/**
 * AgentRouter resolves which agent config to use for a given channel+sender.
 *
 * Resolution order (first match wins):
 * 1. Exact sender match (channel:senderId)
 * 2. Glob pattern sender match
 * 3. Channel match
 * 4. default_agent fallback
 */

import type { RoutingConfig } from '../config/schema.js';

export type { RoutingConfig };

/**
 * Convert a simple glob pattern to a RegExp.
 * Supports `*` (match any sequence of characters).
 * All other regex-special characters are escaped.
 */
function patternToRegex(pattern: string): RegExp {
  const escaped = pattern
    .replace(/[.+^${}()|[\]\\]/g, '\\$&')
    .replace(/\*/g, '.*');
  return new RegExp(`^${escaped}$`);
}

export class AgentRouter {
  private config: RoutingConfig;

  constructor(config: RoutingConfig) {
    this.config = config;
  }

  /**
   * Resolve the agent config name for a channel + sender pair.
   * Returns undefined if no match and no default is configured.
   */
  resolve(channel: string, senderId: string): string | undefined {
    const senderKey = `${channel}:${senderId}`;

    // 1. Exact sender match
    if (this.config.senders[senderKey]) {
      return this.config.senders[senderKey];
    }

    // 2. Glob pattern sender match
    for (const [pattern, agentName] of Object.entries(this.config.senders)) {
      if (pattern.includes('*') && patternToRegex(pattern).test(senderKey)) {
        return agentName;
      }
    }

    // 3. Channel match
    if (this.config.channels[channel]) {
      return this.config.channels[channel];
    }

    // 4. Default fallback
    return this.config.default_agent;
  }
}