split/src/expense.rs

// SPDX-FileCopyrightText: 2023 Aravinth Manivannan <realaravinth@batsense.net>
//
// SPDX-License-Identifier: AGPL-3.0-or-later

use std::rc::Rc;

use rust_decimal::prelude::*;
use rust_decimal_macros::dec;

use crate::actor::*;
use crate::purchase::*;
use crate::strategy::*;

#[derive(Clone)]
pub struct Split {
    pub(crate) purchase: Rc<dyn Purchasable>,
    pub(crate) split_strategy: SplitStrategy,
    pub(crate) parties: Vec<Rc<dyn Actor>>,
}

impl Split {
    pub fn new(
        purchase: Rc<dyn Purchasable>,
        split_strategy: SplitStrategy,
        parties: Vec<Rc<dyn Actor>>,
    ) -> Self {
        Self {
            split_strategy,
            parties,
            purchase,
        }
    }

    pub fn money_owed(&self) -> ShareHashMap {
        match &self.split_strategy {
            SplitStrategy::Unequal(shares) => {
                let mut s = shares.clone();
                let payer = self.purchase.paid_by();
                if let Some((_, money)) = s.get_mut(payer.name()) {
                    *money = dec!(0.0);
                }
                s
            }
            SplitStrategy::Equal => {
                let mut shares = ShareHashMap::default();
                let cost = self.purchase.cost();
                let total_parties = Decimal::new(self.parties.len() as i64, 0);
                for actor in self.parties.iter() {
                    if *actor == self.purchase.paid_by() {
                        shares.insert(actor.name().to_owned(), (actor.clone(), dec!(0.00)));
                    } else {
                        shares.insert(
                            actor.name().to_owned(),
                            (actor.clone(), cost / total_parties),
                        );
                    }
                }

                shares
            }
            SplitStrategy::Shares(c) => {
                let mut shares = ShareHashMap::default();
                let cost = self.purchase.cost();
                for (actor_name, (actor, share)) in c.iter() {
                    //if actor.name() == split.purchase.paid_by().name() {
                    if *actor == self.purchase.paid_by() {
                        shares.insert(actor_name.clone(), (actor.clone(), dec!(0.00)));
                    } else {
                        shares.insert(actor_name.clone(), (actor.clone(), cost * share));
                    }
                }
                shares
            }
        }
    }

    pub fn get(&mut self, actor: Rc<dyn Actor>) -> Option<Decimal> {
        unimplemented!();
        //        if let Some((_actor, cost)) = self.shares.get(actor.name()) {
        //            Some(*cost)
        //        } else {
        //            None
        //        }
    }

    pub fn validate(&self) -> bool {
        self.split_strategy.validate(self.purchase.as_ref())
    }
}

//impl Actor for Person {
//    fn spends<P: Purchasable>(&self, i: &I);
//    fn owes<T: Actor>(&self, amount: usize);
//}

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

    #[test]
    fn split_works() {
        let person1: Rc<dyn Actor> = Rc::new(Person::new("person1".into(), Uuid::new_v4()));
        let person2: Rc<dyn Actor> = Rc::new(Person::new("person2".into(), Uuid::new_v4()));
        let person3: Rc<dyn Actor> = Rc::new(Person::new("person3".into(), Uuid::new_v4()));
        let person4: Rc<dyn Actor> = Rc::new(Person::new("person4".into(), Uuid::new_v4()));

        let item = Item::new("test item".into(), dec!(240.00), person1.clone());
        let actors = vec![
            person1.clone(),
            person2.clone(),
            person3.clone(),
            person4.clone(),
        ];

        // equal split
        let strategy = SplitStrategy::Equal;

        let mut split = Split::new(Rc::new(item), strategy, actors);
        assert!(split.validate());
        let dues = split.money_owed();
        for (_actor_name, (actor, due)) in dues.iter() {
            if split.purchase.paid_by().name() == actor.name() {
                assert_eq!(*due, dec!(0.00));
            } else {
                assert_eq!(
                    *due,
                    split.purchase.cost() / Decimal::new(split.parties.len() as i64, 0)
                );
            }
        }

        // share split
        let mut shares = ShareHashMap::default();
        shares.insert(person1.name().to_owned(), (person1.clone(), dec!(0.3)));
        shares.insert(person2.name().to_owned(), (person2.clone(), dec!(0.4)));
        shares.insert(person3.name().to_owned(), (person3.clone(), dec!(0.2)));
        shares.insert(person4.name().to_owned(), (person4.clone(), dec!(0.1)));
        let strategy = SplitStrategy::Shares(shares.clone());

        split.split_strategy = strategy;
        assert!(split.validate());

        let dues = split.money_owed();
        for (actor_name, (actor, due)) in dues.iter() {
            println!("Testing for actor: {actor_name} with due: {due}");
            if split.purchase.paid_by().name() == actor.name() {
                assert_eq!(*due, dec!(0.00));
            } else {
                let (_, share) = shares.get(actor_name).unwrap();
                assert_eq!(*due, split.purchase.cost() * *share);
            }
        }

        // Unequal split
        let mut shares = ShareHashMap::default();
        shares.insert(
            person1.name().to_owned(),
            (person1.clone(), dec!(0.3) * split.purchase.cost()),
        );
        shares.insert(
            person2.name().to_owned(),
            (person2.clone(), dec!(0.4) * split.purchase.cost()),
        );
        shares.insert(
            person3.name().to_owned(),
            (person3.clone(), dec!(0.2) * split.purchase.cost()),
        );
        shares.insert(
            person4.name().to_owned(),
            (person4.clone(), dec!(0.1) * split.purchase.cost()),
        );
        let strategy = SplitStrategy::Unequal(shares);
        split.split_strategy = strategy;
        assert!(split.validate());
    }
}