use crate::*;


pub struct PackedBinaryLiteral {
    pub source: SourceSpan,
    pub value: usize,
    pub bits: usize,
    pub fields: Vec<BitField>,
    pub errors: Vec<PackedBinaryLiteralParseError>,
}

pub struct BitField {
    pub name: char,
    pub source: SourceSpan,
    /// Length of field in bits
    pub bits: usize,
    /// Distance to left-shift field in value
    pub shift: usize,
}

pub struct PackedBinaryLiteralParseError {
    pub source: SourceSpan,
    pub variant: PackedBinaryLiteralParseErrorVariant,
}

pub enum PackedBinaryLiteralParseErrorVariant {
    DuplicateFieldName(char),
    InvalidCharacter(char),
}


impl std::fmt::Display for PackedBinaryLiteral {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
        if self.value == 0 {
            write!(f, "0")?;
        } else {
            let bitcount = (self.value.ilog2() + 1) as usize;
            'bit: for i in (0..bitcount).rev() {
                let is_first_bit = i+1 == bitcount;
                if !is_first_bit && (i+1) % 4 == 0 {
                    write!(f, "_")?;
                }
                for field in &self.fields {
                    if i <= field.bits + field.shift - 1 && i >= field.shift {
                        write!(f, "{}", field.name)?;
                        continue 'bit;
                    }
                }
                match (self.value >> i) & 1 {
                    0 => write!(f, "0")?,
                    _ => write!(f, "1")?,
                }
            }
        }
        return Ok(());
    }
}