feat(lib/parachain): Implement request and response message for /req_…

…chunk/1 protocol (#3362)

- Added `ChunkFetchingRequest` and `ChunkFetchingResponse` types.

- implemented network.Message interface in `ChunkFetchingRequest` and 'network.ResponseMessage' interface in `ChunkFetchingResponse`

lib/parachain/chunk_fetching.go

@@ -0,0 +1,93 @@
+package parachain
+
+import (
+	"fmt"
+
+	"github.com/ChainSafe/gossamer/pkg/scale"
+)
+
+// ChunkFetchingRequest represents a request to retrieve chunks of a parachain candidate
+type ChunkFetchingRequest struct {
+	// Hash of candidate we want a chunk for.
+	CandidateHash CandidateHash `scale:"1"`
+
+	// The index of the chunk to fetch.
+	Index ValidatorIndex `scale:"2"`
+}
+
+// Encode returns the SCALE encoding of the ChunkFetchingRequest
+func (c ChunkFetchingRequest) Encode() ([]byte, error) {
+	return scale.Marshal(c)
+}
+
+// ChunkFetchingResponse represents the response for a requested erasure chunk
+type ChunkFetchingResponse scale.VaryingDataType
+
+// NewChunkFetchingResponse returns a new chunk fetching response varying data type
+func NewChunkFetchingResponse() ChunkFetchingResponse {
+	vdt := scale.MustNewVaryingDataType(ChunkResponse{}, NoSuchChunk{})
+	return ChunkFetchingResponse(vdt)
+}
+
+// Set will set a value using the underlying  varying data type
+func (c *ChunkFetchingResponse) Set(val scale.VaryingDataTypeValue) (err error) {
+	vdt := scale.VaryingDataType(*c)
+	err = vdt.Set(val)
+	if err != nil {
+		return
+	}
+	*c = ChunkFetchingResponse(vdt)
+	return
+}
+
+// Value returns the value from the underlying varying data type
+func (c *ChunkFetchingResponse) Value() (val scale.VaryingDataTypeValue, err error) {
+	vdt := scale.VaryingDataType(*c)
+	return vdt.Value()
+}
+
+// ChunkResponse represents the requested chunk data
+type ChunkResponse struct {
+	// The erasure-encoded chunk of data belonging to the candidate block
+	Chunk []byte `scale:"1"`
+
+	// Proof for this chunk's branch in the Merkle tree
+	Proof [][]byte `scale:"2"`
+}
+
+// Index returns the index of varying data type
+func (ChunkResponse) Index() uint {
+	return 0
+}
+
+// NoSuchChunk indicates that the requested chunk was not found
+type NoSuchChunk struct{}
+
+// Index returns the index of varying data type
+func (NoSuchChunk) Index() uint {
+	return 1
+}
+
+// Encode returns the SCALE encoding of the ChunkFetchingResponse
+func (c *ChunkFetchingResponse) Encode() ([]byte, error) {
+	return scale.Marshal(*c)
+}
+
+// Decode returns the SCALE decoding of the ChunkFetchingResponse.
+func (c *ChunkFetchingResponse) Decode(in []byte) (err error) {
+	return scale.Unmarshal(in, c)
+}
+
+// String formats a ChunkFetchingResponse as a string
+func (c *ChunkFetchingResponse) String() string {
+	if c == nil {
+		return "ChunkFetchingResponse=nil"
+	}
+
+	v, _ := c.Value()
+	chunkRes, ok := v.(ChunkResponse)
+	if !ok {
+		return "ChunkFetchingResponse=NoSuchChunk"
+	}
+	return fmt.Sprintf("ChunkFetchingResponse ChunkResponse=%+v", chunkRes)
+}

lib/parachain/chunk_fetching_test.go

@@ -0,0 +1,83 @@
+package parachain
+
+import (
+	"testing"
+
+	"github.com/ChainSafe/gossamer/lib/common"
+	"github.com/ChainSafe/gossamer/pkg/scale"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEncodeChunkFetchingRequest(t *testing.T) {
+	chunkFetchingRequest := ChunkFetchingRequest{
+		CandidateHash: CandidateHash{
+			common.MustHexToHash("0x677811d2f3ded2489685468dbdb2e4fa280a249fba9356acceb2e823820e2c19"),
+		},
+		Index: ValidatorIndex(8),
+	}
+
+	actualEncode, err := chunkFetchingRequest.Encode()
+	require.NoError(t, err)
+
+	expextedEncode := common.MustHexToBytes("0x677811d2f3ded2489685468dbdb2e4fa280a249fba9356acceb2e823820e2c1908000000")
+	require.Equal(t, expextedEncode, actualEncode)
+}
+
+func TestChunkFetchingResponse(t *testing.T) {
+	t.Parallel()
+
+	testBytes := common.MustHexToBytes("0x677811d2f3ded2489685468dbdb2e4fa280a249fba9356acceb2e823820e2c19")
+	testCases := []struct {
+		name        string
+		value       scale.VaryingDataTypeValue
+		encodeValue []byte
+	}{
+		{
+			name: "chunkResponse",
+			value: ChunkResponse{
+				Chunk: testBytes,
+				Proof: [][]byte{testBytes},
+			},
+			encodeValue: common.MustHexToBytes("0x0080677811d2f3ded2489685468dbdb2e4fa280a249fba9356acceb2e823820e2c190480677811d2f3ded2489685468dbdb2e4fa280a249fba9356acceb2e823820e2c19"), //nolint:lll
+		},
+		{
+			name:        "NoSuchChunk",
+			value:       NoSuchChunk{},
+			encodeValue: []byte{1},
+		},
+	}
+
+	for _, c := range testCases {
+		c := c
+		t.Run(c.name, func(t *testing.T) {
+			t.Parallel()
+
+			t.Run("encode", func(t *testing.T) {
+				t.Parallel()
+
+				chunkFetchingResponse := NewChunkFetchingResponse()
+				err := chunkFetchingResponse.Set(c.value)
+				require.NoError(t, err)
+
+				actualEncode, err := chunkFetchingResponse.Encode()
+				require.NoError(t, err)
+
+				require.Equal(t, c.encodeValue, actualEncode)
+			})
+
+			t.Run("decode", func(t *testing.T) {
+				t.Parallel()
+
+				chunkFetchingResponse := NewChunkFetchingResponse()
+				err := chunkFetchingResponse.Decode(c.encodeValue)
+				require.NoError(t, err)
+
+				actualData, err := chunkFetchingResponse.Value()
+				require.NoError(t, err)
+
+				require.EqualValues(t, c.value, actualData)
+			})
+
+		})
+	}
+}