feat(log): add structured logging handler [LEVEL] [TIME] [FILE:LINE]

internal/log/handler.go

@@ -0,0 +1,125 @@
+package log
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+type Handler struct {
+	mu     sync.Mutex
+	w      io.Writer
+	level  slog.Level
+	attrs  []slog.Attr
+	groups []string
+}
+
+func New(w io.Writer, level slog.Level) *Handler {
+	return &Handler{w: w, level: level}
+}
+
+func (h *Handler) Enabled(_ context.Context, l slog.Level) bool {
+	return l >= h.level
+}
+
+func (h *Handler) Handle(_ context.Context, r slog.Record) error {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	level := r.Level.String()
+	switch r.Level {
+	case slog.LevelDebug:
+		level = "DEBUG"
+	case slog.LevelInfo:
+		level = "INFO"
+	case slog.LevelWarn:
+		level = "WARN"
+	case slog.LevelError:
+		level = "ERROR"
+	}
+
+	_, file, line, ok := runtime.Caller(4)
+	if !ok {
+		file = "???"
+	}
+	short := file
+	for i := len(file) - 1; i > 0; i-- {
+		if file[i] == '/' {
+			short = file[i+1:]
+			break
+		}
+	}
+
+	t := r.Time.Format("2006-01-02 15:04:05.000")
+
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf("[%s] [%s] [%s:%d]", level, t, short, line))
+
+	if len(h.groups) > 0 {
+		b.WriteString(" [" + strings.Join(h.groups, ".") + "]")
+	}
+	if r.Message != "" {
+		b.WriteString(" " + r.Message)
+	}
+
+	r.Attrs(func(a slog.Attr) bool {
+		b.WriteString(fmt.Sprintf(" %s=%v", a.Key, a.Value.Any()))
+		return true
+	})
+	for _, a := range h.attrs {
+		b.WriteString(fmt.Sprintf(" %s=%v", a.Key, a.Value.Any()))
+	}
+
+	b.WriteString("\n")
+	_, err := h.w.Write([]byte(b.String()))
+	return err
+}
+
+func (h *Handler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	if len(attrs) == 0 {
+		return h
+	}
+	h2 := h.clone()
+	h2.attrs = append(h2.attrs, attrs...)
+	return h2
+}
+
+func (h *Handler) WithGroup(name string) slog.Handler {
+	if name == "" {
+		return h
+	}
+	h2 := h.clone()
+	h2.groups = append(h2.groups, name)
+	return h2
+}
+
+func (h *Handler) clone() *Handler {
+	return &Handler{
+		w:      h.w,
+		level:  h.level,
+		attrs:  append([]slog.Attr{}, h.attrs...),
+		groups: append([]string{}, h.groups...),
+	}
+}
+
+func Init(level string) {
+	var l slog.Level
+	switch strings.ToUpper(level) {
+	case "DEBUG":
+		l = slog.LevelDebug
+	case "INFO":
+		l = slog.LevelInfo
+	case "WARN":
+		l = slog.LevelWarn
+	case "ERROR":
+		l = slog.LevelError
+	default:
+		l = slog.LevelInfo
+	}
+	slog.SetDefault(slog.New(New(os.Stderr, l)))
+}