use bls::verify_proof_of_possession;
use types::{ValidatorRecord, Deposit, ValidatorStatus, BeaconState};

/// The size of a validators deposit in GWei.
pub const DEPOSIT_GWEI: u64 = 32_000_000_000;

/// Inducts validators into a `CrystallizedState`.
pub struct ValidatorInductor {
    pub current_slot: u64,
    pub shard_count: u16,
    beacon_state: BeaconState,
    empty_validator_start: usize,
}

#[derive(Debug, PartialEq, Clone)]
pub enum ValidatorInductionError {
    InvalidShard,
    InvaidProofOfPossession,
}

impl ValidatorInductor {
    pub fn new(current_slot: u64, shard_count: u16, beacon_state: BeaconState) -> Self {
        Self {
            current_slot,
            shard_count,
            beacon_state,
            empty_validator_start: 0,
        }
    }

    /// Attempt to induct a validator into the CrystallizedState.
    ///
    /// Returns an error if the registration is invalid, otherwise returns the index of the
    /// validator in `CrystallizedState.validators`.
    pub fn induct(
        &mut self,
        deposit: &Deposit,
        status: ValidatorStatus,
    ) -> Result<usize, ValidatorInductionError> {
        let v = self.process_registration(deposit, status)?;
        Ok(self.add_validator(v))
    }

    /// Verify a `ValidatorRegistration` and return a `ValidatorRecord` if valid.
    fn process_deposit(
        &self,
        deposit: &Deposit,
        status: ValidatorStatus,
    ) -> Result<ValidatorRecord, ValidatorInductionError> {
        let deposit_input = &deposit.deposit_data.deposit_input;
        /*
         * Ensure withdrawal shard is not too high.
         */
        /* 
        if r.withdrawal_shard > self.shard_count {
            return Err(ValidatorInductionError::InvalidShard);
        }
        */

        /*
         * Prove validator has knowledge of their secret key.
         */
        if !verify_proof_of_possession(&deposit_input.proof_of_possession, &deposit_input.pubkey) {
            return Err(ValidatorInductionError::InvaidProofOfPossession);
        }

        Ok(ValidatorRecord {
            pubkey: deposit_input.pubkey.clone(),
            withdrawal_credentials: deposit_input.withdrawal_credentials,
            randao_commitment: deposit_input.randao_commitment,
            // TODO: revisit this
            randao_layers: 0,
            balance: DEPOSIT_GWEI,
            status: status,
            latest_status_change_slot: self.beacon_state.validator_registry_latest_change_slot,
            exit_count: self.beacon_state.validator_registry_exit_count
        })
    }

    /// Returns the index of the first `ValidatorRecord` in the `CrystallizedState` where
    /// `validator.status == Withdrawn`. If no such record exists, `None` is returned.
    fn first_withdrawn_validator(&mut self) -> Option<usize> {
        let validators = self.beacon_state.validator_registry;
        for i in self.empty_validator_start..validators.len() {
            if validators[i].status == ValidatorStatus::Withdrawn {
                self.empty_validator_start = i + 1;
                return Some(i);
            }
        }
        None
    }

    /// Adds a `ValidatorRecord` to the `CrystallizedState` by replacing first validator where
    /// `validator.status == Withdraw`. If no such withdrawn validator exists, adds the new
    /// validator to the end of the list.
    fn add_validator(&mut self, v: ValidatorRecord) -> usize {
        match self.first_withdrawn_validator() {
            Some(i) => {
                self.beacon_state.validator_registry[i] = v;
                i
            }
            None => {
                self.beacon_state.validator_registry.push(v);
                self.beacon_state.validator_registry.len() - 1
            }
        }
    }

    pub fn to_vec(self) -> Vec<ValidatorRecord> {
        self.beacon_state.validator_registry
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use bls::{Keypair, Signature};
    use hashing::proof_of_possession_hash;
    use types::{Address, Hash256};

    /*
    fn registration_equals_record(reg: &ValidatorRegistration, rec: &ValidatorRecord) -> bool {
        (reg.pubkey == rec.pubkey)
            & (reg.withdrawal_shard == rec.withdrawal_shard)
            & (reg.withdrawal_address == rec.withdrawal_address)
            & (reg.randao_commitment == rec.randao_commitment)
            & (verify_proof_of_possession(&reg.proof_of_possession, &rec.pubkey))
    }
    */

