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use std::fmt;

use crate::{Result, Tape, Value};

/// A tag.
#[derive(Clone, Copy, Default, Eq, Hash, PartialEq)]
pub struct Tag(pub [u8; 4]);

impl Tag {
    /// Create an instance from a string if possible.
    pub fn from_str(value: &str) -> Option<Self> {
        if let Ok(value) = value.as_bytes().try_into() {
            Some(Self(value))
        } else {
            None
        }
    }

    /// Convert into a string if possible.
    pub fn as_str(&self) -> Option<&str> {
        if !self.0.iter().any(u8::is_ascii_control) {
            std::str::from_utf8(&self.0[..]).ok()
        } else {
            None
        }
    }
}

dereference! { Tag::0 => [u8; 4] }

impl fmt::Debug for Tag {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        match self.as_str() {
            Some(value) => write!(formatter, "Tag({value})"),
            _ => write!(formatter, "Tag(0x{:08X})", u32::from(*self)),
        }
    }
}

impl From<u32> for Tag {
    #[inline(always)]
    fn from(value: u32) -> Self {
        Tag(u32::from_be(value).to_ne_bytes())
    }
}

impl From<Tag> for u32 {
    #[inline(always)]
    fn from(tag: Tag) -> Self {
        u32::from_be_bytes(tag.0)
    }
}

impl Value for Tag {
    #[inline(always)]
    fn read<T: Tape>(tape: &mut T) -> Result<Self> {
        Ok(Tag(tape.take()?))
    }
}

#[cfg(test)]
mod tests {
    use std::io::Cursor;

    use super::Tag;
    use crate::Value;

    macro_rules! ok(($result:expr) => ($result.unwrap()));

    #[test]
    fn from_str() {
        assert_eq!(ok!(Tag::from_str("true")), Tag(*b"true"));
    }

    #[test]
    fn as_str() {
        assert_eq!(Tag(*b"CFF ").as_str(), Some("CFF "));
        assert_eq!(Tag(*b"OS/2").as_str(), Some("OS/2"));
        assert_eq!(Tag(*b"true").as_str(), Some("true"));
        assert_eq!(Tag([0, 1, 0, 0]).as_str(), None);
    }

    #[test]
    fn debug() {
        assert_eq!(format!("{:?}", Tag(*b"true")), "Tag(true)");
        assert_eq!(format!("{:?}", Tag([0, 1, 0, 0])), "Tag(0x00010000)");
    }

    #[test]
    fn from() {
        assert_eq!(Tag(*b"true"), Tag::from(0x74727565));
    }

    #[test]
    fn into() {
        assert_eq!(u32::from(Tag(*b"true")), 0x74727565);
    }

    #[test]
    fn read() {
        let mut tape = Cursor::new(b"true".to_vec());
        assert_eq!(Tag::read(&mut tape).unwrap(), Tag(*b"true"));
    }
}