gix-config-value 0.20.0

use std::{borrow::Cow, fmt::Display, str::FromStr};

use bstr::{BStr, BString, ByteSlice};
use gix_error::{ErrorExt, Message, ResultExt, validation};

use crate::Integer;

impl Integer {
    /// Canonicalize values as simple decimal numbers.
    /// An optional suffix of k, m, or g (case-insensitive), will cause the
    /// value to be multiplied by 1024 (k), 1048576 (m), or 1073741824 (g) respectively.
    ///
    /// Returns the result if there is no multiplication overflow.
    pub fn to_decimal(&self) -> Option<i64> {
        match self.suffix {
            None => Some(self.value),
            Some(suffix) => match suffix {
                Suffix::Kibi => self.value.checked_mul(1024),
                Suffix::Mebi => self.value.checked_mul(1024 * 1024),
                Suffix::Gibi => self.value.checked_mul(1024 * 1024 * 1024),
            },
        }
    }
}

impl Display for Integer {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.value)?;
        if let Some(suffix) = self.suffix {
            write!(f, "{suffix}")
        } else {
            Ok(())
        }
    }
}

#[cfg(feature = "serde")]
impl serde::Serialize for Integer {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        if let Some(suffix) = self.suffix {
            serializer.serialize_i64(self.value << suffix.bitwise_offset())
        } else {
            serializer.serialize_i64(self.value)
        }
    }
}

fn int_err(input: impl Into<BString>) -> Message {
    validation("Integers needs to be positive or negative numbers which may have a suffix like 1k, 42, or 50G")
        .with("input", gix_error::MetadataValue::Bytes(input.into()))
}

/// Parse `input` the way `git_parse_signed()` does, which hands the value to
/// `strtoimax()` with a base of `0`: an optional sign, then hexadecimal behind a `0x`
/// prefix, binary behind a `0b` prefix, octal behind a `0` prefix, and decimal otherwise.
fn parse_like_git(input: &str) -> Option<i64> {
    let (negative, rest) = match input.as_bytes().first() {
        Some(b'+') => (false, &input[1..]),
        Some(b'-') => (true, &input[1..]),
        _ => (false, input),
    };

    let Some(prefixed) = rest.strip_prefix('0') else {
        return input.parse().ok();
    };
    let (digits, radix) = if let Some(hexadecimal) = prefixed.strip_prefix(['x', 'X']) {
        (hexadecimal, 16)
    } else if let Some(binary) = prefixed.strip_prefix(['b', 'B']) {
        (binary, 2)
    } else if !prefixed.is_empty() {
        (prefixed, 8)
    } else {
        return input.parse().ok();
    };

    if digits.starts_with('+') || digits.starts_with('-') {
        return None;
    }
    let magnitude = i128::from_str_radix(digits, radix).ok()?;
    i64::try_from(if negative { -magnitude } else { magnitude }).ok()
}

impl TryFrom<&BStr> for Integer {
    type Error = gix_error::Exn<gix_error::Message>;

    fn try_from(s: &BStr) -> Result<Self, Self::Error> {
        let s = std::str::from_utf8(s).or_raise(|| int_err(s))?;
        if let Some(value) = parse_like_git(s) {
            return Ok(Self { value, suffix: None });
        }

        if s.len() <= 1 {
            return Err(int_err(s).raise());
        }

        let last_idx = s.len() - 1;
        if !s.is_char_boundary(last_idx) {
            return Err(int_err(s).raise());
        }

        let (number, suffix) = s.split_at(s.len() - 1);
        if let (Some(value), Ok(suffix)) = (parse_like_git(number), suffix.parse()) {
            Ok(Self {
                value,
                suffix: Some(suffix),
            })
        } else {
            Err(int_err(s).raise())
        }
    }
}

impl TryFrom<&str> for Integer {
    type Error = gix_error::Exn<gix_error::Message>;

    fn try_from(value: &str) -> Result<Self, Self::Error> {
        Self::try_from(BStr::new(value))
    }
}

impl TryFrom<Cow<'_, BStr>> for Integer {
    type Error = gix_error::Exn<gix_error::Message>;

    fn try_from(c: Cow<'_, BStr>) -> Result<Self, Self::Error> {
        Self::try_from(c.as_ref())
    }
}

impl TryFrom<BString> for Integer {
    type Error = gix_error::Exn<gix_error::Message>;

    fn try_from(value: BString) -> Result<Self, Self::Error> {
        Self::try_from(BStr::new(&value))
    }
}

/// Integer suffixes that are supported by `git-config`.
///
/// These values are base-2 unit of measurements, not the base-10 variants.
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
pub enum Suffix {
    /// Multiply the value by 2^10.
    Kibi,
    /// Multiply the value by 2^20.
    Mebi,
    /// Multiply the value by 2^30.
    Gibi,
}

impl Suffix {
    /// Returns the number of bits that the suffix shifts left by.
    #[must_use]
    pub const fn bitwise_offset(self) -> usize {
        match self {
            Self::Kibi => 10,
            Self::Mebi => 20,
            Self::Gibi => 30,
        }
    }
}

impl Display for Suffix {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Kibi => write!(f, "k"),
            Self::Mebi => write!(f, "m"),
            Self::Gibi => write!(f, "g"),
        }
    }
}

#[cfg(feature = "serde")]
impl serde::Serialize for Suffix {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        serializer.serialize_str(match self {
            Self::Kibi => "k",
            Self::Mebi => "m",
            Self::Gibi => "g",
        })
    }
}

impl FromStr for Suffix {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Self::try_from(BStr::new(s))
    }
}

impl TryFrom<&BStr> for Suffix {
    type Error = ();

    fn try_from(s: &BStr) -> Result<Self, Self::Error> {
        match s.as_bytes() {
            b"k" | b"K" => Ok(Self::Kibi),
            b"m" | b"M" => Ok(Self::Mebi),
            b"g" | b"G" => Ok(Self::Gibi),
            _ => Err(()),
        }
    }
}