Create Stellar payment transaction builder utility

[davedumto]

Description

Create a utility module for building Stellar payment transactions using @stellar/stellar-sdk. This will be used by the tip modal to construct XLM payment transactions from viewer to creator.

---

Current State

We have @stellar/stellar-sdk installed (from the Stellar migration), but no payment-specific utilities yet. We need a clean abstraction for building tip transactions.

---

What needs to happen

1. Create lib/stellar/payments.ts with the following functions:

import {
  Server,
  TransactionBuilder,
  Networks,
  Operation,
  Asset,
  BASE_FEE,
  Memo,
  Transaction,
} from "@stellar/stellar-sdk";

interface BuildTipTransactionParams {
  sourcePublicKey: string;      // Viewer's Stellar wallet
  destinationPublicKey: string; // Creator's Stellar wallet
  amount: string;               // XLM amount (e.g., "10.0000000")
  network: "testnet" | "mainnet";
}

export async function buildTipTransaction(
  params: BuildTipTransactionParams
): Promise<Transaction>

export async function submitTransaction(
  transaction: Transaction,
  network: "testnet" | "mainnet"
): Promise<{ success: boolean; hash?: string; ledger?: number; error?: string }>

2. Implementation details:

   • Use Server from @stellar/stellar-sdk to connect to Horizon API
   • Testnet: https://horizon-testnet.stellar.org
   • Mainnet: https://horizon.stellar.org
   • Load source account with server.loadAccount(sourcePublicKey)
   • Build transaction with TransactionBuilder
   • Add Operation.payment() with Asset.native() (XLM)
   • Add memo: Memo.text("StreamFi Tip")
   • Set timeout: 30 seconds
   • Use BASE_FEE for transaction fee

3. Error handling:

   • Catch and return errors from server.loadAccount() (account not found)
   • Catch and return errors from server.submitTransaction() (insufficient balance, etc.)
   • Include Stellar result codes in error responses

4. Get network from environment variable:

   • Read NEXT_PUBLIC_STELLAR_NETWORK (set by user: "testnet" or "mainnet")

---

Files affected

• New file: lib/stellar/payments.ts

---

Acceptance criteria

• lib/stellar/payments.ts file created with both functions
• buildTipTransaction() constructs valid Stellar payment transaction
• submitTransaction() submits to Horizon API and returns result
• Network selection works (testnet vs mainnet based on param)
• Transactions include memo: "StreamFi Tip"
• TypeScript types defined for all params and returns
• Error handling implemented with clear error messages
• Tested on Stellar Testnet with real wallet addresses

---

Useful resources

• Stellar SDK TransactionBuilder
• Send and receive payments guide
• Operation.payment() docs

---

Loom Video Requirement

Before submitting your PR, you must record a short Loom video demonstrating:

1. The lib/stellar/payments.ts file and its code
2. Testing buildTipTransaction() with console.log showing the transaction object
3. Testing submitTransaction() on Testnet and showing the returned hash
4. Viewing the transaction on Stellar Expert Testnet explorer

Include the Loom link in your PR description.

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[Hallab7]

@Hallab7 has applied to work on this issue as part of the Stellar Wave Program's 2nd wave.

i would like to take this issue

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Congratulations, @Hallab7! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on February 26, 2026.

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[drips-wave]

This issue has been completed by @Hallab7 as part of the Stellar Wave Program's 2nd Wave 🥳

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