feat: add custom queryFilter (#57)

* add custom fetcher

* improve fetch in chunks

* remove comment

* fetch in portions of 5

* allow to configure fetch params

* add error log

src/rln_contract.ts

@@ -13,6 +13,12 @@ type ContractOptions = {
   provider: ethers.Signer | ethers.providers.Provider;
 };
 
+type FetchMembersOptions = {
+  fromBlock?: number;
+  fetchRange?: number;
+  fetchChunks?: number;
+};
+
 export class RLNContract {
   private _contract: ethers.Contract;
   private membersFilter: ethers.EventFilter;
@@ -46,12 +52,12 @@ export class RLNContract {
 
   public async fetchMembers(
     rlnInstance: RLNInstance,
-    fromBlock?: number
+    options: FetchMembersOptions = {}
   ): Promise<void> {
-    const registeredMemberEvents = await this.contract.queryFilter(
-      this.membersFilter,
-      fromBlock
-    );
+    const registeredMemberEvents = await queryFilter(this.contract, {
+      ...options,
+      membersFilter: this.membersFilter,
+    });
 
     for (const event of registeredMemberEvents) {
       this.addMemberFromEvent(rlnInstance, event);
@@ -109,3 +115,90 @@ export class RLNContract {
     return txRegisterReceipt?.events?.[0];
   }
 }
+
+type CustomQueryOptions = FetchMembersOptions & {
+  membersFilter: ethers.EventFilter;
+};
+
+// these value should be tested on other networks
+const FETCH_CHUNK = 5;
+const BLOCK_RANGE = 3000;
+
+async function queryFilter(
+  contract: ethers.Contract,
+  options: CustomQueryOptions
+): Promise<ethers.Event[]> {
+  const {
+    fromBlock,
+    membersFilter,
+    fetchRange = BLOCK_RANGE,
+    fetchChunks = FETCH_CHUNK,
+  } = options;
+
+  if (!fromBlock) {
+    return contract.queryFilter(membersFilter);
+  }
+
+  if (!contract.signer.provider) {
+    throw Error("No provider found on the contract's signer.");
+  }
+
+  const toBlock = await contract.signer.provider.getBlockNumber();
+
+  if (toBlock - fromBlock < fetchRange) {
+    return contract.queryFilter(membersFilter);
+  }
+
+  const events: ethers.Event[][] = [];
+  const chunks = splitToChunks(fromBlock, toBlock, fetchRange);
+
+  for (const portion of takeN<[number, number]>(chunks, fetchChunks)) {
+    const promises = portion.map(([left, right]) =>
+      ignoreErrors(contract.queryFilter(membersFilter, left, right), [])
+    );
+    const fetchedEvents = await Promise.all(promises);
+    events.push(fetchedEvents.flatMap((v) => v));
+  }
+
+  return events.flatMap((v) => v);
+}
+
+function splitToChunks(
+  from: number,
+  to: number,
+  step: number
+): Array<[number, number]> {
+  const chunks = [];
+
+  let left = from;
+  while (left < to) {
+    const right = left + step < to ? left + step : to;
+
+    chunks.push([left, right] as [number, number]);
+
+    left = right;
+  }
+
+  return chunks;
+}
+
+function* takeN<T>(array: T[], size: number): Iterable<T[]> {
+  let start = 0;
+  let skip = size;
+
+  while (skip < array.length) {
+    const portion = array.slice(start, skip);
+
+    yield portion;
+
+    start = skip;
+    skip += size;
+  }
+}
+
+function ignoreErrors<T>(promise: Promise<T>, defaultValue: T): Promise<T> {
+  return promise.catch((err) => {
+    console.error(`Ignoring an error during query: ${err?.message}`);
+    return defaultValue;
+  });
+}