README

A solidity library for fee management. That is, every dApp usually charge a fee for his services, these library will help you with that.

Architecture

Broadly speaking contracts in these repo can be divided in components, contracts and presets.

• Components are minimal building blocks used by contracts.
• Contracts has more complete features for certain use cases but without assuming any security/access mechanism.
• Presets are ready to use contracts which use predefined security/access mechanism.

Contracts are divided in those designed so they can manage fees for a single contract and the fee charging functionality is part of the inheritor contract(FeeCharger*) and those that manage fees for a set of contract or a complete smart contract system and that functionality wants to be kept external(FeeManager*). In the case of FeeManager* family of contracts they usually enforce and manage a default fee.

Additionally, these contracts are divided in those who charge fees using native cryptocurrency which have Value in their name like FeeChargerValue or FeeManagerValue or those how use ERC20 tokens which have ERC20 in their name like FeeChargerERC20 and FeeManagerERC20.

Lastly is how the amount to charge is managed. The amount could be static, dynamic, operations or internal.

• The static case is where the fee amount to charge is a predefined parameter or state variable.
• The dynamic case is where the fee must be calculated in execution time according to certain parameters.
• The operations case allow to set a fee per function(only external or public make sense).
• The internal case only for Value related contracts is like static but stored the fees internally.

Example:

• Contracts FeeChargerValue and FeeChargerERC20 obtain the fee amount to charge by reading a predefined state variable(statically).
• Contracts FeeChargerValueDynamic and FeeChargerERC20Dynamic calculate the current fee acording to arbitrary parameters(dynamically).
• Contracts FeeChargerValueOperations and FeeChargerERC20Operations allow to define a fee amount for every function and charge accordingly to current function being called, aditionally allow to define a default fee.