/**
 * Subscriber-match logic. Pure: given an event and a subscriber's
 * match rule, decide whether to deliver. Glob support is intentionally
 * tiny (`*` and `**`); the existing dot-glob matcher in pattern.ts
 * targets local-bus event names with strict segment semantics — a
 * different problem.
 */

import type { PublishEvent, Subscriber, SubscriberMatch } from './types';

/**
 * Test a glob against a literal package name. `*` matches zero or
 * more non-slash characters; `**` matches across slashes (useful for
 * scope walks like `@celilo/**` matching `@celilo/sub/util`). Other
 * regex meta-characters are escaped literally so package names can
 * contain `.`/`+`/etc. without surprise.
 *
 * Pure — no caching, regex is rebuilt per call. Subscriber lists are
 * small and matching is per-publish, so allocations don't matter.
 */
export function globMatchPackage(pattern: string, name: string): boolean {
  // Tokenize so `**` doesn't collide with `*` during escape.
  const tokens = pattern.split(/(\*\*|\*)/);
  let regex = '^';
  for (const token of tokens) {
    if (token === '**') regex += '.*';
    else if (token === '*') regex += '[^/]*';
    else regex += escapeRegex(token);
  }
  regex += '$';
  return new RegExp(regex).test(name);
}

function escapeRegex(s: string): string {
  return s.replace(/[.+?^${}()|[\]\\]/g, '\\$&');
}

/**
 * Match check for a single (event, match-rule) pair. Pure; every
 * non-undefined field in the rule must match the corresponding field
 * on the event. Absent fields are wildcards.
 */
export function matchesRule(event: PublishEvent, rule: SubscriberMatch): boolean {
  if (rule.registry !== undefined && event.registry !== rule.registry) return false;
  if (rule.tag !== undefined && event.tag !== rule.tag) return false;
  if (
    rule.packagePattern !== undefined &&
    !globMatchPackage(rule.packagePattern, event.package.name)
  ) {
    return false;
  }
  return true;
}

/**
 * Filter subscribers down to those whose match rules fire for this
 * event. Caller fans out to the result.
 */
export function subscribersFor(event: PublishEvent, subscribers: Subscriber[]): Subscriber[] {
  return subscribers.filter((s) => matchesRule(event, s.match));
}