> ## Documentation Index
> Fetch the complete documentation index at: https://thrackle.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Pricing Invariants

## ERC20-Pricing Invariants

* Version will never be blank
* Version will never change.
* Any user can get the contract's version
* It will always return a price, even if it is 0
* Prices can be set for any valid address, regardless of the type(EOA or contract)
* A non-owner address can never set a price
* Any user can get the token's price
* Any user can retrieve the price mapping
* Setting a price will always emit TokenPrice event

## ERC721-Pricing Invariants

##### Note: Not implemented yet

* Version will never be blank
* Version will never change.
* Any user can get the contract's version
* It will always return a price, even if it is 0
* Prices cannot be for non ERC721 compliant NFT's
* Trying to set a price for non ERC721 compliant NFT's always reverts with NotAnNFTContract
* Trying to set a price for non ERC721 compliant NFT collections always reverts with NotAnNFTContract
* A non-owner address can never set a price
* Any user can get a token's price
* Any user can get a collection's price
* Any user can retrieve the nft price mapping
* Any user can retrieve the collection price mapping
* When using an ERC721 compliant NFT's address, setting an NFT price always emits SingleTokenPrice event with the correct address, id, and price.
* When using an ERC721 compliant NFT's address, setting an NFT collection price always emits CollectionPrice event with the correct address and price.
* When a specific tokenId price is set and a collection price is set and that specific tokenId's price is retrieved, it always returns the specific tokenId's price and not the collection's price.
* When no specific tokenId price is set and a collection price is set, it always retrieves the collection price.
* When no specific tokenId price is set and no collection price is set, it always returns 0.
* When a specific tokenId prices are set and a collection price is set, it always returns the specific tokenId's price.