import { ReadableSpan, SpanProcessor, Span } from '@opentelemetry/sdk-trace-base';
import { Context } from '@opentelemetry/api';

/**
 * Filtering Span Processor
 *
 * Filters spans based on a user-provided predicate function.
 * Runs filtering on onEnd() to have access to complete span data.
 *
 * @example Filter out Next.js instrumentation spans
 * ```typescript
 * init({
 *   service: 'my-app',
 *   spanFilter: (span) => span.instrumentationScope.name !== 'next.js'
 * })
 * ```
 *
 * @example Filter out health check endpoints
 * ```typescript
 * init({
 *   service: 'my-app',
 *   spanFilter: (span) => !span.name.includes('/health')
 * })
 * ```
 */

/**
 * Predicate function for filtering spans
 *
 * @param span - The completed span (ReadableSpan) with all attributes and metadata
 * @returns true to keep the span, false to drop it
 *
 * Available span properties for filtering:
 * - `span.name` - Span name
 * - `span.attributes` - All span attributes
 * - `span.instrumentationScope` - `{ name, version }` of the instrumentation
 * - `span.status` - Span status code and message
 * - `span.duration` - Span duration as `[seconds, nanoseconds]`
 * - `span.kind` - SpanKind (INTERNAL, SERVER, CLIENT, etc.)
 */
type SpanFilterPredicate = (span: ReadableSpan) => boolean;
interface FilteringSpanProcessorOptions {
    /**
     * Predicate function to determine if a span should be kept
     * Return true to keep the span, false to drop it
     */
    filter: SpanFilterPredicate;
}
/**
 * Span processor that filters spans based on a predicate function.
 *
 * The filter is applied on onEnd() when the span has complete data including:
 * - All attributes
 * - Status code and message
 * - Duration
 * - Events and links
 * - Instrumentation scope (useful for filtering by library)
 *
 * onStart() passes through unchanged to ensure child spans can still be created.
 *
 * Error handling: If the filter predicate throws, the span is forwarded (fail-open).
 */
declare class FilteringSpanProcessor implements SpanProcessor {
    private readonly wrappedProcessor;
    private readonly filter;
    constructor(wrappedProcessor: SpanProcessor, options: FilteringSpanProcessorOptions);
    /**
     * Pass through onStart - we need spans to start so child spans work
     */
    onStart(span: Span, parentContext: Context): void;
    /**
     * Apply filter predicate on span end
     * If filter returns false, span is dropped (not forwarded)
     */
    onEnd(span: ReadableSpan): void;
    forceFlush(): Promise<void>;
    shutdown(): Promise<void>;
}

export { FilteringSpanProcessor, type FilteringSpanProcessorOptions, type SpanFilterPredicate };