Implement fetching token info from node via rpc call

erc20kit/src/main/java/io/horizontalsystems/erc20kit/contract/DecimalsMethod.kt

@@ -0,0 +1,8 @@
+package io.horizontalsystems.erc20kit.contract
+
+import io.horizontalsystems.ethereumkit.contracts.ContractMethod
+
+class DecimalsMethod: ContractMethod() {
+    override var methodSignature = "decimals()"
+    override fun getArguments() = listOf<Any>()
+}

erc20kit/src/main/java/io/horizontalsystems/erc20kit/contract/NameMethod.kt

@@ -0,0 +1,8 @@
+package io.horizontalsystems.erc20kit.contract
+
+import io.horizontalsystems.ethereumkit.contracts.ContractMethod
+
+class NameMethod: ContractMethod() {
+    override var methodSignature = "name()"
+    override fun getArguments() = listOf<Any>()
+}

erc20kit/src/main/java/io/horizontalsystems/erc20kit/contract/SymbolMethod.kt

@@ -0,0 +1,8 @@
+package io.horizontalsystems.erc20kit.contract
+
+import io.horizontalsystems.ethereumkit.contracts.ContractMethod
+
+class SymbolMethod: ContractMethod() {
+    override var methodSignature = "symbol()"
+    override fun getArguments() = listOf<Any>()
+}

erc20kit/src/main/java/io/horizontalsystems/erc20kit/core/Eip20Provider.kt

@@ -0,0 +1,95 @@
+package io.horizontalsystems.erc20kit.core
+
+import io.horizontalsystems.erc20kit.contract.DecimalsMethod
+import io.horizontalsystems.erc20kit.contract.NameMethod
+import io.horizontalsystems.erc20kit.contract.SymbolMethod
+import io.horizontalsystems.erc20kit.events.TokenInfo
+import io.horizontalsystems.ethereumkit.api.core.IRpcApiProvider
+import io.horizontalsystems.ethereumkit.api.core.RpcBlockchain
+import io.horizontalsystems.ethereumkit.contracts.ContractMethodHelper
+import io.horizontalsystems.ethereumkit.core.EthereumKit
+import io.horizontalsystems.ethereumkit.models.Address
+import io.horizontalsystems.ethereumkit.models.DefaultBlockParameter
+import io.horizontalsystems.ethereumkit.models.RpcSource
+import io.horizontalsystems.ethereumkit.spv.core.toBigInteger
+import io.reactivex.Single
+
+class Eip20Provider(private val provider: IRpcApiProvider) {
+
+    class TokenNotFoundException : Throwable()
+
+    fun getTokenInfo(contractAddress: Address): Single<TokenInfo> {
+        val nameSingle = getTokenName(contractAddress)
+        val symbolSingle = getTokenSymbol(contractAddress)
+        val decimalsSingle = getDecimals(contractAddress)
+
+        return Single
+            .zip(nameSingle, symbolSingle, decimalsSingle) { name, symbol, decimals ->
+                TokenInfo(name, symbol, decimals)
+            }
+    }
+
+    private fun getDecimals(contractAddress: Address): Single<Int> {
+        val callRpc = RpcBlockchain.callRpc(
+            contractAddress,
+            DecimalsMethod().encodedABI(),
+            DefaultBlockParameter.Latest
+        )
+
+        return provider.single(callRpc)
+            .map {
+                if (it.isEmpty()) throw TokenNotFoundException()
+
+                it.sliceArray(IntRange(0, 31)).toBigInteger().toInt()
+            }
+    }
+
+    private fun getTokenSymbol(contractAddress: Address): Single<String> {
+        val callRpc = RpcBlockchain.callRpc(
+            contractAddress,
+            SymbolMethod().encodedABI(),
+            DefaultBlockParameter.Latest
+        )
+
+        return provider.single(callRpc)
+            .map {
+                if (it.isEmpty()) throw TokenNotFoundException()
+
+                val argumentTypes = listOf(ByteArray::class)
+
+                val parsedArguments = ContractMethodHelper.decodeABI(it, argumentTypes)
+                val stringBytes = parsedArguments[0] as? ByteArray ?: throw TokenNotFoundException()
+
+                String(stringBytes)
+            }
+    }
+
+    private fun getTokenName(contractAddress: Address): Single<String> {
+        val callRpc = RpcBlockchain.callRpc(
+            contractAddress,
+            NameMethod().encodedABI(),
+            DefaultBlockParameter.Latest
+        )
+
+        return provider.single(callRpc)
+            .map {
+                if (it.isEmpty()) throw TokenNotFoundException()
+
+                val argumentTypes = listOf(ByteArray::class)
+
+                val parsedArguments = ContractMethodHelper.decodeABI(it, argumentTypes)
+                val stringBytes = parsedArguments[0] as? ByteArray ?: throw TokenNotFoundException()
+
+                String(stringBytes)
+            }
+    }
+
+    companion object {
+
+        fun instance(rpcSource: RpcSource.Http): Eip20Provider {
+            return Eip20Provider(EthereumKit.getNodeApiProvider(rpcSource))
+        }
+
+    }
+
+}

erc20kit/src/main/java/io/horizontalsystems/erc20kit/events/TransferEventInstance.kt

@@ -39,5 +39,5 @@ class TransferEventInstance(
     }
 }
 
-class TokenInfo(val tokenName: String, val tokenSymbol: String, val tokenDecimal: Int)
+data class TokenInfo(val tokenName: String, val tokenSymbol: String, val tokenDecimal: Int)
 

ethereumkit/src/main/java/io/horizontalsystems/ethereumkit/core/EthereumKit.kt

@@ -438,6 +438,10 @@ class EthereumKit(
             EthereumDatabaseManager.clear(context, chain, walletId)
         }
 
+        fun getNodeApiProvider(rpcSource: RpcSource.Http): NodeApiProvider {
+            return NodeApiProvider(rpcSource.urls, gson, rpcSource.auth)
+        }
+
         private fun transactionProvider(transactionSource: TransactionSource, address: Address): ITransactionProvider {
             when (transactionSource.type) {
                 is TransactionSource.SourceType.Etherscan -> {