From f3eb89cbe4611c9372ece05eaf5cb7a609954b8e Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Wed, 19 Aug 2020 23:34:33 -0400
Subject: ...

---
 plugin/evm/export_tx.go | 155 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 plugin/evm/export_tx.go

diff --git a/plugin/evm/export_tx.go b/plugin/evm/export_tx.go
new file mode 100644
index 0000000..3a544a6
--- /dev/null
+++ b/plugin/evm/export_tx.go
@@ -0,0 +1,155 @@
+// (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/gecko/database"
+	"github.com/ava-labs/gecko/ids"
+	"github.com/ava-labs/gecko/snow"
+	"github.com/ava-labs/gecko/utils/crypto"
+	"github.com/ava-labs/gecko/vms/components/avax"
+	"github.com/ava-labs/gecko/vms/secp256k1fx"
+
+	safemath "github.com/ava-labs/gecko/utils/math"
+)
+
+var (
+	errNoExportOutputs  = errors.New("no export outputs")
+	errOutputsNotSorted = errors.New("outputs not sorted")
+	errOverflowExport   = errors.New("overflow when computing export amount + txFee")
+
+	_ UnsignedAtomicTx = &UnsignedExportTx{}
+)
+
+// UnsignedExportTx is an unsigned ExportTx
+type UnsignedExportTx struct {
+	avax.Metadata
+	// true iff this transaction has already passed syntactic verification
+	syntacticallyVerified bool
+	// ID of the network on which this tx was issued
+	NetworkID uint32 `serialize:"true" json:"networkID"`
+	// ID of this blockchain.
+	BlockchainID ids.ID `serialize:"true" json:"blockchainID"`
+	// Which chain to send the funds to
+	DestinationChain ids.ID `serialize:"true" json:"destinationChain"`
+	// Inputs
+	Ins []EVMInput `serialize:"true" json:"inputs"`
+	// Outputs that are exported to the chain
+	ExportedOutputs []*avax.TransferableOutput `serialize:"true" json:"exportedOutputs"`
+}
+
+// InputUTXOs returns an empty set
+func (tx *UnsignedExportTx) InputUTXOs() ids.Set { return ids.Set{} }
+
+// Verify this transaction is well-formed
+func (tx *UnsignedExportTx) Verify(
+	avmID ids.ID,
+	ctx *snow.Context,
+	feeAmount uint64,
+	feeAssetID ids.ID,
+) error {
+	switch {
+	case tx == nil:
+		return errNilTx
+	case tx.syntacticallyVerified: // already passed syntactic verification
+		return nil
+	case tx.DestinationChain.IsZero():
+		return errWrongChainID
+	case !tx.DestinationChain.Equals(avmID):
+		return errWrongChainID
+	case len(tx.ExportedOutputs) == 0:
+		return errNoExportOutputs
+	case tx.NetworkID != ctx.NetworkID:
+		return errWrongNetworkID
+	case !ctx.ChainID.Equals(tx.BlockchainID):
+		return errWrongBlockchainID
+	}
+
+	for _, in := range tx.Ins {
+		if err := in.Verify(); err != nil {
+			return err
+		}
+	}
+
+	for _, out := range tx.ExportedOutputs {
+		if err := out.Verify(); err != nil {
+			return err
+		}
+	}
+	if !avax.IsSortedTransferableOutputs(tx.ExportedOutputs, Codec) {
+		return errOutputsNotSorted
+	}
+
+	tx.syntacticallyVerified = true
+	return nil
+}
+
+// SemanticVerify this transaction is valid.
+func (tx *UnsignedExportTx) SemanticVerify(
+	vm *VM,
+	stx *Tx,
+) TxError {
+	if err := tx.Verify(vm.ctx.XChainID, vm.ctx, vm.txFee, vm.ctx.AVAXAssetID); err != nil {
+		return permError{err}
+	}
+
+	// TODO: credential check
+	// TODO: flow check
+	// TODO: verify UTXO outputs via gRPC
+	return nil
+}
+
+// Accept this transaction.
+func (tx *UnsignedExportTx) Accept(ctx *snow.Context, batch database.Batch) error {
+	// TODO: finish this function via gRPC
+	return nil
+}
+
+// Create a new transaction
+func (vm *VM) newExportTx(
+	amount uint64, // Amount of tokens to export
+	chainID ids.ID, // Chain to send the UTXOs to
+	to ids.ShortID, // Address of chain recipient
+	keys []*crypto.PrivateKeySECP256K1R, // Pay the fee and provide the tokens
+) (*Tx, error) {
+	if !vm.ctx.XChainID.Equals(chainID) {
+		return nil, errWrongChainID
+	}
+
+	toBurn, err := safemath.Add64(amount, vm.txFee)
+	if err != nil {
+		return nil, errOverflowExport
+	}
+	ins, signers, err := vm.GetSpendableCanonical(keys, toBurn)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't generate tx inputs/outputs: %w", err)
+	}
+
+	// Create the transaction
+	utx := &UnsignedExportTx{
+		NetworkID:        vm.ctx.NetworkID,
+		BlockchainID:     vm.ctx.ChainID,
+		DestinationChain: chainID,
+		Ins:              ins,
+		ExportedOutputs: []*avax.TransferableOutput{{ // Exported to X-Chain
+			Asset: avax.Asset{ID: vm.ctx.AVAXAssetID},
+			Out: &secp256k1fx.TransferOutput{
+				Amt: amount,
+				OutputOwners: secp256k1fx.OutputOwners{
+					Locktime:  0,
+					Threshold: 1,
+					Addrs:     []ids.ShortID{to},
+				},
+			},
+		}},
+	}
+	tx := &Tx{UnsignedTx: utx}
+	if err := tx.Sign(vm.codec, signers); err != nil {
+		return nil, err
+	}
+	return tx, utx.Verify(vm.ctx.XChainID, vm.ctx, vm.txFee, vm.ctx.AVAXAssetID)
+}
-- 
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