# Price aggregator

## Overview

The price-aggregator smart contract keeps track of the price between multiple pairs of tokens.
Compared to the other chainlink contracts, it is a simplified and easier to use version.

## Deployment

Arguments:
- `staking_token` - the token used for staking and slashing
- `staking_amount` - the minimum staked amount required for a used to be considered a board member
- `slash_amount` - the amount to be slashed from a board member on a successful slash vote
- `slash_quorum` - the minimum number of board members required for a vote to be considered successful
- `oracles` - the list of addresses which are allowed to submit price feed updates
- `submission_count` - the minimum number of submissions from different oracles which trigger an update of the price feed

## Configuring the number of decimals

The number of decimals for a given token pair can be set by calling `setPairDecimals(from, to, decimals)`. Notes:
- only the owner can configure the number of decimals
- the contract must be paused first
- this method also clears the submissions accumulated so far
- no submissions will be accepted for any given pair unless the number of decimals is configured first
- every oracle must change its configuration to provide submissions with the new number of decimals, as any mismatch will be considered a configuration error and the submission will be rejected

## Submitting price feed updates

An oracle can submit a price feed update using one of the endpoints:
- `submit` - submit a single price feed as 5 arguments (`from`, `to`, `submission_timestamp`, `price` and `decimals`).
- `submitBatch` - submit multiple price feeds simultaneously. The number of arguments must be a multiple of 5.

Note: the decimals argument must match the value returned by `getPairDecimals` for that specific pair, otherwise the submission will be rejected.

## Rounds

Price feeds from multiple oracles are collected. When a certain threshold number of submissions has been reached (given by `submission_count`), a new round is created.
The price feed recorded in the round is the median value out of all submissions made.

## Querying the price feeds

Endpoints:
- `latestRoundData` takes no arguments and returns all the latest price feeds.
- `latestPriceFeed` takes a filter (as the `from` and `to` token identifiers) and returns a single price feed. The transaction fails if there is no price feed for the given filter.
- `latestPriceFeedOptional` behaves like `latestPriceFeed` but it returns an option so that the caller can handle the lack of a price feed.

A price feed contains:
- `round_id` - the ID of the current round (not related to the blockchain round ID)
- `from` - the first token
- `to` - the second token
- `price` - the price between the two tokens
- `decimals` - the number of decimals for the price