1 files changed, 93 insertions, 0 deletions
diff --git a/third_party/rust/sync15/src/clients_engine/mod.rs b/third_party/rust/sync15/src/clients_engine/mod.rs
new file mode 100644
index 0000000000..7346712dc7
--- /dev/null
+++ b/third_party/rust/sync15/src/clients_engine/mod.rs
@@ -0,0 +1,93 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! The client engine is a [crate::engine](Sync Engine) used to manage the
+//! "clients" collection. The clients engine manages the client record for
+//! "this device, and also manages "commands".
+//! In short, commands target one or more engines and instruct them to
+//! perform various operations - such as wiping all local data.
+//! These commands are used very rarely - currently the only command used
+//! in practice is for bookmarks to wipe all their data, which is sent when
+//! a desktop device restores all bookmarks from a backup. In this scenario,
+//! desktop will delete all local bookmarks then replace them with the backed
+//! up set, which without a "wipe" command would almost certainly cause other
+//! connected devices to "resurrect" the deleted bookmarks.
+use std::collections::HashSet;
+
+mod engine;
+mod record;
+mod ser;
+
+use crate::DeviceType;
+use anyhow::Result;
+pub use engine::Engine;
+
+// These are what desktop uses.
+const CLIENTS_TTL: u32 = 15_552_000; // 180 days
+pub(crate) const CLIENTS_TTL_REFRESH: u64 = 604_800; // 7 days
+
+/// A command processor applies incoming commands like wipes and resets for all
+/// stores, and returns commands to send to other clients. It also manages
+/// settings like the device name and type, which is stored in the special
+/// `clients` collection.
+///
+/// In practice, this trait only has one implementation, in the sync manager.
+/// It's split this way because the clients engine depends on internal `sync15`
+/// structures, and can't be implemented as a syncable store...but `sync15`
+/// doesn't know anything about multiple engines. This lets the sync manager
+/// provide its own implementation for handling wipe and reset commands for all
+/// the engines that it manages.
+pub trait CommandProcessor {
+    fn settings(&self) -> &Settings;
+
+    /// Fetches commands to send to other clients. An error return value means
+    /// commands couldn't be fetched, and halts the sync.
+    fn fetch_outgoing_commands(&self) -> Result<HashSet<Command>>;
+
+    /// Applies a command sent to this client from another client. This method
+    /// should return a `CommandStatus` indicating whether the command was
+    /// processed.
+    ///
+    /// An error return value means the sync manager encountered an error
+    /// applying the command, and halts the sync to prevent unexpected behavior
+    /// (for example, merging local and remote bookmarks, when we were told to
+    /// wipe our local bookmarks).
+    fn apply_incoming_command(&self, command: Command) -> Result<CommandStatus>;
+}
+
+/// Indicates if a command was applied successfully, ignored, or not supported.
+/// Applied and ignored commands are removed from our client record, and never
+/// retried. Unsupported commands are put back into our record, and retried on
+/// subsequent syncs. This is to handle clients adding support for new data
+/// types.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub enum CommandStatus {
+    Applied,
+    Ignored,
+    Unsupported,
+}
+
+/// Information about this device to include in its client record. This should
+/// be persisted across syncs, as part of the sync manager state.
+#[derive(Clone, Debug, Eq, Hash, PartialEq)]
+pub struct Settings {
+    /// The FxA device ID of this client, also used as this client's record ID
+    /// in the clients collection.
+    pub fxa_device_id: String,
+    /// The name of this client. This should match the client's name in the
+    /// FxA device manager.
+    pub device_name: String,
+    /// The type of this client: mobile, tablet, desktop, or other.
+    pub device_type: DeviceType,
+}
+
+#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub enum Command {
+    /// Erases all local data for a specific engine.
+    Wipe(String),
+    /// Resets local sync state for all engines.
+    ResetAll,
+    /// Resets local sync state for a specific engine.
+    Reset(String),
+}