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use crate::{Call, Future, Generator, Stream, Value, Vm, VmError, VmExecution};

/// An instruction to push a virtual machine to the execution.
#[derive(Debug)]
pub struct VmCall {
    pub(crate) call: Call,
    pub(crate) vm: Vm,
}

impl VmCall {
    /// Construct a new nested vm call.
    pub(crate) fn new(call: Call, vm: Vm) -> Self {
        Self { call, vm }
    }

    /// Encode the push itno an execution.
    pub(crate) fn into_execution<'vm>(self, execution: &mut VmExecution) -> Result<(), VmError> {
        let value = match self.call {
            Call::Async => Value::from(Future::new(self.vm.async_complete())),
            Call::Stream => Value::from(Stream::new(self.vm)),
            Call::Generator => Value::from(Generator::new(self.vm)),
            Call::Immediate => {
                execution.push_vm(self.vm);
                return Ok(());
            }
        };

        let vm = execution.vm_mut()?;
        vm.stack_mut().push(value);
        vm.advance();
        Ok(())
    }
}