Base Access Fee Manager for Farecho (Farcaster Mini-App)

Keywords: base blockchain solidity smart-contract web3 ethereum defi farcaster crypto onchain

This repository documents the smart contract and pattern I use to manage access fees for my Farcaster mini-app Farecho, running on Base mainnet.

• Mini-app name: Farecho
• Mini-app link (Farcaster): https://farcaster.xyz/miniapps/U7FUwxLHV7p9/farecho

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Why I built this

Originally, Farecho was already live:

• Users connected with their Farcaster wallet.
• They paid an access fee.
• The fee was sent directly to my wallet.

This worked, but had some limitations:

1. No clear onchain "builder footprint"
2. Hard to track usage & revenue
3. Not future-proof

So I created a simple contract pattern to make the flow onchain and transparent.

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Contract details

Network: Base mainnet
Contract name: AccessFeeManager
Contract address: 0x12dbC9a0B45d735d82895a952F112Ee380a16671

Contract source

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract AccessFeeManager {
    address public owner;
    uint256 public constant ACCESS_PRICE = 0.00005 ether;

    event AccessPaid(address indexed user, uint256 amount);
    event Withdraw(address indexed to, uint256 amount);

    constructor() {
        owner = msg.sender;
    }

    function payAccess() external payable {
        require(msg.value == ACCESS_PRICE, "Must pay exactly 0.00005 ETH");
        emit AccessPaid(msg.sender, msg.value);
    }

    function withdrawAll() external {
        require(msg.sender == owner, "Not owner");
        uint256 balance = address(this).balance;
        require(balance > 0, "No balance");
        payable(owner).transfer(balance);
        emit Withdraw(owner, balance);
    }
}

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Key functions overview

🔹 payAccess()

• Accepts exactly 0.00005 ETH
• Emits AccessPaid
• Called automatically inside Farecho

🔹 withdrawAll()

• Only deployer can call it
• Transfers 100% of contract balance

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Integration with Farecho

Farecho mini-app link:
https://farcaster.xyz/miniapps/U7FUwxLHV7p9/farecho

Only 1 change was required:

❗ Instead of sending ETH directly to my wallet,
Farecho now calls payAccess() with 0.00005 ETH.

Everything else stayed the same:

• Same Farcaster login flow
• Same UI
• Same user experience

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Notes for developers

• Contract must run on Base mainnet
• Owner = deployer
• Don’t expose private keys
• Always test with small amounts
• Only replace where payment is triggered

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Future enhancements

• Adjustable fees
• Free access list
• Subscription model
• Analytics via emitted events

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TR Özet

Farecho’ya giriş yapan kullanıcılar 0.00005 ETH öder.
Bu ücret doğrudan cüzdana değil, önce kontrata gider.
Ben withdrawAll() ile toplu çekerim.

Bu sistem:

• Onchain builder izi bırakır
• Geliri şeffaf yapar
• Gelecekte abonelik ve fiyatlandırma eklemeyi kolaylaştırır