Legal holds, step 6: what each hold keeps

inbuxa:LegalHold/get answers accountsCovered, itemsHeld and sizeHeld
when asked: the accounts a hold reaches now (deleted ones it keeps
included) and the archived items it keeps, with their size. Worked out
in one pass over accounts and archive, only for requests that name them.
Held items stay out of the user's quota, as all archived copies do
(LH-9).

crates/jmap/src/inbuxa/legal_hold.rs

@@ -9,7 +9,7 @@
 //! this: the tenant ceiling strips the permissions from everyone in a
 //! tenant (LH-13). What a hold keeps is the undelete hooks' job.
 
-use common::{Server, auth::AccessToken};
+use common::{Server, auth::AccessToken, hold::HoldSummary};
 use inbuxa_features::hold::{self, Hold, Refusal, Release, Scope};
 use jmap_proto::{
     error::set::SetError,
@@ -67,7 +67,7 @@ fn ids(list: &[u32]) -> LValue {
     )
 }
 
-fn to_value(hold: &Hold, properties: &[P]) -> LValue {
+fn to_value(hold: &Hold, properties: &[P], summary: Option<&HoldSummary>) -> LValue {
     let mut out = Map::with_capacity(properties.len());
     for property in properties {
         let value = match property {
@@ -99,6 +99,9 @@ fn to_value(hold: &Hold, properties: &[P]) -> LValue {
                 .released
                 .as_ref()
                 .map_or(Value::Null, |r| Value::Str(r.reason.clone().into())),
+            P::AccountsCovered => Value::Number(summary.map_or(0, |s| s.accounts).into()),
+            P::ItemsHeld => Value::Number(summary.map_or(0, |s| s.items).into()),
+            P::SizeHeld => Value::Number(summary.map_or(0, |s| s.size).into()),
         };
         out.insert_unchecked(Key::Property(property.clone()), value);
     }
@@ -119,10 +122,21 @@ pub async fn get(
         not_found,
     };
     let data = server.store();
+    // LH-9: only when asked for, since it walks the archive
+    let summaries = if properties
+        .iter()
+        .any(|p| matches!(p, P::AccountsCovered | P::ItemsHeld | P::SizeHeld))
+    {
+        server.hold_summaries().await?
+    } else {
+        Default::default()
+    };
     match ids {
         None => {
             for current in hold::all(data).await? {
-                response.list.push(to_value(&current, &properties));
+                response
+                    .list
+                    .push(to_value(&current, &properties, summaries.get(&current.id)));
             }
         }
         Some(ids) => {
@@ -132,7 +146,11 @@ pub async fn get(
                     .map(|id| hold::get(data, id))
                 {
                     Some(found) => match found.await? {
-                        Some(current) => response.list.push(to_value(&current, &properties)),
+                        Some(current) => response.list.push(to_value(
+                            &current,
+                            &properties,
+                            summaries.get(&current.id),
+                        )),
                         None => response.push_not_found(id),
                     },
                     None => response.push_not_found(id),