parse 0.1.2

use std;

pub fn literal<'a, T: AsRef<[u8]>>(src: &mut &'a[u8], what: T) -> ::Result<()> {
    let what = what.as_ref();
    if !src.starts_with(what) {
        return Err("invalid literal")
    }
    *src = &src[what.len()..];
    Ok(())
}

#[test]
fn test_literal() {
    let mut src = "tuonen joutsen 123%&#".as_bytes();
    literal(&mut src, "tuonen").unwrap();
    assert_eq!(b" joutsen 123%&#", src);
    literal(&mut src, "").unwrap();
    literal(&mut src, " joutsen 123%").unwrap();
    assert_eq!(b"&#", src);
    assert!(literal(&mut src, "k").is_err());
    assert!(literal(&mut src, "&#o").is_err());
    literal(&mut src, "&#").unwrap();
    assert_eq!(0, src.len());
}

pub fn whitespace_if_any<'a>(src: &mut &'a[u8]) {
    let mut i = 0;
    while i < src.len() && is_whitespace(src[i]) {
        i += 1;
    }
    *src = &src[i..];
}

// requires at least one whitespace character.
pub fn whitespace<'a>(src: &mut &'a[u8]) -> ::Result<()> {
    if src.len() < 1 || !is_whitespace(src[0]) {
        return Err("no whitespace")
    }
    *src = &src[1..];
    Ok(whitespace_if_any(src))
}

#[test]
fn test_whitespace() {
    let mut src = "\n\t\r\n yyy \n\r\t\nzzz".as_bytes();
    whitespace(&mut src).unwrap();
    assert_eq!(b"yyy \n\r\t\nzzz", src);
    literal(&mut src, "yyy").unwrap();
    whitespace_if_any(&mut src);
    assert_eq!(b"zzz", src);
    whitespace_if_any(&mut src);
    assert_eq!(b"zzz", src);
}

macro_rules! uint {
    ($T:ident) => {
        pub fn $T(src: &mut &[u8]) -> ::Result<$T> {
            let mut v = 0 as $T;
            let mut i = 0;
            let q = std::$T::MAX / 10;
            let e = std::$T::MAX % 10;
            while i < src.len() && is_digit(src[i]) {
                let number = (src[i] - b'0') as $T;
                if v > q || (v == q && number > e) {
                    return Err("invalid uint: overflow")
                }
                v = v * 10 + number;
                i += 1;
            }
            if i == 0 {
                return Err("invalid uint")
            }
            *src = &src[i..];
            Ok(v)
        }
    }
}
uint!(u8);
uint!(u16);
uint!(u32);
uint!(u64);

#[test]
fn test_uint() {
    let mut src = "1k".as_bytes();
    assert_eq!(1u8, u8(&mut src).unwrap());
    assert_eq!(b"k", src);
    assert_eq!(1u8, u8(&mut "01".as_bytes()).unwrap());
    assert_eq!(0u8, u8(&mut "0".as_bytes()).unwrap());
    assert_eq!(255_u8, u8(&mut "255".as_bytes()).unwrap());
    assert_eq!(256_u16, u16(&mut "256".as_bytes()).unwrap());
    assert_eq!(65535_u16, u16(&mut "65535".as_bytes()).unwrap());
    assert_eq!(4294967295_u32, u32(&mut "4294967295".as_bytes()).unwrap());
    assert_eq!(18446744073709551615_u64, u64(&mut "18446744073709551615".as_bytes()).unwrap());
    assert!(u8(&mut "256".as_bytes()).is_err());
    assert!(u8(&mut "1000".as_bytes()).is_err());
    assert!(u16(&mut "65536".as_bytes()).is_err());
    assert!(u16(&mut "100000".as_bytes()).is_err());
    assert!(u32(&mut "4294967296".as_bytes()).is_err());
    assert!(u32(&mut "10000000000".as_bytes()).is_err());
    assert!(u64(&mut "18446744073709551616".as_bytes()).is_err());
    assert!(u64(&mut "100000000000000000000".as_bytes()).is_err());
    assert!(u32(&mut "".as_bytes()).is_err());
    assert!(u32(&mut "-255".as_bytes()).is_err());
    assert!(u32(&mut "q".as_bytes()).is_err());
}

