From 6558e05fd071d666ddd1e81021d27083779995a6 Mon Sep 17 00:00:00 2001
From: Justin Starry <justin@solana.com>
Date: Thu, 21 May 2020 16:58:17 +0800
Subject: [PATCH] feat: add minimumLedgerSlot api

---
 web3.js/module.d.ts             |  1 +
 web3.js/module.flow.js          |  1 +
 web3.js/src/connection.js       | 26 ++++++++++++++++++++++++++
 web3.js/test/connection.test.js | 19 +++++++++++++++++++
 4 files changed, 47 insertions(+)

diff --git a/web3.js/module.d.ts b/web3.js/module.d.ts
index 4653c9e89..c9ad93a6d 100644
--- a/web3.js/module.d.ts
+++ b/web3.js/module.d.ts
@@ -199,6 +199,7 @@ declare module '@solana/web3.js' {
     ): Promise<RpcResponseAndContext<number>>;
     getBalance(publicKey: PublicKey, commitment?: Commitment): Promise<number>;
     getBlockTime(slot: number): Promise<number | null>;
+    getMinimumLedgerSlot(): Promise<number>;
     getClusterNodes(): Promise<Array<ContactInfo>>;
     getConfirmedBlock(slot: number): Promise<ConfirmedBlock>;
     getConfirmedTransaction(
diff --git a/web3.js/module.flow.js b/web3.js/module.flow.js
index 5455d6b48..fe28f5a6c 100644
--- a/web3.js/module.flow.js
+++ b/web3.js/module.flow.js
@@ -212,6 +212,7 @@ declare module '@solana/web3.js' {
     ): Promise<RpcResponseAndContext<number>>;
     getBalance(publicKey: PublicKey, commitment: ?Commitment): Promise<number>;
     getBlockTime(slot: number): Promise<number | null>;
+    getMinimumLedgerSlot(): Promise<number>;
     getClusterNodes(): Promise<Array<ContactInfo>>;
     getConfirmedBlock(slot: number): Promise<ConfirmedBlock>;
     getConfirmedTransaction(
diff --git a/web3.js/src/connection.js b/web3.js/src/connection.js
index 23ebd773a..baeb8491f 100644
--- a/web3.js/src/connection.js
+++ b/web3.js/src/connection.js
@@ -370,6 +370,16 @@ const GetBlockTimeRpcResult = struct({
   result: struct.union(['null', 'number']),
 });
 
+/**
+ * Expected JSON RPC response for the "minimumLedgerSlot" message
+ */
+const MinimumLedgerSlotRpcResult = struct({
+  jsonrpc: struct.literal('2.0'),
+  id: 'string',
+  error: 'any?',
+  result: 'number',
+});
+
 /**
  * Expected JSON RPC response for the "getVersion" message
  */
@@ -964,6 +974,22 @@ export class Connection {
     return res.result;
   }
 
+  /**
+   * Fetch the lowest slot that the node has information about in its ledger.
+   * This value may increase over time if the node is configured to purge older ledger data
+   */
+  async getMinimumLedgerSlot(): Promise<number> {
+    const unsafeRes = await this._rpcRequest('minimumLedgerSlot', []);
+    const res = MinimumLedgerSlotRpcResult(unsafeRes);
+    if (res.error) {
+      throw new Error(
+        'failed to get minimum ledger slot: ' + res.error.message,
+      );
+    }
+    assert(typeof res.result !== 'undefined');
+    return res.result;
+  }
+
   /**
    * Fetch all the account info for the specified public key, return with context
    */
diff --git a/web3.js/test/connection.test.js b/web3.js/test/connection.test.js
index 94f174427..e16cdc0f0 100644
--- a/web3.js/test/connection.test.js
+++ b/web3.js/test/connection.test.js
@@ -1089,6 +1089,25 @@ test('get block time', async () => {
   }
 });
 
+test('get minimum ledger slot', async () => {
+  const connection = new Connection(url);
+
+  mockRpc.push([
+    url,
+    {
+      method: 'minimumLedgerSlot',
+      params: [],
+    },
+    {
+      error: null,
+      result: 0,
+    },
+  ]);
+
+  const minimumLedgerSlot = await connection.getMinimumLedgerSlot();
+  expect(minimumLedgerSlot).toBeGreaterThanOrEqual(0);
+});
+
 test('getVersion', async () => {
   const connection = new Connection(url);