package contract

import (
	"errors"

	"github.com/didiercrunch/filou/helper"
)

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 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, helper.JoinAsError(errs)
}