Add ERC: Sustainable NFT Collections

ERCS/erc-xxxx.md

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+---
+eip: xxxx
+title: Sustainable Collections
+description: A standard for managing NFTs with dynamic fees and donation-based engagement.
+author: Gustavo Lobo (@gflobo)
+discussions-to: <URL>
+status: Draft
+type: Standards Track
+category: ERC
+created: 2024-12-04
+requires: 721
+---
+
+### Abstract  
+
+This EIP defines a standard for economically sustainable NFTs using features derived from the ERC721 standard. It integrates dynamic minting fees, role-based access control, and donation-based engagement. These mechanisms align tokenomics with principles of scarcity and value attribution while enabling creators to foster community engagement through contributions. Additionally, the standard supports optional features like token raffles to further incentivize community participation.
+
+---
+
+### Motivation  
+
+NFT systems often face issues like inflationary supply and lack of mechanisms to incentivize meaningful engagement between creators and contributors. This EIP addresses these gaps by introducing:  
+- **Dynamic Minting Fees**: To align token costs with user activity and ownership.  
+- **Donation-Based Engagement**: Encouraging contributions to creators.  
+- **Role-Based Access**: Empowering creators while ensuring transparent governance.  
+- **Optional Raffles**: Providing a mechanism for creators to reward contributors in a gamified manner.
+
+---
+
+### Specification  
+
+#### Core Functionalities  
+
+1. **Dynamic Minting Fees:**  
+   Minting fees increase dynamically based on the number of tokens owned by the user. This discourages hoarding and promotes equitable token distribution.  
+   - Formula:  
+     ```solidity
+     function mintFee() public view returns (uint256) {
+        if (hasRole(DEFAULT_ADMIN_ROLE, msg.sender)) return 0;
+        uint256 baseFee = mintBaseFee;
+        uint256 incrementPercentage = mintRateIncrementPercentage;
+        uint256 userTokenCount = balanceOf(msg.sender);
+        return baseFee * (1 + incrementPercentage / 100) ** userTokenCount;
+      }
+     ```  
+
+2. **Donation System:**  
+   Contributors can support creators by donating ETH. Upon donation, users may receive the **Contributor Role**, granting them special access to features like raffles or exclusive minting rights.  
+   - Function:  
+     ```solidity
+     function donate(address creator) external payable;
+     ```
+
+3. **Role-Based Access:**  
+   - **Creator Role:** Enables minting and managing collections. Users can acquire this role by paying a creator signature fee.  
+   - **Contributor Role:** Granted to users who donate ETH to creators, enabling participation in additional features.  
+   - **Administrator:** Grants roles, updates contract parameters, and manages withdrawals.  
+
+
+4. **Administrative Controls:**  
+   - **Pause/Unpause:** Allows administrators to halt or resume contract operations during emergencies.  
+   - **Withdraw:** Administrators can withdraw ETH from the contract with complete transparency.  
+
+#### Optional Raffle Mechanism (Extra Feature)  
+
+Creators can optionally organize raffles to reward contributors. Raffles encourage engagement by allowing contributors to compete for ownership of specific tokens.  
+- **Creating a Raffle:**  
+  - Creators specify the token ID, expected donation amount, and participant limits.  
+  - Example function:  
+    ```solidity
+    function createRaffle(uint256 tokenId, uint256 expectedAmount) external;
+    ```
+
+- **Joining a Raffle:**  
+  - Contributors can join active raffles by donating ETH to the creator. If the donation pool reaches the expected amount, a winner is randomly selected.  
+  - Example function:  
+    ```solidity
+    function joinRaffle(uint256 tokenId) external payable;
+    ```
+
+- **Random Winner Selection:**  
+  - Winners are selected using a random mechanism based on on-chain factors like block timestamp and randomness (`block.prevrandao`).  
+
+
+### Security Considerations  
+
+- **Reentrancy Protection:**  
+  Implements `ReentrancyGuard` to prevent recursive call vulnerabilities in donation and raffle functions.  
+- **Access Management:**  
+  Utilizes OpenZeppelin's `AccessControl` to enforce role-based restrictions.  
+- **Raffle Transparency:**  
+  Raffle mechanics use auditable and on-chain randomness for fairness.  
+- **Paused State:**  
+  Allows administrators to pause the contract in emergencies, ensuring safety during unexpected events.  
+
+---
+
+### Rationale  
+
+Below are the key considerations and justifications for the design choices:
+
+1. **Dynamic Minting Fees**  
+   - **Problem**: Fixed minting fees often lead to hoarding and disproportionate ownership, limiting equitable access to NFTs.  
+   - **Solution**: Introducing a dynamic fee structure discourages hoarding by progressively increasing costs based on ownership. This mechanism incentivizes broader token distribution and aligns with principles of scarcity and value attribution.  
+
+2. **Donation-Based Engagement**  
+   - **Problem**: Creators often lack sustainable models for fostering community engagement and receiving contributions.  
+   - **Solution**: A donation system provides creators with a direct channel to receive support while offering contributors tangible benefits (e.g., roles or access to raffles). This fosters a mutually beneficial relationship.  
+
+3. **Optional Raffle Mechanism**  
+   - **Problem**: Traditional giveaways and rewards lack transparency and often exclude smaller contributors.  
+   - **Solution**: The optional raffle system introduces fairness by leveraging on-chain randomness, encouraging smaller contributors to participate without feeling excluded.  
+   - **Alternative Considered**: Replacing raffles with auctions. However, auctions tend to favor wealthier participants and do not align with the goal of equitable community engagement.
+
+---
+
+### Backwards Compatibility  
+
+This EIP is fully compatible with ERC721. Extensions like dynamic minting fees, donation systems, and optional raffles are modular and do not impact existing ERC721 token functionalities.
+
+---
+
+### Test Cases  
+
+- Validate dynamic minting fees with varying ownership levels.  
+- Verify role-based access control for minting and donations.  
+- Ensure proper donation flow and ETH transfer to creators.  
+- Test contract pause and unpause functionalities.  
+- Simulate raffle creation, participation, and winner selection scenarios.  
+- Simulate unauthorized access attempts and validate security safeguards.  
+
+---
+
+### Reference Implementation  
+
+The reference implementation is provided at [Collectible](https://github.com/gfLobo/Collectible). It includes all specified functionalities, including dynamic fees, donation systems, role-based access, and optional raffle mechanisms.
+
+---
+
+### Backwards Compatibility  
+
+This EIP is fully compatible with ERC721. Extensions like dynamic minting fees, donation systems, and optional raffles are modular and do not impact existing ERC721 token functionalities.
+
+---
+
+### Copyright  
+Copyright and related rights waived via [CC0](../LICENSE.md).