Contract DIARandomOracle(
    mut admin: Address,
    mut lastRound: U256
) extends DIAOracleBase(admin) implements IDIARandomOracle {

    mapping[U256, DIARandomValue] randomValues

    event OracleUpdate(
        round: U256,
        randomness: ByteVec,
        signature: ByteVec
    )

    const MaxSlot = 1000

    enum ErrorCodes {
        InvalidRound = 1
        RoundKeyNotExist = 2
        RoundIsExpired = 3
    }

    pub fn getLastRound() -> U256 {
        return lastRound
    }

    pub fn getRandomValue(realRound: U256) -> DIARandomValue {
        let roundKey = realRound % MaxSlot
        assert!(randomValues.contains!(roundKey), ErrorCodes.RoundKeyNotExist)

        let randomValue = randomValues[roundKey]
        assert!(randomValue.round == realRound, ErrorCodes.RoundIsExpired)
        return randomValue
    }

    @using(preapprovedAssets = true, updateFields = true)
    pub fn setRandomValue(value: DIARandomValue) -> () {
        checkAdmin(callerAddress!())
        assert!(value.round > lastRound, ErrorCodes.InvalidRound)
 
        let roundKey = value.round % MaxSlot
        lastRound = value.round

        if (randomValues.contains!(roundKey)) {
            randomValues[roundKey] = value
        } else {
            randomValues.insert!(admin, roundKey, value)
        }

        emit OracleUpdate(value.round, value.randomness, value.signature)
    }
}