Merge pull request #470 from 0xPolygonID/feature/crosschain_resolver

Added crosschain proof data retrieval function.

analysis_options.yaml

@@ -27,4 +27,5 @@ analyzer:
 
 linter:
   rules:
-    prefer_double_quotes: false
+    prefer_double_quotes: false
+    unnecessary_this: false

lib/common/abi_encode/abi_encode.dart

@@ -0,0 +1,92 @@
+import 'package:flutter/foundation.dart';
+
+import 'package:web3dart/crypto.dart';
+import 'package:web3dart/web3dart.dart';
+
+/// An object that can be encoded to ABI.
+abstract interface class AbiEncodable {
+  /// Serialize the object to a list of arguments that can be passed to the ABI encoder.
+  /// Example class represented by the object:
+  /// {
+  ///   a: "c",
+  ///   b: "d",
+  /// }
+  /// should return
+  /// ["c", 896314698613489613]
+  List toAbiEncodeArgs();
+
+  /// The ABI type of the object.
+  /// Should be retrieved from actual contract ABI.
+  /// Example:
+  /// {
+  ///   a: "c",
+  ///   b: 896314698613489613,
+  /// }
+  /// should return
+  /// [StringType(), UintType()]
+  AbiType get abiType;
+}
+
+extension EncodableExtension on AbiEncodable {
+  /// Encode the object to a byte array.
+  Uint8List encode() {
+    final buffer = LengthTrackingByteSink();
+
+    abiType.encode(
+      toAbiEncodeArgs(),
+      buffer,
+    );
+
+    return buffer.asBytes();
+  }
+
+  /// Encode the object to a hex string.
+  String encodeToHex() {
+    return bytesToHex(encode());
+  }
+}
+
+/// An extension on [Iterable] of [AbiEncodable] objects.
+extension EncodableIterable<T extends AbiEncodable> on Iterable<T> {
+  /// Encode the list of objects to a byte array.
+  AbiType getAbiType(AbiType elementType) {
+    return TupleType([
+      DynamicLengthArray(
+        type: elementType,
+      ),
+    ]);
+  }
+
+  Uint8List encode() {
+    if (isEmpty) {
+      // TODO Check that this is correct
+      return Uint8List(0);
+    }
+
+    final type = getAbiType(first.abiType);
+
+    final buffer = LengthTrackingByteSink();
+
+    type.encode(
+      [
+        map((m) => m.toAbiEncodeArgs()).toList(),
+      ],
+      buffer,
+    );
+
+    return buffer.asBytes();
+  }
+
+  String encodeToHex() => bytesToHex(encode());
+}
+
+extension HexEncodable on AbiType {
+  String encodeToHex(List<dynamic> params) {
+    final buffer = LengthTrackingByteSink();
+    encode(params, buffer);
+
+    final result = bytesToHex(buffer.asBytes());
+
+    return result;
+  }
+}