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

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

	"galaxy/notification/internal/api/intentstream"

	"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.
func TraceAttrsFromContext(ctx context.Context) []any {
	if ctx == nil {
		return nil
	}

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

	return []any{
		"otel_trace_id", spanContext.TraceID().String(),
		"otel_span_id", spanContext.SpanID().String(),
	}
}

// NotificationAttrs returns structured notification-identifying log fields.
func NotificationAttrs(
	notificationID string,
	notificationType intentstream.NotificationType,
	producer intentstream.Producer,
	audienceKind intentstream.AudienceKind,
	idempotencyKey string,
	requestID string,
	traceID string,
) []any {
	attrs := []any{
		"notification_id", notificationID,
		"notification_type", string(notificationType),
		"producer", string(producer),
		"audience_kind", string(audienceKind),
		"idempotency_key", idempotencyKey,
	}
	if strings.TrimSpace(requestID) != "" {
		attrs = append(attrs, "request_id", requestID)
	}
	if strings.TrimSpace(traceID) != "" {
		attrs = append(attrs, "trace_id", traceID)
	}

	return attrs
}

// IntentAttrs returns structured intent-identifying log fields when a durable
// notification record does not yet exist.
func IntentAttrs(intent intentstream.Intent) []any {
	attrs := []any{
		"notification_type", string(intent.NotificationType),
		"producer", string(intent.Producer),
		"audience_kind", string(intent.AudienceKind),
		"idempotency_key", intent.IdempotencyKey,
	}
	if strings.TrimSpace(intent.RequestID) != "" {
		attrs = append(attrs, "request_id", intent.RequestID)
	}
	if strings.TrimSpace(intent.TraceID) != "" {
		attrs = append(attrs, "trace_id", intent.TraceID)
	}

	return attrs
}

// RouteAttrs returns structured route-identifying log fields.
func RouteAttrs(
	notificationID string,
	notificationType intentstream.NotificationType,
	producer intentstream.Producer,
	audienceKind intentstream.AudienceKind,
	idempotencyKey string,
	requestID string,
	traceID string,
	routeID string,
	channel intentstream.Channel,
) []any {
	attrs := NotificationAttrs(notificationID, notificationType, producer, audienceKind, idempotencyKey, requestID, traceID)
	attrs = append(attrs,
		"route_id", routeID,
		"channel", string(channel),
	)

	return attrs
}