/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2023 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use darkfi_money_contract::{
    error::MoneyError,
    model::{ConsensusUnstakeParamsV1, ConsensusUnstakeUpdateV1, MoneyUnstakeParamsV1},
    MoneyFunction, CONSENSUS_CONTRACT_NULLIFIERS_TREE, CONSENSUS_CONTRACT_UNSTAKED_COIN_ROOTS_TREE,
    CONSENSUS_CONTRACT_ZKAS_BURN_NS_V1,
};
use darkfi_sdk::{
    crypto::{pasta_prelude::*, ContractId, MONEY_CONTRACT_ID},
    db::{db_contains_key, db_lookup, db_set},
    error::{ContractError, ContractResult},
    msg,
    pasta::pallas,
    util::get_verifying_slot_epoch,
    ContractCall,
};
use darkfi_serial::{deserialize, serialize, Encodable, WriteExt};

use crate::{error::ConsensusError, model::GRACE_PERIOD, ConsensusFunction};

/// `get_metadata` function for `Consensus::UnstakeV1`
pub(crate) fn consensus_unstake_get_metadata_v1(
    _cid: ContractId,
    call_idx: u32,
    calls: Vec<ContractCall>,
) -> Result<Vec<u8>, ContractError> {
    let self_ = &calls[call_idx as usize];
    let params: ConsensusUnstakeParamsV1 = deserialize(&self_.data[1..])?;
    let input = &params.input;

    // Public inputs for the ZK proofs we have to verify
    let mut zk_public_inputs: Vec<(String, Vec<pallas::Base>)> = vec![];
    // Public keys for the transaction signatures we have to verify
    let signature_pubkeys = vec![input.signature_public];

    // Grab the pedersen commitment and signature pubkey coordinates from the
    // anonymous input
    let value_coords = input.value_commit.to_affine().coordinates().unwrap();
    let (sig_x, sig_y) = input.signature_public.xy();

    // It is very important that these are in the same order as the
    // `constrain_instance` calls in the zkas code.
    // Otherwise verification will fail.
    zk_public_inputs.push((
        CONSENSUS_CONTRACT_ZKAS_BURN_NS_V1.to_string(),
        vec![
            input.nullifier.inner(),
            pallas::Base::from(input.epoch),
            sig_x,
            sig_y,
            input.merkle_root.inner(),
            *value_coords.x(),
            *value_coords.y(),
        ],
    ));

    // Serialize everything gathered and return it
    let mut metadata = vec![];
    zk_public_inputs.encode(&mut metadata)?;
    signature_pubkeys.encode(&mut metadata)?;
    Ok(metadata)
}

/// `process_instruction` function for `Consensus::UnstakeV1`
pub(crate) fn consensus_unstake_process_instruction_v1(
    cid: ContractId,
    call_idx: u32,
    calls: Vec<ContractCall>,
) -> Result<Vec<u8>, ContractError> {
    let self_ = &calls[call_idx as usize];
    let params: ConsensusUnstakeParamsV1 = deserialize(&self_.data[1..])?;
    let input = &params.input;

    // Access the necessary databases where there is information to
    // validate this state transition.
    let nullifiers_db = db_lookup(cid, CONSENSUS_CONTRACT_NULLIFIERS_TREE)?;
    let unstaked_coin_roots_db = db_lookup(cid, CONSENSUS_CONTRACT_UNSTAKED_COIN_ROOTS_TREE)?;

    // ===================================
    // Perform the actual state transition
    // ===================================

    // Check next call is money contract
    let next_call_idx = call_idx + 1;
    if next_call_idx >= calls.len() as u32 {
        msg!("[ConsensusUnstakeV1] Error: next_call_idx out of bounds");
        return Err(MoneyError::CallIdxOutOfBounds.into())
    }

    let next = &calls[next_call_idx as usize];
    if next.contract_id.inner() != MONEY_CONTRACT_ID.inner() {
        msg!("[ConsensusUnstakeV1] Error: Next contract call is not money contract");
        return Err(MoneyError::UnstakeNextCallNotMoneyContract.into())
    }

    // Verify next call corresponds to Money::UnstakeV1
    if next.data[0] != MoneyFunction::UnstakeV1 as u8 {
        msg!("[ConsensusUnstakeV1] Error: Next call function mismatch");
        return Err(MoneyError::NextCallFunctionMismatch.into())
    }

    // Verify next call input is the same as this calls input
    let next_params: MoneyUnstakeParamsV1 = deserialize(&next.data[1..])?;
    if input != &next_params.input {
        msg!("[ConsensusUnstakeV1] Error: Next call input mismatch");
        return Err(MoneyError::NextCallInputMismatch.into())
    }

    msg!("[ConsensusUnstakeV1] Validating anonymous input");
    // The coin has passed through the grace period and is allowed to get unstaked.
    if get_verifying_slot_epoch() - input.epoch <= GRACE_PERIOD {
        msg!("[ConsensusUnstakeV1] Error: Coin is not allowed to get unstaked yet");
        return Err(ConsensusError::CoinStillInGracePeriod.into())
    }

    // The Merkle root is used to know whether this is an unstaked coin that
    // existed in a previous state.
    if !db_contains_key(unstaked_coin_roots_db, &serialize(&input.merkle_root))? {
        msg!("[ConsensusUnstakeV1] Error: Merkle root not found in previous state");
        return Err(MoneyError::TransferMerkleRootNotFound.into())
    }

    // The nullifiers should not already exist. It is the double-spend protection.
    if db_contains_key(nullifiers_db, &serialize(&input.nullifier))? {
        msg!("[ConsensusUnstakeV1] Error: Duplicate nullifier found");
        return Err(MoneyError::DuplicateNullifier.into())
    }

    // At this point the state transition has passed, so we create a state update
    let update = ConsensusUnstakeUpdateV1 { nullifier: input.nullifier };
    let mut update_data = vec![];
    update_data.write_u8(ConsensusFunction::UnstakeV1 as u8)?;
    update.encode(&mut update_data)?;
    Ok(update_data)
}

/// `process_update` function for `Consensus::UnstakeV1`
pub(crate) fn consensus_unstake_process_update_v1(
    cid: ContractId,
    update: ConsensusUnstakeUpdateV1,
) -> ContractResult {
    // Grab all necessary db handles for where we want to write
    let nullifiers_db = db_lookup(cid, CONSENSUS_CONTRACT_NULLIFIERS_TREE)?;

    msg!("[ConsensusUnstakeV1] Adding new nullifier to the set");
    db_set(nullifiers_db, &serialize(&update.nullifier), &[])?;

    Ok(())
}
