feat: Add FDv2 source traits and result types

launchdarkly-server-sdk/src/fdv2/mod.rs

@@ -1,3 +1,4 @@
 pub mod model;
 mod protocol;
+mod source;
 mod wire;

launchdarkly-server-sdk/src/fdv2/source.rs

@@ -0,0 +1,52 @@
+use std::time::Duration;
+
+use futures::future::BoxFuture;
+
+use crate::stores::change_set::ChangeSet;
+
+use super::model::Selector;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum ErrorKind {
+    Unknown,
+    NetworkError,
+    ErrorResponse { status_code: u16 },
+    InvalidData,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct ErrorInfo {
+    #[allow(dead_code)] // Will be read by data source status provider, once implemented.
+    pub(crate) kind: ErrorKind,
+    pub(crate) message: String,
+}
+
+#[derive(Debug)]
+pub(crate) struct FDv1FallbackDirective {
+    pub(crate) ttl: Duration,
+}
+
+#[derive(Debug)]
+pub(crate) enum FDv2SourceResult {
+    ChangeSet(ChangeSet),
+    Interrupted(ErrorInfo),
+    TerminalError(ErrorInfo),
+    Shutdown,
+    Goodbye,
+}
+
+#[derive(Debug)]
+pub(crate) struct FDv2SourceEvent {
+    pub(crate) result: FDv2SourceResult,
+    pub(crate) fdv1_fallback: Option<FDv1FallbackDirective>,
+}
+
+pub(crate) trait Initializer: Send {
+    fn run(&mut self) -> BoxFuture<'_, FDv2SourceEvent>;
+    fn name(&self) -> &str;
+}
+
+pub(crate) trait Synchronizer: Send {
+    fn next(&mut self, selector: Selector) -> BoxFuture<'_, FDv2SourceEvent>;
+    fn name(&self) -> &str;
+}