package rlog

import (
	"log/slog"
	"os"

	"github.com/rs/zerolog"
	slogmulti "github.com/samber/slog-multi"
	slogzerolog "github.com/samber/slog-zerolog"
)

const errKey = "error"
const labelGroupKey = "labelGroup"

var zl = zerolog.New(&zerolog.ConsoleWriter{Out: os.Stderr})

var handlers = []slog.Handler{
	slogzerolog.Option{Logger: &zl}.NewZerologHandler(),
}

var defaultLogger = slog.New(slogmulti.Fanout(handlers...))

func init() {
	slog.SetDefault(defaultLogger)
}

func AddHandler(nh slog.Handler) {
	handlers = append(handlers, nh)
	defaultLogger = slog.New(slogmulti.Fanout(handlers...))
	slog.SetDefault(defaultLogger)
}

func ComponentLog(name string) *slog.Logger {
	return defaultLogger.With(slog.String("component", name))
}

func ServiceLog(name string) *slog.Logger {
	return ComponentLog("service/" + name)
}

func FunctionLog(log *slog.Logger, name string) *slog.Logger {
	return log.With(slog.String("function", name))
}

func EndpointLog(log *slog.Logger, name string) *slog.Logger {
	return log.With(slog.String("endpoint", name))
}

func Err(err error) slog.Attr {
	return slog.Attr{Key: errKey, Value: fmtErr(err)}
}

func Label(args ...any) slog.Attr {
	return slog.Group(labelGroupKey, args...)
}

// fmtErr returns a slog.GroupValue with keys "msg" and "trace". If the error
// does not implement interface { StackTrace() errors.StackTrace }, the "trace"
// key is omitted.
func fmtErr(err error) slog.Value {
	if err == nil {
		return slog.AnyValue(nil)
	}

	var groupValues []slog.Attr

	groupValues = append(groupValues, slog.String("msg", err.Error()))

	return slog.GroupValue(groupValues...)
}