feat(eth): add rpc methods for retrieving previous 256 parentHashes / blocks from blockID (#144)

* skeleton

* Update taiko_api_backend.go

* add getl2parenthashes test

* use blocks[i].hash instead of str

* add getl2parentblocks test

* standardize

* changes according to comments

* refactor according to comments

* refactor again

* spaces

eth/taiko_api_backend.go

@@ -89,3 +89,26 @@ func (s *TaikoAPIBackend) TxPoolContent(
 		maxTransactionsLists,
 	)
 }
+
+// Get L2ParentHashes retrieves the preceding 256 parent hashes given a block number.
+func (s *TaikoAPIBackend) GetL2ParentHashes(blockID uint64) ([]common.Hash, error) {
+	var hashes []common.Hash
+	headers, err := s.GetL2ParentHeaders(blockID)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, x := range headers {
+		hashes = append(hashes, x.Hash())
+	}
+	return hashes, nil
+}
+
+// Get L2ParentBlocks retrieves the preceding 256 parent blocks given a block number.
+func (s *TaikoAPIBackend) GetL2ParentHeaders(blockID uint64) ([]*types.Header, error) {
+	var headers []*types.Header
+	for i := blockID; i != 0 && (blockID-i) < 256; i-- {
+		headers = append(headers, s.eth.blockchain.GetHeaderByNumber(blockID-i))
+	}
+	return headers, nil
+}

ethclient/taiko_api.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 )
@@ -29,3 +30,23 @@ func (ec *Client) L1OriginByID(ctx context.Context, blockID *big.Int) (*rawdb.L1
 
 	return res, nil
 }
+
+func (ec *Client) GetL2ParentHashes(ctx context.Context, blockID uint64) ([]common.Hash, error) {
+	var res []common.Hash
+
+	if err := ec.c.CallContext(ctx, &res, "taiko_getL2ParentHashes", blockID); err != nil {
+		return nil, err
+	}
+
+	return res, nil
+}
+
+func (ec *Client) GetL2ParentHeaders(ctx context.Context, blockID uint64) ([]map[string]interface{}, error) {
+	var res []map[string]interface{}
+
+	if err := ec.c.CallContext(ctx, &res, "taiko_getL2ParentHeaders", blockID); err != nil {
+		return nil, err
+	}
+
+	return res, nil
+}

ethclient/taiko_api_test.go

@@ -104,6 +104,55 @@ func TestL1OriginByID(t *testing.T) {
 	require.Equal(t, testL1Origin, l1OriginFound)
 }
 
+func TestGetL2ParentHashes(t *testing.T) {
+	ec, blocks, _ := newTaikoAPITestClient(t)
+
+	hashes, err := ec.GetL2ParentHashes(context.Background(), common.Big3.Uint64())
+	require.Nil(t, err)
+
+	log.Info("hashes", "a", hashes)
+	require.Equal(t, 3, len(hashes))
+	require.Equal(t, blocks[0].Hash(), hashes[0])
+	require.Equal(t, blocks[1].Hash(), hashes[1])
+	require.Equal(t, blocks[2].Hash(), hashes[2])
+
+	hashes, err = ec.GetL2ParentHashes(context.Background(), common.Big2.Uint64())
+	require.Nil(t, err)
+
+	require.Equal(t, 2, len(hashes))
+	require.Equal(t, blocks[0].Hash(), hashes[0])
+	require.Equal(t, blocks[1].Hash(), hashes[1])
+
+	hashes, err = ec.GetL2ParentHashes(context.Background(), common.Big0.Uint64())
+	require.Nil(t, err)
+
+	require.Equal(t, 0, len(hashes))
+}
+
+func TestGetL2ParentBlocks(t *testing.T) {
+	ec, blocks, _ := newTaikoAPITestClient(t)
+
+	res, err := ec.GetL2ParentHeaders(context.Background(), common.Big3.Uint64())
+	require.Nil(t, err)
+
+	require.Equal(t, 3, len(res))
+	require.Equal(t, res[0]["hash"], blocks[0].Hash().String())
+	require.Equal(t, res[1]["hash"], blocks[1].Hash().String())
+	require.Equal(t, res[2]["hash"], blocks[2].Hash().String())
+
+	res, err = ec.GetL2ParentHeaders(context.Background(), common.Big2.Uint64())
+	require.Nil(t, err)
+
+	require.Equal(t, 2, len(res))
+	require.Equal(t, res[0]["hash"], blocks[0].Hash().String())
+	require.Equal(t, res[1]["hash"], blocks[1].Hash().String())
+
+	res, err = ec.GetL2ParentHeaders(context.Background(), common.Big0.Uint64())
+	require.Nil(t, err)
+
+	require.Equal(t, 0, len(res))
+}
+
 // randomHash generates a random blob of data and returns it as a hash.
 func randomHash() common.Hash {
 	var hash common.Hash