package observability

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

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp"
	"go.opentelemetry.io/otel/log/global"
	sdklog "go.opentelemetry.io/otel/sdk/log"
	"go.opentelemetry.io/otel/sdk/resource"
	corelog "tangled.org/core/log"
	"tangled.org/core/spindle/config"
)

func InitLogging(ctx context.Context, cfg config.Logging) (slog.Handler, func(context.Context) error, error) {
	if cfg.Endpoint == "" {
		return nil, func(context.Context) error { return nil }, nil
	}

	opts := []otlploghttp.Option{
		otlploghttp.WithEndpoint(cfg.Endpoint),
		otlploghttp.WithURLPath("/otlp/v1/logs"),
	}
	if cfg.Insecure {
		opts = append(opts, otlploghttp.WithInsecure())
	}

	exporter, err := otlploghttp.New(ctx, opts...)
	if err != nil {
		return nil, nil, fmt.Errorf("creating OTLP log exporter: %w", err)
	}

	res, err := resource.Merge(
		resource.Default(),
		resource.NewSchemaless(attribute.String("service.name", cfg.ServiceName)),
	)
	if err != nil {
		return nil, nil, fmt.Errorf("creating logging resource: %w", err)
	}

	processor := sdklog.NewBatchProcessor(exporter)
	provider := sdklog.NewLoggerProvider(
		sdklog.WithProcessor(processor),
		sdklog.WithResource(res),
	)
	global.SetLoggerProvider(provider)

	otelH := corelog.NewOtelHandler(provider, cfg.ServiceName)

	shutdown := func(shutdownCtx context.Context) error {
		if err := provider.Shutdown(shutdownCtx); err != nil {
			return fmt.Errorf("shutting down logger provider: %w", err)
		}
		return nil
	}

	return otelH, shutdown, nil
}