package eth

import (
	"fmt"
	"os"
	"strconv"
	"sync"
)

const CONTRACT_ADDRESS string = "ERC20_USDT_CONTRACT_ADDRESS"
const CONTRACT_DECIMALS string = "ERC20_USDT_CONTRACT_DECIMALS"
const ETH_RPC_NODE string = "ETH_RPC_NODE"

type EthNode struct {
	usdtContractAddress  string
	usdtContractDecimals int
	rpcNode              string
}

var ethNode *EthNode
var once sync.Once

func GetERC20ContractAddress() string {
	return ethNode.usdtContractAddress
}

func (e EthNode) Init() (*EthNode, error) {

	if ethNode != nil {
		return ethNode, nil
	}

	usdtContract, isAddressPresent := os.LookupEnv(CONTRACT_ADDRESS)
	if !isAddressPresent {
		return nil, fmt.Errorf("missing environment variable: %s", CONTRACT_ADDRESS)
	}

	usdtContractDecimals, isDecimalsPresent := os.LookupEnv(CONTRACT_DECIMALS)
	if !isDecimalsPresent {
		return nil, fmt.Errorf("missing environment variable: %s", CONTRACT_DECIMALS)
	}

	rpcNode, isRpcNodePresent := os.LookupEnv(ETH_RPC_NODE)
	if !isRpcNodePresent {
		return nil, fmt.Errorf("missing environment variable: %s", ETH_RPC_NODE)
	}

	if ethNode == nil {
		once.Do(func() {
			e.usdtContractAddress = usdtContract
			e.usdtContractDecimals, _ = strconv.Atoi(usdtContractDecimals)
			e.rpcNode = rpcNode
			ethNode = &e
		})
	}

	return ethNode, nil
}

const COMMON_ABI string = `
[
  {
    "constant": true,
    "inputs": [],
    "name": "name",
    "outputs": [ { "name": "", "type": "string" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": false,
    "inputs": [
      { "name": "_spender", "type": "address" },
      { "name": "_value", "type": "uint256" }
    ],
    "name": "approve",
    "outputs": [ { "name": "", "type": "bool" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [],
    "name": "totalSupply",
    "outputs": [ { "name": "", "type": "uint256" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": false,
    "inputs": [
      { "name": "_from", "type": "address" },
      { "name": "_to", "type": "address" },
      { "name": "_value", "type": "uint256" }
    ],
    "name": "transferFrom",
    "outputs": [ { "name": "", "type": "bool" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [],
    "name": "decimals",
    "outputs": [ { "name": "", "type": "uint8" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [ { "name": "_owner", "type": "address" } ],
    "name": "balanceOf",
    "outputs": [ { "name": "", "type": "uint256" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [],
    "name": "symbol",
    "outputs": [ { "name": "", "type": "string" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": false,
    "inputs": [
      { "name": "_to", "type": "address" },
      { "name": "_value", "type": "uint256" }
    ],
    "name": "transfer",
    "outputs": [ { "name": "", "type": "bool" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": false,
    "inputs": [
      { "name": "_token", "type": "address" },
      { "name": "_from", "type": "address" },
      { "name": "_to", "type": "address" },
      { "name": "_value", "type": "uint256" },
      { "name": "_camount", "type": "uint256" }
    ],
    "name": "chargeTransfer",
    "outputs": [ { "name": "", "type": "bool" } ],
    "payable": false,
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [
      { "name": "_owner", "type": "address" },
      { "name": "_spender", "type": "address" }
    ],
    "name": "allowance",
    "outputs": [ { "name": "", "type": "uint256" } ],
    "payable": false,
    "type": "function"
  },
  { "inputs": [], "payable": false, "type": "constructor" },
  {
    "anonymous": false,
    "inputs": [
      { "indexed": true, "name": "_from", "type": "address" },
      { "indexed": true, "name": "_to", "type": "address" },
      { "indexed": false, "name": "_value", "type": "uint256" }
    ],
    "name": "Transfer",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      { "indexed": true, "name": "_owner", "type": "address" },
      { "indexed": true, "name": "_spender", "type": "address" },
      { "indexed": false, "name": "_value", "type": "uint256" }
    ],
    "name": "Approval",
    "type": "event"
  }
]
`