chore(sdk): support DefaultFallbackRoutingIsm in sdk metadata builder (#4162)

### Description

Support DefaultFallbackRoutingIsm in sdk metadata builder


### Backward compatibility

Yes

### Testing

Manually processed
https://explorer.hyperlane.xyz/message/0x7d5f8450965a97735e39007f7cb9db135852123d589d81f81c113d84e3a70ceb

.changeset/nice-deers-tan.md

@@ -0,0 +1,5 @@
+---
+"@hyperlane-xyz/sdk": patch
+---
+
+Support DefaultFallbackRoutingIsm in metadata builder

typescript/sdk/src/ism/metadata/builder.ts

@@ -23,7 +23,10 @@ import {
 import { ArbL2ToL1Metadata, ArbL2ToL1MetadataBuilder } from './arbL2ToL1.js';
 import { MultisigMetadata, MultisigMetadataBuilder } from './multisig.js';
 import { NullMetadata, NullMetadataBuilder } from './null.js';
-import { RoutingMetadata, RoutingMetadataBuilder } from './routing.js';
+import {
+  DefaultFallbackRoutingMetadataBuilder,
+  RoutingMetadata,
+} from './routing.js';
 
 export type StructuredMetadata =
   | NullMetadata
@@ -50,7 +53,7 @@ export class BaseMetadataBuilder implements MetadataBuilder {
   public nullMetadataBuilder: NullMetadataBuilder;
   public multisigMetadataBuilder: MultisigMetadataBuilder;
   public aggregationMetadataBuilder: AggregationMetadataBuilder;
-  public routingMetadataBuilder: RoutingMetadataBuilder;
+  public routingMetadataBuilder: DefaultFallbackRoutingMetadataBuilder;
   public arbL2ToL1MetadataBuilder: ArbL2ToL1MetadataBuilder;
 
   public multiProvider: MultiProvider;
@@ -59,7 +62,9 @@ export class BaseMetadataBuilder implements MetadataBuilder {
   constructor(core: HyperlaneCore) {
     this.multisigMetadataBuilder = new MultisigMetadataBuilder(core);
     this.aggregationMetadataBuilder = new AggregationMetadataBuilder(this);
-    this.routingMetadataBuilder = new RoutingMetadataBuilder(this);
+    this.routingMetadataBuilder = new DefaultFallbackRoutingMetadataBuilder(
+      this,
+    );
     this.nullMetadataBuilder = new NullMetadataBuilder(core.multiProvider);
     this.arbL2ToL1MetadataBuilder = new ArbL2ToL1MetadataBuilder(core);
     this.multiProvider = core.multiProvider;
@@ -99,6 +104,7 @@ export class BaseMetadataBuilder implements MetadataBuilder {
         });
 
       case IsmType.ROUTING:
+      case IsmType.FALLBACK_ROUTING:
         return this.routingMetadataBuilder.build(
           {
             ...context,
@@ -123,7 +129,7 @@ export class BaseMetadataBuilder implements MetadataBuilder {
       }
 
       default:
-        throw new Error(`Unsupported ISM type: ${ism.type}`);
+        throw new Error(`Unsupported ISM: ${ism}`);
     }
   }
 
@@ -144,7 +150,10 @@ export class BaseMetadataBuilder implements MetadataBuilder {
         return AggregationMetadataBuilder.decode(metadata, { ...context, ism });
 
       case IsmType.ROUTING:
-        return RoutingMetadataBuilder.decode(metadata, { ...context, ism });
+        return DefaultFallbackRoutingMetadataBuilder.decode(metadata, {
+          ...context,
+          ism,
+        });
 
       case IsmType.ARB_L2_TO_L1:
         return ArbL2ToL1MetadataBuilder.decode(metadata, {

typescript/sdk/src/ism/metadata/routing.ts

@@ -1,7 +1,8 @@
+import { DefaultFallbackRoutingIsm__factory } from '@hyperlane-xyz/core';
 import { WithAddress, assert } from '@hyperlane-xyz/utils';
 
 import { ChainName } from '../../types.js';
-import { DerivedIsmConfig } from '../EvmIsmReader.js';
+import { DerivedIsmConfig, EvmIsmReader } from '../EvmIsmReader.js';
 import { IsmType, RoutingIsmConfig } from '../types.js';
 
 import {
@@ -56,3 +57,49 @@ export class RoutingMetadataBuilder implements MetadataBuilder {
     };
   }
 }
+
+export class DefaultFallbackRoutingMetadataBuilder extends RoutingMetadataBuilder {
+  public async build(
+    context: MetadataContext<WithAddress<RoutingIsmConfig>>,
+    maxDepth = 10,
+  ): Promise<string> {
+    const originChain = this.baseMetadataBuilder.multiProvider.getChainName(
+      context.message.parsed.origin,
+    );
+
+    const isRouted = !!context.ism.domains[originChain];
+    if (isRouted) {
+      return super.build(context, maxDepth);
+    }
+
+    if (context.ism.type !== IsmType.FALLBACK_ROUTING) {
+      throw new Error(
+        `Origin domain ${originChain} is not enrolled in DomainRoutingIsm`,
+      );
+    }
+
+    const destinationProvider =
+      this.baseMetadataBuilder.multiProvider.getProvider(
+        context.message.parsed.destination,
+      );
+    const fallbackIsm = DefaultFallbackRoutingIsm__factory.connect(
+      context.ism.address,
+      destinationProvider,
+    );
+    const defaultIsmAddress = await fallbackIsm.module(
+      context.message.parsed.origin,
+    );
+
+    const ismReader = new EvmIsmReader(
+      this.baseMetadataBuilder.multiProvider,
+      context.message.parsed.destination,
+    );
+    const defaultIsmConfig = await ismReader.deriveIsmConfig(defaultIsmAddress);
+
+    const originContext = {
+      ...context,
+      ism: defaultIsmConfig,
+    };
+    return this.baseMetadataBuilder.build(originContext, maxDepth - 1);
+  }
+}