listening to "garoche ta sacoche"

contract/best_contract.go

@@ -0,0 +1,79 @@
+package contract
+
+import (
+	"errors"
+	"strings"
+)
+
+type AcceptedContract struct {
+	Hash                  string
+	BlockCipher           string
+	BlockCipherMode       string
+	AsymetricCryptography string
+}
+
+func listContains(lst []string, elm string) bool {
+	for _, elm_ := range lst {
+		if elm == elm_ {
+			return true
+		}
+	}
+	return false
+}
+
+func joinAsError(msg []string) error {
+	if len(msg) > 0 {
+		return errors.New(strings.Join(msg, "\n"))
+	}
+	return nil
+}
+
+func getFirstItemInList1ThatIsAlsoInList2(lst1, lst2 []string) (string, error) {
+	for _, elm := range lst1 {
+		if listContains(lst2, elm) {
+			return elm, nil
+		}
+	}
+	return "", errors.New("no items in list1 is in list2")
+}
+
+func getBestBlockCipher(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if b, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedBlockCyphers, prvCtr.AcceptedBlockCyphers); err != nil {
+		return "", errors.New("cannot find a block cypher that satisfy both contracts")
+	} else {
+		return b, nil
+	}
+}
+
+func getBestBlockCipherMode(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if m, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedBlockCypherModes, prvCtr.AcceptedBlockCypherModes); err != nil {
+		return "", errors.New("cannot find a block cypher mode that satisfy both contracts")
+	} else {
+		return m, nil
+	}
+}
+
+func getBestHash(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if h, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedHashes, prvCtr.AcceptedHashes); err != nil {
+		return "", errors.New("cannot find a hash that satisfy both contracts")
+	} else {
+		return h, nil
+	}
+}
+
+func GetAcceptedContract(prvCtr *PrivateContract, pubCtr *PublicContract) (*AcceptedContract, error) {
+	ret := new(AcceptedContract)
+	errs := make([]string, 0, 4)
+	var err error
+	if ret.Hash, err = getBestHash(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+	if ret.BlockCipher, err = getBestBlockCipher(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+	if ret.BlockCipherMode, err = getBestBlockCipherMode(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+
+	return ret, joinAsError(errs)
+}