// Package logging configures the Game Lobby Service process logger and
// provides context-aware helpers for trace fields.
package logging

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

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

// New constructs the process-wide JSON logger from level.
func New(level string) (*slog.Logger, error) {
	var slogLevel slog.Level
	if err := slogLevel.UnmarshalText([]byte(strings.TrimSpace(level))); err != nil {
		return nil, fmt.Errorf("build logger: %w", err)
	}

	return slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: slogLevel,
	})), nil
}

// TraceAttrsFromContext returns slog key-value pairs for the active
// OpenTelemetry span when ctx carries a valid span context. The keys match
// the frozen `lobby/README.md` §Observability log fields `trace_id` and
// `span_id`.
func TraceAttrsFromContext(ctx context.Context) []any {
	if ctx == nil {
		return nil
	}

	spanContext := trace.SpanContextFromContext(ctx)
	if !spanContext.IsValid() {
		return nil
	}

	return []any{
		"trace_id", spanContext.TraceID().String(),
		"span_id", spanContext.SpanID().String(),
	}
}