msg: add new package for CLI output.

README.md

@@ -84,6 +84,7 @@ Contents:
     lib/            Commonly-useful functions for writing Go programs.
     log/            A syslog library.
     logging/        A logging library.
+    msg/            Output library for command line programs.
     mwc/            MultiwriteCloser implementation.
     sbuf/           A byte buffer that can be wiped.
     seekbuf/        A read-seekable byte buffer.

lib/lib.go

@@ -336,6 +336,10 @@ type DummyWriteCloser struct {
 	w io.Writer
 }
 
+func WithCloser(w io.Writer) io.WriteCloser {
+	return &DummyWriteCloser{w: w}
+}
+
 func (dwc *DummyWriteCloser) Write(p []byte) (int, error) {
 	return dwc.w.Write(p)
 }

msg/msg.go

@@ -0,0 +1,127 @@
+// Package msg is a tool for handling commandline output based on
+// flags for quiet, verbose, and debug modes. The default is to
+// have all modes disabled.
+//
+// The QPrint messages will only output messages if quiet mode is
+// disabled
+// The VPrint messages will only output messages if verbose mode
+// is enabled.
+// The DPrint messages will only output messages if debug mode
+// is enabled.
+package msg
+
+import (
+	"fmt"
+	"io"
+
+	"git.wntrmute.dev/kyle/goutils/lib"
+
+	"git.wntrmute.dev/kyle/goutils/dbg"
+)
+
+var (
+	enableQuiet   bool
+	enableVerbose bool
+	debug         *dbg.DebugPrinter
+	w             io.Writer
+)
+
+func SetQuiet(q bool) {
+	enableQuiet = q
+}
+
+func SetVerbose(v bool) {
+	enableVerbose = v
+}
+
+func SetDebug(d bool) {
+	debug.Enabled = d
+}
+
+func Set(q, v, d bool) {
+	SetQuiet(q)
+	SetVerbose(v)
+	SetDebug(d)
+}
+
+func QPrint(a ...any) {
+	if enableQuiet {
+		return
+	}
+
+	fmt.Fprint(w, a...)
+}
+
+func QPrintf(format string, a ...any) {
+	if enableQuiet {
+		return
+	}
+
+	fmt.Fprintf(w, format, a...)
+}
+
+func QPrintln(a ...any) {
+	if enableQuiet {
+		return
+	}
+
+	fmt.Fprintln(w, a...)
+}
+
+func DPrint(a ...any) {
+	debug.Print(a...)
+}
+
+func DPrintf(format string, a ...any) {
+	debug.Printf(format, a...)
+}
+
+func DPrintln(a ...any) {
+	debug.Println(a...)
+}
+
+func StackTrace() {
+	debug.StackTrace()
+}
+
+func VPrint(a ...any) {
+	if !enableVerbose {
+		return
+	}
+
+	fmt.Fprint(w, a...)
+}
+
+func VPrintf(format string, a ...any) {
+	if !enableVerbose {
+		return
+	}
+
+	fmt.Fprintf(w, format, a...)
+}
+
+func VPrintln(a ...any) {
+	if !enableVerbose {
+		return
+	}
+
+	fmt.Fprintln(w, a...)
+}
+
+func Print(a ...any) {
+	fmt.Fprint(w, a...)
+}
+
+func Printf(format string, a ...any) {
+	fmt.Fprintf(w, format, a...)
+}
+
+func Println(a ...any) {
+	fmt.Fprintln(w, a...)
+}
+
+// SetWriter changes the output for messages.
+func SetWriter(dst io.Writer) {
+	w = dst
+	debug = dbg.To(lib.WithCloser(w))
+}