feat(kanban): recover from missing sync history

req: sync/007\nreq: sync/020

examples/kanban/tests/browser_e2e.rs

@@ -494,6 +494,120 @@ async fn exhausted_offline_retries_keep_command_until_later_reconnect() -> WebDr
     result.and(quit)
 }
 
+#[tokio::test]
+async fn missing_history_loads_snapshot_and_preserves_pending_intent() -> WebDriverResult<()> {
+    // test req: sync/007 req: sync/020
+    let app_port = available_port();
+    let app_addr = format!("127.0.0.1:{app_port}");
+    let mut app_command = Command::new(env!("CARGO_BIN_EXE_hemx-kanban-example"));
+    app_command
+        .env("HEMX_KANBAN_ADDR", &app_addr)
+        .env("HEMX_KANBAN_RETAINED_AFTER", "1");
+    let _app = TestProcess::start(app_command, "hemx-kanban", &app_addr, STARTUP_TIMEOUT)
+        .expect("start ready hemx-kanban");
+
+    let webdriver_port = available_port();
+    let webdriver_addr = format!("127.0.0.1:{webdriver_port}");
+    let mut webdriver = Command::new("geckodriver");
+    webdriver.arg("--port").arg(webdriver_port.to_string());
+    let _webdriver = TestProcess::start(webdriver, "geckodriver", &webdriver_addr, STARTUP_TIMEOUT)
+        .expect("start ready geckodriver");
+    let mut caps = DesiredCapabilities::firefox();
+    caps.set_headless()?;
+    let driver = WebDriver::new(&format!("http://{webdriver_addr}"), caps).await?;
+
+    let result = async {
+        driver.goto(&format!("http://{app_addr}/")).await?;
+        let seeded_server = driver
+            .execute_async(
+                r#"
+                const done = arguments[arguments.length - 1];
+                fetch('/sync/commands?command_id=history%3A1&card_id=1', { method: 'POST' })
+                  .then(async (response) => done({ status: response.status, body: await response.json() }))
+                  .catch((error) => done({ error: String(error) }));
+                "#,
+                Vec::new(),
+            )
+            .await?
+            .json()
+            .clone();
+        assert_eq!(seeded_server["status"], 200);
+        assert_eq!(seeded_server["body"]["serverSequence"], 1);
+
+        let seeded_local = driver
+            .execute_async(
+                r#"
+                const done = arguments[arguments.length - 1];
+                const open = indexedDB.open('hemx-kanban-v1', 1);
+                open.onupgradeneeded = () => {
+                  const database = open.result;
+                  if (!database.objectStoreNames.contains('commands')) database.createObjectStore('commands', { keyPath: 'id' });
+                  if (!database.objectStoreNames.contains('meta')) database.createObjectStore('meta');
+                };
+                open.onsuccess = () => {
+                  const tx = open.result.transaction('commands', 'readwrite');
+                  tx.objectStore('commands').add({
+                    id: 'history:2', schemaVersion: 1, actor: 'history', session: 'history-session',
+                    causal: 2, kind: 'reorder_card', cardId: '2', eventKind: 'click', key: null,
+                  });
+                  tx.oncomplete = () => done({ seeded: true });
+                  tx.onabort = () => done({ error: tx.error && tx.error.name });
+                };
+                "#,
+                Vec::new(),
+            )
+            .await?
+            .json()
+            .clone();
+        assert_eq!(seeded_local["seeded"], true);
+
+        driver.goto(&format!("http://{app_addr}/sync-demo")).await?;
+        wait_until(
+            &driver,
+            "return document.querySelector('[data-kanban-sync]')?.getAttribute('data-sync-phase') === 'rebase-required'",
+        )
+        .await?;
+        let fallback = driver
+            .execute(
+                "const root = document.querySelector('[data-kanban-sync]'); return { phase: root.getAttribute('data-sync-phase'), uploadSequence: root.getAttribute('data-sync-upload-sequence'), snapshotSequence: root.getAttribute('data-sync-snapshot-sequence'), snapshotSchema: root.getAttribute('data-sync-snapshot-schema'), snapshotCards: root.getAttribute('data-sync-snapshot-card-count'), pending: root.getAttribute('data-sync-pending-count'), rebasePending: root.getAttribute('data-sync-rebase-pending-count'), canonicalColumn: root.getAttribute('data-sync-canonical-column'), status: root.querySelector('[role=status]').textContent, error: root.getAttribute('data-sync-error') }",
+                Vec::new(),
+            )
+            .await?
+            .json()
+            .clone();
+        assert_eq!(fallback["phase"], "rebase-required");
+        assert_eq!(fallback["uploadSequence"], "2");
+        assert_eq!(fallback["snapshotSequence"], "2");
+        assert_eq!(fallback["snapshotSchema"], "1");
+        assert_eq!(fallback["snapshotCards"], "3");
+        assert_eq!(fallback["pending"], "1");
+        assert_eq!(fallback["rebasePending"], "1");
+        assert_eq!(fallback["canonicalColumn"], "done");
+        assert_eq!(
+            fallback["status"],
+            "History is unavailable; loaded snapshot 2 and preserved 1 pending command for rebase."
+        );
+        assert!(fallback["error"].is_null());
+        assert_eq!(command_count(&driver).await?, 1);
+
+        driver.goto(&format!("http://{app_addr}/")).await?;
+        let canonical = driver
+            .execute(
+                "return [...document.querySelectorAll('section.column')].map((column) => ({ title: column.querySelector('h2').textContent, cards: [...column.querySelectorAll('[data-key]')].map((card) => card.dataset.key) }))",
+                Vec::new(),
+            )
+            .await?
+            .json()
+            .clone();
+        assert_eq!(canonical[2]["title"], "Done");
+        assert_eq!(canonical[2]["cards"], serde_json::json!(["1", "2", "3"]));
+        Ok(())
+    }
+    .await;
+    let quit = driver.quit().await;
+    result.and(quit)
+}
+
 #[tokio::test]
 async fn canonical_acknowledgement_survives_server_restart() -> WebDriverResult<()> {
     // test req: sync/001 req: sync/005 req: sync/007 req: sync/008 req: sync/013