Improve names of entities. Add description to fields in schema.

schema.graphql

@@ -1,33 +1,76 @@
 #
-# Main entities
+# Provides information about an Ethereum account
 #
-
 type Account @entity {
+  " Equals to: <accountAddress>"
   id: ID!
+
+  " Account address "
   address: Bytes!
+
+  " Token balances that this account holds "
+  balances: [AccountBalance!]! @derivedFrom(field: "account")
 }
 
+#
+# Current token balance of a particular Ethereum account
+#
 type AccountBalance @entity {
+  " Equals to: <accountAddress>-<tokenAddress>"
   id: ID!
+
+  " Account address "
   account: Account!
+
+  " Token address "
   token: Token!
+
+  " Current account balance "
   amount: BigDecimal!
+
+  " Block number in which the balance was last modified "
+  block: BigInt
+
+  " Last modified timestamp in seconds "
+  modified: BigInt
+
+  " Hash of the last transaction that modified the balance "
+  transaction: Bytes
 }
 
-# This entity is used to provide information about evolution of account balances
-type AccountBalanceLog @entity {
+#
+# Token balance of a particular Ethereum account in a certain timestamp. This entity is used to
+# provide information about evolution of account balances
+#
+type AccountBalanceSnapshot @entity {
+  " Equals to: <accountAddress>-<tokenAddress>-<timestamp>"
   id: ID!
+
+  " Account address "
   account: Account!
+
+  " Token addess "
   token: Token!
+
+  " Account balance "
   amount: BigDecimal!
 
+  # TODO: Add description and check if could be non-optional
   event: TokenEvent
 
+  " Block number "
   block: BigInt!
-  transaction: Bytes!
+
+  " Timestamp in seconds "
   timestamp: BigInt!
+
+  " Transaction hash "
+  transaction: Bytes!
 }
 
+#
+# Provides information about an ERC20 token
+#
 type Token @entity {
   id: ID!
 
@@ -68,10 +111,9 @@ type Token @entity {
 }
 
 #
-# Events
+# Token events
 #
-
-interface TokenEvent @entity {
+interface TokenEvent {
   id: ID!
   token: Token!
   amount: BigDecimal!

src/mappings/account.ts

@@ -1,35 +1,22 @@
 import { BigDecimal, BigInt, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
 
-import { Account, AccountBalance, AccountBalanceLog, Token } from '../../generated/schema'
-
-export function createAccountBalance(balance: AccountBalance, event: EthereumEvent): AccountBalanceLog {
-  let logEntity = new AccountBalanceLog(event.transaction.hash.toHex() + '-' + event.logIndex.toString())
-  logEntity.account = balance.account
-  logEntity.token = balance.token
-  logEntity.amount = balance.amount
-
-  logEntity.block = event.block.number
-  logEntity.transaction = event.transaction.hash
-  logEntity.timestamp = event.block.timestamp
-
-  return logEntity
-}
+import { Account, AccountBalance, AccountBalanceSnapshot, Token } from '../../generated/schema'
 
 export function getOrCreateAccount(accountAddress: Bytes): Account {
   let accountId = accountAddress.toHex()
-  let existingEntity = Account.load(accountId)
+  let existingAccount = Account.load(accountId)
 
-  if (existingEntity != null) {
-    return existingEntity as Account
+  if (existingAccount != null) {
+    return existingAccount as Account
   }
 
-  let newEntity = new Account(accountId)
-  newEntity.address = accountAddress
+  let newAccount = new Account(accountId)
+  newAccount.address = accountAddress
 
-  return newEntity
+  return newAccount
 }
 
-export function getOrCreateAccountBalance(account: Account, token: Token): AccountBalance {
+function getOrCreateAccountBalance(account: Account, token: Token): AccountBalance {
   let balanceId = account.id + '-' + token.id
   let previousBalance = AccountBalance.load(balanceId)
 
@@ -58,3 +45,18 @@ export function decreaseAccountBalance(account: Account, token: Token, amount: B
 
   return balance
 }
+
+export function saveAccountBalanceSnapshot(balance: AccountBalance, eventId: string, event: EthereumEvent): void {
+  let snapshot = new AccountBalanceSnapshot(balance.id + '-' + event.block.timestamp.toString())
+  snapshot.account = balance.account
+  snapshot.token = balance.token
+  snapshot.amount = balance.amount
+
+  snapshot.block = event.block.number
+  snapshot.transaction = event.transaction.hash
+  snapshot.timestamp = event.block.timestamp
+
+  snapshot.event = eventId
+
+  snapshot.save()
+}

src/mappings/token.ts

@@ -1,12 +1,17 @@
-import { BigInt, BigDecimal, Bytes, EthereumEvent, log } from '@graphprotocol/graph-ts'
+import { BigInt, BigDecimal, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
 
 import { Transfer } from '../../generated/TokenRegistry/templates/StandardToken/ERC20'
 import { Burn } from '../../generated/TokenRegistry/templates/BurnableToken/Burnable'
 import { Mint } from '../../generated/TokenRegistry/templates/MintableToken/Mintable'
 
