using GLib;

namespace Spry.Cli {

    /**
     * `spry` — the Spry application CLI.
     *
     * Scaffolds Statum + Spry applications (`spry new`, including their USM
     * packaging), grows them with app-owned page/action/resource/auth
     * templates (`spry add …`), maintains the static key material in
     * `web-config.json` (`spry keys`), and ships them as container images
     * through USM (`spry deploy`). Edits to generated projects happen only
     * within `// spry:*-begin/end` markers in `src/main.vala` and
     * `# spry:*-begin/end` markers in `meson.build`, so `add` commands are
     * idempotent and never reformat surrounding user code.
     */
    public class SpryCli : Object {

        private static string? tools_dir = null;
        private static string? libdir = null;
        private static bool force = false;
        private static string? route = null;
        private static string? out_path = null;
        private static string? usm = null;
        private static string? deploy_exec = null;
        private static string? deploy_base = null;
        [CCode (array_length = false, null_terminated = true)]
        private static string[] deploy_repositories = null;
        private static string? deploy_installer_url = null;
        private static bool deploy_no_build = false;
        private static bool deploy_verbose = false;
        private static int dev_port = 8080;
        private static bool dev_fresh = false;
        private static bool dev_no_run = false;

        private const OptionEntry[] global_options = {
            { "tools-dir", '\0', 0, OptionArg.STRING, ref tools_dir, "Directory containing the statum-* tools (default: search PATH, then ~/.local/bin)", "DIR" },
            { "libdir", '\0', 0, OptionArg.STRING, ref libdir, "Library directory prepended to spawned tools' LD_LIBRARY_PATH/PKG_CONFIG_PATH (default: pkg-config spry-0.2 libdir)", "DIR" },
            { null }
        };

        private const OptionEntry[] new_options = {
            { "force", 'f', 0, OptionArg.NONE, ref force, "Overwrite generated files when the target directory already exists", null },
            { null }
        };

        private const OptionEntry[] page_options = {
            { "route", 'r', 0, OptionArg.STRING, ref route, "Page route (default: /<name>)", "PATH" },
            { null }
        };

        private const OptionEntry[] keys_options = {
            { "out", 'o', 0, OptionArg.FILENAME, ref out_path, "Configuration file to merge into (default: web-config.json)", "FILE" },
            { null }
        };

        private const OptionEntry[] deploy_options = {
            { "usm", '\0', 0, OptionArg.FILENAME, ref usm, "usm binary to delegate to (default: search PATH)", "FILE" },
            { "exec", '\0', 0, OptionArg.STRING, ref deploy_exec, "Container command (default: \"<app> 8080\")", "CMD" },
            { "base", '\0', 0, OptionArg.STRING, ref deploy_base, "Base image (default: usm's fedora:43)", "IMAGE" },
            { "repository", '\0', 0, OptionArg.STRING_ARRAY, ref deploy_repositories, "USM repository (.usmr) to resolve from; repeatable (default: the machine's configured repositories)", "FILE" },
            { "installer-url", '\0', 0, OptionArg.STRING, ref deploy_installer_url, "USM installer source override (file://… for local testing)", "URL" },
            { "no-build", '\0', 0, OptionArg.NONE, ref deploy_no_build, "Only generate the deploy context; do not build the image", null },
            { "verbose", 'v', 0, OptionArg.NONE, ref deploy_verbose, "Stream package script output to the terminal during the image build", null },
            { null }
        };

        private const OptionEntry[] dev_options = {
            { "port", 'p', 0, OptionArg.INT, ref dev_port, "Port to run the application on (default: 8080)", "N" },
            { "fresh", '\0', 0, OptionArg.NONE, ref dev_fresh, "Delete the SQLite database before starting", null },
            { "no-run", '\0', 0, OptionArg.NONE, ref dev_no_run, "Build once and exit; do not run or watch", null },
            { null }
        };

        private const string MESON_PAGES_BEGIN = "# spry:pages-begin";
        private const string MESON_PAGES_END = "# spry:pages-end";
        private const string MESON_RESOURCES_BEGIN = "# spry:resources-begin";
        private const string MESON_RESOURCES_END = "# spry:resources-end";
        private const string MESON_SOURCES_BEGIN = "# spry:sources-begin";
        private const string MESON_SOURCES_END = "# spry:sources-end";
        private const string MESON_GENERATED_BEGIN = "# spry:generated-begin";
        private const string MESON_GENERATED_END = "# spry:generated-end";
        private const string VALA_PAGES_BEGIN = "// spry:pages-begin";
        private const string VALA_PAGES_END = "// spry:pages-end";
        private const string VALA_ACTIONS_BEGIN = "// spry:actions-begin";
        private const string VALA_ACTIONS_END = "// spry:actions-end";
        private const string VALA_RESOURCES_BEGIN = "// spry:resources-begin";
        private const string VALA_RESOURCES_END = "// spry:resources-end";
        private const string VALA_AUTH_BEGIN = "// spry:auth-begin";
        private const string VALA_AUTH_END = "// spry:auth-end";
        private const string NAV_BEGIN = "<!-- spry:nav-begin -->";
        private const string NAV_END = "<!-- spry:nav-end -->";
        private const string NAV_AUTH_BEGIN = "<!-- spry:nav-auth-begin -->";
        private const string NAV_AUTH_END = "<!-- spry:nav-auth-end -->";

