1 files changed, 208 insertions, 0 deletions
diff --git a/log/logger.go b/log/logger.go
new file mode 100644
index 000000000..a9d42b8da
--- /dev/null
+++ b/log/logger.go
@@ -0,0 +1,208 @@
+package log
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/go-stack/stack"
+)
+
+const timeKey = "t"
+const lvlKey = "lvl"
+const msgKey = "msg"
+const errorKey = "LOG15_ERROR"
+
+type Lvl int
+
+const (
+	LvlCrit Lvl = iota
+	LvlError
+	LvlWarn
+	LvlInfo
+	LvlDebug
+)
+
+// Returns the name of a Lvl
+func (l Lvl) String() string {
+	switch l {
+	case LvlDebug:
+		return "dbug"
+	case LvlInfo:
+		return "info"
+	case LvlWarn:
+		return "warn"
+	case LvlError:
+		return "eror"
+	case LvlCrit:
+		return "crit"
+	default:
+		panic("bad level")
+	}
+}
+
+// Returns the appropriate Lvl from a string name.
+// Useful for parsing command line args and configuration files.
+func LvlFromString(lvlString string) (Lvl, error) {
+	switch lvlString {
+	case "debug", "dbug":
+		return LvlDebug, nil
+	case "info":
+		return LvlInfo, nil
+	case "warn":
+		return LvlWarn, nil
+	case "error", "eror":
+		return LvlError, nil
+	case "crit":
+		return LvlCrit, nil
+	default:
+		return LvlDebug, fmt.Errorf("Unknown level: %v", lvlString)
+	}
+}
+
+// A Record is what a Logger asks its handler to write
+type Record struct {
+	Time     time.Time
+	Lvl      Lvl
+	Msg      string
+	Ctx      []interface{}
+	Call     stack.Call
+	KeyNames RecordKeyNames
+}
+
+type RecordKeyNames struct {
+	Time string
+	Msg  string
+	Lvl  string
+}
+
+// A Logger writes key/value pairs to a Handler
+type Logger interface {
+	// New returns a new Logger that has this logger's context plus the given context
+	New(ctx ...interface{}) Logger
+
+	// GetHandler gets the handler associated with the logger.
+	GetHandler() Handler
+
+	// SetHandler updates the logger to write records to the specified handler.
+	SetHandler(h Handler)
+
+	// Log a message at the given level with context key/value pairs
+	Debug(msg string, ctx ...interface{})
+	Info(msg string, ctx ...interface{})
+	Warn(msg string, ctx ...interface{})
+	Error(msg string, ctx ...interface{})
+	Crit(msg string, ctx ...interface{})
+}
+
+type logger struct {
+	ctx []interface{}
+	h   *swapHandler
+}
+
+func (l *logger) write(msg string, lvl Lvl, ctx []interface{}) {
+	l.h.Log(&Record{
+		Time: time.Now(),
+		Lvl:  lvl,
+		Msg:  msg,
+		Ctx:  newContext(l.ctx, ctx),
+		Call: stack.Caller(2),
+		KeyNames: RecordKeyNames{
+			Time: timeKey,
+			Msg:  msgKey,
+			Lvl:  lvlKey,
+		},
+	})
+}
+
+func (l *logger) New(ctx ...interface{}) Logger {
+	child := &logger{newContext(l.ctx, ctx), new(swapHandler)}
+	child.SetHandler(l.h)
+	return child
+}
+
+func newContext(prefix []interface{}, suffix []interface{}) []interface{} {
+	normalizedSuffix := normalize(suffix)
+	newCtx := make([]interface{}, len(prefix)+len(normalizedSuffix))
+	n := copy(newCtx, prefix)
+	copy(newCtx[n:], normalizedSuffix)
+	return newCtx
+}
+
+func (l *logger) Debug(msg string, ctx ...interface{}) {
+	l.write(msg, LvlDebug, ctx)
+}
+
+func (l *logger) Info(msg string, ctx ...interface{}) {
+	l.write(msg, LvlInfo, ctx)
+}
+
+func (l *logger) Warn(msg string, ctx ...interface{}) {
+	l.write(msg, LvlWarn, ctx)
+}
+
+func (l *logger) Error(msg string, ctx ...interface{}) {
+	l.write(msg, LvlError, ctx)
+}
+
+func (l *logger) Crit(msg string, ctx ...interface{}) {
+	l.write(msg, LvlCrit, ctx)
+}
+
+func (l *logger) GetHandler() Handler {
+	return l.h.Get()
+}
+
+func (l *logger) SetHandler(h Handler) {
+	l.h.Swap(h)
+}
+
+func normalize(ctx []interface{}) []interface{} {
+	// if the caller passed a Ctx object, then expand it
+	if len(ctx) == 1 {
+		if ctxMap, ok := ctx[0].(Ctx); ok {
+			ctx = ctxMap.toArray()
+		}
+	}
+
+	// ctx needs to be even because it's a series of key/value pairs
+	// no one wants to check for errors on logging functions,
+	// so instead of erroring on bad input, we'll just make sure
+	// that things are the right length and users can fix bugs
+	// when they see the output looks wrong
+	if len(ctx)%2 != 0 {
+		ctx = append(ctx, nil, errorKey, "Normalized odd number of arguments by adding nil")
+	}
+
+	return ctx
+}
+
+// Lazy allows you to defer calculation of a logged value that is expensive
+// to compute until it is certain that it must be evaluated with the given filters.
+//
+// Lazy may also be used in conjunction with a Logger's New() function
+// to generate a child logger which always reports the current value of changing
+// state.
+//
+// You may wrap any function which takes no arguments to Lazy. It may return any
+// number of values of any type.
+type Lazy struct {
+	Fn interface{}
+}
+
+// Ctx is a map of key/value pairs to pass as context to a log function
+// Use this only if you really need greater safety around the arguments you pass
+// to the logging functions.
+type Ctx map[string]interface{}
+
+func (c Ctx) toArray() []interface{} {
+	arr := make([]interface{}, len(c)*2)
+
+	i := 0
+	for k, v := range c {
+		arr[i] = k
+		arr[i+1] = v
+		i += 2
+	}
+
+	return arr
+}