-import { Account, BurnEvent, MintEvent, Token, TransferEvent } from '../../generated/schema'
+import { BurnEvent, MintEvent, Token, TransferEvent } from '../../generated/schema'
 
-import { getOrCreateAccount, decreaseAccountBalance, increaseAccountBalance, createAccountBalance } from './account'
+import {
+  decreaseAccountBalance,
+  getOrCreateAccount,
+  increaseAccountBalance,
+  saveAccountBalanceSnapshot
+} from './account'
 
 const GENESIS_ADDRESS = '0x0000000000000000000000000000000000000000'
 
@@ -43,30 +48,32 @@ export function handleTransfer(event: Transfer): void {
     // Updates balances of accounts
     if (isTransfer || isBurn) {
       let sourceAccount = getOrCreateAccount(event.params.from)
+
       let accountBalance = decreaseAccountBalance(sourceAccount, token as Token, amount)
+      accountBalance.block = event.block.number
+      accountBalance.modified = event.block.timestamp
+      accountBalance.transaction = event.transaction.hash
 
       sourceAccount.save()
       accountBalance.save()
 
-      // To provide information about evolution of account balance
-      let accountBalanceLog = createAccountBalance(accountBalance, event)
-      accountBalanceLog.event = eventEntityId
-
-      accountBalanceLog.save()
+      // To provide information about evolution of account balances
+      saveAccountBalanceSnapshot(accountBalance, eventEntityId, event)
     }
 
     if (isTransfer || isMint) {
       let destinationAccount = getOrCreateAccount(event.params.to)
+
       let accountBalance = increaseAccountBalance(destinationAccount, token as Token, amount)
+      accountBalance.block = event.block.number
+      accountBalance.modified = event.block.timestamp
+      accountBalance.transaction = event.transaction.hash
 
       destinationAccount.save()
       accountBalance.save()
 
-      // To provide information about evolution of account balance
-      let accountBalanceLog = createAccountBalance(accountBalance, event)
-      accountBalanceLog.event = eventEntityId
-
-      accountBalanceLog.save()
+      // To provide information about evolution of account balances
+      saveAccountBalanceSnapshot(accountBalance, eventEntityId, event)
     }
   }
 }
@@ -83,16 +90,17 @@ export function handleBurn(event: Burn): void {
 
     // Update source account balance
     let account = getOrCreateAccount(event.params.burner)
-    account.save()
 
     let accountBalance = decreaseAccountBalance(account, token as Token, amount)
+    accountBalance.block = event.block.number
+    accountBalance.modified = event.block.timestamp
+    accountBalance.transaction = event.transaction.hash
+
+    account.save()
     accountBalance.save()
 
-    // To provide information about evolution of account balance
-    let accountBalanceLog = createAccountBalance(accountBalance, event)
-    accountBalanceLog.event = eventEntity.id
-
-    accountBalanceLog.save()
+    // To provide information about evolution of account balances
+    saveAccountBalanceSnapshot(accountBalance, eventEntity.id, event)
   }
 }
 
@@ -107,17 +115,18 @@ export function handleMint(event: Mint): void {
     eventEntity.save()
 
     // Update destination account balance
-    let account: Account = getOrCreateAccount(event.params.to)
-    account.save()
+    let account = getOrCreateAccount(event.params.to)
 
     let accountBalance = increaseAccountBalance(account, token as Token, amount)
+    accountBalance.block = event.block.number
+    accountBalance.modified = event.block.timestamp
+    accountBalance.transaction = event.transaction.hash
+
+    account.save()
     accountBalance.save()
 
-    // To provide information about evolution of account balance
-    let accountBalanceLog = createAccountBalance(accountBalance, event)
-    accountBalanceLog.event = eventEntity.id
-
-    accountBalanceLog.save()
+    // To provide information about evolution of account balances
+    saveAccountBalanceSnapshot(accountBalance, eventEntity.id, event)
   }
 }