// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package evm

import (
	"errors"
	"fmt"

	"github.com/ava-labs/coreth/core/state"

	"github.com/ava-labs/avalanchego/database"
	"github.com/ava-labs/avalanchego/ids"
	"github.com/ava-labs/avalanchego/snow"
	"github.com/ava-labs/avalanchego/utils/codec"
	"github.com/ava-labs/avalanchego/utils/crypto"
	"github.com/ava-labs/avalanchego/utils/hashing"
	"github.com/ava-labs/avalanchego/vms/components/verify"
	"github.com/ava-labs/avalanchego/vms/secp256k1fx"
	"github.com/ava-labs/go-ethereum/common"
)

// Max size of memo field
// Don't change without also changing avm.maxMemoSize
const maxMemoSize = 256

var (
	errWrongBlockchainID = errors.New("wrong blockchain ID provided")
	errWrongNetworkID    = errors.New("tx was issued with a different network ID")
	errNilTx             = errors.New("tx is nil")
)

type EVMOutput struct {
	Address common.Address `serialize:"true" json:"address"`
	Amount  uint64         `serialize:"true" json:"amount"`
	Nonce   uint64         `serialize:"true" json:"nonce"`
}

func (out *EVMOutput) Verify() error {
	return nil
}

type EVMInput EVMOutput

func (in *EVMInput) Verify() error {
	return nil
}

// UnsignedTx is an unsigned transaction
type UnsignedTx interface {
	Initialize(unsignedBytes, signedBytes []byte)
	ID() ids.ID
	UnsignedBytes() []byte
	Bytes() []byte
}

// UnsignedAtomicTx is an unsigned operation that can be atomically accepted
type UnsignedAtomicTx interface {
	UnsignedTx

	// UTXOs this tx consumes
	InputUTXOs() ids.Set
	// Attempts to verify this transaction with the provided state.
	SemanticVerify(vm *VM, stx *Tx) TxError

	// Accept this transaction with the additionally provided state transitions.
	Accept(ctx *snow.Context, batch database.Batch) error

	EVMStateTransfer(state *state.StateDB) error
}

// Tx is a signed transaction
type Tx struct {
	// The body of this transaction
	UnsignedTx `serialize:"true" json:"unsignedTx"`

	// The credentials of this transaction
	Creds []verify.Verifiable `serialize:"true" json:"credentials"`
}

// (*secp256k1fx.Credential)

// Sign this transaction with the provided signers
func (tx *Tx) Sign(c codec.Codec, signers [][]*crypto.PrivateKeySECP256K1R) error {
	unsignedBytes, err := c.Marshal(&tx.UnsignedTx)
	if err != nil {
		return fmt.Errorf("couldn't marshal UnsignedTx: %w", err)
	}

	// Attach credentials
	hash := hashing.ComputeHash256(unsignedBytes)
	for _, keys := range signers {
		cred := &secp256k1fx.Credential{
			Sigs: make([][crypto.SECP256K1RSigLen]byte, len(keys)),
		}
		for i, key := range keys {
			sig, err := key.SignHash(hash) // Sign hash
			if err != nil {
				return fmt.Errorf("problem generating credential: %w", err)
			}
			copy(cred.Sigs[i][:], sig)
		}
		tx.Creds = append(tx.Creds, cred) // Attach credential
	}

	signedBytes, err := c.Marshal(tx)
	if err != nil {
		return fmt.Errorf("couldn't marshal ProposalTx: %w", err)
	}
	tx.Initialize(unsignedBytes, signedBytes)
	return nil
}