1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132

use crate::compile::{InstallWith, Named};
use crate::runtime::{
    FromValue, GeneratorState, Mut, RawMut, RawRef, RawStr, Ref, Shared, UnsafeFromValue, Value,
    Vm, VmError, VmErrorKind, VmExecution,
};
use std::fmt;

/// A stream with a stored virtual machine.
pub struct Stream<T>
where
    T: AsMut<Vm>,
{
    execution: Option<VmExecution<T>>,
}

impl<T> Stream<T>
where
    T: AsMut<Vm>,
{
    /// Construct a stream from a virtual machine.
    pub(crate) fn new(vm: T) -> Self {
        Self {
            execution: Some(VmExecution::new(vm)),
        }
    }

    /// Construct a generator from a complete execution.
    pub(crate) fn from_execution(execution: VmExecution<T>) -> Self {
        Self {
            execution: Some(execution),
        }
    }

    /// Get the next value produced by this stream.
    pub async fn next(&mut self) -> Result<Option<Value>, VmError> {
        Ok(match self.resume(Value::Unit).await? {
            GeneratorState::Yielded(value) => Some(value),
            GeneratorState::Complete(_) => None,
        })
    }

    /// Get the next value produced by this stream.
    pub async fn resume(&mut self, value: Value) -> Result<GeneratorState, VmError> {
        let execution = self
            .execution
            .as_mut()
            .ok_or(VmErrorKind::GeneratorComplete)?;

        let state = if execution.is_resumed() {
            execution.async_resume_with(value).await?
        } else {
            execution.async_resume().await?
        };

        if state.is_complete() {
            self.execution = None;
        }

        Ok(state)
    }
}

impl Stream<&mut Vm> {
    /// Convert the current stream into one which owns its virtual machine.
    pub fn into_owned(self) -> Stream<Vm> {
        Stream {
            execution: self.execution.map(|e| e.into_owned()),
        }
    }
}

impl<T> Named for Stream<T>
where
    T: AsMut<Vm>,
{
    const BASE_NAME: RawStr = RawStr::from_str("Stream");
}

impl<T> InstallWith for Stream<T> where T: AsMut<Vm> {}

impl<T> fmt::Debug for Stream<T>
where
    T: AsMut<Vm>,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Stream")
            .field("completed", &self.execution.is_none())
            .finish()
    }
}

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

impl FromValue for Stream<Vm> {
    fn from_value(value: Value) -> Result<Self, VmError> {
        let stream = value.into_stream()?;
        Ok(stream.take()?)
    }
}

impl UnsafeFromValue for &Stream<Vm> {
    type Output = *const Stream<Vm>;
    type Guard = RawRef;

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

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

impl UnsafeFromValue for &mut Stream<Vm> {
    type Output = *mut Stream<Vm>;
    type Guard = RawMut;

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

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