Add download lifecycle controls

crates/ely_domain/src/download.rs

@@ -49,6 +49,52 @@ impl DownloadEntry {
         })
     }
 
+    pub fn pause(&mut self) -> Result<(), DomainError> {
+        self.require_state("pause", &[DownloadState::InProgress])?;
+        self.state = DownloadState::Paused;
+        Ok(())
+    }
+
+    pub fn resume(&mut self) -> Result<(), DomainError> {
+        self.require_state("resume", &[DownloadState::Paused])?;
+        self.state = DownloadState::InProgress;
+        Ok(())
+    }
+
+    pub fn cancel(&mut self) -> Result<(), DomainError> {
+        self.require_state("cancel", &[DownloadState::InProgress, DownloadState::Paused])?;
+        self.state = DownloadState::Cancelled;
+        Ok(())
+    }
+
+    pub fn retry(&mut self) -> Result<(), DomainError> {
+        self.require_state("retry", &[DownloadState::Cancelled, DownloadState::Failed])?;
+        self.state = DownloadState::InProgress;
+        self.received_bytes = 0;
+        Ok(())
+    }
+
+    pub fn update_progress(&mut self, received_bytes: u64) -> Result<(), DomainError> {
+        self.require_state("update progress", &[DownloadState::InProgress])?;
+        self.validate_received_bytes(received_bytes)?;
+        self.received_bytes = received_bytes;
+        Ok(())
+    }
+
+    pub fn complete(&mut self, received_bytes: u64) -> Result<(), DomainError> {
+        self.require_state("complete", &[DownloadState::InProgress])?;
+        self.validate_received_bytes(received_bytes)?;
+        self.received_bytes = received_bytes;
+        self.state = DownloadState::Completed;
+        Ok(())
+    }
+
+    pub fn fail(&mut self) -> Result<(), DomainError> {
+        self.require_state("fail", &[DownloadState::InProgress, DownloadState::Paused])?;
+        self.state = DownloadState::Failed;
+        Ok(())
+    }
+
     #[must_use]
     pub fn id(&self) -> &DownloadId {
         &self.id
@@ -88,4 +134,39 @@ impl DownloadEntry {
     pub fn started_at(&self) -> SystemTime {
         self.started_at
     }
+
+    fn require_state(
+        &self,
+        action: &'static str,
+        allowed_states: &[DownloadState],
+    ) -> Result<(), DomainError> {
+        if allowed_states.iter().any(|state| state == &self.state) {
+            return Ok(());
+        }
+
+        Err(DomainError::InvalidDownloadTransition { action, state: self.state.as_str() })
+    }
+
+    fn validate_received_bytes(&self, received_bytes: u64) -> Result<(), DomainError> {
+        if let Some(total_bytes) = self.total_bytes
+            && received_bytes > total_bytes
+        {
+            return Err(DomainError::InvalidDownloadProgress { received_bytes, total_bytes });
+        }
+
+        Ok(())
+    }
+}
+
+impl DownloadState {
+    #[must_use]
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::InProgress => "in_progress",
+            Self::Paused => "paused",
+            Self::Completed => "completed",
+            Self::Cancelled => "cancelled",
+            Self::Failed => "failed",
+        }
+    }
 }

crates/ely_domain/src/error.rs

@@ -10,4 +10,10 @@ pub enum DomainError {
 
     #[error("invalid command query")]
     InvalidCommand,
+
+    #[error("cannot {action} download while state is {state}")]
+    InvalidDownloadTransition { action: &'static str, state: &'static str },
+
+    #[error("download progress {received_bytes} exceeds total {total_bytes}")]
+    InvalidDownloadProgress { received_bytes: u64, total_bytes: u64 },
 }