#[cfg(feature = "std")]

use std::error;

use core::fmt::{self, Display, Formatter};

use core::str::{from_utf8, Utf8Error};

use super::{read_marker, RmpRead, RmpReadErr, ValueReadError};

use crate::Marker;

#[derive(Debug)]

#[allow(deprecated)] // Only for compatibility

pub enum DecodeStringError<'a, E: RmpReadErr = super::Error> {

    InvalidMarkerRead(E),

    InvalidDataRead(E),

    TypeMismatch(Marker),

    /// The given buffer is not large enough to accumulate the specified amount of bytes.

    BufferSizeTooSmall(u32),

    InvalidUtf8(&'a [u8], Utf8Error),

}

#[cfg(feature = "std")]

impl<'a, E: RmpReadErr> error::Error for DecodeStringError<'a, E> {

    #[cold]

    fn source(&self) -> Option<&(dyn error::Error + 'static)> {

        match *self {

            DecodeStringError::InvalidMarkerRead(ref err) |

            DecodeStringError::InvalidDataRead(ref err) => Some(err),

            DecodeStringError::TypeMismatch(..) |

            DecodeStringError::BufferSizeTooSmall(..) => None,

            DecodeStringError::InvalidUtf8(_, ref err) => Some(err),

        }

    }

}

impl<'a, E: RmpReadErr> Display for DecodeStringError<'a, E> {

    #[cold]

    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), fmt::Error> {

        f.write_str("error while decoding string")

    }

}

impl<'a, E: RmpReadErr> From<ValueReadError<E>> for DecodeStringError<'a, E> {

    #[cold]

    fn from(err: ValueReadError<E>) -> DecodeStringError<'a, E> {

        match err {

            ValueReadError::InvalidMarkerRead(err) => DecodeStringError::InvalidMarkerRead(err),

            ValueReadError::InvalidDataRead(err) => DecodeStringError::InvalidDataRead(err),

            ValueReadError::TypeMismatch(marker) => DecodeStringError::TypeMismatch(marker),

        }

    }

}

/// Attempts to read up to 9 bytes from the given reader and to decode them as a string `u32` size

/// value.

///

/// According to the MessagePack specification, the string format family stores an byte array in 1,

/// 2, 3, or 5 bytes of extra bytes in addition to the size of the byte array.

///

/// # Errors

///

/// This function will return `ValueReadError` on any I/O error while reading either the marker or

/// the data.

///

/// It also returns `ValueReadError::TypeMismatch` if the actual type is not equal with the

/// expected one, indicating you with the actual type.

#[inline]

pub fn read_str_len<R: RmpRead>(rd: &mut R) -> Result<u32, ValueReadError<R::Error>> {

    Ok(read_str_len_with_nread(rd)?.0)

}

fn read_str_len_with_nread<R>(rd: &mut R) -> Result<(u32, usize), ValueReadError<R::Error>>

    where R: RmpRead

{

    match read_marker(rd)? {

        Marker::FixStr(size) => Ok((u32::from(size), 1)),

        Marker::Str8 => Ok((u32::from(rd.read_data_u8()?), 2)),

        Marker::Str16 => Ok((u32::from(rd.read_data_u16()?), 3)),

        Marker::Str32 => Ok((rd.read_data_u32()?, 5)),

        marker => Err(ValueReadError::TypeMismatch(marker)),

    }

}

/// Attempts to read a string data from the given reader and copy it to the buffer provided.

///

/// On success returns a borrowed string type, allowing to view the copied bytes as properly utf-8

/// string.

/// According to the spec, the string's data must to be encoded using utf-8.

///

/// # Errors

///

/// Returns `Err` in the following cases:

///

///  - if any IO error (including unexpected EOF) occurs, while reading an `rd`, except the EINTR,

///    which is handled internally.

///  - if the `out` buffer size is not large enough to keep all the data copied.

