//! General purpose combinators

use nom::bytes::streaming::take;

use nom::combinator::map_parser;

use nom::error::{make_error, ErrorKind, ParseError};

use nom::{IResult, Needed, Parser};

use nom::{InputIter, InputTake};

use nom::{InputLength, ToUsize};

#[deprecated(since = "3.0.1", note = "please use `be_var_u64` instead")]

/// Read an entire slice as a big-endian value.

///

/// Returns the value as `u64`. This function checks for integer overflows, and returns a

/// `Result::Err` value if the value is too big.

pub fn bytes_to_u64(s: &[u8]) -> Result<u64, &'static str> {

    let mut u: u64 = 0;

    if s.is_empty() {

        return Err("empty");

    };

    if s.len() > 8 {

        return Err("overflow");

    }

    for &c in s {

        let u1 = u << 8;

        u = u1 | (c as u64);

    }

    Ok(u)

}

/// Read the entire slice as a big endian unsigned integer, up to 8 bytes

#[inline]

pub fn be_var_u64<'a, E: ParseError<&'a [u8]>>(input: &'a [u8]) -> IResult<&'a [u8], u64, E> {

    if input.is_empty() {

        return Err(nom::Err::Incomplete(Needed::new(1)));

    }

    if input.len() > 8 {

        return Err(nom::Err::Error(make_error(input, ErrorKind::TooLarge)));

    }

    let mut res = 0u64;

    for byte in input {

        res = (res << 8) + *byte as u64;

    }

    Ok((&b""[..], res))

}

/// Read the entire slice as a little endian unsigned integer, up to 8 bytes

#[inline]

pub fn le_var_u64<'a, E: ParseError<&'a [u8]>>(input: &'a [u8]) -> IResult<&'a [u8], u64, E> {

    if input.is_empty() {

        return Err(nom::Err::Incomplete(Needed::new(1)));

    }

    if input.len() > 8 {

        return Err(nom::Err::Error(make_error(input, ErrorKind::TooLarge)));

    }

    let mut res = 0u64;

    for byte in input.iter().rev() {

        res = (res << 8) + *byte as u64;

    }

    Ok((&b""[..], res))

}

/// Read a slice as a big-endian value.

#[inline]

pub fn parse_hex_to_u64<S>(i: &[u8], size: S) -> IResult<&[u8], u64>

where

    S: ToUsize + Copy,

{

    map_parser(take(size.to_usize()), be_var_u64)(i)

}

/// Apply combinator, automatically converts between errors if the underlying type supports it

pub fn upgrade_error<I, O, E1: ParseError<I>, E2: ParseError<I>, F>(

    mut f: F,

) -> impl FnMut(I) -> IResult<I, O, E2>

where

    F: FnMut(I) -> IResult<I, O, E1>,

    E2: From<E1>,

{

    move |i| f(i).map_err(nom::Err::convert)

}

/// Create a combinator that returns the provided value, and input unchanged

pub fn pure<I, O, E: ParseError<I>>(val: O) -> impl Fn(I) -> IResult<I, O, E>

where

    O: Clone,

{

    move |input: I| Ok((input, val.clone()))

}

/// Return a closure that takes `len` bytes from input, and applies `parser`.

pub fn flat_take<I, C, O, E: ParseError<I>, F>(

    len: C,

    mut parser: F,

) -> impl FnMut(I) -> IResult<I, O, E>

where

    I: InputTake + InputLength + InputIter,

    C: ToUsize + Copy,

    F: Parser<I, O, E>,

{

    // Note: this is the same as `map_parser(take(len), parser)`

    move |input: I| {

        let (input, o1) = take(len.to_usize())(input)?;

        let (_, o2) = parser.parse(o1)?;

        Ok((input, o2))

    }

}

/// Take `len` bytes from `input`, and apply `parser`.

pub fn flat_takec<I, O, E: ParseError<I>, C, F>(input: I, len: C, parser: F) -> IResult<I, O, E>

where

    C: ToUsize + Copy,

    F: Parser<I, O, E>,

    I: InputTake + InputLength + InputIter,

    O: InputLength,

{

    flat_take(len, parser)(input)

