// © 2023 John Breaux
//! A [JumpTarget] contains the [pc-relative offset](Number) or [Identifier]
//! for a [Jump instruction encoding](Encoding::Jump)
use super::*;

/// The target of a [Jump](Encoding::Jump)
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct JumpTarget(Number);

impl JumpTarget {
    pub fn word(&self) -> u16 { u16::from(self.0) & 0x3ff }
}

impl Parsable for JumpTarget {
    /// - Identifier
    /// - Number
    /// - Negative
    ///   - Number
    fn parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Self, Error>
    where T: crate::TokenStream<'text> {
        // Try to parse a number
        let target = Number::parse(p, stream)?;
        match target.into() {
            i if i % 2 != 0 => Err(Error::JumpedOdd(i).context(stream.context()))?,
            i if (-1024..=1022).contains(&(i - 2)) => Ok(Self((target - 2) >> 1)),
            i => Err(Error::JumpedTooFar(i).context(stream.context()))?,
        }
    }
}

impl From<JumpTarget> for u16 {
    fn from(value: JumpTarget) -> Self { value.0.into() }
}

impl Display for JumpTarget {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", (1 + isize::from(self.0)) << 1)
    }
}