dex_sdk/
flow.rs

1// Copyright (c) 2026 Super Durable, Inc.
2//
3// Licensed under the Sustainable Use License 1.0.
4// You may not use this file except in compliance with the License.
5// See the LICENSE file in the repository root.
6//
7// SPDX-License-Identifier: LicenseRef-Sustainable-Use-1.0
8
9use crate::{
10    Context, HandlerResult, PersistenceSchema, RpcList, StepDecision, StepList, Value,
11    short_type_name,
12};
13
14/// Function registered by a [`Flow`] to handle expiration of its soft timeout.
15pub type FlowTimeoutHandler<SomeFlow> = fn(&SomeFlow, &mut Context) -> HandlerResult<StepDecision>;
16
17/// Defines a durable application Flow and its registered API surface.
18///
19/// A Flow owns a typed start input, Step list, persistence schema, and RPC list. Implementations are
20/// registered as owned values in [`crate::Registry`] and shared safely across Worker invocations.
21/// Keep [`Self::flow_type`] and all subordinate names stable while any execution is running.
22///
23/// # Examples
24///
25/// ```
26/// use dex_sdk::{Flow, StepList};
27///
28/// struct OrderFlow;
29///
30/// impl Flow for OrderFlow {
31///     type StartInput = String;
32///
33///     fn steps(&self) -> StepList<'_, Self::StartInput> {
34///         StepList::empty()
35///     }
36/// }
37/// ```
38pub trait Flow: Send + Sync + 'static {
39    /// Value accepted by [`crate::Client::start_flow`] and the starting Step.
40    type StartInput: Value;
41
42    /// Returns the stable Flow type sent to Dex.
43    ///
44    /// The default is the final Rust type-name segment.
45    fn flow_type(&self) -> &'static str {
46        short_type_name::<Self>()
47    }
48
49    /// Returns the starting Step and all other Step definitions.
50    ///
51    /// The default is an empty list, which is valid only for Flows driven entirely by RPCs.
52    fn steps(&self) -> StepList<'_, Self::StartInput> {
53        StepList::empty()
54    }
55
56    /// Declares every Attribute and Channel used by this Flow.
57    ///
58    /// The default schema is empty.
59    fn persistence(&self) -> PersistenceSchema {
60        PersistenceSchema::new()
61    }
62
63    /// Returns the optional handler invoked after this Flow's durable timeout timer expires.
64    ///
65    /// Returning `Some` makes a positive timeout default to [`crate::FlowTimeoutPolicy::Handler`].
66    /// One logical execution may retry, and its decision uses normal Step Execute validation.
67    fn timeout_handler(&self) -> Option<FlowTimeoutHandler<Self>>
68    where
69        Self: Sized,
70    {
71        None
72    }
73
74    /// Binds public RPC names to methods on this Flow implementation.
75    ///
76    /// The default list is empty.
77    fn rpcs(&self) -> RpcList<Self>
78    where
79        Self: Sized,
80    {
81        RpcList::new()
82    }
83}
dex_sdk/flow.rs

dex_sdk/
flow.rs
