Guides section update + ABI encoding/decoding clarifications

src/config/sidebar.ts

@@ -518,10 +518,6 @@ export const SIDEBAR: Partial<Record<Sections, SectionEntry[]>> = {
           title: "Call an API",
           url: "chainlink-functions/tutorials/api-query-parameters",
         },
-        {
-          title: "Return Custom Data Types",
-          url: "chainlink-functions/tutorials/api-custom-response",
-        },
         {
           title: "POST Data to an API",
           url: "chainlink-functions/tutorials/api-post-data",
@@ -530,6 +526,14 @@ export const SIDEBAR: Partial<Record<Sections, SectionEntry[]>> = {
           title: "Using DON-hosted Secrets in Requests",
           url: "chainlink-functions/tutorials/api-use-secrets",
         },
+        {
+          title: "Using Imports with Functions",
+          url: "chainlink-functions/tutorials/importing-packages",
+        },
+        {
+          title: "Return multiple responses and decode them in your smart contract",
+          url: "chainlink-functions/tutorials/abi-decoding",
+        },
         {
           title: "Offchain secrets - Using Gists",
           url: "chainlink-functions/tutorials/api-use-secrets-gist",
@@ -554,14 +558,6 @@ export const SIDEBAR: Partial<Record<Sections, SectionEntry[]>> = {
           title: "Automate your Functions (Custom Logic Automation)",
           url: "chainlink-functions/tutorials/automate-functions-custom-logic",
         },
-        {
-          title: "Using Imports with Functions",
-          url: "chainlink-functions/tutorials/importing-packages",
-        },
-        {
-          title: "Return multiple responses and decode them in your smart contract",
-          url: "chainlink-functions/tutorials/abi-decoding",
-        },
       ],
     },
     {

src/content/chainlink-functions/tutorials/abi-decoding.mdx

@@ -224,3 +224,104 @@ The primary function that the script executes is `makeRequestMumbai`. This funct
 
    - Call the `s_answer`, `s_updatedAt`, `s_decimals`, and `s_description` functions of your consumer contract to fetch the decoded values.
    - Log the decoded values to the console.
+
+## Handling complex data types with ABI Encoding and Decoding
+
+This section details the process of encoding complex data types into [`Uint8Array` typed arrays](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) to fulfill the Ethereum Virtual Machine (EVM) data handling requirements for transactions and smart contract interactions. It will then outline the steps for decoding these byte arrays to align with corresponding structures defined in Solidity.
+
+Consider a scenario where a contract needs to interact with a data structure that encapsulates multiple properties, including nested objects:
+
+```json
+{
+  "id": 1,
+  "metadata": {
+    "description": "Decentralized Oracle Network",
+    "awesome": true
+  }
+}
+```
+
+Transferring and storing this kind of structured data requires encoding it into a format (array of 8-bit unsigned integers) that smart contracts can accept and process.
+
+### Encoding in JavaScript
+
+Because Chainlink Functions supports important external modules, you can import a web3 library such as `ethers.js` and perform encoding.
+To encode complex data structures, you can use the [`defaultAbiCoder.encode`](https://docs.ethers.org/v6/api/abi/abi-coder/#AbiCoder-encode) function from the `ethers.js` library. The function takes two arguments:
+
+- An array of Solidity data types.
+- The corresponding data in JavaScript format.
+
+and returns the encoded data as a hexadecimal string.
+
+Here's how you can encode the aforementioned complex data:
+
+```javascript
+const { ethers } = await import("npm:ethers@6.10.0") // Import ethers.js v6.10.0
+
+const abiCoder = ethers.AbiCoder.defaultAbiCoder()
+
+// Define the data structure
+const complexData = {
+  id: 1,
+  metadata: {
+    description: "Decentralized Oracle Network",
+    awesome: true,
+  },
+}
+
+// Define the Solidity types for encoding
+const types = ["tuple(uint256 id, tuple(string description, bool awesome) metadata)"]
+
+// Data to encode
+const data = [
+  [
+    complexData.id,
+    {
+      description: complexData.metadata.description,
+      awesome: complexData.metadata.awesome,
+    },
+  ],
+]
+
+// Encoding the data
+const encodedData = abiCoder.encode(types, data)
+```
+
+After encoding the data, it's necessary to format it as a `Uint8Array` array for smart contract interactions and blockchain transactions. In Solidity, the data type for byte arrays data is `bytes`. However, when working in a JavaScript environment, such as when using the `ethers.js` library, the equivalent data structure is a `Uint8Array`.
+
+The `ethers.js` library provides the [`getBytes`](https://docs.ethers.org/v6/api/utils/#getBytes) function to convert encoded hexadecimal strings into a `Uint8Array`:
+
+```javascript
+return ethers.getBytes(encodedData) // Return the encoded data converted into a Uint8Array
+```
+
+### Decoding in Solidity
+
+The encoded data can be decoded using the `abi.decode` function. To decode the data, you'll need to handle the decoding in your `fulfillRequest` function:
+
+```solidity
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.19;
+
+contract DataDecoder {
+  // Example of a structure to hold the complex data
+  struct Metadata {
+    string description;
+    bool awesome;
+  }
+
+  struct ComplexData {
+    uint256 id;
+    Metadata metadata;
+  }
+
+  // ... other contract functions (including the send request function)
+
+  // Fulfill function (callback function)
+  function fulfillRequest(bytes32 requestId, bytes memory response, bytes memory err) internal override {
+    // Decode the response
+    ComplexData memory metadata = abi.decode(response, (ComplexData));
+    // ... rest of the function
+  }
+}
+```