}

/// Helper macro for nom parsers: run first parser if condition is true, else second parser

pub fn cond_else<I, O, E: ParseError<I>, C, F, G>(

    cond: C,

    mut first: F,

    mut second: G,

) -> impl FnMut(I) -> IResult<I, O, E>

where

    C: Fn() -> bool,

    F: Parser<I, O, E>,

    G: Parser<I, O, E>,

{

    move |input: I| {

        if cond() {

            first.parse(input)

        } else {

            second.parse(input)

        }

    }

}

/// Align input value to the next multiple of n bytes

/// Valid only if n is a power of 2

pub const fn align_n2(x: usize, n: usize) -> usize {

    (x + (n - 1)) & !(n - 1)

}

/// Align input value to the next multiple of 4 bytes

pub const fn align32(x: usize) -> usize {

    (x + 3) & !3

}

#[cfg(test)]

mod tests {

    use super::{align32, be_var_u64, cond_else, flat_take, pure};

    use nom::bytes::streaming::take;

    use nom::number::streaming::{be_u16, be_u32, be_u8};

    use nom::{Err, IResult, Needed};

    #[test]

    fn test_be_var_u64() {

        let res: IResult<&[u8], u64> = be_var_u64(b"\x12\x34\x56");

        let (_, v) = res.expect("be_var_u64 failed");

        assert_eq!(v, 0x123456);

    }

    #[test]

    fn test_flat_take() {

        let input = &[0x00, 0x01, 0xff];

        // read first 2 bytes and use correct combinator: OK

        let res: IResult<&[u8], u16> = flat_take(2u8, be_u16)(input);

        assert_eq!(res, Ok((&input[2..], 0x0001)));

        // read 3 bytes and use 2: OK (some input is just lost)

        let res: IResult<&[u8], u16> = flat_take(3u8, be_u16)(input);

        assert_eq!(res, Ok((&b""[..], 0x0001)));

        // read 2 bytes and a combinator requiring more bytes

        let res: IResult<&[u8], u32> = flat_take(2u8, be_u32)(input);

        assert_eq!(res, Err(Err::Incomplete(Needed::new(2))));

    }

    #[test]

    fn test_flat_take_str() {

        let input = "abcdef";

        // read first 2 bytes and use correct combinator: OK

        let res: IResult<&str, &str> = flat_take(2u8, take(2u8))(input);

        assert_eq!(res, Ok(("cdef", "ab")));

        // read 3 bytes and use 2: OK (some input is just lost)

        let res: IResult<&str, &str> = flat_take(3u8, take(2u8))(input);

        assert_eq!(res, Ok(("def", "ab")));

        // read 2 bytes and a use combinator requiring more bytes

        let res: IResult<&str, &str> = flat_take(2u8, take(4u8))(input);

        assert_eq!(res, Err(Err::Incomplete(Needed::Unknown)));

    }

    #[test]

    fn test_cond_else() {

        let input = &[0x01][..];

        let empty = &b""[..];

        let a = 1;

        fn parse_u8(i: &[u8]) -> IResult<&[u8], u8> {

            be_u8(i)

        }

        assert_eq!(

            cond_else(|| a == 1, parse_u8, pure(0x02))(input),

            Ok((empty, 0x01))

        );

        assert_eq!(

            cond_else(|| a == 1, parse_u8, pure(0x02))(input),

            Ok((empty, 0x01))

        );

        assert_eq!(

            cond_else(|| a == 2, parse_u8, pure(0x02))(input),

            Ok((input, 0x02))

        );

        assert_eq!(

            cond_else(|| a == 1, pure(0x02), parse_u8)(input),

            Ok((input, 0x02))

        );

        let res: IResult<&[u8], u8> = cond_else(|| a == 1, parse_u8, parse_u8)(input);

        assert_eq!(res, Ok((empty, 0x01)));

    }

    #[test]

    fn test_align32() {

        assert_eq!(align32(3), 4);

        assert_eq!(align32(4), 4);

        assert_eq!(align32(5), 8);

        assert_eq!(align32(5usize), 8);

    }

}