macro_rules! int {
    ($T:ident) => {
        pub fn $T(src: &mut &[u8]) -> ::Result<$T> {
            if src.len() == 0 {
                return Err("invalid int: nothing to parse")
            }

            let mut i = 0;
            let digit_offset;
            let positive = src[0] != b'-';
            if src[0] == b'-' || src[0] == b'+' {
                i += 1;
                digit_offset = 1;
            } else {
                digit_offset = 0;
            }
            let mut v = 0 as $T;
            let q = if positive { std::$T::MAX / 10 } else { -(std::$T::MIN / 10) };
            let e = if positive { std::$T::MAX % 10 } else { -(std::$T::MIN % 10) };

            while i < src.len() && is_digit(src[i]) {
                let number = (src[i] - b'0') as $T;
                if v > q || (v == q && number > e) {
                    return Err("invalid int: overflow")
                }
                v = (v * 10).wrapping_add(number);    // let MAX+1 wrap to MIN
                i += 1;
            }
            if i <= digit_offset {
                return Err("invalid int")
            }
            *src = &src[i..];
            Ok(if positive { v } else { v.wrapping_neg() })     // -MIN == MIN
        }
    }
}
int!(i8);
int!(i16);
int!(i32);
int!(i64);

#[test]
fn test_int() {
    let mut src = "1k".as_bytes();
    assert_eq!(1i8, i8(&mut src).unwrap());
    assert_eq!(b"k", src);
    assert_eq!(1i8, i8(&mut "01".as_bytes()).unwrap());
    assert_eq!(0i8, i8(&mut "0".as_bytes()).unwrap());
    assert_eq!(1i8, i8(&mut "+1".as_bytes()).unwrap());

    assert_eq!(-8i8, i8(&mut "-8".as_bytes()).unwrap());
    assert_eq!(-128i8, i8(&mut "-128".as_bytes()).unwrap());
    assert_eq!(127i8, i8(&mut "127".as_bytes()).unwrap());
    assert_eq!(-32768_i16, i16(&mut "-32768".as_bytes()).unwrap());
    assert_eq!(32767_i16, i16(&mut "32767".as_bytes()).unwrap());
    assert_eq!(-2147483648_i32, i32(&mut "-2147483648".as_bytes()).unwrap());
    assert_eq!(2147483647_i32, i32(&mut "2147483647".as_bytes()).unwrap());
    assert_eq!(-9223372036854775808_i64, i64(&mut "-9223372036854775808".as_bytes()).unwrap());
    assert_eq!(9223372036854775807_i64, i64(&mut "9223372036854775807".as_bytes()).unwrap());

    assert!(i8(&mut "-129".as_bytes()).is_err());
    assert!(i8(&mut "-1000".as_bytes()).is_err());
    assert!(i8(&mut "128".as_bytes()).is_err());
    assert!(i8(&mut "1000".as_bytes()).is_err());
    assert!(i16(&mut "-32769".as_bytes()).is_err());
    assert!(i16(&mut "-100000".as_bytes()).is_err());
    assert!(i16(&mut "32768".as_bytes()).is_err());
    assert!(i16(&mut "100000".as_bytes()).is_err());
    assert!(i32(&mut "-2147483649".as_bytes()).is_err());
    assert!(i32(&mut "-10000000000".as_bytes()).is_err());
    assert!(i32(&mut "2147483648".as_bytes()).is_err());
    assert!(i32(&mut "10000000000".as_bytes()).is_err());
    assert!(i64(&mut "-9223372036854775809".as_bytes()).is_err());
    assert!(i64(&mut "-10000000000000000000".as_bytes()).is_err());
    assert!(i64(&mut "9223372036854775808".as_bytes()).is_err());
    assert!(i64(&mut "10000000000000000000".as_bytes()).is_err());

    assert!(i32(&mut "".as_bytes()).is_err());
    assert!(i32(&mut "-".as_bytes()).is_err());
    assert!(i32(&mut "+".as_bytes()).is_err());
    assert!(i32(&mut "q".as_bytes()).is_err());
}

pub fn f32(src: &mut &[u8]) -> ::Result<f32> {
    use std::str::{self, FromStr};

