import * as Y from 'yjs';

import type { PagePersistence, StoreResult } from '../persistence.js';

/**
 * In-memory {@link PagePersistence} for tests: it keeps the last merged state
 * per page so a "server restart" (destroy + recreate around the same instance)
 * still reloads content, without needing a database. The Postgres implementation
 * is covered separately by `persistence.db.test.ts`.
 */
export class InMemoryPagePersistence implements PagePersistence {
  private readonly states = new Map<string, Uint8Array>();
  /** Page ids that should report as missing (to exercise the not-found path). */
  readonly missing = new Set<string>();
  /** Overridable size ceiling so a test can trip it without a 5 MiB document. */
  sizeLimit = Number.POSITIVE_INFINITY;
  /** store() call count, for assertions. */
  storeCalls = 0;

  async loadInto(pageId: string, doc: Y.Doc): Promise<boolean> {
    if (this.missing.has(pageId)) return false;
    const state = this.states.get(pageId);
    if (state) Y.applyUpdate(doc, state);
    return true;
  }

  async store(pageId: string, doc: Y.Doc): Promise<StoreResult> {
    this.storeCalls += 1;
    const full = Y.encodeStateAsUpdate(doc);
    if (full.byteLength > this.sizeLimit) {
      return { outcome: 'too_large', bytes: full.byteLength, durationMs: 0, merged: false };
    }
    if (this.missing.has(pageId)) {
      return { outcome: 'not_found', bytes: full.byteLength, durationMs: 0, merged: false };
    }
    this.states.set(pageId, full);
    return { outcome: 'stored', bytes: full.byteLength, durationMs: 0, merged: false };
  }

  forget(): void {
    // Nothing to release for the in-memory fake.
  }
}