/**
 * Metrics Plugin
 *
 * Automatically collects metrics for requests and responses
 */

import { defaultMetricsCollector } from '../../observability/metrics.js';
import type { Plugin, PluginContext, PluginResponse, MetricsPluginConfig } from '../types.js';

/**
 * Default configuration
 */
const DEFAULT_CONFIG: Required<MetricsPluginConfig> = {
  enabled: true,
  prefix: 'elasticsearch',
  recordDuration: true,
  recordSize: true,
  recordResponseSize: true,
};

/**
 * Create metrics plugin
 */
export function createMetricsPlugin(config: MetricsPluginConfig = {}): Plugin {
  const pluginConfig = { ...DEFAULT_CONFIG, ...config };
  const metrics = defaultMetricsCollector;

  return {
    name: 'metrics',
    version: '1.0.0',
    priority: 20, // Execute early, after logging

    beforeRequest: (context: PluginContext) => {
      if (!pluginConfig.enabled) {
        return context;
      }

      // Record request counter
      metrics.recordCounter(`${pluginConfig.prefix}.requests`, 1, {
        method: context.request.method,
        path: extractIndexFromPath(context.request.path),
      });

      // Record request size if enabled
      if (pluginConfig.recordSize && context.request.body) {
        const size = Buffer.byteLength(JSON.stringify(context.request.body), 'utf8');
        metrics.recordHistogram(`${pluginConfig.prefix}.request.size`, size, {
          method: context.request.method,
        });
      }

      return context;
    },

    afterResponse: <T>(context: PluginContext, response: PluginResponse<T>) => {
      if (!pluginConfig.enabled) {
        return response;
      }

      const duration = Date.now() - context.request.startTime;

      // Record request duration if enabled
      if (pluginConfig.recordDuration) {
        metrics.recordHistogram(`${pluginConfig.prefix}.request.duration`, duration, {
          method: context.request.method,
          path: extractIndexFromPath(context.request.path),
          status: response.statusCode.toString(),
        });
      }

      // Record response size if enabled
      if (pluginConfig.recordResponseSize && response.body) {
        const size = Buffer.byteLength(JSON.stringify(response.body), 'utf8');
        metrics.recordHistogram(`${pluginConfig.prefix}.response.size`, size, {
          method: context.request.method,
          status: response.statusCode.toString(),
        });
      }

      // Record success/failure
      const success = response.statusCode >= 200 && response.statusCode < 300;
      metrics.recordCounter(
        `${pluginConfig.prefix}.requests.${success ? 'success' : 'failure'}`,
        1,
        {
          method: context.request.method,
          status: response.statusCode.toString(),
        }
      );

      return response;
    },

    onError: (context) => {
      if (!pluginConfig.enabled) {
        return null;
      }

      const duration = Date.now() - context.request.startTime;

      // Record error
      metrics.recordCounter(`${pluginConfig.prefix}.errors`, 1, {
        method: context.request.method,
        path: extractIndexFromPath(context.request.path),
        error: context.error.name,
      });

      // Record error duration
      if (pluginConfig.recordDuration) {
        metrics.recordHistogram(`${pluginConfig.prefix}.error.duration`, duration, {
          method: context.request.method,
          error: context.error.name,
        });
      }

      // Don't handle error
      return null;
    },
  };
}

/**
 * Extract index name from path
 */
function extractIndexFromPath(path: string): string {
  // Remove leading slash
  const cleanPath = path.startsWith('/') ? path.slice(1) : path;

  // Split by slash and get first segment
  const segments = cleanPath.split('/');

  // Common patterns:
  // /{index}/_search
  // /{index}/_doc/{id}
  // /_cat/indices
  if (segments[0].startsWith('_')) {
    return segments[0]; // API endpoint like _cat, _search
  }

  return segments[0] || 'unknown';
}