package observability

import (
	"context"
	"log/slog"
	"os"

	"go.opentelemetry.io/otel/trace"
)

// Configure installs the process-wide JSON logger used by every GL adapter.
func Configure(service string, level slog.Leveler) *slog.Logger {
	handler := slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
		AddSource: true,
		Level:     level,
		ReplaceAttr: func(_ []string, attr slog.Attr) slog.Attr {
			switch attr.Key {
			case slog.TimeKey:
				attr.Key = "timestamp"
			case slog.LevelKey:
				attr.Key = "severity"
				attr.Value = slog.StringValue(levelName(attr.Value))
			case slog.MessageKey:
				attr.Key = "message"
			case slog.SourceKey:
				attr.Key = "source"
			}
			return attr
		},
	})
	logger := slog.New(&traceHandler{Handler: handler}).With("service", service)
	slog.SetDefault(logger)
	return logger
}

func levelName(value slog.Value) string {
	if value.Kind() == slog.KindInt64 {
		return slog.Level(value.Int64()).String()
	}
	if level, ok := value.Any().(slog.Level); ok {
		return level.String()
	}
	return value.String()
}

type traceHandler struct{ slog.Handler }

func (h *traceHandler) Handle(ctx context.Context, record slog.Record) error {
	spanContext := trace.SpanContextFromContext(ctx)
	if spanContext.IsValid() {
		record.AddAttrs(slog.String("trace_id", spanContext.TraceID().String()), slog.String("span_id", spanContext.SpanID().String()))
	}
	return h.Handler.Handle(ctx, record)
}

func (h *traceHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	return &traceHandler{Handler: h.Handler.WithAttrs(attrs)}
}
func (h *traceHandler) WithGroup(name string) slog.Handler {
	return &traceHandler{Handler: h.Handler.WithGroup(name)}
}