Initial open-source release

packages/cli/src/io/mode.ts

@@ -0,0 +1,40 @@
+import type { KloCliIo } from '../cli-runtime.js';
+
+export type KloOutputMode = 'pretty' | 'plain' | 'json';
+
+const MODES: ReadonlySet<string> = new Set(['pretty', 'plain', 'json']);
+
+export interface ResolveOutputModeArgs {
+  explicit?: string;
+  json?: boolean;
+  io: KloCliIo;
+  env?: NodeJS.ProcessEnv;
+}
+
+export function resolveOutputMode(args: ResolveOutputModeArgs): KloOutputMode {
+  if (args.json === true) {
+    return 'json';
+  }
+  if (args.explicit !== undefined) {
+    if (!MODES.has(args.explicit)) {
+      throw new Error(`Invalid --output value: ${args.explicit}. Expected one of pretty, plain, json.`);
+    }
+    return args.explicit as KloOutputMode;
+  }
+  const env = args.env ?? process.env;
+  const envMode = env.KLO_OUTPUT;
+  if (envMode !== undefined && envMode !== '') {
+    if (!MODES.has(envMode)) {
+      throw new Error(`Invalid KLO_OUTPUT value: ${envMode}. Expected one of pretty, plain, json.`);
+    }
+    return envMode as KloOutputMode;
+  }
+  const ci = env.CI;
+  if (ci !== undefined && ci !== '' && ci !== '0' && ci !== 'false') {
+    return 'plain';
+  }
+  if (args.io.stdout.isTTY === true) {
+    return 'pretty';
+  }
+  return 'plain';
+}