    if src.len() == 0 {
        return Err("invalid float: nothing to parse")
    }

    let mut i = 0;
    if src[i] == b'-' || src[i] == b'+' {
        i += 1;
    }

    while i < src.len() && is_digit(src[i]) {
        i += 1;
    }

    if i < src.len() && src[i] == b'.' {
        i += 1;
        while i < src.len() && is_digit(src[i]) {
            i += 1;
        }
    }

    if i + 1 < src.len() && src[i] == b'e' {
        if is_digit(src[i+1]) {
            i += 2;
        } else if i + 2 < src.len() && src[i+1] == b'-' && is_digit(src[i+2]) {
            i += 3;
        } else {
            return Err("invalid float")
        }
        while i < src.len() && is_digit(src[i]) {
            i += 1;
        }
    }

    let s = unsafe { str::from_utf8_unchecked(&src[..i]) };
    if let Ok(v) = FromStr::from_str(s) {
        *src = &src[i..];
        return Ok(v)
    }
    Err("invalid float")
}

#[test]
fn test_f32() {
    assert_eq!(32.,    f32(&mut "+32".as_bytes()).unwrap());
    assert_eq!(-32.,   f32(&mut "-32".as_bytes()).unwrap());
    assert_eq!(32.,    f32(&mut "32".as_bytes()).unwrap());
    assert_eq!(32e2,   f32(&mut "32e2".as_bytes()).unwrap());
    assert_eq!(32.,    f32(&mut "32.".as_bytes()).unwrap());
    assert_eq!(32e2,   f32(&mut "32.e2".as_bytes()).unwrap());
    assert_eq!(32_f32, f32(&mut "32.0".as_bytes()).unwrap());
    assert_eq!(32e2,   f32(&mut "32.0e2".as_bytes()).unwrap());
    assert_eq!(0.32,   f32(&mut "32.0e-2".as_bytes()).unwrap());
}

pub fn bool(src: &mut &[u8]) -> ::Result<bool> {
    if src.starts_with(b"true") {
        *src = &src[4..];
        return Ok(true)
    } else if src.starts_with(b"false") {
        *src = &src[5..];
        return Ok(false)
    }
    Err("invalid bool")
}

#[test]
fn test_bool() {
    assert_eq!(true, bool(&mut "true".as_bytes()).unwrap());
    assert_eq!(false, bool(&mut "false".as_bytes()).unwrap());
    assert_eq!(false, bool(&mut "falsee".as_bytes()).unwrap());   // NOTE
    assert!(bool(&mut "tru".as_bytes()).is_err());
    assert!(bool(&mut "trudat".as_bytes()).is_err());
    assert!(bool(&mut "fals".as_bytes()).is_err());
}

macro_rules! hex {
    ($T:ident, $name:ident) => {
        pub fn $name(src: &mut &[u8]) -> ::Result<$T> {
            let mut v = 0 as $T;
            let mut i = 0;
            let q = std::$T::MAX / 16;  // note that MAX % 16 == 15, for all the types.
            let mut number = 0;
            while i < src.len() && hex_digit_to_value(src[i], &mut number) {
                if v > q {
                    return Err("invalid hex: overflow")
                }
                v = v * 16 + number as $T;
                i += 1;
            }
            if i == 0 {
                return Err("invalid hex")
            }
            *src = &src[i..];
            Ok(v)
        }
    }
}
hex!(u8, hex_u8);
hex!(u16, hex_u16);
hex!(u32, hex_u32);
hex!(u64, hex_u64);

#[test]
fn test_hex() {
    let mut src = "1k".as_bytes();
    assert_eq!(1u8, hex_u8(&mut src).unwrap());
    assert_eq!(b"k", src);
    assert_eq!(1u8, hex_u8(&mut "01".as_bytes()).unwrap());
    assert_eq!(10u8, hex_u8(&mut "a".as_bytes()).unwrap());
    assert_eq!(16u8, hex_u8(&mut "10".as_bytes()).unwrap());
    assert_eq!(255u8, hex_u8(&mut "ff".as_bytes()).unwrap());
    assert_eq!(256u16, hex_u16(&mut "100".as_bytes()).unwrap());
    assert_eq!(65535_u16, hex_u16(&mut "ffff".as_bytes()).unwrap());
    assert_eq!(0xffff_ffff_u32, hex_u32(&mut "ffffffff".as_bytes()).unwrap());
    assert_eq!(0xffff_ffff_u32, hex_u32(&mut "FFFFFFFF".as_bytes()).unwrap());
    assert_eq!(0xffff_ffff_ffff_ffff_u64, hex_u64(&mut "ffffffffffffffff".as_bytes()).unwrap());
    assert!(hex_u8(&mut "100".as_bytes()).is_err());
    assert!(hex_u16(&mut "10000".as_bytes()).is_err());
    assert!(hex_u32(&mut "100000000".as_bytes()).is_err());
    assert!(hex_u64(&mut "10000000000000000".as_bytes()).is_err());
}

