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use std::ops::{Add, Sub};

use candid::CandidType;
use ex3_serde::bincode;
use ic_stable_structures::{storable::Bound, Storable};
use serde::{Deserialize, Serialize};

use crate::{AssetAmount, CandidAssetAmount};

#[derive(Deserialize, Serialize, Debug, Clone, PartialEq, Eq)]
pub enum BalanceChanged {
    Increase(AssetAmount),
    Decrease(AssetAmount),
}

impl Storable for BalanceChanged {
    fn to_bytes(&self) -> std::borrow::Cow<[u8]> {
        bincode::serialize(self).unwrap().into()
    }

    fn from_bytes(bytes: std::borrow::Cow<[u8]>) -> Self {
        bincode::deserialize(bytes.as_ref()).unwrap()
    }

    const BOUND: Bound = Bound::Bounded {
        max_size: 48,
        is_fixed_size: false,
    };
}

#[derive(Debug, Clone, Deserialize, CandidType)]
pub enum CandidBalanceChanged {
    Increase(CandidAssetAmount),
    Decrease(CandidAssetAmount),
}

impl BalanceChanged {
    pub fn merge(self, other: Self) -> Self {
        match (self, other) {
            (BalanceChanged::Increase(a), BalanceChanged::Increase(b)) => {
                BalanceChanged::Increase(a.add(b))
            }
            (BalanceChanged::Decrease(a), BalanceChanged::Decrease(b)) => {
                BalanceChanged::Decrease(a.add(b))
            }
            (BalanceChanged::Increase(a), BalanceChanged::Decrease(b)) => {
                if a >= b {
                    BalanceChanged::Increase(a.sub(b))
                } else {
                    BalanceChanged::Decrease(b.sub(a))
                }
            }
            (BalanceChanged::Decrease(a), BalanceChanged::Increase(b)) => {
                if a >= b {
                    BalanceChanged::Decrease(a.sub(b))
                } else {
                    BalanceChanged::Increase(b.sub(a))
                }
            }
        }
    }
}

impl From<CandidBalanceChanged> for BalanceChanged {
    fn from(candid_balance_changed: CandidBalanceChanged) -> Self {
        match candid_balance_changed {
            CandidBalanceChanged::Increase(candid_asset_amount) => {
                BalanceChanged::Increase(candid_asset_amount.into())
            }
            CandidBalanceChanged::Decrease(candid_asset_amount) => {
                BalanceChanged::Decrease(candid_asset_amount.into())
            }
        }
    }
}

impl From<BalanceChanged> for CandidBalanceChanged {
    fn from(balance_changed: BalanceChanged) -> Self {
        match balance_changed {
            BalanceChanged::Increase(asset_amount) => {
                CandidBalanceChanged::Increase(asset_amount.into())
            }
            BalanceChanged::Decrease(asset_amount) => {
                CandidBalanceChanged::Decrease(asset_amount.into())
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::BalanceChanged;
    use ic_stable_structures::storable::Storable;
    #[test]
    fn test_storable_for_balance_changed() {
        let balance_changed = BalanceChanged::Increase(u128::MAX.into());
        let bytes = balance_changed.to_bytes();
        assert!(bytes.len() <= 48);
        let balance_changed2 = BalanceChanged::from_bytes(bytes);
        assert_eq!(balance_changed, balance_changed2);
    }
}