curve LP oracle overview

doc/dev/oracles/CurveLPOracle.md

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+# CurveLPOracle Smart Contract Technical Overview
+
+## Contract Overview
+`CurveLPOracle` is a smart contract designed to provide USD pricing for Curve Finance liquidity pool (LP) tokens. It interacts with various Curve and Chainlink interfaces to achieve this.
+
+## Key Features
+
+### 1. Interfaces and Libraries
+- Implements `IOracleUsd` for USD pricing functionality.
+- Uses `SafeMath` library for safe mathematical operations.
+- Interacts with various interfaces including `ERC20Like`, `ICurveProvider`, `ICurveRegistry`, `ICurvePool`, and `IOracleRegistry`.
+
+### 2. State Variables
+- `curveProvider`: Immutable address of the Curve Provider contract.
+- `oracleRegistry`: Immutable address of the OracleRegistry contract.
+- `Q112`: A constant for Q112 encoding, representing a fixed-point number with 112 fractional bits.
+- `PRECISION`: A constant representing the precision level (1e18) used in calculations.
+
+### 3. Constructor
+Initializes the contract with the addresses of the Curve Provider and OracleRegistry contracts.
+
+### 4. Functions
+- `assetToUsd`: Main function of the contract. It takes a Curve LP token address and an amount, returning its USD price in Q112-encoded format. The function performs several checks and calculations:
+  - Validates that the input amount is non-zero.
+  - Retrieves the Curve pool associated with the LP token.
+  - Checks that the LP token has standard 18 decimals.
+  - Determines the number of coins in the Curve pool.
+  - Iterates through each coin in the Curve pool to find the minimum USD price using registered oracles.
+  - Calculates the USD price of the LP token based on the virtual price of the Curve pool and the minimum coin price.
+
+### 5. Error Handling and Validation
+- Ensures the Curve pool address for the LP token is valid.
+- Validates that the LP token adheres to 18 decimals standard.
+- Confirms that the coins count in the Curve pool is non-zero.
+- Checks for the existence of a registered oracle for each coin in the Curve pool.
+
+### 6. External Dependencies
+- Depends on external Curve and Chainlink contracts for fetching pool information, coin details, and USD pricing.
+- Utilizes OracleRegistry for determining the appropriate oracle for each coin in a Curve pool.
+
+## Conclusion
+`CurveLPOracle` is a specialized oracle contract for determining the USD price of Curve LP tokens. It leverages Curve's pool mechanics and integrates with Chainlink oracles, ensuring accurate and up-to-date pricing for assets within Curve liquidity pools.