From 0d419d3899293919aa5bc1f9ab4b374a81640020 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 4 Mar 2020 13:18:49 +0300
Subject: [PATCH] smartcontract: implement ParameterContext

---
 pkg/smartcontract/context/context.go      | 92 +++++++++++++++++++++++
 pkg/smartcontract/context/context_test.go | 64 ++++++++++++++++
 2 files changed, 156 insertions(+)
 create mode 100644 pkg/smartcontract/context/context.go
 create mode 100644 pkg/smartcontract/context/context_test.go

diff --git a/pkg/smartcontract/context/context.go b/pkg/smartcontract/context/context.go
new file mode 100644
index 000000000..3dd73ca5a
--- /dev/null
+++ b/pkg/smartcontract/context/context.go
@@ -0,0 +1,92 @@
+package context
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+)
+
+// ParameterContext represents smartcontract parameter's context.
+type ParameterContext struct {
+	// Type is a type of a verifiable item.
+	Type string
+	// Verifiable is an object which can be (de-)serialized.
+	Verifiable io.Serializable
+	// Items is a map from script hashes to context items.
+	Items map[util.Uint160]*Item
+}
+
+type paramContext struct {
+	Type  string                     `json:"type"`
+	Hex   string                     `json:"hex"`
+	Items map[string]json.RawMessage `json:"items"`
+}
+
+// MarshalJSON implements json.Marshaler interface.
+func (c ParameterContext) MarshalJSON() ([]byte, error) {
+	bw := io.NewBufBinWriter()
+	c.Verifiable.EncodeBinary(bw.BinWriter)
+	if bw.Err != nil {
+		return nil, bw.Err
+	}
+	items := make(map[string]json.RawMessage, len(c.Items))
+	for u := range c.Items {
+		data, err := json.Marshal(c.Items[u])
+		if err != nil {
+			return nil, err
+		}
+		items["0x"+u.StringBE()] = data
+	}
+	pc := &paramContext{
+		Type:  c.Type,
+		Hex:   hex.EncodeToString(bw.Bytes()),
+		Items: items,
+	}
+	return json.Marshal(pc)
+}
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (c *ParameterContext) UnmarshalJSON(data []byte) error {
+	pc := new(paramContext)
+	if err := json.Unmarshal(data, pc); err != nil {
+		return err
+	}
+	data, err := hex.DecodeString(pc.Hex)
+	if err != nil {
+		return err
+	}
+
+	var verif io.Serializable
+	switch pc.Type {
+	case "Neo.Core.ContractTransaction":
+		verif = new(transaction.Transaction)
+	default:
+		return fmt.Errorf("unsupported type: %s", c.Type)
+	}
+	br := io.NewBinReaderFromBuf(data)
+	verif.DecodeBinary(br)
+	if br.Err != nil {
+		return br.Err
+	}
+	items := make(map[util.Uint160]*Item, len(pc.Items))
+	for h := range pc.Items {
+		u, err := util.Uint160DecodeStringBE(strings.TrimPrefix(h, "0x"))
+		if err != nil {
+			return err
+		}
+		item := new(Item)
+		if err := json.Unmarshal(pc.Items[h], item); err != nil {
+			return err
+		}
+		items[u] = item
+	}
+	c.Type = pc.Type
+	c.Verifiable = verif
+	c.Items = items
+	return nil
+}
diff --git a/pkg/smartcontract/context/context_test.go b/pkg/smartcontract/context/context_test.go
new file mode 100644
index 000000000..4cf7d967f
--- /dev/null
+++ b/pkg/smartcontract/context/context_test.go
@@ -0,0 +1,64 @@
+package context
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParameterContext_MarshalJSON(t *testing.T) {
+	priv, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	tx := getContractTx()
+	data := tx.GetSignedPart()
+	sign := priv.Sign(data)
+
+	expected := &ParameterContext{
+		Type:       "Neo.Core.ContractTransaction",
+		Verifiable: tx,
+		Items: map[util.Uint160]*Item{
+			priv.GetScriptHash(): {
+				Script: priv.GetScriptHash(),
+				Parameters: []smartcontract.Parameter{{
+					Type:  smartcontract.SignatureType,
+					Value: sign,
+				}},
+				Signatures: map[string][]byte{
+					hex.EncodeToString(priv.PublicKey().Bytes()): sign,
+				},
+			},
+		},
+	}
+
+	data, err = json.Marshal(expected)
+	require.NoError(t, err)
+
+	actual := new(ParameterContext)
+	require.NoError(t, json.Unmarshal(data, actual))
+	require.Equal(t, expected, actual)
+}
+
+func getContractTx() *transaction.Transaction {
+	tx := transaction.NewContractTX()
+	tx.AddInput(&transaction.Input{
+		PrevHash:  util.Uint256{1, 2, 3, 4},
+		PrevIndex: 5,
+	})
+	tx.AddOutput(&transaction.Output{
+		AssetID:    util.Uint256{7, 8, 9},
+		Amount:     10,
+		ScriptHash: util.Uint160{11, 12},
+	})
+	tx.Data = new(transaction.ContractTX)
+	tx.Attributes = make([]transaction.Attribute, 0)
+	tx.Scripts = make([]transaction.Witness, 0)
+	tx.Hash()
+	return tx
+}