From 5f0bd1e1feefb2f2b323fa6ae727e71e0638660d Mon Sep 17 00:00:00 2001
From: Peter Kieltyka <pkieltyka@users.noreply.github.com>
Date: Mon, 16 Dec 2024 18:46:18 -0500
Subject: [PATCH] ethcoder: auto-detect primaryType if unspecified (#151)

---
 ethcoder/typed_data.go      | 52 ++++++++++++++++++++++++++++++++++++-
 ethcoder/typed_data_test.go |  6 +++--
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/ethcoder/typed_data.go b/ethcoder/typed_data.go
index 5cca8c3..9551b55 100644
--- a/ethcoder/typed_data.go
+++ b/ethcoder/typed_data.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"math/big"
+	"slices"
 	"sort"
 	"strings"
 
@@ -320,7 +321,12 @@ func (t *TypedData) UnmarshalJSON(data []byte) error {
 
 	// Ensure primary type is defined
 	if raw.PrimaryType == "" {
-		return fmt.Errorf("primary type is required")
+		// detect primary type if its unspecified
+		primaryType, err := typedDataDetectPrimaryType(raw.Types.Map(), raw.Message)
+		if err != nil {
+			return err
+		}
+		raw.PrimaryType = primaryType
 	}
 	_, ok = raw.Types[raw.PrimaryType]
 	if !ok {
@@ -346,6 +352,50 @@ func (t *TypedData) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+func typedDataDetectPrimaryType(typesMap map[string]map[string]string, message map[string]interface{}) (string, error) {
+	// If there are only two types, and one is the EIP712Domain, then the other is the primary type
+	if len(typesMap) == 2 {
+		_, ok := typesMap["EIP712Domain"]
+		if ok {
+			for typ := range typesMap {
+				if typ == "EIP712Domain" {
+					continue
+				}
+				return typ, nil
+			}
+		}
+	}
+
+	// Otherwise search for the primary type by looking for the first type that has a message field keys
+	messageKeys := []string{}
+	for k := range message {
+		messageKeys = append(messageKeys, k)
+	}
+	sort.Strings(messageKeys)
+
+	for typ := range typesMap {
+		if typ == "EIP712Domain" {
+			continue
+		}
+		if len(typesMap[typ]) != len(messageKeys) {
+			continue
+		}
+
+		typKeys := []string{}
+		for k := range typesMap[typ] {
+			typKeys = append(typKeys, k)
+		}
+		sort.Strings(typKeys)
+
+		if !slices.Equal(messageKeys, typKeys) {
+			continue
+		}
+		return typ, nil
+	}
+
+	return "", fmt.Errorf("no primary type found")
+}
+
 func typedDataDecodeRawMessageMap(typesMap map[string]map[string]string, primaryType string, data interface{}) (interface{}, error) {
 	// Handle array types
 	if arr, ok := data.([]interface{}); ok {
diff --git a/ethcoder/typed_data_test.go b/ethcoder/typed_data_test.go
index 44492cd..28eee59 100644
--- a/ethcoder/typed_data_test.go
+++ b/ethcoder/typed_data_test.go
@@ -310,9 +310,12 @@ func TestTypedDataFromJSONPart3(t *testing.T) {
 				{"name": "count", "type": "uint8"},
 				{"name": "data", "type": "bytes"},
 				{"name": "hash", "type": "bytes32"}
+			],
+			"Blah": [
+				{"name": "name", "type": "string"},
+				{"name": "another", "type": "address"}
 			]
 		},
-		"primaryType": "Person",
 		"domain": {
 			"name": "Ether Mail",
 			"version": "1",
@@ -379,7 +382,6 @@ func TestTypedDataFromJSONPart4(t *testing.T) {
 			"verifyingContract": "0xc0ffee254729296a45a3885639AC7E10F9d54979",
 			"salt": "0x70736575646f2d72616e646f6d2076616c756500000000000000000000000000"
 		},
-		"primaryType": "ExampleMessage",
 		"message": {
 			"message": "Test message",
 			"value": 10000,