import { CCliCommand } from './c-cli-command';
import { CCliCommandGroup } from './c-cli-command-group';
import { CCliTree, CCliRoot } from './c-cli-tree';

/** FOR INTERNAL USE ONLY. The result of calling {@link navigateCommandTree} */
export type NavigateCCliTreeResult = {
	/** Passed args past those used during navigation */
	args: string[];
	/** An error message describing why navigation stopped */
	message?: string;
	/** The point in the command tree at which navigation stopped */
	tree: CCliTree;
};

/** FOR INTERNAL USE ONLY. Walk a tree of commands to find the one selected by
 * the arguments provided
 * @param root - A command tree root
 * @param args - An array of command-line arguments
 * @returns The result of the search */
export function navigateCCliTree(
	root: CCliRoot,
	args: string[],
): NavigateCCliTreeResult {
	return recursiveNavigateCliTree({
		tree: { current: root, parents: [] },
		args,
	});
}

function recursiveNavigateCliTree(
	result: NavigateCCliTreeResult,
): NavigateCCliTreeResult {
	// Terminate recursion if current is a command
	if (result.tree.current instanceof CCliCommand) {
		return result;
	}

	if (result.tree.current instanceof CCliCommandGroup) {
		if (result.args.length === 0) {
			// Example: Full command is "cli user login". They've done "cli user". In
			// this case we want to print the usage string but not an error message.
			return result;
		}

		// So that we don't show a "Bad command" error message on "--help"
		if (result.args[0] === '--help') {
			return result;
		}

		const next = result.tree.current.subcommands.find(
			(subcommand) => subcommand.name === result.args[0],
		);

		if (!next) {
			// E.g. Should be "cli login". Is "cli log".
			return { ...result, message: `Bad command "${result.args[0]}"` };
		}

		return recursiveNavigateCliTree({
			tree: {
				parents: [...result.tree.parents, result.tree.current],
				current: next,
			},
			args: result.args.slice(1),
		});
	}

	throw new Error('Unexpected kind');
}