fix(bc): fixup headerIndexCache, surprised this didn't come up before

packages/neo-one-node-blockchain/package.json

@@ -33,9 +33,11 @@
     "@types/leveldown": "^4.0.0",
     "@types/lodash": "^4.14.138",
     "@types/lru-cache": "^5.1.0",
+    "@types/memdown": "^3.0.0",
     "leveldown": "^5.1.1",
     "levelup": "4.1.0",
     "gulp": "~4.0.2",
+    "memdown": "^5.0.0",
     "tslib": "^1.10.0"
   }
 }

packages/neo-one-node-blockchain/src/HeaderIndexCache.ts

@@ -59,7 +59,7 @@ export class HeaderIndexCache {
       return this.getHeaderHashIndexFromCurrent(hashListHashIndex);
     }
 
-    const hashListIndex = (index - hashListHashIndex) / 2000;
+    const hashListIndex = index - hashListHashIndex;
     const headerHashList = await this.getHeaderHashList(hashListIndex);
     if (headerHashList === undefined) {
       return undefined;

packages/neo-one-node-blockchain/src/__tests__/headerIndexCache.test.ts

@@ -0,0 +1,37 @@
+// tslint:disable: readonly-keyword no-object-mutation
+import { crypto } from '@neo-one/client-common';
+import { Storage } from '@neo-one/node-core';
+import { storage as levelStorage } from '@neo-one/node-storage-levelup';
+import { randomBytes } from 'crypto';
+import LevelUp from 'levelup';
+import _ from 'lodash';
+import MemDown from 'memdown';
+import { HeaderIndexCache } from '../HeaderIndexCache';
+
+const getUInt = () => crypto.hash256(randomBytes(32));
+const getUInts = (n: number) => _.range(n).map(getUInt);
+
+describe('headerIndexCache tests', () => {
+  const context = { messageMagic: 1951352142, validatorsCount: 7 };
+
+  let storage: Storage;
+  let db: any;
+  beforeEach(() => {
+    db = new LevelUp(new MemDown());
+    storage = levelStorage({ db, context });
+  });
+
+  test('headerCacheIndex push 2500 hashes -- retrieves something from different headerHashLists', async () => {
+    const cache = new HeaderIndexCache({ storage, initCurrentHeaderHashes: [], initStorageCount: 0 });
+    const testHashes = getUInts(2500);
+    // tslint:disable-next-line: no-loop-statement
+    for (const hash of testHashes) {
+      await cache.push(hash);
+    }
+
+    const [listZeroHash, listTwoThousandHash] = await Promise.all([cache.get(11), cache.get(2005)]);
+
+    expect(listZeroHash.equals(testHashes[11])).toEqual(true);
+    expect(listTwoThousandHash.equals(testHashes[2005])).toEqual(true);
+  });
+});