walletd_bitcoin 0.2.0

use crate::Error;
use std::ops;
use walletd_coin_core::CryptoAmount;

/// Contains a field representing the amount of satoshis in the amount.
/// Has functions to convert to and from the main unit (BTC) and the smallest unit (satoshi).
#[derive(Default, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub struct BitcoinAmount {
    /// The number of satoshis (the smallest unit of the bitcoin currency) in the [amount][BitcoinAmount].
    ///
    /// There are 100 million satoshis per bitcoin (BTC).
    pub satoshi: u64,
}

impl ops::Add<Self> for BitcoinAmount {
    type Output = Result<Self, Error>;

    fn add(self, rhs: Self) -> Result<Self, Error> {
        Ok(Self {
            satoshi: self
                .satoshi
                .checked_add(rhs.satoshi)
                .ok_or(Error::Overflow(format!(
                    "Overflow in u64 when adding {} to {}",
                    self.satoshi, rhs.satoshi
                )))?,
        })
    }
}

impl ops::Sub for BitcoinAmount {
    type Output = Result<Self, Error>;

    fn sub(self, rhs: Self) -> Result<Self, Error> {
        Ok(Self {
            satoshi: self
                .satoshi
                .checked_sub(rhs.satoshi)
                .ok_or(Error::Overflow(format!(
                    "Overflow in u64 when subtracting {} from {}",
                    self.satoshi, rhs.satoshi
                )))?,
        })
    }
}

impl ops::Mul<f64> for BitcoinAmount {
    type Output = Result<Self, Error>;

    fn mul(self, rhs: f64) -> Self::Output {
        let result = self.satoshi as f64 * rhs;
        if !(f64::MIN..=f64::MAX).contains(&result) {
            return Err(Error::Overflow(format!(
                "Overflow in f64 when multiplying {} by {}",
                self.satoshi, rhs
            )));
        }

        let as_u64 = result as u64;

        Ok(Self { satoshi: as_u64 })
    }
}

impl BitcoinAmount {
    /// Returns a [BitcoinAmount] struct from a decimal value representing the amount in BTC.
    pub fn from_btc(btc_amount: f64) -> Self {
        let satoshi = (btc_amount * 100_000_000.0) as u64; // 100 million satoshis per bitcoin
        Self { satoshi }
    }

    /// Returns a [BitcoinAmount] struct from an integer value representing the amount in satoshis.
    pub fn from_satoshi(satoshi_amount: u64) -> Self {
        Self {
            satoshi: satoshi_amount,
        }
    }

    /// Returns the amount in BTC as a f64.
    pub fn btc(&self) -> f64 {
        self.satoshi as f64 / 100_000_000.0 // 100 million satoshis per bitcoin
    }

    /// Returns the amount in satoshis as a u64.
    pub fn satoshi(&self) -> u64 {
        self.satoshi
    }
}

impl CryptoAmount for BitcoinAmount {
    fn from_main_unit_decimal_value(value: f64) -> Self {
        Self::from_btc(value)
    }

    fn from_smallest_unit_integer_value(value: u64) -> Self {
        Self::from_satoshi(value)
    }

    fn to_main_unit_decimal_value(&self) -> f64 {
        self.btc()
    }

    fn to_smallest_unit_integer_value(&self) -> u64 {
        self.satoshi()
    }
}

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

    #[test]
    fn test_add() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = BitcoinAmount::from_btc(2.0);
        let c = (a + b)?;
        assert_eq!(c.btc(), 3.0);
        Ok(())
    }

    #[test]
    fn test_add_overflow() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = BitcoinAmount::from_btc(f64::MAX);
        let c = a + b;
        assert!(c.is_err());
        Ok(())
    }

    #[test]
    fn test_sub() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = BitcoinAmount::from_btc(2.0);
        let c = (b - a)?;
        assert_eq!(c.btc(), 1.0);
        Ok(())
    }

    #[test]
    fn test_sub_overflow() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = BitcoinAmount::from_btc(2.0);
        let c = a - b;
        assert!(c.is_err());
        Ok(())
    }

    #[test]
    fn test_multiply() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = 3.5;
        let c = (a * b)?;
        assert_eq!(c.btc(), 3.5);
        Ok(())
    }

    #[test]
    fn test_multiply_overflow() -> Result<(), Error> {
        let a = BitcoinAmount::from_btc(1.0);
        let b = f64::MAX;
        let c = a * b;
        assert!(c.is_err());
        Ok(())
    }
}