop early.
+func (lw *LogWriter) Write(p []byte) (n int, err error) {
+	r := bufio.NewReader(bytes.NewReader(p))
+
+	for {
+		line, err := r.ReadString('\n')
+		if err == io.EOF && len(line) > 0 {
+			nn, err := io.WriteString(lw.writer, lw.prefix()+" "+line)
+			n += nn
+			if err != nil {
+				return n, err
+			}
+
+			if line[len(line)-1] == '\n' {
+				lw.newLine = true // TODO: uncovered or unused?
+			} else {
+				lw.newLine = false
+			}
+			break
+		}
+		if err == io.EOF {
+			break
+		}
+
+		if lw.newLine {
+			nn, err := io.WriteString(lw.writer, lw.prefix()+" "+line)
+			n += nn
+			if err != nil {
+				return n, err
+			}
+		} else {
+			nn, err := io.WriteString(lw.writer, line)
+			n += nn
+			if err != nil {
+				return n, err
+			}
+			lw.newLine = true
+		}
+	}
+
+	return n, nil
+}
+
+func (lw *LogWriter) Close() error {
+	if lw.newLine {
+		return nil
+	}
+
+	_, err := io.WriteString(lw, "\n")
+	if err != nil {
+		return err
+	}
+
+	lw.newLine = true
+
+	return nil
+}
+
+func (lw *LogWriter) prefix() string {
+	return fmt.Sprintf("%s", time.Now().Format(lw.TimeFormat))
+}