package main 
 
import ( 
   "fmt" 
   "strconv" 
   "github.com/hyperledger/fabric/core/chaincode/shim"
   pb "github.com/hyperledger/fabric/protos/peer" 
)

type SimpleChaincode struct {
}

// 初始化数据状态，实例化/升级链代码时被自动调用
func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
	// println函数的输出信息会出现在链代码容器的日志中
	fmt.Println("ex02 Init")

	// 获取用户传递给调用链代码的所需参数
	_, args := stub.GetFunctionAndParameters()

	var A, B string    // 两个账户
	var Aval, Bval int // 两个账户的余额
	var err error

	// 检查合法性, 检查参数数量是否为4个, 如果不是, 则返回错误信息
	if len(args) != 4 {
		return shim.Error("Incorrect number of arguments. Expecting 4")
	}

	A = args[0]  // 账户A用户名
	Aval, err = strconv.Atoi(args[1])  // 账户A余额
	if err != nil {
		return shim.Error("Expecting integer value for asset holding")
	}

	B = args[2]  // 账户B用户名
	Bval, err = strconv.Atoi(args[3])  // 账户B余额
	if err != nil {
		return shim.Error("Expecting integer value for asset holding")
	}

	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)

	// 将账户A的状态写入账本中
	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	// 将账户B的状态写入账本中
	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	return shim.Success(nil)
}

// 对账本数据进行操作时(query, invoke)被自动调用
func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response {
	fmt.Println("ex02 Invoke")
	// 获取用户传递给调用链代码的函数名称及参数
	function, args := stub.GetFunctionAndParameters()

	// 对获取到的函数名称进行判断
	if function == "invoke" {
		// 调用 invoke 函数实现转账操作
		return t.invoke(stub, args)
	} else if function == "delete" {
		// 调用 delete 函数实现账户注销
		return t.delete(stub, args)
	} else if function == "query" {
		// 调用 query 实现账户查询操作
		return t.query(stub, args)
	}
	// 传递的函数名出错，返回 shim.Error()
	return shim.Error("Invalid invoke function name. Expecting \"invoke\" \"delete\" \"query\"")
}

// 账户间转钱
func (t *SimpleChaincode) invoke(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var A, B string    // 账户A和B
	var Aval, Bval int // 账户余额
	var X int          // 转账金额
	var err error

	if len(args) != 3 {
		return shim.Error("Incorrect number of arguments. Expecting 3")
	}

	A = args[0]       // 账户A用户名
	B = args[1]       // 账户B用户名

	// 从账本中获取A的余额
	Avalbytes, err := stub.GetState(A)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Avalbytes == nil {
		return shim.Error("Entity not found")
	}
	Aval, _ = strconv.Atoi(string(Avalbytes))

	// 从账本中获取B的余额
	Bvalbytes, err := stub.GetState(B)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Bvalbytes == nil {
		return shim.Error("Entity not found")
	}
	Bval, _ = strconv.Atoi(string(Bvalbytes))

	// X为转账金额
	X, err = strconv.Atoi(args[2])
	if err != nil {
		return shim.Error("Invalid transaction amount, expecting a integer value")
	}
	// 转账
	Aval = Aval - X
	Bval = Bval + X
	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)

	// 更新转账后账本中A余额
	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	// 更新转账后账本中B余额
	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	return shim.Success(nil)
}

// 账户注销
func (t *SimpleChaincode) delete(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	A := args[0]   // 账户用户名

	// 从账本中删除该账户状态
	err := stub.DelState(A)
	if err != nil {
		return shim.Error("Failed to delete state")
	}

	return shim.Success(nil)
}

// 账户查询
func (t *SimpleChaincode) query(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var A string
	var err error

	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting name of the person to query")
	}

	A = args[0]   // 账户用户名

	// 从账本中获取该账户余额
	Avalbytes, err := stub.GetState(A)
	if err != nil {
		jsonResp := "{\"Error\":\"Failed to get state for " + A + "\"}"
		return shim.Error(jsonResp)
	}

	if Avalbytes == nil {
		jsonResp := "{\"Error\":\"Nil amount for " + A + "\"}"
		return shim.Error(jsonResp)
	}

	jsonResp := "{\"Name\":\"" + A + "\",\"Amount\":\"" + string(Avalbytes) + "\"}"
	fmt.Printf("Query Response:%s\n", jsonResp)
	// 返回转账金额
	return shim.Success(Avalbytes)
}

func main() {
	err := shim.Start(new(SimpleChaincode))
	if err != nil {
		fmt.Printf("Error starting Simple chaincode: %s", err)
	}
}