feat: get_epoch_schedule rpc (#536)

web3.js/module.flow.js

@@ -86,6 +86,23 @@ declare module '@solana/web3.js' {
     Err: Object,
   |};
 
+  declare export type Inflation = {
+    foundation: number,
+    foundation_term: number,
+    initial: number,
+    storage: number,
+    taper: number,
+    terminal: number,
+  };
+
+  declare export type EpochSchedule = {
+    slots_per_epoch: number,
+    leader_schedule_slot_offset: number,
+    warmup: boolean,
+    first_normal_epoch: number,
+    first_normal_slot: number,
+  };
+
   declare export class Connection {
     constructor(endpoint: string): Connection;
     getAccountInfo(publicKey: PublicKey): Promise<AccountInfo>;
@@ -103,6 +120,8 @@ declare module '@solana/web3.js' {
     ): Promise<SignatureSuccess | TransactionError | null>;
     getTransactionCount(): Promise<number>;
     getTotalSupply(): Promise<number>;
+    getInflation(): Promise<Inflation>;
+    getEpochSchedule(): Promise<EpochSchedule>;
     getRecentBlockhash(): Promise<[Blockhash, FeeCalculator]>;
     requestAirdrop(
       to: PublicKey,

web3.js/src/connection.js

@@ -68,16 +68,15 @@ type VoteAccountStatus = {
 
 /**
  * Network Inflation parameters
+ * (see https://docs.solana.com/book/v/master/implemented-proposals/ed_overview)
  *
- * @typedef {Object} Inflation TODO - link to book terminology?
- * @property {number} foundation TODO - link to book terminology?
- * @property {number} foundation_term TODO - link to book terminology?
- * @property {number} grant TODO - link to book terminology?
- * @property {number} grant_term TODO - link to book terminology?
- * @property {number} initial TODO - link to book terminology?
- * @property {number} storage TODO - link to book terminology?
- * @property {number} taper TODO - link to book terminology?
- * @property {number} terminal TODO - link to book terminology?
+ * @typedef {Object} Inflation
+ * @property {number} foundation 
+ * @property {number} foundation_term
+ * @property {number} initial
+ * @property {number} storage
+ * @property {number} taper
+ * @property {number} terminal
  */
 const GetInflationResult = struct({
   foundation: 'number',
@@ -88,6 +87,25 @@ const GetInflationResult = struct({
   terminal: 'number',
 });
 
+/**
+ * EpochSchedule parameters
+ * (see https://docs.solana.com/book/v/master/terminology#epoch)
+ * 
+ * @typedef {Object} EpochSchedule
+ * @property {number} slots_per_epoch
+ * @property {number} leader_schedule_slot_offset
+ * @property {boolean} warmup
+ * @property {number} first_normal_epoch
+ * @property {number} first_normal_slot
+ */
+const GetEpochScheduleResult = struct({
+  slots_per_epoch: 'number',
+  leader_schedule_slot_offset: 'number',
+  warmup: 'boolean',
+  first_normal_epoch: 'number',
+  first_normal_slot: 'number',
+});
+
 function createRpcRequest(url): RpcRequest {
   const server = jayson(async (request, callback) => {
     const options = {
@@ -130,6 +148,16 @@ const GetInflationRpcResult = struct({
   result: GetInflationResult,
 });
 
+/**
+ * Expected JSON RPC response for the "getEpochSchedule" message
+ */
+const GetEpochScheduleRpcResult = struct({
+  jsonrpc: struct.literal('2.0'),
+  id: 'string',
+  error: 'any?',
+  result: GetEpochScheduleResult,
+});
+
 /**
  * Expected JSON RPC response for the "getBalance" message
  */
@@ -678,7 +706,7 @@ export class Connection {
   }
 
   /**
-   * Fetch the cluster Inflation parameters (TODO - book link/terminology?)
+   * Fetch the cluster Inflation parameters
    */
   async getInflation(): Promise<GetInflationRpcResult> {
     const unsafeRes = await this._rpcRequest('getInflation', []);
@@ -690,6 +718,19 @@ export class Connection {
     return GetInflationResult(res.result);
   }
 
+  /**
+   * Fetch the Epoch Schedule parameters
+   */
+  async getEpochSchedule(): Promise<GetEpochScheduleRpcResult> {
+    const unsafeRes = await this._rpcRequest('getEpochSchedule', []);
+    const res = GetEpochScheduleRpcResult(unsafeRes);
+    if (res.error) {
+      throw new Error(res.error.message);
+    }
+    assert(typeof res.result !== 'undefined');
+    return GetEpochScheduleResult(res.result);
+  }
+
   /**
    * Fetch the minimum balance needed to exempt an account of `dataLength`
    * size from rent

web3.js/test/connection.test.js

@@ -170,6 +170,43 @@ test('get inflation', async () => {
   }
 });
 
+test('get epoch schedule', async () => {
+  const connection = new Connection(url);
+
+  mockRpc.push([
+    url,
+    {
+      method: 'getEpochSchedule',
+      params: [],
+    },
+    {
+      error: null,
+      result: {
+        first_normal_epoch: 8,
+        first_normal_slot: 8160,
+        leader_schedule_slot_offset: 8192,
+        slots_per_epoch: 8192,
+        warmup: true,
+      },
+    },
+  ]);
+
+  const epochSchedule = await connection.getEpochSchedule();
+
+  for (const key of [
+    'first_normal_epoch',
+    'first_normal_slot',
+    'leader_schedule_slot_offset',
+    'slots_per_epoch',
+  ]) {
+    expect(epochSchedule).toHaveProperty(key);
+    expect(epochSchedule[key]).toBeGreaterThan(0);
+  }
+
+  expect(epochSchedule).toHaveProperty('warmup');
+  expect(epochSchedule.warmup).toBeTruthy();
+});
+
 test('get slot', async () => {
   const connection = new Connection(url);