///  - if the data is not utf-8, with a description as to why the provided data is not utf-8 and

///    with a size of bytes actually copied to be able to get them from `out`.

///

/// # Examples

/// ```

/// use rmp::decode::read_str;

///

/// let buf = [0xaa, 0x6c, 0x65, 0x20, 0x6d, 0x65, 0x73, 0x73, 0x61, 0x67, 0x65];

/// let mut out = [0u8; 16];

///

/// assert_eq!("le message", read_str(&mut &buf[..], &mut &mut out[..]).unwrap());

/// ```

///

/// # Unstable

///

/// This function is **unstable**, because it needs review.

// TODO: Stabilize. Mark error values for each error case (in docs).

pub fn read_str<'r, R>(rd: &mut R, buf: &'r mut [u8]) -> Result<&'r str, DecodeStringError<'r, R::Error>>

where

    R: RmpRead,

{

    let len = read_str_len(rd)?;

    let ulen = len as usize;

    if buf.len() < ulen {

        return Err(DecodeStringError::BufferSizeTooSmall(len));

    }

    read_str_data(rd, len, &mut buf[0..ulen])

}

pub fn read_str_data<'r, R>(rd: &mut R,

                            len: u32,

                            buf: &'r mut [u8])

                            -> Result<&'r str, DecodeStringError<'r, R::Error>>

    where R: RmpRead

{

    debug_assert_eq!(len as usize, buf.len());

    // Trying to copy exact `len` bytes.

    match rd.read_exact_buf(buf) {

        Ok(()) => match from_utf8(buf) {

            Ok(decoded) => Ok(decoded),

            Err(err) => Err(DecodeStringError::InvalidUtf8(buf, err)),

        },

        Err(err) => Err(DecodeStringError::InvalidDataRead(err)),

    }

}

/// Attempts to read and decode a string value from the reader, returning a borrowed slice from it.

///

// TODO: Also it's possible to implement all borrowing functions for all `BufRead` implementors.

#[deprecated(since = "0.8.6", note = "useless, use `read_str_from_slice` instead")]

pub fn read_str_ref(rd: &[u8]) -> Result<&[u8], DecodeStringError<'_, super::bytes::BytesReadError>> {

    let mut cur = super::Bytes::new(rd);

    let len = read_str_len(&mut cur)?;

    Ok(&cur.remaining_slice()[..len as usize])

}

/// Attempts to read and decode a string value from the reader, returning a borrowed slice from it.

///

/// # Examples

///

/// ```

/// use rmp::encode::write_str;

/// use rmp::decode::read_str_from_slice;

///

/// let mut buf = Vec::new();

/// write_str(&mut buf, "Unpacking").unwrap();

/// write_str(&mut buf, "multiple").unwrap();

/// write_str(&mut buf, "strings").unwrap();

///

/// let mut chunks = Vec::new();

/// let mut unparsed = &buf[..];

/// while let Ok((chunk, tail)) = read_str_from_slice(unparsed) {

///     chunks.push(chunk);

///     unparsed = tail;

/// }

///

/// assert_eq!(vec!["Unpacking", "multiple", "strings"], chunks);

/// ```

pub fn read_str_from_slice<T: ?Sized + AsRef<[u8]>>(

    buf: &T,

) -> Result<(&str, &[u8]), DecodeStringError<'_, super::bytes::BytesReadError>> {

    let buf = buf.as_ref();

    let (len, nread) = read_str_len_with_nread(&mut super::Bytes::new(buf))?;

    let ulen = len as usize;

    if buf[nread..].len() >= ulen {

        let (head, tail) = buf.split_at(nread + ulen);

        match from_utf8(&head[nread..]) {

            Ok(val) => Ok((val, tail)),

            Err(err) => Err(DecodeStringError::InvalidUtf8(buf, err)),

        }

    } else {

        Err(DecodeStringError::BufferSizeTooSmall(len))

    }

}