From c302c553a288d90c879720e9b9825ee9ede84958 Mon Sep 17 00:00:00 2001
From: Mike Dilger <mike@mikedilger.com>
Date: Tue, 20 Feb 2024 07:50:32 +1300
Subject: [PATCH] Store: migrations

---
 src/store/migrations.rs | 46 +++++++++++++++++++++++++++++++++++++++++
 src/store/mod.rs        | 11 ++++++++--
 2 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 src/store/migrations.rs

diff --git a/src/store/migrations.rs b/src/store/migrations.rs
new file mode 100644
index 0000000..c746ad7
--- /dev/null
+++ b/src/store/migrations.rs
@@ -0,0 +1,46 @@
+use super::Store;
+use crate::error::Error;
+use heed::RwTxn;
+
+pub const CURRENT_MIGRATION_LEVEL: u32 = 0;
+
+impl Store {
+    pub fn migrate(&self) -> Result<(), Error> {
+        let mut txn = self.env.write_txn()?;
+
+        let mut migration_level = {
+            let zero_bytes = 0_u32.to_be_bytes();
+            let migration_level_bytes = self
+                .general
+                .get(&txn, b"migration_level")?
+                .unwrap_or(zero_bytes.as_slice());
+            u32::from_be_bytes(migration_level_bytes[..4].try_into().unwrap())
+        };
+
+        log::info!("Storage migration level = {}", migration_level);
+
+        while migration_level < CURRENT_MIGRATION_LEVEL {
+            self.migrate_to(&mut txn, migration_level + 1)?;
+            migration_level += 1;
+            self.general.put(
+                &mut txn,
+                b"migration_level",
+                migration_level.to_be_bytes().as_slice(),
+            )?;
+        }
+
+        txn.commit()?;
+
+        Ok(())
+    }
+
+    #[allow(unreachable_code)]
+    fn migrate_to(&self, _txn: &mut RwTxn<'_>, level: u32) -> Result<(), Error> {
+        log::info!("Migrating database to {}", level);
+        match level {
+            _ => panic!("Unknown migration level {level}"),
+        }
+
+        Ok(())
+    }
+}
diff --git a/src/store/mod.rs b/src/store/mod.rs
index 7c5671c..edddf3a 100644
--- a/src/store/mod.rs
+++ b/src/store/mod.rs
@@ -1,6 +1,8 @@
 pub mod event_store;
 pub use event_store::EventStore;
 
+mod migrations;
+
 use crate::error::{ChorusError, Error};
 use crate::types::{Event, Filter, Id, Kind, Pubkey, Time};
 use heed::byteorder::BigEndian;
@@ -94,7 +96,7 @@ impl Store {
 
         let events = EventStore::new(event_map_file)?;
 
-        Ok(Store {
+        let store = Store {
             general,
             events,
             env,
@@ -105,7 +107,12 @@ impl Store {
             deleted_offsets,
             deleted_events,
             allow_scraping,
-        })
+        };
+
+        // This is in migrations.rs
+        store.migrate()?;
+
+        Ok(store)
     }
 
     /// Sync the data to disk. This happens periodically, but sometimes it's useful to force