entropy-api 0.1.6

API for interacting with the Entropy program
Documentation 
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use steel::*;

use super::EntropyAccount;

#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq, Pod, Zeroable)]
pub struct Var {
    /// The creator of the variable.
    pub authority: Pubkey,

    /// The id of the variable.
    pub id: u64,

    /// The provider of the entropy data.
    pub provider: Pubkey,

    /// The commit provided by Entropy provider.
    pub commit: [u8; 32],

    /// The revealed seed.
    pub seed: [u8; 32],

    /// The slot hash
    pub slot_hash: [u8; 32],

    /// The current value of the variable.
    pub value: [u8; 32],

    /// The number of random variables remaining to be sampled.
    pub samples: u64,

    /// Whether or not the Entropy provider should automatically sample the slot hash.
    pub is_auto: u64,

    /// The slot at which the variable was opened.
    pub start_at: u64,

    /// The slot at which the variable should sample the slothash.
    pub end_at: u64,
}

impl Var {
    pub fn finalize(&mut self, seed: [u8; 32]) -> ProgramResult {
        // Silent return.
        if self.seed != [0; 32] {
            return Ok(());
        }

        // Validate the seed.
        if !self.is_valid(seed) {
            return Err(trace("Invalid seed", ProgramError::InvalidInstructionData));
        }

        // Record the revealed seed.
        self.seed = seed;

        // Finalize the value.
        self.value = solana_program::keccak::hashv(&[
            &self.slot_hash,
            &self.seed,
            &self.samples.to_le_bytes(),
        ])
        .to_bytes();

        Ok(())
    }

    pub fn is_valid(&self, seed: [u8; 32]) -> bool {
        if self.slot_hash == [0; 32] {
            return false;
        }
        if self.value != [0; 32] {
            return false;
        }
        if self.samples == 0 {
            return false;
        }
        let expected_commit = solana_program::keccak::hash(&seed).to_bytes();
        expected_commit == self.commit
    }
}

account!(EntropyAccount, Var);