You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: fin_plan_program.rs
    path of file: ./repos/hypercube/src
    
    the code of the file until where you have to start completion: //! fin_plan program
use bincode::{self, deserialize, serialize_into, serialized_size};
use fin_plan::FinPlan;
use fin_plan_instruction::Instruction;
use chrono::prelude::{DateTime, Utc};
use trx_out::Witness;
use xpz_program_interface::account::Account;
use xpz_program_interface::pubkey::Pubkey;
use std::io;
use transaction::Transaction;

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
pub enum FinPlanError {
    InsufficientFunds(Pubkey),
    ContractAlreadyExists(Pubkey),
    ContractNotPending(Pubkey),
    SourceIsPendingContract(Pubkey),
    UninitializedContract(Pubkey),
    NegativeTokens,
    DestinationMissing(Pubkey),
    FailedWitness,
    UserdataTooSmall,
    UserdataDeserializeFailure,
}

#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq)]
pub struct FinPlanState {
    pub initialized: bool,
    pub pending_fin_plan: Option<FinPlan>,
}

pub const BUDGET_PROGRAM_ID: [u8; 32] = [
    1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
];
impl FinPlanState {
    fn is_pending(&self) -> bool {
        self.pending_fin_plan != None
    }
    pub fn id() -> Pubkey {
        Pubkey::new(&BUDGET_PROGRAM_ID)
    }
    pub fn check_id(program_id: &Pubkey) -> bool {
        program_id.as_ref() == BUDGET_PROGRAM_ID
    }

    /// Process a Witness Signature. Any payment plans waiting on this signature
    /// will progress one step.
    fn apply_signature(
        &mut self,
        keys: &[Pubkey],
        account: &mut [Account],
    ) -> Result<(), FinPlanError> {
        let mut final_payment = None;
        if let Some(ref mut fin_plan) = self.pending_fin_plan {
            fin_plan.apply_witness(&Witness::Signature, &keys[0]);
            final_
    
    fn test_transfer_on_date() {
        let mut accounts = vec![
            Account::new(1, 0, FinPlanState::id()),
            Account::new(0, 512, FinPlanState::id()),
            Account::new(0, 0, FinPlanState::id()),
        ];
        let from_account = 0;
        let contract_account = 1;
        let to_account = 2;
        let from = Keypair::new();
        let contract = Keypair::new();
        let to = Keypair::new();
        let rando = Keypair::new();
        let dt = Utc::now();
        let tx = Transaction::fin_plan_new_on_date(
            &from,
            to.pubkey(),
            contract.pubkey(),
            dt,
            from.pubkey(),
            None,
            1,
            Hash::default(),
        );
        FinPlanState::process_transaction(&tx, &mut accounts).unwrap();
        assert_eq!(accounts[from_account].tokens, 0);
        assert_eq!(accounts[contract_account].tokens, 1);
        let state = FinPlanState::deserialize(&accounts[contract_account].userdata).unwrap();
        assert!(state.is_pending());

        // Attack! Try to payout to a rando key
        let tx = Transaction::fin_plan_new_timestamp(
            &from,
            contract.pubkey(),
            rando.pubkey(),
            dt,
            Hash::default(),
        );
        assert_eq!(
            FinPlanState::process_transaction(&tx, &mut accounts),
            Err(FinPlanError::DestinationMissing(to.pubkey()))
        );
        assert_eq!(accounts[from_account].tokens, 0);
        assert_eq!(accounts[contract_account].tokens, 1);
        assert_eq!(accounts[to_account].tokens, 0);

        let state = FinPlanState::deserialize(&accounts[contract_account].userdata).unwrap();
        assert!(state.is_pending());

        // Now, acknowledge the time in the condition occurred and
        // that pubkey's funds are now available.
        let tx = Transaction::fin_plan_new_timestamp(
            &from,
            contract.pubkey(),
            to.pubkey(),
            dt,
            Hash::default(),
        );
        FinPlanState::process_transaction(&tx, &mut accounts).unwrap();
        assert_eq!(accounts[from_account].tokens, 0);
        assert_eq!(accounts[contract_account].tokens, 0);
        assert_eq!(accounts[to_account].tokens, 1);

        let state = FinPlanState::deserialize(&accounts[contract_account].userdata).unwrap();
        assert!(!state.is_pending());

        // try to replay the timestamp contract
        assert_eq!(
            FinPlanState::process_transaction(&tx, &mut accounts),
            Err(FinPlanError::ContractNotPending(contract.pubkey()))
        );
        assert_eq!(accounts[from_account].tokens, 0);
        assert_eq!(accounts[contract_account].tokens, 0);
        assert_eq!(accounts[to_account].tokens, 1);
    }