Split the server into three crates (#56)

This will make it easier to build variations on the server, or embed it
into larger projects.

src/storage/mod.rs

@@ -1,95 +0,0 @@
-use chrono::{DateTime, Utc};
-use uuid::Uuid;
-
-#[cfg(debug_assertions)]
-mod inmemory;
-
-#[cfg(debug_assertions)]
-pub use inmemory::InMemoryStorage;
-
-mod sqlite;
-pub use self::sqlite::SqliteStorage;
-
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub struct Client {
-    /// The latest version for this client (may be the nil version)
-    pub latest_version_id: Uuid,
-    /// Data about the latest snapshot for this client
-    pub snapshot: Option<Snapshot>,
-}
-
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub struct Snapshot {
-    /// ID of the version at which this snapshot was made
-    pub version_id: Uuid,
-
-    /// Timestamp at which this snapshot was set
-    pub timestamp: DateTime<Utc>,
-
-    /// Number of versions since this snapshot was made
-    pub versions_since: u32,
-}
-
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub struct Version {
-    pub version_id: Uuid,
-    pub parent_version_id: Uuid,
-    pub history_segment: Vec<u8>,
-}
-
-pub trait StorageTxn {
-    /// Get information about the given client
-    fn get_client(&mut self, client_id: Uuid) -> anyhow::Result<Option<Client>>;
-
-    /// Create a new client with the given latest_version_id
-    fn new_client(&mut self, client_id: Uuid, latest_version_id: Uuid) -> anyhow::Result<()>;
-
-    /// Set the client's most recent snapshot.
-    fn set_snapshot(
-        &mut self,
-        client_id: Uuid,
-        snapshot: Snapshot,
-        data: Vec<u8>,
-    ) -> anyhow::Result<()>;
-
-    /// Get the data for the most recent snapshot.  The version_id
-    /// is used to verify that the snapshot is for the correct version.
-    fn get_snapshot_data(
-        &mut self,
-        client_id: Uuid,
-        version_id: Uuid,
-    ) -> anyhow::Result<Option<Vec<u8>>>;
-
-    /// Get a version, indexed by parent version id
-    fn get_version_by_parent(
-        &mut self,
-        client_id: Uuid,
-        parent_version_id: Uuid,
-    ) -> anyhow::Result<Option<Version>>;
-
-    /// Get a version, indexed by its own version id
-    fn get_version(&mut self, client_id: Uuid, version_id: Uuid)
-        -> anyhow::Result<Option<Version>>;
-
-    /// Add a version (that must not already exist), and
-    ///  - update latest_version_id
-    ///  - increment snapshot.versions_since
-    fn add_version(
-        &mut self,
-        client_id: Uuid,
-        version_id: Uuid,
-        parent_version_id: Uuid,
-        history_segment: Vec<u8>,
-    ) -> anyhow::Result<()>;
-
-    /// Commit any changes made in the transaction.  It is an error to call this more than
-    /// once.  It is safe to skip this call for read-only operations.
-    fn commit(&mut self) -> anyhow::Result<()>;
-}
-
-/// A trait for objects able to act as storage.  Most of the interesting behavior is in the
-/// [`crate::storage::StorageTxn`] trait.
-pub trait Storage: Send + Sync {
-    /// Begin a transaction
-    fn txn<'a>(&'a self) -> anyhow::Result<Box<dyn StorageTxn + 'a>>;
-}