feat: add vote account decoder (#418)

module.flow.js

@@ -158,6 +158,31 @@ declare module '@solana/web3.js' {
     static fromConfigData(buffer: Buffer): ?ValidatorInfo;
   }
 
+  // === src/vote-account.js ===
+  declare export type Lockout = {|
+    slot: number,
+    confirmationCount: number,
+  |};
+
+  declare export type EpochCredits = {|
+    epoch: number,
+    credits: number,
+    prevCredits: number,
+  |};
+
+  declare export class VoteAccount {
+    votes: Array<Lockout>;
+    nodePubkey: PublicKey;
+    authorizedVoterPubkey: PublicKey;
+    commission: number;
+    rootSlot: number | null;
+    epoch: number;
+    credits: number;
+    lastEpochCredits: number;
+    epochCredits: Array<EpochCredits>;
+    static fromAccountData(buffer: Buffer): VoteAccount;
+  }
+
   // === src/transaction.js ===
   declare export type TransactionSignature = string;
 

src/index.js

@@ -9,6 +9,7 @@ export {SystemProgram} from './system-program';
 export {Token, TokenAmount} from './token-program';
 export {Transaction, TransactionInstruction} from './transaction';
 export {ValidatorInfo} from './validator-info';
+export {VoteAccount} from './vote-account';
 export {sendAndConfirmTransaction} from './util/send-and-confirm-transaction';
 export {
   sendAndConfirmRawTransaction,

src/vote-account.js

@@ -0,0 +1,85 @@
+// @flow
+import * as BufferLayout from 'buffer-layout';
+
+import * as Layout from './layout';
+import {PublicKey} from './publickey';
+
+export type Lockout = {|
+  slot: number,
+  confirmationCount: number,
+|};
+
+/**
+ * History of how many credits earned by the end of each epoch
+ */
+export type EpochCredits = {|
+  epoch: number,
+  credits: number,
+  prevCredits: number,
+|};
+
+/**
+ * See https://github.com/solana-labs/solana/blob/8a12ed029cfa38d4a45400916c2463fb82bbec8c/programs/vote_api/src/vote_state.rs#L68-L88
+ *
+ * @private
+ */
+const VoteAccountLayout = BufferLayout.struct([
+  BufferLayout.nu64(), // votes.length
+  BufferLayout.seq(
+    BufferLayout.struct([
+      BufferLayout.nu64('slot'),
+      BufferLayout.u32('confirmationCount'),
+    ]),
+    BufferLayout.offset(BufferLayout.u32(), -8),
+    'votes',
+  ),
+  Layout.publicKey('nodePubkey'),
+  Layout.publicKey('authorizedVoterPubkey'),
+  BufferLayout.u8('commission'),
+  BufferLayout.u8('rootSlotValid'),
+  BufferLayout.nu64('rootSlot'),
+  BufferLayout.nu64('epoch'),
+  BufferLayout.nu64('credits'),
+  BufferLayout.nu64('lastEpochCredits'),
+  BufferLayout.nu64(), // epochCredits.length
+  BufferLayout.seq(
+    BufferLayout.struct([
+      BufferLayout.nu64('epoch'),
+      BufferLayout.nu64('credits'),
+      BufferLayout.nu64('prevCredits'),
+    ]),
+    BufferLayout.offset(BufferLayout.u32(), -8),
+    'epochCredits',
+  ),
+]);
+
+/**
+ * VoteAccount class
+ */
+export class VoteAccount {
+  votes: Array<Lockout>;
+  nodePubkey: PublicKey;
+  authorizedVoterPubkey: PublicKey;
+  commission: number;
+  rootSlot: number | null;
+  epoch: number;
+  credits: number;
+  lastEpochCredits: number;
+  epochCredits: Array<EpochCredits>;
+
+  /**
+   * Deserialize VoteAccount from the account data.
+   *
+   * @param buffer account data
+   * @return VoteAccount
+   */
+  static fromAccountData(buffer: Buffer): VoteAccount {
+    const va = VoteAccountLayout.decode(buffer, 0);
+    va.nodePubkey = new PublicKey(va.nodePubkey);
+    va.authorizedVoterPubkey = new PublicKey(va.authorizedVoterPubkey);
+    if (!va.rootSlotValid) {
+      va.rootSlot = null;
+    }
+    return va;
+  }
+}