From f6870d88dc0e81ddb3a7a598f31143a3c4b326d9 Mon Sep 17 00:00:00 2001
From: Ashwin Phatak <ashwinpphatak@gmail.com>
Date: Tue, 1 Jun 2021 18:13:41 +0530
Subject: [PATCH] Support GQL query for name, symbol, totalSupply (#24)

* Update mock server and tests for additional ERC20 state vars.

* Refactor eth-client getStorageAt, impl totalSupply.

* Impl ERC20 API for name, symbol.
---
 packages/ipld-eth-client/src/eth-client.ts | 24 +++++-
 packages/watcher/src/erc20.graphql         | 55 ++++++++++---
 packages/watcher/src/indexer.ts            | 90 +++++++++++++---------
 packages/watcher/src/mock/data.ts          |  4 +-
 packages/watcher/src/mock/resolvers.ts     | 36 +++++++++
 packages/watcher/src/mock/server.spec.ts   | 53 ++++++++++++-
 packages/watcher/src/queries.ts            | 44 +++++++++++
 packages/watcher/src/resolvers.ts          | 20 +++++
 8 files changed, 274 insertions(+), 52 deletions(-)

diff --git a/packages/ipld-eth-client/src/eth-client.ts b/packages/ipld-eth-client/src/eth-client.ts
index b0e9ad79..e4b88c4a 100644
--- a/packages/ipld-eth-client/src/eth-client.ts
+++ b/packages/ipld-eth-client/src/eth-client.ts
@@ -4,6 +4,7 @@ import { GraphQLClient } from 'graphql-request';
 import { Cache } from '@vulcanize/cache';
 
 import ethQueries from './eth-queries';
+import { padKey } from './utils';
 
 export class EthClient {
 
@@ -21,11 +22,28 @@ export class EthClient {
     this._cache = cache;
   }
 
-  async getStorageAt(vars) {
-    const result = await this._getCachedOrFetch('getStorageAt', vars);
+  async getStorageAt({ blockHash, contract, slot }) {
+    slot = `0x${padKey(slot)}`;
+
+    const result = await this._getCachedOrFetch('getStorageAt', { blockHash, contract, slot });
     const { getStorageAt: { value, cid, ipldBlock } } = result;
 
-    return { value, cid, ipldBlock };
+    return {
+      value,
+      proof: {
+        // TODO: Return proof only if requested.
+        data: JSON.stringify({
+          blockHash,
+          account: {
+            address: contract,
+            storage: {
+              cid,
+              ipldBlock
+            }
+          }
+        })
+      }
+    };
   }
 
   async getLogs(vars) {
diff --git a/packages/watcher/src/erc20.graphql b/packages/watcher/src/erc20.graphql
index 690647b0..8dc958a2 100644
--- a/packages/watcher/src/erc20.graphql
+++ b/packages/watcher/src/erc20.graphql
@@ -1,6 +1,9 @@
 #
 # ERC20 GQL schema
 #
+# See: https://eips.ethereum.org/EIPS/eip-20
+# ABI: https://ethereumdev.io/abi-for-erc20-contract-on-ethereum/
+#
 
 # Types
 
@@ -13,6 +16,14 @@ type Proof {
   data: String!
 }
 
+# Result type, with proof, for string method return values.
+type ResultString {
+  value: String
+
+  # Proof from state/storage trie.
+  proof: Proof
+}
+
 # Result type, with proof, for uint256 method return values.
 type ResultUInt256 {
   value: BigInt!
@@ -21,15 +32,6 @@ type ResultUInt256 {
   proof: Proof
 }
 
-# ERC20 Token https://eips.ethereum.org/EIPS/eip-20
-# ABI: https://ethereumdev.io/abi-for-erc20-contract-on-ethereum/
-type Token {
-  name: String!
-  symbol: String!
-  decimals: Int!
-  totalSupply: BigInt!
-}
-
 # Transfer Event
 # Emitted by: `function transfer(address _to, uint256 _value) public returns (bool success)`
 # Emitted by: `function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)`
@@ -65,6 +67,17 @@ type ResultEvent {
 
 type Query {
 
+  #
+  # Interface of the ERC20 standard as defined in the EIP.
+  # https://docs.openzeppelin.com/contracts/2.x/api/token/erc20#IERC20
+  #
+
+  # `function totalSupply() public view returns (uint256)`
+  totalSupply(
+    blockHash: String!
+    token: String!
+  ): ResultUInt256!
+
   # `function balanceOf(address _owner) public view returns (uint256 balance)`
   balanceOf(
     blockHash: String!
@@ -82,6 +95,30 @@ type Query {
     spender: String!
   ): ResultUInt256!
 
