refactor(subagents): share token usage formatting

src/shared/subagents-format.ts

@@ -39,3 +39,58 @@ export function truncateLine(value: string, maxLength: number) {
   }
   return `${value.slice(0, maxLength).trimEnd()}...`;
 }
+
+export type TokenUsageLike = {
+  totalTokens?: unknown;
+  inputTokens?: unknown;
+  outputTokens?: unknown;
+};
+
+export function resolveTotalTokens(entry?: TokenUsageLike) {
+  if (!entry || typeof entry !== "object") {
+    return undefined;
+  }
+  if (typeof entry.totalTokens === "number" && Number.isFinite(entry.totalTokens)) {
+    return entry.totalTokens;
+  }
+  const input = typeof entry.inputTokens === "number" ? entry.inputTokens : 0;
+  const output = typeof entry.outputTokens === "number" ? entry.outputTokens : 0;
+  const total = input + output;
+  return total > 0 ? total : undefined;
+}
+
+export function resolveIoTokens(entry?: TokenUsageLike) {
+  if (!entry || typeof entry !== "object") {
+    return undefined;
+  }
+  const input =
+    typeof entry.inputTokens === "number" && Number.isFinite(entry.inputTokens)
+      ? entry.inputTokens
+      : 0;
+  const output =
+    typeof entry.outputTokens === "number" && Number.isFinite(entry.outputTokens)
+      ? entry.outputTokens
+      : 0;
+  const total = input + output;
+  if (total <= 0) {
+    return undefined;
+  }
+  return { input, output, total };
+}
+
+export function formatTokenUsageDisplay(entry?: TokenUsageLike) {
+  const io = resolveIoTokens(entry);
+  const promptCache = resolveTotalTokens(entry);
+  const parts: string[] = [];
+  if (io) {
+    const input = formatTokenShort(io.input) ?? "0";
+    const output = formatTokenShort(io.output) ?? "0";
+    parts.push(`tokens ${formatTokenShort(io.total)} (in ${input} / out ${output})`);
+  } else if (typeof promptCache === "number" && promptCache > 0) {
+    parts.push(`tokens ${formatTokenShort(promptCache)} prompt/cache`);
+  }
+  if (typeof promptCache === "number" && io && promptCache > io.total) {
+    parts.push(`prompt/cache ${formatTokenShort(promptCache)}`);
+  }
+  return parts.join(", ");
+}