Subscription NFTs on Aptos: User Guide

Overview

Purpose:

Subscription NFTs act as keys for accessing services, such as a trading bot. They include properties that allow fine-grained control over subscription terms.

Key Features:

• Support for multiple collections with unique NFTs.

• Precision-based properties that determine usage limitations, refill rates, and subscription impact. 

NFT Structure

Each NFT includes attributes to control the subscription model with 5-decimal precision (stored as u128).

Properties:

• Energy: Core property, ranges from 0 to 100.00000.
• Refill: Rate at which energy can be refilled (0 to 1.00000).
• Profit, Volume, Time: Usage coefficients:
• • profit: A multiplier for energy consumption based on profit.
  • volume: A multiplier based on trade volume in USDT.
  • time: A multiplier based on time duration.

• • Note: If any of these are zero, they won’t impact the energy calculations.

Contract Functions

Function 1:

mint_nft

Creates NFTs with specific attributes and associates them with a collection.

public fun mint_nft(
    account: &signer,
    collection_name: &str,
    nft_name: &str,
    description: &str,
    energy: u128,
    refill: u128,
    profit: u128,
    volume: u128,
    time: u128
): TokenId

Description:

• Takes energy, refill, profit, volume, and time as parameters with 5-decimal precision.
• Creates an NFT with these properties in the specified collection.

Function 2:

use_energy

Applies energy usage based on provided values for profit, volume, and time.

moveCopy codepublic fun use_energy(
    account: &signer,
    nft_id: &TokenId,
    profit_val: u128,
    volume_val: u128,
    time_val: u128
) acquires SubscriptionNft

Description:

• Uses non-zero coefficients to calculate energy usage.
• Formula: (input_value * nft_property) / 100_000
• Ensures energy isn’t deducted if the property value is zero.

Function 3:

refill_energy

Replenishes energy based on the refill rate and the current energy level.

moveCopy codepublic fun refill_energy(
	​account: &signer,
	​nft_id: &TokenId
) acquires SubscriptionNft

Description:

• Calculates refill amount based on refill and available energy capacity.
• Ensures that energy doesn’t exceed 100%.

Implementation Details

• Data Types: Properties are stored as u128, with precision allowing 5 decimal places.
• Calculation Conditions:
  • Properties with zero values are skipped in calculations to prevent unwanted deductions.
  • Refill amount is capped to ensure energy remains within allowed limits.

Testing and Validation

This contract includes comprehensive tests to validate functionality and property handling.

Tests:

1. NFT Creation: Checks that NFT properties are stored and retrieved accurately.
2. Energy Usage: Confirms that use_energy applies correct deductions based on the provided values.
3. Energy Refill: Ensures refill limits are respected and energy caps at 100%.

Assertions:

• Ensures signer access control.
• Handles errors for invalid refill rates and insufficient energy.
  

Code Walkthrough

Each function is detailed below:

1. Minting Function: mint_nft
   • Creates NFT with precise properties.
   • Ensures properties such as energy and refill are set accurately for future usage.
2. Energy Consumption Function: use_energy
   • Deducts energy based on non-zero usage values.
   • Skips properties with zero values, preventing unintended deductions.
3. Energy Refill Function: refill_energy
   • Calculates refill based on refill rate.
   • Enforces energy cap at 100% to avoid overflow.

Summary and Future Potential

• Precision in Subscription Management:
  Fine-grained control over subscriptions with energy-based management tailored to usage patterns.

• Future Enhancements:
• • Integration with the trading bot to monitor energy in real time.
  • Further customization of properties and usage formulas to support diverse subscription models.