+  #
+  # Optional functions from the ERC20 standard.
+  # https://docs.openzeppelin.com/contracts/2.x/api/token/erc20#ERC20Detailed
+  #
+
+  name(
+    blockHash: String!
+    token: String!
+  ): ResultString!
+
+  symbol(
+    blockHash: String!
+    token: String!
+  ): ResultString!
+
+  decimals(
+    blockHash: String!
+    token: String!
+  ): ResultUInt256!
+
+  #
+  # Additional watcher queries.
+  #
+
   # Get token events at a certain block, optionally filter by event name.
   events(
     blockHash: String!
diff --git a/packages/watcher/src/indexer.ts b/packages/watcher/src/indexer.ts
index e2b4fbbb..bdaac03d 100644
--- a/packages/watcher/src/indexer.ts
+++ b/packages/watcher/src/indexer.ts
@@ -22,6 +22,21 @@ export class Indexer {
     this._ethClient = ethClient;
   }
 
+  async totalSupply(blockHash, token) {
+    const { slot } = getStorageInfo(storageLayout, '_totalSupply');
+
+    const vars = {
+      blockHash,
+      contract: token,
+      slot
+    };
+
+    const result = await this._ethClient.getStorageAt(vars);
+    log(JSON.stringify(result, null, 2));
+
+    return result;
+  }
+
   async getBalanceOf(blockHash, token, owner) {
     const { slot: balancesSlot } = getStorageInfo(storageLayout, '_balances');
     const slot = getMappingSlot(balancesSlot, owner);
@@ -35,24 +50,7 @@ export class Indexer {
     const result = await this._ethClient.getStorageAt(vars);
     log(JSON.stringify(result, null, 2));
 
-    const { value, cid, ipldBlock } = result;
-
-    return {
-      value,
-      proof: {
-        // TODO: Return proof only if requested.
-        data: JSON.stringify({
-          blockHash,
-          account: {
-            address: token,
-            storage: {
-              cid,
-              ipldBlock
-            }
-          }
-        })
-      }
-    }
+    return result;
   }
 
   async getAllowance(blockHash, token, owner, spender) {
@@ -68,24 +66,46 @@ export class Indexer {
     const result = await this._ethClient.getStorageAt(vars);
     log(JSON.stringify(result, null, 2));
 
-    const { value, cid, ipldBlock } = result;
+    return result;
+  }
 
-    return {
-      value,
-      proof: {
-        // TODO: Return proof only if requested.
-        data: JSON.stringify({
-          blockHash,
-          account: {
-            address: token,
-            storage: {
-              cid,
-              ipldBlock
-            }
-          }
-        })
-      }
-    }
+  async name(blockHash, token) {
+    const { slot } = getStorageInfo(storageLayout, '_name');
+
+    const vars = {
+      blockHash,
+      contract: token,
+      slot
+    };
+
+    // TODO: Integrate with storage-mapper to get string value (currently hex encoded).
+    const result = await this._ethClient.getStorageAt(vars);
+    log(JSON.stringify(result, null, 2));
+
+    return result;
+  }
+
+  async symbol(blockHash, token) {
+    const { slot } = getStorageInfo(storageLayout, '_symbol');
+
+    const vars = {
+      blockHash,
+      contract: token,
+      slot
+    };
+
+    // TODO: Integrate with storage-mapper to get string value (currently hex encoded).
+    const result = await this._ethClient.getStorageAt(vars);
+    log(JSON.stringify(result, null, 2));
+
+    return result;
+  }
+
+  async decimals(blockHash, token) {
+    // Not a state variable, uses hardcoded return value in contract function.
+    // See https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol#L86
+
+    throw new Error('Not implemented.');
   }
 
   async getEvents(blockHash, token, name) {
diff --git a/packages/watcher/src/mock/data.ts b/packages/watcher/src/mock/data.ts
index 26f5541e..977fbe14 100644
--- a/packages/watcher/src/mock/data.ts
+++ b/packages/watcher/src/mock/data.ts
@@ -4,7 +4,7 @@ export const tokens = {
   '0xd87fea54f506972e3267239ec8e159548892074a': {
     name: 'ChainLink Token',
     symbol: 'LINK',
-    decimals: 18,
+    decimals: '18',
     totalSupply: '1000000'
   }
 };
@@ -15,6 +15,8 @@ export const blocks = {
 
