1 files changed, 71 insertions, 0 deletions
diff --git a/database/src/indices/reference.rs b/database/src/indices/reference.rs
new file mode 100644
index 0000000..66efa24
--- /dev/null
+++ b/database/src/indices/reference.rs
@@ -0,0 +1,71 @@
+/*
+    This file is part of jellything (https://codeberg.org/metamuffin/jellything)
+    which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
+    Copyright (C) 2026 metamuffin <metamuffin.org>
+*/
+
+use crate::{
+    backends::{ReadTransaction, WriteTransaction},
+    indices::Index,
+    prefix_iterator::PrefixIterator,
+    table::{RowNum, TableNum},
+};
+use anyhow::Result;
+use bytemuck::{NoUninit, bytes_of};
+use jellycommon::jellyobject::{Object, TypedTag};
+
+pub struct ReferenceIndex {
+    id: TableNum,
+    tag: TypedTag<RowNum>,
+}
+
+#[repr(C)]
+#[derive(NoUninit, Clone, Copy)]
+pub struct Key(TableNum, RowNum, RowNum);
+
+impl ReferenceIndex {
+    pub fn new(id: TableNum, tag: TypedTag<RowNum>) -> Self {
+        Self { id, tag }
+    }
+    pub fn lookup<'a>(
+        &self,
+        db: &'a dyn ReadTransaction,
+        to: RowNum,
+    ) -> Result<PrefixIterator<'a>> {
+        let mut prefix = Vec::new();
+        prefix.extend(self.id.to_be_bytes());
+        prefix.extend(to.to_be_bytes());
+        Ok(PrefixIterator {
+            inner: db.iter(&prefix, false)?,
+            prefix: prefix.into(),
+        })
+    }
+}
+impl Index for ReferenceIndex {
+    fn add(&self, db: &mut dyn WriteTransaction, id: RowNum, val: Object) -> Result<()> {
+        for to in val.iter(self.tag) {
+            db.set(bytes_of(&Key(self.id, to, id)), &[])?;
+        }
+        Ok(())
+    }
+    fn remove(&self, db: &mut dyn WriteTransaction, id: RowNum, val: Object) -> Result<()> {
+        for to in val.iter(self.tag) {
+            db.del(bytes_of(&Key(self.id, to, id)))?;
+        }
+        Ok(())
+    }
+    fn compare(&self, before: Object, after: Object) -> bool {
+        let mut before = before.iter(self.tag);
+        let mut after = after.iter(self.tag);
+        loop {
+            let b = before.next();
+            let a = after.next();
+            if a.is_none() && b.is_none() {
+                break true;
+            }
+            if a != b {
+                break false;
+            }
+        }
+    }
+}