import { parseHttpUrl } from '../utils/validation';

export interface FeedUrlIdentity {
  id: number;
  xmlUrl: string;
}

export type CanonicalizeFeedUrl = (url: string) => string | undefined;

function canonicalizeFeedUrl(url: string): string | undefined {
  const parsed = parseHttpUrl(url);
  return parsed.valid ? parsed.value : undefined;
}

/**
 * In-memory Feed URL identity index used by bulk add operations.
 *
 * Rows must be supplied in ascending id order. The first canonical-equivalent
 * row is retained, which preserves the lookup priority of the legacy scan
 * while making every subsequent lookup constant time.
 */
export class FeedUrlIndex<T extends FeedUrlIdentity> {
  private readonly exact = new Map<string, T>();
  private readonly canonicalEquivalent = new Map<string, T>();
  private readonly claims = new Set<string>();

  constructor(rows: readonly T[], canonicalize: CanonicalizeFeedUrl = canonicalizeFeedUrl) {
    for (const row of rows) {
      this.exact.set(row.xmlUrl, row);
      const canonical = canonicalize(row.xmlUrl);
      if (canonical !== undefined && !this.canonicalEquivalent.has(canonical)) {
        this.canonicalEquivalent.set(canonical, row);
      }
    }
  }

  find(canonicalUrl: string, rawUrl = canonicalUrl): T | undefined {
    return (
      this.exact.get(canonicalUrl) ??
      (rawUrl !== canonicalUrl ? this.exact.get(rawUrl) : undefined) ??
      this.canonicalEquivalent.get(canonicalUrl)
    );
  }

  /** Reserve an identity for this session. Returns false for any duplicate. */
  claim(canonicalUrl: string, rawUrl = canonicalUrl): boolean {
    if (this.find(canonicalUrl, rawUrl) !== undefined || this.claims.has(canonicalUrl)) return false;
    this.claims.add(canonicalUrl);
    return true;
  }

  release(canonicalUrl: string): void {
    this.claims.delete(canonicalUrl);
  }

  /** Add a successfully inserted row without re-canonicalizing existing data. */
  record(row: T, canonicalUrl: string): void {
    this.claims.delete(canonicalUrl);
    this.exact.set(row.xmlUrl, row);
    if (!this.canonicalEquivalent.has(canonicalUrl)) {
      this.canonicalEquivalent.set(canonicalUrl, row);
    }
  }
}