Price Module Validator and API

[epiro-ps]

To support the storing of price data in a UTxO on-chain for usage as an oracle, we want to build out a validator that ensures the price data is valid and support an API for updating and reading it.

Acceptance Criteria

Price Module Validator

• The validator should have the following parameters
  • Admin public key
  • Oracle ID NFT Asset Class
  • The following configurations that will make testing and tuning the validator easier. The defaults are set to the requirements of the protocol.
  • Update Interval - the amount time that needs to pass for a price update is considered valid. Defaults to an hour.
  • Max Entries - the number of price entries in the datum. Defaults to 48.
• The validator will validate the following:
  • There is a previous price oracle UTxO being spent.
  • Note that initialization does not require spending an Oracle UTxO, hence why it's left out here.
  • Admin signed the transaction.
  • The previous price oracle UTxO contains the Oracle ID NFT.
  • The datum has a list of tuples containing USD Price of ADA and the POSIX timestamp of when the price was observed.
  • The length of the datum list does not exceed the Max Entries.
  • The timestamp of the latest two entries of the datum list are at least the Update Interval apart.
  • The new price list is a continuation of the old price list.
  • The Oracle ID NFT is being moved to the new Price Oracle UTxO.

Price Module Client API

The following action should be supported:

Initialization

Inputs:

• Admin public key
• Timestamp and price at timestamp
• Update Interval

Outputs:

• Oracle ID NFT Asset

Effects:

Submits a transaction performing the following

• Mints an Oracle NFT
• Applies the NFT Asset Class and admin public key to the parameterized Price Module Validator to compute the script address.
• Creates and submits a UTxO at the price oracle address that contains the following
  • The Oracle NFT
  • Datum with a single member list containing price and timestamp.
• Returns the Oracle NFT Asset Class

Update

Inputs:

• Admin public key
• Oracle ID NFT Asset Class
• Timestamp and price at timestamp
• Update Interval

Outputs:

• Data of a type communicating either success, failure (implying a critical error has occurred), or no update was needed.

Effects:

Submits a transaction performing the following

• Retrieves Oracle UTxO by the Oracle ID NFT Asset Class.
• Checks if the datum of UTxO has price data from the last hour
• If so
  • Apply the Oracle ID NFT Asset Class and admin public key to the parameterized Price Module Validator to compute the script and script address.
  • Creates and submits a UTxO at the price oracle address that contains the following
    • The Oracle NFT
    • Datum with the the latest price and timestamp add to a list of prices no larger than 48 elements.

Get datum by Oracle ID NFT

Inputs:

• Oracle ID NFT Asset Class

Outputs:

• Either the price or an error.

Effects:

• Retrieves Oracle UTxO by the Oracle ID NFT Asset Class.

Tests

The following should give a rough idea but we can definitely improve the factoring here:

• When I initialize the oracle with a specific price and timestamp, I see that price and timestamp in the resulting Oracle ID tagged UTxO.
• When I attempt to update the price within the Update Interval, validation fails.
• When I attempt to update the price as a non-admin, validation fails.
• When I attempt to update the price where the timestamp exceeds the Update Interval, the price is reflected in the latest Oracle UTxO.
• When I attempt to submit an update where the length of datum price list exceeds the Max Entries, validation fails
• When I attempt to submit an update where the timestamps of the prices in the datum are not the Update Interval apart, validation fails.