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//! The `plan` module provides a domain-specific language for payment plans. Users create Budget objects that
//! are given to an interpreter. The interpreter listens for `Witness` transactions,
//! which it uses to reduce the payment plan. When the plan is reduced to a
//! `Payment`, the payment is executed.
use chrono::prelude::*;
use signature::PublicKey;
/// The types of events a payment plan can process.
#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
pub enum Witness {
/// The current time.
Timestamp(DateTime<Utc>),
/// A siganture from PublicKey.
Signature(PublicKey),
}
/// Some amount of tokens that should be sent to the `to` `PublicKey`.
#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
pub struct Payment {
/// Amount to be paid.
pub tokens: i64,
/// The `PublicKey` that `tokens` should be paid to.
pub to: PublicKey,
}
/// Interface to smart contracts.
pub trait PaymentPlan {
/// Return Payment if the payment plan requires no additional Witnesses.
fn final_payment(&self) -> Option<Payment>;
/// Return true if the plan spends exactly `spendable_tokens`.
fn verify(&self, spendable_tokens: i64) -> bool;
/// Apply a witness to the payment plan to see if the plan can be reduced.
/// If so, modify the plan in-place.
fn apply_witness(&mut self, witness: &Witness);
}