boleto-utils 0.1.2

Utility library to parse brazilian payment slip (aka 'boleto') barcodes.
Documentation 
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use std::convert::TryInto;
use lazy_static::lazy_static;

use chrono::{Duration, NaiveDate};

// Fator para o dia 1º de Janeiro de 2010
const FATOR_VENC_2010: u16 = 4469;

lazy_static! {
    /// Data base usada até 2025 (1000 == 03/07/2000)
    static ref CURRENT_BASE_DATE: NaiveDate = NaiveDate::from_ymd_opt(1997, 10, 7).unwrap();

    /// Data base usada de 2025 em diante (1000 == 22/02/2025)
    static ref NEXT_BASE_DATE: NaiveDate = NaiveDate::from_ymd_opt(2022, 5, 29).unwrap();
}

pub fn fator_vencimento_to_date(fator: u16) -> Option<NaiveDate> {
    // Para fatores menores que o limite, calculamos datas do passado (de 2010 em diante)
    let base = if fator >= FATOR_VENC_2010 {
        *CURRENT_BASE_DATE
    } else  {
        // Para fatores maiores que o limite, calculamos datas do futuro (de 2025 em diante)
        *NEXT_BASE_DATE
    };

    if fator >= 1000 {
        Some(base + Duration::days(fator.into()))
    } else {
        None
    }
}


pub fn date_to_fator_vencimento(date: NaiveDate) -> Option<u16> {
    let base = if date < NaiveDate::from_ymd_opt(2025, 2, 22).unwrap() {
        *CURRENT_BASE_DATE
    } else {
        *NEXT_BASE_DATE
    };
    (date - base).num_days().try_into().ok()
}

pub fn u8_array_to_u16(slice: &[u8]) -> u16 {
    slice.iter()
        .rev()
        .enumerate()
        .map(|(i, n)| {
            10_u16.pow(i.try_into().unwrap()) * (*n - b'0') as u16
        })
        .sum()
}

pub mod dv_utils {
    pub fn mod_10<'a, I>(values: I) -> u8
    where
        I: DoubleEndedIterator<Item = &'a u8>
    {
        let soma: usize = values.rev()
            .zip([2, 1].iter().cycle())
            .map(|(n, i)| {
                match (n - b'0') * i {
                    x if x > 9 => ((x / 10) + (x % 10)) as usize,
                    x => x as usize,
                }
            })
            .sum();

        ((10 - (soma % 10)) % 10) as u8 + b'0'
    }

    pub fn mod_11<'a, I>(values: I) -> Option<u8>
    where
        I: DoubleEndedIterator<Item = &'a u8>
    {
        let soma: usize = values.rev()
            .zip((2..=9).cycle())
            .map(|(n, i)| (n - b'0') as usize * i)
            .sum();

        match 11 - (soma % 11) {
            10 | 11 => None,
            dv => Some((dv as u8) + b'0'),
        }
    }
}

#[cfg(test)]
mod tests {
    use chrono::NaiveDate;

    use crate::utils::{date_to_fator_vencimento, fator_vencimento_to_date, u8_array_to_u16, FATOR_VENC_2010};
    use crate::utils::dv_utils::{mod_10, mod_11};

    #[test]
    fn convert_fator_vencimento_to_naive_date_correctly() {
        assert_eq!(
            fator_vencimento_to_date(FATOR_VENC_2010),
            Some(NaiveDate::from_ymd_opt(2010, 1, 1).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(FATOR_VENC_2010 + 1),
            Some(NaiveDate::from_ymd_opt(2010, 1, 2).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(FATOR_VENC_2010 - 1),
            Some(NaiveDate::from_ymd_opt(2034, 8, 22).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(4789),
            Some(NaiveDate::from_ymd_opt(2010, 11, 17).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(9999),
            Some(NaiveDate::from_ymd_opt(2025, 2, 21).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(1000),
            Some(NaiveDate::from_ymd_opt(2025, 2, 22).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(1002),
            Some(NaiveDate::from_ymd_opt(2025, 2, 24).unwrap()),
        );
        assert_eq!(
            fator_vencimento_to_date(1667),
            Some(NaiveDate::from_ymd_opt(2026, 12, 21).unwrap()),
        );
    }

    #[test]
    fn convert_naive_date_to_fator_vencimento_correctly() {
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2010, 1, 2).unwrap()),
            Some(FATOR_VENC_2010 + 1),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2034, 8, 22).unwrap()),
            Some(FATOR_VENC_2010 - 1),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2010, 11, 17).unwrap()),
            Some(4789),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2025, 2, 21).unwrap()),
            Some(9999),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2025, 2, 22).unwrap()),
            Some(1000),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2025, 2, 24).unwrap()),
            Some(1002),
        );
        assert_eq!(
            date_to_fator_vencimento(NaiveDate::from_ymd_opt(2026, 12, 21).unwrap()),
            Some(1667),
        );
    }

    #[test]
    fn calculate_mod_10_correctly() {
        assert_eq!(mod_10(b"01230067896".iter()), b'3');
        assert_eq!(mod_10(b"01230167896".iter()), b'2');
        assert_eq!(mod_10(b"01230267896".iter()), b'1');
        assert_eq!(mod_10(b"01230367896".iter()), b'0');
        assert_eq!(mod_10(b"01230467896".iter()), b'9');
        assert_eq!(mod_10(b"01230567896".iter()), b'8');
        assert_eq!(mod_10(b"01230667896".iter()), b'7');
        assert_eq!(mod_10(b"01230767896".iter()), b'6');
        assert_eq!(mod_10(b"01230867896".iter()), b'5');
        assert_eq!(mod_10(b"01230967896".iter()), b'4');
    }

    #[test]
    fn calculate_mod_11_correctly() {
        assert_eq!(mod_11(b"8220000215048200974123220154098290108605940".iter()), None);
        assert_eq!(mod_11(b"01230067896".iter()), None);
        assert_eq!(mod_11(b"31230067896".iter()), None);
        assert_eq!(mod_11(b"01231068896".iter()), Some(b'9'));
        assert_eq!(mod_11(b"01230267896".iter()), Some(b'8'));
        assert_eq!(mod_11(b"01231167896".iter()), Some(b'7'));
        assert_eq!(mod_11(b"01232067896".iter()), Some(b'6'));
        assert_eq!(mod_11(b"01241067896".iter()), Some(b'5'));
        assert_eq!(mod_11(b"01250067896".iter()), Some(b'4'));
        assert_eq!(mod_11(b"02232067896".iter()), Some(b'3'));
        assert_eq!(mod_11(b"01250067897".iter()), Some(b'2'));
        assert_eq!(mod_11(b"01230367896".iter()), Some(b'1'));
    }

    #[test]
    fn convert_u8_array_to_u32_correctly() {
        assert_eq!(u8_array_to_u16(b"001"), 1);
        assert_eq!(u8_array_to_u16(b"010"), 10);
        assert_eq!(u8_array_to_u16(b"100"), 100);
        assert_eq!(u8_array_to_u16(b"999"), 999);
        assert_eq!(u8_array_to_u16(b"9999"), 9999);
    }
}