1 files changed, 108 insertions, 0 deletions
diff --git a/packages/cli/src/args.ts b/packages/cli/src/args.ts
new file mode 100644
index 0000000..2c554e8
--- /dev/null
+++ b/packages/cli/src/args.ts
@@ -0,0 +1,108 @@
+/**
+ * Pure argument parser — zero I/O, zero ambient state.
+ *
+ * Parses process.argv-style strings into a discriminated command union.
+ * Validates required flags and reports unknown flags as errors.
+ */
+
+export type ParsedCommand =
+	| { readonly kind: "models"; readonly server: string }
+	| {
+			readonly kind: "chat";
+			readonly server: string;
+			readonly modelName: string;
+			readonly text?: string | undefined;
+			readonly file?: string | undefined;
+			readonly cwd?: string | undefined;
+			readonly conversationId?: string | undefined;
+			readonly showReasoning: boolean;
+	  }
+	| { readonly kind: "help" }
+	| { readonly kind: "error"; readonly message: string };
+
+interface ParseOpts {
+	readonly defaultServer: string;
+}
+
+export function parseArgs(argv: readonly string[], opts: ParseOpts): ParsedCommand {
+	if (argv.length === 0) {
+		return { kind: "help" };
+	}
+
+	const first = argv[0] as string;
+
+	if (first === "--help" || first === "-h") {
+		return { kind: "help" };
+	}
+
+	if (first === "models") {
+		let server = opts.defaultServer;
+		for (let i = 1; i < argv.length; i++) {
+			if (argv[i] === "--server" && i + 1 < argv.length) {
+				server = argv[++i] as string;
+			} else {
+				return { kind: "error", message: `Unknown argument for 'models': ${argv[i]}` };
+			}
+		}
+		return { kind: "models", server };
+	}
+
+	// Chat mode: first arg is the model name
+	const modelName = first;
+	let text: string | undefined;
+	let file: string | undefined;
+	let cwd: string | undefined;
+	let conversationId: string | undefined;
+	let showReasoning = false;
+	let server = opts.defaultServer;
+
+	for (let i = 1; i < argv.length; i++) {
+		const arg = argv[i] as string;
+		switch (arg) {
+			case "--text":
+				if (i + 1 >= argv.length) return { kind: "error", message: "--text requires a value" };
+				text = argv[++i];
+				break;
+			case "--file":
+				if (i + 1 >= argv.length) return { kind: "error", message: "--file requires a value" };
+				file = argv[++i];
+				break;
+			case "--cwd":
+				if (i + 1 >= argv.length) return { kind: "error", message: "--cwd requires a value" };
+				cwd = argv[++i];
+				break;
+			case "--conversation":
+				if (i + 1 >= argv.length)
+					return { kind: "error", message: "--conversation requires a value" };
+				conversationId = argv[++i];
+				break;
+			case "--server":
+				if (i + 1 >= argv.length) return { kind: "error", message: "--server requires a value" };
+				server = argv[++i] as string;
+				break;
+			case "--show-reasoning":
+				showReasoning = true;
+				break;
+			default:
+				return { kind: "error", message: `Unknown flag: ${arg}` };
+		}
+	}
+
+	if (!text && !file) {
+		return {
+			kind: "error",
+			message: "At least one of --text or --file is required for a chat command",
+		};
+	}
+
+	return {
+		kind: "chat",
+		server,
+		modelName,
+		text,
+		file,
+		cwd,
+		conversationId,
+		showReasoning,
+	};
+}