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pub mod calculation;
pub mod constructor;

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

/// A trait for defining currency localization methods.
pub trait CurrencyLocale {
    /// Retrieves the separator used for the currency.
    fn separator(&self) -> char;
    /// Retrieves the thousand separator used for the currency.
    fn thousand_separator(&self) -> char;
    /// Retrieves the currency symbol.
    fn currency_symbol(&self) -> &'static str;
}

/// Represents a currency value with specified localization.
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub struct Currency<L: CurrencyLocale + Default> {
    negative: bool,
    full: usize,
    part: u8,
    locale: L,
}

impl<L> std::fmt::Display for Currency<L>
where
    L: CurrencyLocale + Default,
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut buffer = self.full.to_string();
        if buffer.len() > 3 {
            let len = buffer.len() - 2;
            for idx in (1..len).rev().step_by(3) {
                buffer.insert(idx, self.locale.thousand_separator());
            }
        }
        if self.negative {
            write!(f, "-")?;
        }
        write!(
            f,
            "{}{}{:02} {}",
            buffer,
            self.locale.separator(),
            self.part,
            self.locale.currency_symbol()
        )
    }
}

impl<L: CurrencyLocale + Default> Currency<L> {
    /// Constructs a new Currency instance.
    ///
    /// # Arguments
    ///
    /// * `negative` - Indicates if the currency value is negative.
    /// * `full` - The whole number part of the currency value.
    /// * `part` - The fractional part of the currency value.
    /// * `locale` - The localization information for the currency.
    ///
    /// # Returns
    ///
    /// A new `Currency` instance.
    #[must_use]
    pub fn new(negative: bool, full: usize, part: u8, locale: L) -> Self {
        Self {
            negative,
            full,
            part,
            locale,
        }
    }

    /// Updates the localization information of the currency.
    ///
    /// # Arguments
    ///
    /// * `locale` - The updated localization information.
    ///
    /// # Returns
    ///
    /// The updated `Currency` instance with the new localization.
    #[must_use]
    pub fn with_locale(mut self, locale: L) -> Self {
        self.locale = locale;
        self
    }
}

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

    #[derive(Clone, Copy, Default, Debug, PartialEq)]
    enum CurrencyL {
        #[default]
        De,
    }

    impl CurrencyLocale for CurrencyL {
        fn separator(&self) -> char {
            ','
        }

        fn thousand_separator(&self) -> char {
            '.'
        }

        fn currency_symbol(&self) -> &'static str {
            "€"
        }
    }

    #[test]
    fn print_currency() {
        let mut curr = Currency::new(false, 2, 22, CurrencyL::De);
        for (full, full_string) in [
            (2, "2"),
            (20, "20"),
            (200, "200"),
            (2_000, "2.000"),
            (20_000, "20.000"),
            (200_000, "200.000"),
            (2_000_000, "2.000.000"),
            (20_000_000, "20.000.000"),
            (200_000_000, "200.000.000"),
        ] {
            curr.full = full;
            assert_eq!(format!("{full_string},22 €"), curr.to_string());
        }

        let curr = Currency::new(false, 2, 2, CurrencyL::De);
        assert_eq!("2,02 €", &curr.to_string());
    }

    #[test]
    fn construct_f32() {
        let first_val = 100.8_f32;
        let second_val = 191.0_f32;

        let expected = Currency::<CurrencyL>::from(first_val + second_val);
        assert_eq!(expected, Currency::new(false, 291, 80, CurrencyL::De));
    }
}