Add debug printer.

dbg/dbg.go

@@ -0,0 +1,76 @@
+// Package dbg implements a debug printer.
+package dbg
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+// A DebugPrinter is a drop-in replacement for fmt.Print*, and also acts as
+// an io.WriteCloser when enabled.
+type DebugPrinter struct {
+	// If Enabled is false, the print statements won't do anything.
+	Enabled bool
+	out     io.WriteCloser
+}
+
+// Close satisfies the Closer interface.
+func (dbg *DebugPrinter) Close() error {
+	return dbg.out.Close()
+}
+
+// Write satisfies the Writer interface.
+func (dbg *DebugPrinter) Write(p []byte) (int, error) {
+	if dbg.Enabled {
+		return dbg.out.Write(p)
+	}
+	return 0, nil
+}
+
+// New returns a new DebugPrinter on os.Stdout.
+func New() *DebugPrinter {
+	return &DebugPrinter{
+		out: os.Stdout,
+	}
+}
+
+// ToFile sets up a new DebugPrinter to a file, truncating it if it exists.
+func ToFile(path string) (*DebugPrinter, error) {
+	file, err := os.Create(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return &DebugPrinter{
+		out: file,
+	}, nil
+}
+
+// To sets up a new DebugPrint to an io.WriteCloser.
+func To(w io.WriteCloser) *DebugPrinter {
+	return &DebugPrinter{
+		out: w,
+	}
+}
+
+// Print calls fmt.Print if Enabled is true.
+func (dbg DebugPrinter) Print(v ...interface{}) {
+	if dbg.Enabled {
+		fmt.Fprint(dbg.out, v...)
+	}
+}
+
+// Println calls fmt.Println if Enabled is true.
+func (dbg DebugPrinter) Println(v ...interface{}) {
+	if dbg.Enabled {
+		fmt.Fprintln(dbg.out, v...)
+	}
+}
+
+// Printf calls fmt.Printf if Enabled is true.
+func (dbg DebugPrinter) Printf(format string, v ...interface{}) {
+	if dbg.Enabled {
+		fmt.Fprintf(dbg.out, format, v...)
+	}
+}

dbg/dbg_test.go

@@ -0,0 +1,120 @@
+package dbg
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/kisom/goutils/testio"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNew(t *testing.T) {
+	buf := testio.NewBufCloser(nil)
+	dbg := New()
+	dbg.out = buf
+
+	dbg.Print("hello")
+	dbg.Println("hello")
+	dbg.Printf("hello %s", "world")
+	require.Equal(t, 0, buf.Len())
+
+	dbg.Enabled = true
+	dbg.Print("hello")              // +5
+	dbg.Println("hello")            // +6
+	dbg.Printf("hello %s", "world") // +11
+	require.Equal(t, 22, buf.Len())
+
+	err := dbg.Close()
+	require.NoError(t, err)
+}
+
+func TestTo(t *testing.T) {
+	buf := testio.NewBufCloser(nil)
+	dbg := To(buf)
+
+	dbg.Print("hello")
+	dbg.Println("hello")
+	dbg.Printf("hello %s", "world")
+	require.Equal(t, 0, buf.Len())
+
+	dbg.Enabled = true
+	dbg.Print("hello")              // +5
+	dbg.Println("hello")            // +6
+	dbg.Printf("hello %s", "world") // +11
+
+	require.Equal(t, 22, buf.Len())
+
+	err := dbg.Close()
+	require.NoError(t, err)
+}
+
+func TestToFile(t *testing.T) {
+	testFile, err := ioutil.TempFile("", "dbg")
+	require.NoError(t, err)
+	err = testFile.Close()
+	require.NoError(t, err)
+
+	testFileName := testFile.Name()
+	defer os.Remove(testFileName)
+
+	dbg, err := ToFile(testFileName)
+	require.NoError(t, err)
+
+	dbg.Print("hello")
+	dbg.Println("hello")
+	dbg.Printf("hello %s", "world")
+
+	stat, err := os.Stat(testFileName)
+	require.NoError(t, err)
+
+	require.EqualValues(t, 0, stat.Size())
+
+	dbg.Enabled = true
+	dbg.Print("hello")              // +5
+	dbg.Println("hello")            // +6
+	dbg.Printf("hello %s", "world") // +11
+
+	stat, err = os.Stat(testFileName)
+	require.NoError(t, err)
+
+	require.EqualValues(t, 22, stat.Size())
+
+	err = dbg.Close()
+	require.NoError(t, err)
+}
+
+func TestWriting(t *testing.T) {
+	data := []byte("hello, world")
+	buf := testio.NewBufCloser(nil)
+	dbg := To(buf)
+
+	n, err := dbg.Write(data)
+	require.NoError(t, err)
+	require.EqualValues(t, 0, n)
+
+	dbg.Enabled = true
+	n, err = dbg.Write(data)
+	require.NoError(t, err)
+	require.EqualValues(t, 12, n)
+
+	err = dbg.Close()
+	require.NoError(t, err)
+}
+
+func TestToFileError(t *testing.T) {
+	testFile, err := ioutil.TempFile("", "dbg")
+	require.NoError(t, err)
+	err = testFile.Chmod(0400)
+	require.NoError(t, err)
+	err = testFile.Close()
+	require.NoError(t, err)
+
+	testFileName := testFile.Name()
+
+	_, err = ToFile(testFileName)
+	require.Error(t, err)
+
+	err = os.Remove(testFileName)
+	require.NoError(t, err)
+}