Extract log utils into pkg/log

Docker-DCO-1.1-Signed-off-by: Josiah Kiehl <josiah@capoferro.net> (github: capoferro)

log/log.go

@@ -0,0 +1,77 @@
+package log
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"strings"
+)
+
+type priority int
+
+const (
+	errorFormat = "[%s] %s:%d %s\n"
+	logFormat   = "[%s] %s\n"
+
+	fatal priority = iota
+	error
+	info
+	debug
+)
+
+func (p priority) String() string {
+	switch p {
+	case fatal:
+		return "fatal"
+	case error:
+		return "error"
+	case info:
+		return "info"
+	case debug:
+		return "debug"
+	}
+
+	return ""
+}
+
+// Debug function, if the debug flag is set, then display. Do nothing otherwise
+// If Docker is in damon mode, also send the debug info on the socket
+func Debugf(format string, a ...interface{}) {
+	if os.Getenv("DEBUG") != "" {
+		logf(os.Stderr, debug, format, a...)
+	}
+}
+
+func Infof(format string, a ...interface{}) {
+	logf(os.Stdout, info, format, a...)
+}
+
+func Errorf(format string, a ...interface{}) {
+	logf(os.Stderr, error, format, a...)
+}
+
+func Fatalf(format string, a ...interface{}) {
+	logf(os.Stderr, fatal, format, a...)
+	os.Exit(1)
+}
+
+func logf(stream io.Writer, level priority, format string, a ...interface{}) {
+	var prefix string
+
+	if level <= error || level == debug {
+		// Retrieve the stack infos
+		_, file, line, ok := runtime.Caller(2)
+		if !ok {
+			file = "<unknown>"
+			line = -1
+		} else {
+			file = file[strings.LastIndex(file, "/")+1:]
+		}
+		prefix = fmt.Sprintf(errorFormat, level.String(), file, line, format)
+	} else {
+		prefix = fmt.Sprintf(logFormat, level.String(), format)
+	}
+
+	fmt.Fprintf(stream, prefix, a...)
+}

log/log_test.go

@@ -0,0 +1,37 @@
+package log
+
+import (
+	"bytes"
+	"regexp"
+
+	"testing"
+)
+
+func TestLogFatalf(t *testing.T) {
+	var output *bytes.Buffer
+
+	tests := []struct {
+		Level           priority
+		Format          string
+		Values          []interface{}
+		ExpectedPattern string
+	}{
+		{fatal, "%d + %d = %d", []interface{}{1, 1, 2}, "\\[fatal\\] testing.go:\\d+ 1 \\+ 1 = 2"},
+		{error, "%d + %d = %d", []interface{}{1, 1, 2}, "\\[error\\] testing.go:\\d+ 1 \\+ 1 = 2"},
+		{info, "%d + %d = %d", []interface{}{1, 1, 2}, "\\[info\\] 1 \\+ 1 = 2"},
+		{debug, "%d + %d = %d", []interface{}{1, 1, 2}, "\\[debug\\] testing.go:\\d+ 1 \\+ 1 = 2"},
+	}
+
+	for i, test := range tests {
+		output = &bytes.Buffer{}
+		logf(output, test.Level, test.Format, test.Values...)
+
+		expected := regexp.MustCompile(test.ExpectedPattern)
+		if !expected.MatchString(output.String()) {
+			t.Errorf("[%d] Log output does not match expected pattern:\n\tExpected: %s\n\tOutput: %s",
+				i,
+				expected.String(),
+				output.String())
+		}
+	}
+}