3 files changed, 192 insertions, 0 deletions
diff --git a/internal/logging/context.go b/internal/logging/context.go
new file mode 100644
index 0000000..29bad62
--- /dev/null
+++ b/internal/logging/context.go
@@ -0,0 +1,39 @@
+package logging
+
+import (
+	"context"
+	"log/slog"
+)
+
+type ctxTracker struct {
+	ctxKey interface{}
+	logKey string
+	next   slog.Handler
+}
+
+func (h ctxTracker) Handle(ctx context.Context, r slog.Record) error {
+	if v := ctx.Value(h.ctxKey); v != nil {
+		r.AddAttrs(slog.Any(h.logKey, v))
+	}
+	return h.next.Handle(ctx, r)
+}
+
+func (h ctxTracker) Enabled(ctx context.Context, lvl slog.Level) bool {
+	return h.next.Enabled(ctx, lvl)
+}
+
+func (h ctxTracker) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return h.next.WithAttrs(attrs)
+}
+
+func (h ctxTracker) WithGroup(name string) slog.Handler {
+	return h.next.WithGroup(name)
+}
+
+func withTrackedContext(current slog.Handler, ctxKey interface{}, logKey string) *ctxTracker {
+	return &ctxTracker{
+		ctxKey: ctxKey,
+		logKey: logKey,
+		next:   current,
+	}
+}
diff --git a/internal/logging/logging.go b/internal/logging/logging.go
new file mode 100644
index 0000000..91a9734
--- /dev/null
+++ b/internal/logging/logging.go
@@ -0,0 +1,92 @@
+package logging
+
+import (
+	"errors"
+	"io"
+	"log/slog"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/ChausseBenjamin/rafta/internal/util"
+	"github.com/charmbracelet/log"
+)
+
+const (
+	ErrKey = "error_message"
+)
+
+var (
+	ErrInvalidLevel  = errors.New("invalid log level")
+	ErrInvalidFormat = errors.New("invalid log format")
+)
+
+func Setup(lvlStr, fmtStr, outStr string) error {
+	output, outputErr := setOutput(outStr)
+	format, formatErr := setFormat(fmtStr)
+	level, levelErr := setLevel(lvlStr)
+
+	prefixStr := ""
+	if format != log.JSONFormatter {
+		prefixStr = "Rafta 🚢"
+	}
+
+	var h slog.Handler = log.NewWithOptions(
+		output,
+		log.Options{
+			TimeFormat:   time.DateTime,
+			Prefix:       prefixStr,
+			Level:        level,
+			ReportCaller: true,
+			Formatter:    format,
+		},
+	)
+
+	h = withTrackedContext(h, util.ReqIDKey, "request_id")
+	h = withStackTrace(h)
+	slog.SetDefault(slog.New(h))
+	return errors.Join(outputErr, formatErr, levelErr)
+}
+
+func setLevel(target string) (log.Level, error) {
+	for _, l := range []struct {
+		prefix string
+		level  log.Level
+	}{
+		{"deb", log.DebugLevel},
+		{"inf", log.InfoLevel},
+		{"warn", log.WarnLevel},
+		{"err", log.ErrorLevel},
+	} {
+		if strings.HasPrefix(strings.ToLower(target), l.prefix) {
+			return l.level, nil
+		}
+	}
+	return log.InfoLevel, ErrInvalidLevel
+}
+
+func setFormat(f string) (log.Formatter, error) {
+	switch f {
+	case "plain", "text":
+		return log.TextFormatter, nil
+	case "json", "structured":
+		return log.JSONFormatter, nil
+	}
+	return log.TextFormatter, ErrInvalidFormat
+}
+
+func setOutput(path string) (io.Writer, error) {
+	switch path {
+	case "stdout":
+		return os.Stdout, nil
+	case "stderr":
+		return os.Stderr, nil
+	default:
+		f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+		if err != nil {
+			return os.Stdout, err
+		} else {
+			return f, nil
+		}
+	}
+}
diff --git a/internal/logging/trace.go b/internal/logging/trace.go
new file mode 100644
index 0000000..8900727
--- /dev/null
+++ b/internal/logging/trace.go
@@ -0,0 +1,61 @@
+package logging
+
+import (
+	"context"
+	"log/slog"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+const (
+	prgCount = 20
+	defSkip  = 6
+)
+
+type stackTracer struct {
+	h     slog.Handler
+	nSkip int
+}
+
+func (h stackTracer) Enabled(ctx context.Context, lvl slog.Level) bool {
+	return h.h.Enabled(ctx, lvl)
+}
+
+func (h stackTracer) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return h.h.WithAttrs(attrs)
+}
+
+func (h stackTracer) WithGroup(name string) slog.Handler {
+	return h.h.WithGroup(name)
+}
+
+func (h stackTracer) Handle(ctx context.Context, r slog.Record) error {
+	if r.Level < slog.LevelError {
+		return h.h.Handle(ctx, r)
+	}
+
+	trace := h.GetTrace()
+	r.AddAttrs(slog.String("trace", trace))
+
+	return h.h.Handle(ctx, r)
+}
+
+func (h stackTracer) GetTrace() string {
+	var b strings.Builder
+	pc := make([]uintptr, prgCount)
+	n := runtime.Callers(h.nSkip, pc)
+	frames := runtime.CallersFrames(pc[:n])
+
+	for frame, more := frames.Next(); more; frame, more = frames.Next() {
+		b.WriteString(frame.Function + "\n    " + frame.File + ":" + strconv.Itoa(frame.Line) + "\n")
+	}
+	return b.String()
+}
+
+func withStackTrace(h slog.Handler) slog.Handler {
+	return stackTracer{
+		h:     h,
+		nSkip: defSkip,
+	}
+}