feat(cli): add solution activity tracking and ordering for test/submit commands

apps/cli/solutions.ts

@@ -1,18 +1,64 @@
 /**
  * Shared work/ solution picker for the test and submit entries: fuzzy-select
- * a solution file, then hand it to leetcode-cli. Library: side-effect-free on
- * import — nothing scans the filesystem until runOnSolution() is called.
+ * a solution file, then hand it to leetcode-cli.
+ *
+ * Every run backfills the db's solutions table with created_at (from the
+ * file's birthtime, mtime when the filesystem has none) so ordering works for
+ * files that predate the db. Ordering is per command — test lists the most
+ * recently tested first (never-tested after, by name); submit lists the most
+ * recently created first. Nothing is ever hidden. Exit 0 of leetcode-cli
+ * stamps last_tested / last_submitted.
+ *
+ * Library: side-effect-free on import — nothing scans the filesystem until
+ * runOnSolution() is called.
  */
 import { autocomplete, cancel, isCancel, log } from "@clack/prompts";
-import { join, relative } from "node:path";
+import { statSync } from "node:fs";
+import { basename, join, relative } from "node:path";
+import { problemDb } from "./db";
 
 const ROOT = join(import.meta.dir, "..", "..");
 const WORK_DIR = join(ROOT, "work");
 
+/** Leading LC number of a work/ file, or undefined for unnumbered names. */
+function lcNumber(rel: string): number | undefined {
+  const m = basename(rel).match(/^(\d+)\./);
+  return m ? Number(m[1]) : undefined;
+}
+
 /** Fuzzy-pick a solution under work/ and run `leetcode <command>` on it. */
 export async function runOnSolution(command: "test" | "submit", message: string): Promise<never> {
-  const files = [...new Bun.Glob("**/*.{js,ts,py,java,c,cpp,go,rs,rb,swift,kt,cs}").scanSync({ cwd: WORK_DIR })]
-    .sort((a, b) => a.localeCompare(b, undefined, { numeric: true }));
+  const db = problemDb();
+
+  const scanned = [...new Bun.Glob("**/*.{js,ts,py,java,c,cpp,go,rs,rb,swift,kt,cs}").scanSync({ cwd: WORK_DIR })];
+
+  // register creation times so files older than the db still sort correctly
+  for (const f of scanned) {
+    const num = lcNumber(f);
+    if (num === undefined) continue;
+    const stat = statSync(join(WORK_DIR, f));
+    db.ensureSolution(num, new Date(stat.birthtimeMs || stat.mtimeMs).toISOString());
+  }
+  const activity = db.solutionActivity();
+
+  // test → most recently tested first; submit → most recently created first
+  const sortKey = (f: string) => {
+    const num = lcNumber(f);
+    const row = num === undefined ? undefined : activity.get(num);
+    return (command === "test" ? row?.lastTested : row?.createdAt) ?? undefined;
+  };
+
+  const files = scanned
+    .sort((a, b) => {
+      const ka = sortKey(a);
+      const kb = sortKey(b);
+      if (ka !== kb) {
+        if (ka === undefined) return 1;
+        if (kb === undefined) return -1;
+        return kb.localeCompare(ka); // ISO timestamps: lexicographic = chronological
+      }
+      return a.localeCompare(b, undefined, { numeric: true });
+    });
 
   if (files.length === 0) {
     log.error(`No solution files found in ${relative(process.cwd(), WORK_DIR)}/`);
@@ -55,5 +101,12 @@ export async function runOnSolution(command: "test" | "submit", message: string)
     ],
     { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
   );
-  process.exit(await proc.exited);
+  const code = await proc.exited;
+  const num = lcNumber(picked);
+  if (code === 0 && num !== undefined) {
+    if (command === "test") db.markTested(num);
+    else db.markSubmitted(num);
+  }
+  db.close();
+  process.exit(code);
 }