# Curation Module

## 1. Introduction (Summary)

The Curation module contains contracts that facilitate the signaling of new and existing subgraphs to Indexers and distributes Graph Curation Shares (GCS) to Curators.

## 2. Module Details

The Curation Module has 3 core components consisting of the `Curation`, `GraphCurationToken` and `BancorFormula` contracts.

### Glossary

- `signaling` - is the process of depositing GRT into a bonding curve for a subgraph to indicate Indexers what subgraph should be indexed.
- `bonding curve` - a type of algorithmic market maker where price is determined by a function.

## 3. Key Mechanisms and Concepts

**Summary of the Curation module**

- `GraphCurationToken` - The GraphCurationToken smart contract is an ERC20 compliant token used to represent shares in curation pools to reward Curators for signaling subgraphs.
- `Curation` - Allows curators to signal subgraphs that might be relevant to Indexers.
- `BancorFormula` - Bonding curve used by the _Curation_ contract to distribute Graph Curation Shares (GCS) to Curators of a signaled subgraph.

**Contract**

- [Curation]
- [GraphCurationToken](https://hackmd.io/_TEMf3PxRpO3xA1KZgNefg)
- [BancorFormula](https://github.com/graphprotocol/contracts/blob/dev/contracts/bancor/BancorFormula.sol)

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## BancorFormula

Is the bonding curve used by the _Curation_ contract to distribute Graph Curation Shares (GCS) to Curators for signaling on a subgraph, and then used to exchange those shares for GRT when they return the signal.

### Key functionalities

#### calculatePurchaseReturn()

calculatePurchaseReturn(
    uint256 _supply,
    uint256 _reserveBalance,
    uint32 _reserveRatio,
    uint256 _depositAmount
)

Given a token supply, reserve balance, ratio and a deposit amount (in the reserve token), calculates the return for a given conversion (in the main token).

##### Formula:

$$
Return = \_supply * (\frac{1 + \_depositAmount}{\_reserveBalance} )^{(\frac{\_reserveRatio}{1000000} - 1)}
$$

##### Arguments

- `_supply` token total supply
- `_reserveBalance` total reserve balance
- `_reserveRatio` reserve ratio, represented in ppm (i.e. 1-1000000)
- `_depositAmount` deposit amount, in reserve token

#### calculateSaleReturn()

calculateSaleReturn(
    uint256 _supply,
    uint256 _reserveBalance,
    uint32 _reserveRatio,
    uint256 _sellAmount
)

Given a token supply, reserve balance, ratio and a sell amount (in the main token), calculates the return for a given conversion (in the reserve token)

##### Formula:
$$
Return = \_reserveBalance * (1 - (\frac{1 - \_sellAmount}{\_supply}) ^{ (\frac{1000000}{\_reserveRatio})})
$$
##### Arguments
- `_supply` token total supply
- `_reserveBalance` total reserve
- `_reserveRatio` constant reserve Ratio, represented in ppm, 1-1000000
- `_sellAmount` sell amount, in the token itself