     // ERC20 token address.
     '0xd87fea54f506972e3267239ec8e159548892074a': {
+      ...tokens['0xd87fea54f506972e3267239ec8e159548892074a'],
+
       balanceOf: {
         '0xDC7d7A8920C8Eecc098da5B7522a5F31509b5Bfc': '10000',
         '0xCA6D29232D1435D8198E3E5302495417dD073d61': '500'
diff --git a/packages/watcher/src/mock/resolvers.ts b/packages/watcher/src/mock/resolvers.ts
index ef80e635..2f66e0d1 100644
--- a/packages/watcher/src/mock/resolvers.ts
+++ b/packages/watcher/src/mock/resolvers.ts
@@ -22,6 +22,15 @@ export const createResolvers = async (config) => {
 
     Query: {
 
+      totalSupply: (_, { blockHash, token }) => {
+        log('totalSupply', blockHash, token);
+
+        return {
+          value: blocks[blockHash][token].totalSupply,
+          proof: { data: '' }
+        }
+      },
+
       balanceOf: (_, { blockHash, token, owner }) => {
         log('balanceOf', blockHash, token, owner);
 
@@ -40,6 +49,33 @@ export const createResolvers = async (config) => {
         }
       },
 
+      name: (_, { blockHash, token }) => {
+        log('name', blockHash, token);
+
+        return {
+          value: blocks[blockHash][token].name,
+          proof: { data: '' }
+        }
+      },
+
+      symbol: (_, { blockHash, token }) => {
+        log('symbol', blockHash, token);
+
+        return {
+          value: blocks[blockHash][token].symbol,
+          proof: { data: '' }
+        }
+      },
+
+      decimals: (_, { blockHash, token }) => {
+        log('decimals', blockHash, token);
+
+        return {
+          value: blocks[blockHash][token].decimals,
+          proof: { data: '' }
+        }
+      },
+
       events: (_, { blockHash, token, name }) => {
         log('events', blockHash, token, name);
         return blocks[blockHash][token].events
diff --git a/packages/watcher/src/mock/server.spec.ts b/packages/watcher/src/mock/server.spec.ts
index a3c6dff9..e51d6080 100644
--- a/packages/watcher/src/mock/server.spec.ts
+++ b/packages/watcher/src/mock/server.spec.ts
@@ -4,14 +4,23 @@ import _ from 'lodash';
 
 import { GraphQLClient } from 'graphql-request';
 
-import { queryBalanceOf, queryAllowance, queryEvents } from '../queries';
+import {
+  queryName,
+  querySymbol,
+  queryDecimals,
+  queryTotalSupply,
+  queryBalanceOf,
+  queryAllowance,
+  queryEvents
+} from '../queries';
 
-import { blocks } from './data';
+import { blocks, tokens as tokenInfo } from './data';
 
 const testCases = {
   'balanceOf': [],
   'allowance': [],
-  'events': []
+  'events': [],
+  'tokens': []
 };
 
 const blockHashes = _.keys(blocks);
@@ -21,7 +30,14 @@ blockHashes.forEach(blockHash => {
   tokens.forEach(token => {
     const tokenObj = block[token];
 
-    // Event tests cases.
+    // Token info test cases.
+    testCases.tokens.push({
+      blockHash,
+      token,
+      info: tokenInfo[token]
+    });
+
+    // Event test cases.
     testCases.events.push({
       blockHash,
       token,
@@ -61,6 +77,35 @@ describe('server', () => {
 
   const client = new GraphQLClient("http://localhost:3001/graphql");
 
