Create explainer for postal service contract

main/.vitepress/config.mjs

@@ -446,11 +446,16 @@ export default defineConfig({
               text: 'Takeaway 2: Swaparoo Contract Overview',
               link: '/guides/getting-started/swaparoo-how-to-swap-assets-explainer',
             },
-
+            
             {
               text: 'Takeaway 3: Sending Invitation Payments using an Address',
               link: '/guides/getting-started/swaparoo-making-a-payment-explainer',
             },
+
+            {
+              text: 'Takeaway 4: Postal Service Contract Overview',
+              link: '/guides/getting-started/postal-service-contract-explainer',
+            },
           ],
         },        
         {

main/guides/getting-started/postal-service-contract-explainer.md

@@ -0,0 +1,64 @@
+# Understanding the Agoric Postal Service Contract
+
+This contract is implemented using the Zoe Contract Facet (ZCF) and demonstrates how to create and manage a basic postal service. Let's break down the main components and functionalities of this contract.
+
+## Contract Structure and Components
+## 1. Contract Setup:
+The contract starts with a setup that includes the terms of the service, typically the price of joining the postal service. This setup is done through the `start` function, which is a standard entry point for Agoric contracts. The function initializes the service and sets up any required assets or parameters.
+```javascript
+export const start = async (zcf) => {
+    const { joinPrice } = zcf.getTerms();
+    const { zcfSeat: postalSeat } = zcf.makeEmptySeatKit();
+    const mint = await zcf.makeZCFMint('PostalToken', AssetKind.NAT);
+
+    // Other initialization logic
+};
+```
+
+## 2. Minting and Managing Assets:
+The contract utilizes the `ZCFMint` object to mint new tokens or assets. In this example, tokens are created to represent the postal services or stamps.
+```javascript
+const mint = await zcf.makeZCFMint('PostalToken', AssetKind.COPY_BAG);
+```
+
+## 3. Handling User Requests:
+User interactions with the contract are managed through invitations. These invitations allow users to perform specific actions, such as joining the postal service or sending a package.
+```javascript
+const joinHandler = userSeat => {
+    const { give, want } = userSeat.getProposal();
+
+    // Ensure the payment is sufficient
+    assert(give.Price.value >= joinPrice.value, 'Insufficient payment');
+
+    // Process the request and update the contract state
+    userSeat.exit();
+    return 'Welcome to the postal service';
+};
+
+const publicFacet = Far('API', {
+    makeJoinInvitation: () => zcf.makeInvitation(joinHandler, 'Join Postal Service'),
+});
+```
+
+## 4. Public Facet:
+The public facet of the contract exposes the functionality that external users can interact with. In this contract, users can create invitations to join the postal service.
+```javascript
+return { publicFacet };
+```
+
+## Deploying and Interacting with the Contract
+To deploy this contract, developers use the Agoric CLI tools. The process typically involves bundling the contract code, deploying it to the blockchain, and setting up any necessary client-side interfaces to interact with the contract.
+
+### 1. Deployment Script:
+The deployment script automates the process of installing the contract on the blockchain.
+```javascript
+const deploy = async (homeP) => {
+    const { zoe } = homeP;
+    const bundle = await bundleSource('./src/contract.js');
+    const installation = await E(zoe).install(bundle);
+    console.log('Contract installed:', installation);
+};
+```
+
+### 2. Client Interaction:
+Users interact with the deployed contract through a web interface or directly using CLI commands. They can create and use invitations to join the service, make payments, and manage their assets.