use crate::common::genesis_deposits;
use eth2_hashing::hash;
use rayon::prelude::*;
use ssz::Encode;
use state_processing::initialize_beacon_state_from_eth1;
use std::time::SystemTime;
use tree_hash::SignedRoot;
use types::{
    BeaconState, ChainSpec, DepositData, Domain, EthSpec, Fork, Hash256, Keypair, PublicKey,
    Signature,
};

/// Builds a genesis state as defined by the Eth2 interop procedure (see below).
///
/// Reference:
/// https://github.com/ethereum/eth2.0-pm/tree/6e41fcf383ebeb5125938850d8e9b4e9888389b4/interop/mocked_start
pub fn interop_genesis_state<T: EthSpec>(
    keypairs: &[Keypair],
    genesis_time: u64,
    spec: &ChainSpec,
) -> Result<BeaconState<T>, String> {
    let eth1_block_hash = Hash256::from_slice(&[0x42; 32]);
    let eth1_timestamp = 2_u64.pow(40);
    let amount = spec.max_effective_balance;

    let withdrawal_credentials = |pubkey: &PublicKey| {
        let mut credentials = hash(&pubkey.as_ssz_bytes());
        credentials[0] = spec.bls_withdrawal_prefix_byte;
        Hash256::from_slice(&credentials)
    };

    let datas = keypairs
        .into_par_iter()
        .map(|keypair| {
            let mut data = DepositData {
                withdrawal_credentials: withdrawal_credentials(&keypair.pk),
                pubkey: keypair.pk.clone().into(),
                amount,
                signature: Signature::empty_signature().into(),
            };

            let domain = spec.get_domain(
                spec.genesis_slot.epoch(T::slots_per_epoch()),
                Domain::Deposit,
                &Fork::default(),
            );
            data.signature = Signature::new(&data.signed_root()[..], domain, &keypair.sk).into();

            data
        })
        .collect::<Vec<_>>();

    let mut state = initialize_beacon_state_from_eth1(
        eth1_block_hash,
        eth1_timestamp,
        genesis_deposits(datas, spec)?,
        spec,
    )
    .map_err(|e| format!("Unable to initialize genesis state: {:?}", e))?;

    state.genesis_time = genesis_time;

    // Invalid all the caches after all the manual state surgery.
    state.drop_all_caches();

    Ok(state)
}

/// Returns the system time, mod 30 minutes.
///
/// Used for easily creating testnets.
pub fn recent_genesis_time(minutes: u64) -> u64 {
    let now = SystemTime::now()
        .duration_since(SystemTime::UNIX_EPOCH)
        .unwrap()
        .as_secs();
    let secs_after_last_period = now.checked_rem(minutes * 60).unwrap_or(0);
    now - secs_after_last_period
}

#[cfg(test)]
mod test {
    use super::*;
    use types::{test_utils::generate_deterministic_keypairs, EthSpec, MinimalEthSpec};

    type TestEthSpec = MinimalEthSpec;

    #[test]
    fn interop_state() {
        let validator_count = 16;
        let genesis_time = 42;
        let spec = &TestEthSpec::default_spec();

        let keypairs = generate_deterministic_keypairs(validator_count);

        let state = interop_genesis_state::<TestEthSpec>(&keypairs, genesis_time, spec)
            .expect("should build state");

        assert_eq!(
            state.eth1_data.block_hash,
            Hash256::from_slice(&[0x42; 32]),
            "eth1 block hash should be co-ordinated junk"
        );

        assert_eq!(
            state.genesis_time, genesis_time,
            "genesis time should be as specified"
        );

        for b in &state.balances {
            assert_eq!(
                *b, spec.max_effective_balance,
                "validator balances should be max effective balance"
            );
        }

        for v in &state.validators {
            let creds = v.withdrawal_credentials.as_bytes();
            assert_eq!(
                creds[0], spec.bls_withdrawal_prefix_byte,
                "first byte of withdrawal creds should be bls prefix"
            );
            assert_eq!(
                &creds[1..],
                &hash(&v.pubkey.as_ssz_bytes())[1..],
                "rest of withdrawal creds should be pubkey hash"
            )
        }

        assert_eq!(
            state.balances.len(),
            validator_count,
            "validator balances len should be correct"
        );

        assert_eq!(
            state.validators.len(),
            validator_count,
            "validator count should be correct"
        );
    }
}