/*!

Provides convenience routines for escaping raw bytes.

Since this crate tends to deal with `&[u8]` everywhere and the default

`Debug` implementation just shows decimal integers, it makes debugging those

representations quite difficult. This module provides types that show `&[u8]`

as if it were a string, with invalid UTF-8 escaped into its byte-by-byte hex

representation.

*/

use crate::util::utf8;

/// Provides a convenient `Debug` implementation for a `u8`.

///

/// The `Debug` impl treats the byte as an ASCII, and emits a human readable

/// representation of it. If the byte isn't ASCII, then it's emitted as a hex

/// escape sequence.

#[derive(Clone, Copy)]

pub struct DebugByte(pub u8);

impl core::fmt::Debug for DebugByte {

    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {

        // Special case ASCII space. It's too hard to read otherwise, so

        // put quotes around it. I sometimes wonder whether just '\x20' would

        // be better...

        if self.0 == b' ' {

            return write!(f, "' '");

        }

        // 10 bytes is enough to cover any output from ascii::escape_default.

        let mut bytes = [0u8; 10];

        let mut len = 0;

        for (i, mut b) in core::ascii::escape_default(self.0).enumerate() {

            // capitalize \xab to \xAB

            if i >= 2 && b'a' <= b && b <= b'f' {

                b -= 32;

            }

            bytes[len] = b;

            len += 1;

        }

        write!(f, "{}", core::str::from_utf8(&bytes[..len]).unwrap())

    }

}

/// Provides a convenient `Debug` implementation for `&[u8]`.

///

/// This generally works best when the bytes are presumed to be mostly UTF-8,

/// but will work for anything. For any bytes that aren't UTF-8, they are

/// emitted as hex escape sequences.

pub struct DebugHaystack<'a>(pub &'a [u8]);

impl<'a> core::fmt::Debug for DebugHaystack<'a> {

    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {

        write!(f, "\"")?;

        // This is a sad re-implementation of a similar impl found in bstr.

        let mut bytes = self.0;

        while let Some(result) = utf8::decode(bytes) {

            let ch = match result {

                Ok(ch) => ch,

                Err(byte) => {

                    write!(f, r"\x{:02x}", byte)?;

                    bytes = &bytes[1..];

                    continue;

                }

            };

            bytes = &bytes[ch.len_utf8()..];

            match ch {

                '\0' => write!(f, "\\0")?,

                // ASCII control characters except \0, \n, \r, \t

                '\x01'..='\x08'

                | '\x0b'

                | '\x0c'

                | '\x0e'..='\x19'

                | '\x7f' => {

                    write!(f, "\\x{:02x}", u32::from(ch))?;

                }

                '\n' | '\r' | '\t' | _ => {

                    write!(f, "{}", ch.escape_debug())?;

                }

            }

        }

        write!(f, "\"")?;

        Ok(())

    }

}