rune 0.12.0

use crate::runtime::{
    FromValue, Mut, RawMut, RawRef, RawStr, Ref, Shared, UnsafeFromValue, Value, VmError,
};
use crate::{compile::Named, InstallWith};

/// The state of a generator.
///
/// ```
/// use rune::{Context, FromValue, Value, Vm};
/// use rune::runtime::{Generator, GeneratorState};
/// use std::sync::Arc;
///
/// # fn main() -> rune::Result<()> {
/// let mut sources = rune::sources! {
///     entry => {
///         pub fn main() {
///             let n = yield 1;
///             let out = yield n + 1;
///             out
///         }
///     }
/// };
///
/// let unit = rune::prepare(&mut sources).build()?;
///
/// let mut vm = Vm::without_runtime(Arc::new(unit));
/// let mut execution = vm.execute(&["main"], ())?;
///
/// // Initial resume doesn't take a value.
/// let first = match execution.resume()? {
///     GeneratorState::Yielded(first) => i64::from_value(first)?,
///     GeneratorState::Complete(..) => panic!("generator completed"),
/// };
///
/// assert_eq!(first, 1);
///
/// // Additional resumes require a value.
/// let second = match execution.resume_with(Value::from(2i64))? {
///     GeneratorState::Yielded(second) => i64::from_value(second)?,
///     GeneratorState::Complete(..) => panic!("generator completed"),
/// };
///
/// assert_eq!(second, 3);
///
/// let ret = match execution.resume_with(Value::from(42i64))? {
///     GeneratorState::Complete(ret) => i64::from_value(ret)?,
///     GeneratorState::Yielded(..) => panic!("generator yielded"),
/// };
///
/// assert_eq!(ret, 42);
/// # Ok(()) }
/// ```
#[derive(Debug)]
pub enum GeneratorState {
    /// The generator yielded.
    Yielded(Value),
    /// The generator completed.
    Complete(Value),
}

impl GeneratorState {
    /// Test if the state is yielded.
    pub fn is_yielded(&self) -> bool {
        matches!(self, Self::Yielded(..))
    }

    /// Test if the state is complete.
    pub fn is_complete(&self) -> bool {
        matches!(self, Self::Complete(..))
    }
}

impl FromValue for Shared<GeneratorState> {
    fn from_value(value: Value) -> Result<Self, VmError> {
        value.into_generator_state()
    }
}

impl FromValue for GeneratorState {
    fn from_value(value: Value) -> Result<Self, VmError> {
        let state = value.into_generator_state()?;
        Ok(state.take()?)
    }
}

impl UnsafeFromValue for &GeneratorState {
    type Output = *const GeneratorState;
    type Guard = RawRef;

    fn from_value(value: Value) -> Result<(Self::Output, Self::Guard), VmError> {
        let state = value.into_generator_state()?;
        let (state, guard) = Ref::into_raw(state.into_ref()?);
        Ok((state, guard))
    }

    unsafe fn unsafe_coerce(output: Self::Output) -> Self {
        &*output
    }
}

impl UnsafeFromValue for &mut GeneratorState {
    type Output = *mut GeneratorState;
    type Guard = RawMut;

    fn from_value(value: Value) -> Result<(Self::Output, Self::Guard), VmError> {
        let state = value.into_generator_state()?;
        Ok(Mut::into_raw(state.into_mut()?))
    }

    unsafe fn unsafe_coerce(output: Self::Output) -> Self {
        &mut *output
    }
}

impl Named for GeneratorState {
    const BASE_NAME: RawStr = RawStr::from_str("GeneratorState");
}

impl InstallWith for GeneratorState {}