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allowance.go
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/
allowance.go
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package main
import (
"encoding/json"
"github.com/hyperledger/fabric/core/chaincode/shim"
"errors"
)
func (t *LoyaltyChaincode) getAllowance(stub shim.ChaincodeStubInterface, prefix string, cn1 string, cn2 string) (*Allowance, error) {
key, _ := stub.CreateCompositeKey(prefix, []string{cn1, cn2})
data, err := stub.GetState(key)
if err != nil {
return nil, errors.New("Error fetching user allowance:" + err.Error())
} else if data == nil {
return nil, errors.New("No allowance for '" + cn1 + "<->" + cn2 + "' found")
}
allowance := Allowance{}
err = json.Unmarshal(data, &allowance)
if err != nil {
return nil, errors.New("Error parsing allowance:" + err.Error())
}
return &allowance, nil
}
func (t *LoyaltyChaincode) updateAllowance(stub shim.ChaincodeStubInterface, prefix string, cn1 string, cn2 string, delta uint64, negSign bool) (*Allowance, error) {
allowance, _ := t.getAllowance(stub, prefix, cn1, cn2)
if allowance != nil {
if negSign {
if allowance.Value - delta > allowance.Value {
return nil, errors.New("value of allowance is to small to proceed transaction")
}
allowance.Value = allowance.Value - delta
} else {
allowance.Value += delta
}
} else {
if negSign {
return nil, errors.New("value of allowance is to small to proceed transaction")
} else {
allowance = &Allowance{
Buyer: cn2,
Value: delta,
}
}
}
key, _ := stub.CreateCompositeKey(prefix, []string{cn1, cn2})
data, err := json.Marshal(allowance)
if err != nil {
return nil, errors.New("Error creating allowance: " + err.Error())
}
err = stub.PutState(key, []byte(data))
if err != nil {
return nil, errors.New("Error creating allowance: " + err.Error())
}
return allowance, nil
}