Bound document cache size to prevent long-session UI slowdown

Journal.App/src/routes/+page.svelte

@@ -58,6 +58,7 @@
     busy: boolean;
     error: string;
   };
+  const MAX_CACHED_DOCUMENTS = 5;
 
   const initialEntry = getDefaultEntry(get(entriesStore));
 
@@ -73,6 +74,7 @@
           "# Daily Notes\n\nStart writing today's entry...",
       };
   let savedDocumentContent: Record<string, string> = { ...openDocuments };
+  let documentAccessOrder: string[] = Object.keys(openDocuments);
   let modalOpen = false;
   let modalTitle = "";
   let modalMessage = "";
@@ -165,6 +167,41 @@
     return fileName.replace(/\.template\.md$/i, "");
   }
 
+  function touchDocument(id: string) {
+    documentAccessOrder = [
+      ...documentAccessOrder.filter((item) => item !== id),
+      id,
+    ];
+  }
+
+  function pruneDocumentCache(preserveIds: string[] = []) {
+    const preserve = new Set(
+      preserveIds.filter(Boolean).concat(activeDocumentId ? [activeDocumentId] : []),
+    );
+    const cachedIds = Object.keys(openDocuments);
+    if (cachedIds.length <= MAX_CACHED_DOCUMENTS) return;
+
+    let nextOpen = { ...openDocuments };
+    let nextSaved = { ...savedDocumentContent };
+    let nextOrder = [...documentAccessOrder];
+    let currentSize = cachedIds.length;
+
+    for (const candidate of documentAccessOrder) {
+      if (currentSize <= MAX_CACHED_DOCUMENTS) break;
+      if (preserve.has(candidate)) continue;
+      if (!(candidate in nextOpen)) continue;
+
+      delete nextOpen[candidate];
+      delete nextSaved[candidate];
+      nextOrder = nextOrder.filter((item) => item !== candidate);
+      currentSize -= 1;
+    }
+
+    openDocuments = nextOpen;
+    savedDocumentContent = nextSaved;
+    documentAccessOrder = nextOrder;
+  }
+
   function showModal(options: {
     action:
       | "logout-confirm"
@@ -361,6 +398,9 @@
         openDocuments = rest;
         const { [activeDocumentId]: __, ...savedRest } = savedDocumentContent;
         savedDocumentContent = savedRest;
+        documentAccessOrder = documentAccessOrder.filter(
+          (item) => item !== activeDocumentId,
+        );
         activeDocumentId = "";
         activeDocumentLabel = "";
         editMode = false;
@@ -398,6 +438,7 @@
             ...savedRest,
             [saved.id]: saved.initialContent,
           };
+          touchDocument(saved.id);
           activeDocumentId = saved.id;
           activeDocumentLabel = saved.label;
         } else {
@@ -405,6 +446,7 @@
             ...savedDocumentContent,
             [activeDocumentId]: content,
           };
+          touchDocument(activeDocumentId);
         }
       } else if (
         selectedSection === "lists" &&
@@ -416,7 +458,9 @@
           ...savedDocumentContent,
           [activeDocumentId]: content,
         };
+        touchDocument(activeDocumentId);
       }
+      pruneDocumentCache([activeDocumentId]);
     } catch {
       // best-effort save
     }
@@ -518,11 +562,13 @@
         [resolvedDoc.id]: resolvedDoc.initialContent,
       };
     }
+    touchDocument(resolvedDoc.id);
     savedDocumentContent = {
       ...savedDocumentContent,
       [resolvedDoc.id]:
         openDocuments[resolvedDoc.id] ?? resolvedDoc.initialContent,
     };
+    pruneDocumentCache([resolvedDoc.id]);
     activeDocumentId = resolvedDoc.id;
     activeDocumentLabel = resolvedDoc.label;
   }
@@ -540,7 +586,10 @@
   }
 
   function handleDocumentContentChange(content: string) {
+    if (!activeDocumentId) return;
     openDocuments = { ...openDocuments, [activeDocumentId]: content };
+    touchDocument(activeDocumentId);
+    pruneDocumentCache([activeDocumentId]);
   }
 
   async function handleForceSave() {
@@ -552,6 +601,7 @@
     openDocuments = remaining;
     const { [id]: __, ...savedRemaining } = savedDocumentContent;
     savedDocumentContent = savedRemaining;
+    documentAccessOrder = documentAccessOrder.filter((item) => item !== id);
   }
 
   async function performDelete(id: string) {