moqtap_client/
fetch.rs

1/// Fetch lifecycle states.
2#[derive(Debug, Clone, Copy, PartialEq, Eq)]
3pub enum FetchState {
4    Idle,
5    Pending,
6    Receiving,
7    Done,
8}
9
10#[derive(Debug, thiserror::Error, PartialEq, Eq)]
11pub enum FetchError {
12    #[error("invalid transition from {from:?} on event {event}")]
13    InvalidTransition { from: FetchState, event: String },
14}
15
16/// Pure state machine for a MoQT fetch request.
17/// Transitions: Idle → Pending → Receiving → Done.
18pub struct FetchStateMachine {
19    state: FetchState,
20}
21
22impl Default for FetchStateMachine {
23    fn default() -> Self {
24        Self::new()
25    }
26}
27
28impl FetchStateMachine {
29    pub fn new() -> Self {
30        Self { state: FetchState::Idle }
31    }
32
33    pub fn state(&self) -> FetchState {
34        self.state
35    }
36
37    /// Idle → Pending (FETCH sent).
38    pub fn on_fetch_sent(&mut self) -> Result<(), FetchError> {
39        if self.state == FetchState::Idle {
40            self.state = FetchState::Pending;
41            Ok(())
42        } else {
43            Err(FetchError::InvalidTransition {
44                from: self.state,
45                event: "on_fetch_sent".to_string(),
46            })
47        }
48    }
49
50    /// Pending → Receiving (FETCH_OK received).
51    pub fn on_fetch_ok(&mut self) -> Result<(), FetchError> {
52        if self.state == FetchState::Pending {
53            self.state = FetchState::Receiving;
54            Ok(())
55        } else {
56            Err(FetchError::InvalidTransition {
57                from: self.state,
58                event: "on_fetch_ok".to_string(),
59            })
60        }
61    }
62
63    /// Pending → Done (FETCH_ERROR received).
64    pub fn on_fetch_error(&mut self) -> Result<(), FetchError> {
65        if self.state == FetchState::Pending {
66            self.state = FetchState::Done;
67            Ok(())
68        } else {
69            Err(FetchError::InvalidTransition {
70                from: self.state,
71                event: "on_fetch_error".to_string(),
72            })
73        }
74    }
75
76    /// Pending|Receiving → Done (FETCH_CANCEL sent).
77    pub fn on_fetch_cancel(&mut self) -> Result<(), FetchError> {
78        if self.state == FetchState::Pending || self.state == FetchState::Receiving {
79            self.state = FetchState::Done;
80            Ok(())
81        } else {
82            Err(FetchError::InvalidTransition {
83                from: self.state,
84                event: "on_fetch_cancel".to_string(),
85            })
86        }
87    }
88
89    /// Receiving → Done (stream FIN received).
90    pub fn on_stream_fin(&mut self) -> Result<(), FetchError> {
91        if self.state == FetchState::Receiving {
92            self.state = FetchState::Done;
93            Ok(())
94        } else {
95            Err(FetchError::InvalidTransition {
96                from: self.state,
97                event: "on_stream_fin".to_string(),
98            })
99        }
100    }
101
102    /// Receiving → Done (stream RESET received).
103    pub fn on_stream_reset(&mut self) -> Result<(), FetchError> {
104        if self.state == FetchState::Receiving {
105            self.state = FetchState::Done;
106            Ok(())
107        } else {
108            Err(FetchError::InvalidTransition {
109                from: self.state,
110                event: "on_stream_reset".to_string(),
111            })
112        }
113    }
114}
moqtap_client/fetch.rs

moqtap_client/
fetch.rs