// requires `src` to have two digits for each byte.
pub fn hex_string<'a>(src: &mut &[u8], dst: &'a mut[u8]) -> ::Result<()> {
    if src.len() < 2 * dst.len() {
        return Err("not enough digits for hex string")
    }
    let mut high = 0;
    let mut low = 0;
    let mut i = 0;
    for d in &mut dst[..] {
        if !hex_digit_to_value(src[i], &mut high)
        || !hex_digit_to_value(src[i+1], &mut low) {
            return Err("invalid hex string")
        }
        *d = high * 16 + low;
        i += 2;
    }
    *src = &src[i..];
    Ok(())
}

#[test]
fn test_hex_string() {
    let mut src = "AAbb70b7e752fcc3f51decbc656270834ed45a39 readme.txt".as_bytes();
    let mut hash = [0u8; 20];
    let res = b"\xAA\xbb\x70\xb7\xe7\x52\xfc\xc3\xf5\x1d\
                \xec\xbc\x65\x62\x70\x83\x4e\xd4\x5a\x39";
    hex_string(&mut src, &mut hash[..]).unwrap();
    assert_eq!(&res[..], &hash[..]);
    assert_eq!(b" readme.txt", src);
    let mut src = "bb70b7e752fcc3f51decbc656270834ed45a39".as_bytes();  // missing digits
    assert!(hex_string(&mut src, &mut hash[..]).is_err());
}

#[inline]
pub fn is_whitespace(c: u8) -> bool {
    c == b' ' || c == b'\t' || c == b'\n' || c == b'\r'
}

#[inline]
pub fn is_digit(c: u8) -> bool {
    b'0' <= c && c <= b'9'
}

pub fn hex_digit_to_value(digit: u8, out: &mut u8) -> bool {
    if b'0' <= digit && digit <= b'9' {
        *out = digit - b'0';
    } else if b'a' <= digit && digit <= b'f' {
        *out = digit - b'a' + 10;
    } else if b'A' <= digit && digit <= b'F' {
        *out = digit - b'A' + 10;
    } else {
        return false
    }
    true
}

/// Parse binary data.
pub mod bin {
    use std::mem;
    macro_rules! int_be {
        ($T:ident, $name:ident) => {
            pub fn $name(src: &mut &[u8]) -> ::Result<$T> {
                if src.len() < mem::size_of::<$T>() {
                    return Err("can't parse integer")
                }
                let res = $T::from_be(*unsafe { mem::transmute::<&u8, &$T>(&src[0]) });
                *src = &src[mem::size_of::<$T>()..];
                Ok(res)
            }
        }
    }
    int_be!(u8, u8);
    int_be!(i8, i8);
    int_be!(u16, u16_be);
    int_be!(i16, i16_be);
    int_be!(u32, u32_be);
    int_be!(i32, i32_be);
    int_be!(u64, u64_be);
    int_be!(i64, i64_be);

    macro_rules! int_le {
        ($T:ident, $name:ident) => {
            pub fn $name(src: &mut &[u8]) -> ::Result<$T> {
                if src.len() < mem::size_of::<$T>() {
                    return Err("can't parse integer")
                }
                let res = $T::from_le(*unsafe { mem::transmute::<&u8, &$T>(&src[0]) });
                *src = &src[mem::size_of::<$T>()..];
                Ok(res)
            }
        }
    }
    int_le!(u16, u16_le);
    int_le!(i16, i16_le);
    int_le!(u32, u32_le);
    int_le!(i32, i32_le);
    int_le!(u64, u64_le);
    int_le!(i64, i64_le);

    #[test]
    fn test_bin() {
        let src = [0xff, 0x01];
        assert_eq!(0xff01, u16_be(&mut &src[..]).unwrap());
        assert_eq!(0x01ff, u16_le(&mut &src[..]).unwrap());
    }
}