+  it('query token info', async () => {
+    const tests = testCases.tokens;
+    expect(tests.length).to.be.greaterThan(0);
+
+    for (let i = 0; i < tests.length; i++) {
+      const testCase = tests[i];
+
+      // Token totalSupply.
+      let result = await client.request(queryTotalSupply, testCase);
+      expect(result.totalSupply.value).to.equal(testCase.info.totalSupply);
+      expect(result.totalSupply.proof.data).to.equal('');
+
+      // Token name.
+      result = await client.request(queryName, testCase);
+      expect(result.name.value).to.equal(testCase.info.name);
+      expect(result.name.proof.data).to.equal('');
+
+      // Token symbol.
+      result = await client.request(querySymbol, testCase);
+      expect(result.symbol.value).to.equal(testCase.info.symbol);
+      expect(result.symbol.proof.data).to.equal('');
+
+      // Token decimals.
+      result = await client.request(queryDecimals, testCase);
+      expect(result.decimals.value).to.equal(testCase.info.decimals);
+      expect(result.decimals.proof.data).to.equal('');
+    }
+  });
+
   it('query balanceOf', async () => {
     const tests = testCases.balanceOf;
     expect(tests.length).to.be.greaterThan(0);
diff --git a/packages/watcher/src/queries.ts b/packages/watcher/src/queries.ts
index 52cc6b60..52ed6308 100644
--- a/packages/watcher/src/queries.ts
+++ b/packages/watcher/src/queries.ts
@@ -1,5 +1,16 @@
 import { gql } from 'graphql-request';
 
+export const queryTotalSupply = gql`
+query getTotalSupply($blockHash: String!, $token: String!) {
+  totalSupply(blockHash: $blockHash, token: $token) {
+    value
+    proof {
+      data
+    }
+  }
+}
+`;
+
 export const queryBalanceOf = gql`
 query getBalance($blockHash: String!, $token: String!, $owner: String!) {
   balanceOf(blockHash: $blockHash, token: $token, owner: $owner) {
@@ -22,6 +33,39 @@ query getAllowance($blockHash: String!, $token: String!, $owner: String!, $spend
 }
 `;
 
+export const queryName = gql`
+query getName($blockHash: String!, $token: String!) {
+  name(blockHash: $blockHash, token: $token) {
+    value
+    proof {
+      data
+    }
+  }
+}
+`;
+
+export const querySymbol = gql`
+query getSymbol($blockHash: String!, $token: String!) {
+  symbol(blockHash: $blockHash, token: $token) {
+    value
+    proof {
+      data
+    }
+  }
+}
+`;
+
+export const queryDecimals = gql`
+query getDecimals($blockHash: String!, $token: String!) {
+  decimals(blockHash: $blockHash, token: $token) {
+    value
+    proof {
+      data
+    }
+  }
+}
+`;
+
 export const queryEvents = gql`
 query getEvents($blockHash: String!, $token: String!) {
   events(blockHash: $blockHash, token: $token) {
diff --git a/packages/watcher/src/resolvers.ts b/packages/watcher/src/resolvers.ts
index 9c62b716..6e519d9d 100644
--- a/packages/watcher/src/resolvers.ts
+++ b/packages/watcher/src/resolvers.ts
@@ -44,6 +44,11 @@ export const createResolvers = async (config) => {
 
     Query: {
 
+      totalSupply: (_, { blockHash, token }) => {
+        log('totalSupply', blockHash, token);
+        return indexer.totalSupply(blockHash, token);
+      },
+
       balanceOf: async (_, { blockHash, token, owner }) => {
         log('balanceOf', blockHash, token, owner);
         return indexer.getBalanceOf(blockHash, token, owner);
@@ -54,6 +59,21 @@ export const createResolvers = async (config) => {
         return indexer.getAllowance(blockHash, token, owner, spender);
       },
 
+      name: (_, { blockHash, token }) => {
+        log('name', blockHash, token);
+        return indexer.name(blockHash, token);
+      },
+
+      symbol: (_, { blockHash, token }) => {
+        log('symbol', blockHash, token);
+        return indexer.symbol(blockHash, token);
+      },
+
+      decimals: (_, { blockHash, token }) => {
+        log('decimals', blockHash, token);
+        return indexer.decimals(blockHash, token);
+      },
+
       events: async (_, { blockHash, token, name }) => {
         log('events', blockHash, token, name);
         return indexer.getEvents(blockHash, token, name);