From 812972c8322179e60dcb27035fb177f8af795d62 Mon Sep 17 00:00:00 2001
From: Shawn <44221603+shaspitz@users.noreply.github.com>
Date: Tue, 21 Nov 2023 17:17:58 -0800
Subject: [PATCH] separate precompiles for mint/burn

---
 core/vm/contracts.go          | 18 +++++++++-----
 core/vm/contracts_with_ctx.go | 45 ++++++++++++++++++++++++++---------
 2 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 33a5e0f916..01cf709671 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -49,7 +49,8 @@ var PrecompiledContractsHomestead = map[common.Address]PrecompiledContractWithCt
 	common.BytesToAddress([]byte{2}):    precompileWrapper{&sha256hash{}},
 	common.BytesToAddress([]byte{3}):    precompileWrapper{&ripemd160hash{}},
 	common.BytesToAddress([]byte{4}):    precompileWrapper{&dataCopy{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 // PrecompiledContractsByzantium contains the default set of pre-compiled Ethereum
@@ -63,7 +64,8 @@ var PrecompiledContractsByzantium = map[common.Address]PrecompiledContractWithCt
 	common.BytesToAddress([]byte{6}):    precompileWrapper{&bn256AddByzantium{}},
 	common.BytesToAddress([]byte{7}):    precompileWrapper{&bn256ScalarMulByzantium{}},
 	common.BytesToAddress([]byte{8}):    precompileWrapper{&bn256PairingByzantium{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 // PrecompiledContractsIstanbul contains the default set of pre-compiled Ethereum
@@ -78,7 +80,8 @@ var PrecompiledContractsIstanbul = map[common.Address]PrecompiledContractWithCtx
 	common.BytesToAddress([]byte{7}):    precompileWrapper{&bn256ScalarMulIstanbul{}},
 	common.BytesToAddress([]byte{8}):    precompileWrapper{&bn256PairingIstanbul{}},
 	common.BytesToAddress([]byte{9}):    precompileWrapper{&blake2F{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 // PrecompiledContractsBerlin contains the default set of pre-compiled Ethereum
@@ -93,7 +96,8 @@ var PrecompiledContractsBerlin = map[common.Address]PrecompiledContractWithCtx{
 	common.BytesToAddress([]byte{7}):    precompileWrapper{&bn256ScalarMulIstanbul{}},
 	common.BytesToAddress([]byte{8}):    precompileWrapper{&bn256PairingIstanbul{}},
 	common.BytesToAddress([]byte{9}):    precompileWrapper{&blake2F{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 // PrecompiledContractsCancun contains the default set of pre-compiled Ethereum
@@ -109,7 +113,8 @@ var PrecompiledContractsCancun = map[common.Address]PrecompiledContractWithCtx{
 	common.BytesToAddress([]byte{8}):    precompileWrapper{&bn256PairingIstanbul{}},
 	common.BytesToAddress([]byte{9}):    precompileWrapper{&blake2F{}},
 	common.BytesToAddress([]byte{0x0a}): precompileWrapper{&kzgPointEvaluation{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 // PrecompiledContractsBLS contains the set of pre-compiled Ethereum
@@ -124,7 +129,8 @@ var PrecompiledContractsBLS = map[common.Address]PrecompiledContractWithCtx{
 	common.BytesToAddress([]byte{16}):   precompileWrapper{&bls12381Pairing{}},
 	common.BytesToAddress([]byte{17}):   precompileWrapper{&bls12381MapG1{}},
 	common.BytesToAddress([]byte{18}):   precompileWrapper{&bls12381MapG2{}},
-	common.BytesToAddress([]byte{0x89}): &transfer{},
+	common.BytesToAddress([]byte{0x89}): &mint{},
+	common.BytesToAddress([]byte{0x90}): &burn{},
 }
 
 var (
diff --git a/core/vm/contracts_with_ctx.go b/core/vm/contracts_with_ctx.go
index 93e685c83c..8b36f91b33 100644
--- a/core/vm/contracts_with_ctx.go
+++ b/core/vm/contracts_with_ctx.go
@@ -69,20 +69,18 @@ var mockEVM = &EVM{
 	TxContext: vmTxCtx,
 }
 
-// Native transfer precompile to make bridging to native token possible.
-type transfer struct{}
+// Native token mint precompile to make bridging to native token possible.
+type mint struct{}
 
-func (c *transfer) RequiredGas(input []byte) uint64 {
+func (c *mint) RequiredGas(input []byte) uint64 {
 	// TODO: determine appropriate gas cost
 	return 100
 }
 
-func (c *transfer) Run(input []byte, ctx *precompileContext) ([]byte, error) {
+func (c *mint) Run(input []byte, ctx *precompileContext) ([]byte, error) {
 
 	// TODO: filter out non-allowed callers
-
-	// From
-	_ = common.BytesToAddress(input[0:32])
+	_ = common.BytesToAddress(input[0:32]) // From
 
 	to := common.BytesToAddress(input[32:64])
 
@@ -95,10 +93,35 @@ func (c *transfer) Run(input []byte, ctx *precompileContext) ([]byte, error) {
 	// Mint case: Create native token out of thin air
 	ctx.evm.StateDB.AddBalance(to, value)
 
-	// if !ctx.CanTransfer(ctx.evm.StateDB, from, value) {
-	// 	return nil, ErrInsufficientBalance
-	// }
-	// ctx.Transfer(ctx.evm, from, to, value)
+	return input, nil
+}
+
+// Native token burn precompile to make bridging back to L1 possible.
+type burn struct{}
+
+func (c *burn) RequiredGas(input []byte) uint64 {
+	// TODO: determine appropriate gas cost
+	return 100
+}
+
+func (c *burn) Run(input []byte, ctx *precompileContext) ([]byte, error) {
+
+	// TODO: filter out non-allowed callers
+	_ = common.BytesToAddress(input[0:32]) // From
+
+	// Address to get their tokens burned
+	addrReqTokenBurn := common.BytesToAddress(input[32:64])
+
+	var parsed bool
+	value, parsed := math.ParseBig256(hexutil.Encode(input[64:96]))
+	if !parsed {
+		return nil, fmt.Errorf("Error parsing transfer: unable to parse value from " + hexutil.Encode(input[64:96]))
+	}
+
+	if !ctx.CanTransfer(ctx.evm.StateDB, addrReqTokenBurn, value) {
+		return nil, ErrInsufficientBalance
+	}
+	ctx.evm.StateDB.SubBalance(addrReqTokenBurn, value)
 
 	return input, nil
 }