From 508ee40c3f3175d97ae4c8095462dc918b105364 Mon Sep 17 00:00:00 2001
From: Bartek <bartlomiejkramek@outlook.com>
Date: Thu, 3 Oct 2024 17:22:53 +0200
Subject: [PATCH] feat: sort chain IDs with core chains on top (#1962)

---
 .../src/util/__tests__/networks.test.ts       | 45 +++++++++++++++++++
 .../arb-token-bridge-ui/src/util/networks.ts  | 30 +++++++++++--
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/packages/arb-token-bridge-ui/src/util/__tests__/networks.test.ts b/packages/arb-token-bridge-ui/src/util/__tests__/networks.test.ts
index ff1f88a4d9..554663bf91 100644
--- a/packages/arb-token-bridge-ui/src/util/__tests__/networks.test.ts
+++ b/packages/arb-token-bridge-ui/src/util/__tests__/networks.test.ts
@@ -3,6 +3,7 @@ import { registerCustomArbitrumNetwork } from '@arbitrum/sdk'
 import {
   ChainId,
   getBaseChainIdByChainId,
+  getDestinationChainIds,
   getSupportedChainIds
 } from '../networks'
 import { orbitTestnets } from '../orbitChainsList'
@@ -210,3 +211,47 @@ describe('getSupportedChainIds', () => {
     })
   })
 })
+
+describe('getDestinationChainIds', () => {
+  function isAscending(arr: number[]) {
+    return arr.every(
+      (value, index) => index === 0 || value >= Number(arr[index - 1])
+    )
+  }
+
+  it('should return a sorted list for Ethereum Mainnet', () => {
+    const destinationChainIds = getDestinationChainIds(ChainId.Ethereum)
+    const defaultChainId = destinationChainIds[0]
+    const nonDefaultChainIds = destinationChainIds.slice(1)
+
+    expect(defaultChainId).toBe(ChainId.ArbitrumOne)
+    expect(isAscending(nonDefaultChainIds)).toBe(true)
+  })
+
+  it('should return a sorted list for Arbitrum One', () => {
+    const destinationChainIds = getDestinationChainIds(ChainId.ArbitrumOne)
+    const defaultChainId = destinationChainIds[0]
+    const nonDefaultChainIds = destinationChainIds.slice(1)
+
+    expect(defaultChainId).toBe(ChainId.Ethereum)
+    expect(isAscending(nonDefaultChainIds)).toBe(true)
+  })
+
+  it('should return a sorted list for Sepolia', () => {
+    const destinationChainIds = getDestinationChainIds(ChainId.Sepolia)
+    const defaultChainId = destinationChainIds[0]
+    const nonDefaultChainIds = destinationChainIds.slice(1)
+
+    expect(defaultChainId).toBe(ChainId.ArbitrumSepolia)
+    expect(isAscending(nonDefaultChainIds)).toBe(true)
+  })
+
+  it('should return a sorted list for Arbitrum Sepolia', () => {
+    const destinationChainIds = getDestinationChainIds(ChainId.ArbitrumSepolia)
+    const defaultChainId = destinationChainIds[0]
+    const nonDefaultChainIds = destinationChainIds.slice(1)
+
+    expect(defaultChainId).toBe(ChainId.Sepolia)
+    expect(isAscending(nonDefaultChainIds)).toBe(true)
+  })
+})
diff --git a/packages/arb-token-bridge-ui/src/util/networks.ts b/packages/arb-token-bridge-ui/src/util/networks.ts
index 06252531de..e6b22e9a83 100644
--- a/packages/arb-token-bridge-ui/src/util/networks.ts
+++ b/packages/arb-token-bridge-ui/src/util/networks.ts
@@ -487,6 +487,31 @@ export function getChildChainIds(chain: ArbitrumNetwork | L1Network) {
   return Array.from(new Set(childChainIds))
 }
 
+/**
+ * Sorts an array of chain IDs in ascending order (default) but keep core chains on top.
+ * This is helpful e.g. when we grab the default chain which is the first chain on top.
+ */
+export function sortChainIds(chainIds: number[]) {
+  return chainIds.sort((a, b) => {
+    const { isCoreChain: isCoreChainA } = isNetwork(a)
+    const { isCoreChain: isCoreChainB } = isNetwork(b)
+
+    if (isCoreChainA && isCoreChainB) {
+      // Both are core chains, sort in ascending order
+      return a - b
+    } else if (isCoreChainA) {
+      // Only A is core chain, it should come first
+      return -1
+    } else if (isCoreChainB) {
+      // Only B is core chain, it should come first
+      return 1
+    } else {
+      // Neither are core chains, sort in ascending order
+      return a - b
+    }
+  })
+}
+
 export function getDestinationChainIds(chainId: ChainId): ChainId[] {
   const chain = getChainByChainId(chainId)
 
@@ -499,9 +524,8 @@ export function getDestinationChainIds(chainId: ChainId): ChainId[] {
   const validDestinationChainIds = getChildChainIds(chain)
 
   if (parentChainId) {
-    // always make parent chain the first element
-    return [parentChainId, ...validDestinationChainIds]
+    return sortChainIds([parentChainId, ...validDestinationChainIds])
   }
 
-  return validDestinationChainIds
+  return sortChainIds(validDestinationChainIds)
 }