core/tests/engine/sharded-delta-layering.test.js

import { describe, test } from 'node:test';
import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import { CondensedGraph } from '../../src/core/CondensedGraph.js';
import { ShardedSnapshotBuilder } from '../../src/core/shards/ShardedSnapshotBuilder.js';
import { ShardedSnapshot } from '../../src/core/shards/ShardedSnapshot.js';
import { FileShardStorage } from '../../src/core/shards/FileShardStorage.js';
import { DeltaShardBinary } from '../../src/core/shards/DeltaShardBinary.js';

function buildSnapshot(bucketSize = 4) {
  const graph = new CondensedGraph();
  const nodes = [];
  for (let i = 0; i < 6; i++) {
    nodes.push(graph._ensureNode(`node:${i}`));
  }
  graph.addEdge(nodes[0], 'owner', nodes[1]);
  graph.addEdge(nodes[0], 'owner', nodes[2]);
  graph.addEdge(nodes[3], 'owner', nodes[4]);
  graph.addEdge(nodes[5], 'owner', nodes[0]);

  graph.finalizePerfectHash();
  graph.finalizeWaveletAdjacency({ dropAdjacencyList: true });

  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'sharded-delta-layer-'));
  const builder = new ShardedSnapshotBuilder({ bucketSize, includeDirections: ['out', 'in'] });
  const manifest = builder.build(graph, dir);
  const storage = new FileShardStorage(dir);
  const snapshot = new ShardedSnapshot(manifest, storage, { cacheLimit: 8 });
  snapshot.initializeSync();
  return { snapshot, dir, nodes, manifest };
}

function writeDeltaLayer(snapshot, dir, entries, mode = 'override') {
  fs.mkdirSync(dir, { recursive: true });
  const merged = new Map();
  for (const entry of entries) {
    const shardMeta = snapshot._selectShardMeta(entry.relationId, entry.direction, entry.srcId);
    assert.ok(shardMeta, 'Missing shard meta for delta entry');
    const localSource = snapshot._localSource(entry.srcId, shardMeta);
    const key = shardMeta.cacheKey;
    let bucket = merged.get(key);
    if (!bucket) {
      bucket = { shardMeta, additions: [], removals: [] };
      merged.set(key, bucket);
    }
    for (const add of entry.additions) {
      bucket.additions.push({
        srcLocal: localSource,
        otherId: add.dstId,
        possBits: add.possBits,
        relBits: add.relBits
      });
    }
    for (const rem of entry.removals) {
      bucket.removals.push({
        srcLocal: localSource,
        otherId: rem.dstId
      });
    }
  }

  const shards = [];
  for (const bucket of merged.values()) {
    const shardMeta = bucket.shardMeta;
    const buffer = DeltaShardBinary.serialize({
      relationId: shardMeta.relationId,
      direction: shardMeta.direction,
      rangeStart: shardMeta.rangeStart,
      rangeEnd: shardMeta.rangeEnd,
      nodeCount: snapshot.nodeCount,
      additions: bucket.additions,
      removals: bucket.removals
    });
    const shardKey = `delta-${shardMeta.key}`;
    fs.writeFileSync(path.join(dir, shardKey), new Uint8Array(buffer));
    shards.push({
      key: shardKey,
      relationId: shardMeta.relationId,
      direction: shardMeta.direction,
      rangeStart: shardMeta.rangeStart,
      rangeEnd: shardMeta.rangeEnd,
      cacheKey: shardMeta.cacheKey
    });
  }

  return { shards, storage: new FileShardStorage(dir), mode };
}

// ADR-003: sharded snapshots are stubs in src/core/shards/ — tests are the spec for when the subsystem is implemented.
describe.skip('Sharded delta layering semantics', () => {
  test('later override layers win over earlier layers', () => {
    const { snapshot, dir, nodes } = buildSnapshot(4);
    const relId = snapshot.relationIdToName.indexOf('owner');

    const layer1 = writeDeltaLayer(snapshot, path.join(dir, 'l1'), [
      { relationId: relId, direction: 'out', srcId: nodes[0], additions: [{ dstId: nodes[3], possBits: 65535, relBits: 65535 }], removals: [] }
    ], 'override');

    const layer2 = writeDeltaLayer(snapshot, path.join(dir, 'l2'), [
      { relationId: relId, direction: 'out', srcId: nodes[0], additions: [], removals: [{ dstId: nodes[3] }] }
    ], 'override');

    snapshot.setDeltaLayers([layer1, layer2]);
    const edge = snapshot.findEdgeSync(nodes[0], relId, nodes[3]);
    assert.equal(edge, null);

    fs.rmSync(dir, { recursive: true, force: true });
  });

  test('union overlays do not override writer removals', () => {
    const { snapshot, dir, nodes } = buildSnapshot(4);
    const relId = snapshot.relationIdToName.indexOf('owner');

    const writerLayer = writeDeltaLayer(snapshot, path.join(dir, 'writer'), [
      { relationId: relId, direction: 'out', srcId: nodes[0], additions: [], removals: [{ dstId: nodes[1] }] }
    ], 'override');

    const unionLayer = writeDeltaLayer(snapshot, path.join(dir, 'union'), [
      { relationId: relId, direction: 'out', srcId: nodes[0], additions: [], removals: [{ dstId: nodes[2] }] }
    ], 'union');

    snapshot.setDeltaLayers([writerLayer, unionLayer]);

    const removedByWriter = snapshot.findEdgeSync(nodes[0], relId, nodes[1]);
    assert.equal(removedByWriter, null);

    const unionRemovalIgnored = snapshot.findEdgeSync(nodes[0], relId, nodes[2]);
    assert.ok(unionRemovalIgnored, 'Union overlay must not remove base access');

    fs.rmSync(dir, { recursive: true, force: true });
  });
});