    /// Generate a proof of possession for some keypair.
    fn get_proof_of_possession(kp: &Keypair) -> Signature {
        let pop_message = proof_of_possession_hash(&kp.pk.as_bytes());
        Signature::new_hashed(&pop_message, &kp.sk)
    }

    /// Generate a basic working ValidatorRegistration for use in tests.
    fn get_registration() -> ValidatorRegistration {
        let kp = Keypair::random();
        ValidatorRegistration {
            pubkey: kp.pk.clone(),
            withdrawal_shard: 0,
            withdrawal_address: Address::zero(),
            randao_commitment: Hash256::zero(),
            proof_of_possession: get_proof_of_possession(&kp),
        }
    }

    #[test]
    fn test_validator_inductor_valid_empty_validators() {
        let validators = vec![];

        let r = get_registration();

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();

        assert_eq!(result.unwrap(), 0);
        //assert!(registration_equals_record(&r, &validators[0]));
        assert_eq!(validators.len(), 1);
    }

    #[test]
    fn test_validator_inductor_status() {
        let validators = vec![];

        let r = get_registration();

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let _ = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let _ = inductor.induct(&r, ValidatorStatus::Active);
        let validators = inductor.to_vec();

        assert!(validators[0].status == ValidatorStatus::PendingActivation);
        assert!(validators[1].status == ValidatorStatus::Active);
        assert_eq!(validators.len(), 2);
    }

    #[test]
    fn test_validator_inductor_valid_all_active_validators() {
        let mut validators = vec![];
        for _ in 0..5 {
            let (mut v, _) = ValidatorRecord::zero_with_thread_rand_keypair();
            v.status = ValidatorStatus::Active;
            validators.push(v);
        }

        let r = get_registration();

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();

        assert_eq!(result.unwrap(), 5);
        //assert!(registration_equals_record(&r, &validators[5]));
        assert_eq!(validators.len(), 6);
    }

    #[test]
    fn test_validator_inductor_valid_all_second_validator_withdrawn() {
        let mut validators = vec![];
        let (mut v, _) = ValidatorRecord::zero_with_thread_rand_keypair();
        v.status = ValidatorStatus::Active;
        validators.push(v);
        for _ in 0..4 {
            let (mut v, _) = ValidatorRecord::zero_with_thread_rand_keypair();
            v.status = ValidatorStatus::Withdrawn;
            validators.push(v);
        }

        let r = get_registration();

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();

        assert_eq!(result.unwrap(), 1);
        //assert!(registration_equals_record(&r, &validators[1]));
        assert_eq!(validators.len(), 5);
    }

    #[test]
    fn test_validator_inductor_valid_all_withdrawn_validators() {
        let mut validators = vec![];
        for _ in 0..5 {
            let (mut v, _) = ValidatorRecord::zero_with_thread_rand_keypair();
            v.status = ValidatorStatus::Withdrawn;
            validators.push(v);
        }

        /*
         * Ensure the first validator gets the 0'th slot
         */
        let r = get_registration();
        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();
        assert_eq!(result.unwrap(), 0);
        //assert!(registration_equals_record(&r, &validators[0]));

        /*
         * Ensure the second validator gets the 1'st slot
         */
        let r_two = get_registration();
        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r_two, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();
        assert_eq!(result.unwrap(), 1);
        //assert!(registration_equals_record(&r_two, &validators[1]));
        assert_eq!(validators.len(), 5);
    }

    #[test]
    fn test_validator_inductor_shard_too_high() {
        let validators = vec![];

        let mut r = get_registration();
        r.withdrawal_shard = 1025;

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();

        assert_eq!(result, Err(ValidatorInductionError::InvalidShard));
        assert_eq!(validators.len(), 0);
    }

    #[test]
    fn test_validator_inductor_shard_proof_of_possession_failure() {
        let validators = vec![];

        let mut r = get_registration();
        let kp = Keypair::random();
        r.proof_of_possession = get_proof_of_possession(&kp);

        let mut inductor = ValidatorInductor::new(0, 1024, validators);
        let result = inductor.induct(&r, ValidatorStatus::PendingActivation);
        let validators = inductor.to_vec();

        assert_eq!(
            result,
            Err(ValidatorInductionError::InvaidProofOfPossession)
        );
        assert_eq!(validators.len(), 0);
    }
}