        public static int main(string[] args) {
            if (args.length < 2) {
                print_usage();
                return 1;
            }
            var command = args[1];
            if (command == "--help" || command == "-h" || command == "help") {
                print_usage();
                return 0;
            }

            try {
                switch (command) {
                    case "new":
                        return cmd_new(slice(args, 1));
                    case "add":
                        return cmd_add(slice(args, 1));
                    case "keys":
                        return cmd_keys(slice(args, 1));
                    case "deploy":
                        return cmd_deploy(slice(args, 1));
                    case "dev":
                        return cmd_dev(slice(args, 1));
                    default:
                        stderr.printf("Error: Unknown command '%s'.\n", command);
                        print_usage();
                        return 1;
                }
            } catch (OptionError e) {
                stderr.printf("Error: %s\n", e.message);
                return 1;
            } catch (Error e) {
                stderr.printf("Error: %s\n", e.message);
                return 1;
            }
        }

        private static void print_usage() {
            stdout.printf(
                "Usage:\n" +
                "  spry <command> [options]\n" +
                "\n" +
                "Commands:\n" +
                "  new <name>                       Scaffold a new Statum + Spry application\n" +
                "  add page <name> [--route PATH]   Add a page (HTML + entrypoint + wiring)\n" +
                "  add action <name>                Add a StatumAction skeleton\n" +
                "  add resource <file>              Embed a static resource (statum-mkres)\n" +
                "  add login                        Add the login page (Spry.Actions.LoginAction)\n" +
                "  add register                     Add the registration page\n" +
                "  add user-management              Add the admin user-management page\n" +
                "  keys [--out FILE]                Generate/merge static keys into web-config.json\n" +
                "  deploy [--exec CMD] [--base I]   Build the USM container image (usm manifest\n" +
                "                                   deploy; --repository/--installer-url/\n" +
                "                                   --no-build pass through)\n" +
                "  dev [--port N] [--fresh]         Build, run and watch: rebuild + restart on save\n" +
                "\n" +
                "Options:\n" +
                "  --tools-dir DIR  Directory containing the statum-* tools (default: PATH)\n" +
                "  --libdir DIR     Library dir for spawned tools' LD_LIBRARY_PATH\n" +
                "                   (default: pkg-config spry-0.2 libdir)\n" +
                "  --help           Show this help\n");
        }

        private static void print_add_usage() {
            stdout.printf(
                "Usage:\n" +
                "  spry add page <name> [--route /path]\n" +
                "  spry add action <name>\n" +
                "  spry add resource <file>\n" +
                "  spry add login\n" +
                "  spry add register\n" +
                "  spry add user-management\n");
        }

        // ----------------------------------------------------------------------
        // spry new
        // ----------------------------------------------------------------------

        private static int cmd_new(string[] args) throws Error, OptionError {
            parse(args, "<name> - scaffold a new Statum + Spry application", new_options);
            if (args.length < 2) {
                stderr.printf("Error: No application name specified.\n");
                return 1;
            }
            var name = args[1].down();
            if (!Generator.valid_name(name)) {
                stderr.printf("Error: '%s' is not a valid application name (letters, digits, '-' and '_', starting with a letter).\n", name);
                return 1;
            }

            var app_dir = Path.build_filename(Environment.get_current_dir(), name);
            if (FileUtils.test(app_dir, FileTest.EXISTS) && !force) {
                stderr.printf("Error: %s already exists (use --force to overwrite its generated files).\n", app_dir);
                return 1;
            }

            var vars = base_vars(name);
            write_app_file(app_dir, "meson.build", Generator.fill(Templates.PROJECT_MESON, vars));
            write_app_file(app_dir, "src/main.vala", Generator.fill(Templates.APP_MAIN, vars));
            write_app_file(app_dir, "src/pages/main.html", Generator.fill(Templates.LAYOUT, vars));
            write_app_file(app_dir, "src/pages/home.html", Generator.fill(Templates.HOME, vars));
            write_app_file(app_dir, "src/entrypoints/HomeEntrypoint.vala", Generator.fill(Templates.HOME_ENTRYPOINT, vars));
            write_app_file(app_dir, ".gitignore", Generator.fill(Templates.GITIGNORE, vars));
            write_app_file(app_dir, "README.md", Generator.fill(Templates.README, vars));

            // USM packaging: the manifest + scripts that let `spry deploy`
            // (usm manifest deploy) build and install the app in-container
            write_app_file(app_dir, "MANIFEST.usm", Generator.fill(Templates.MANIFEST_USM, vars));
            write_app_file(app_dir, "usm-scripts/build.sh", Templates.USM_BUILD_SH, 0755);
            write_app_file(app_dir, "usm-scripts/install.sh", Templates.USM_INSTALL_SH, 0755);
            write_app_file(app_dir, ".usmignore", Templates.USMIGNORE);

            var config_path = Path.build_filename(app_dir, "web-config.json");
            try {
                Keys.run(config_path, tools_dir, libdir);
            } catch (Error e) {
                stderr.printf("Warning: %s — wrote an empty config; run `spry keys` later.\n", e.message);
                Generator.write_file(config_path, "{\n  \"statum\": {\n  }\n}\n");
            }

            stdout.printf("Created %s\n", app_dir);
            stdout.printf("Next:\n  cd %s\n  spry dev\n", name);
            return 0;
        }

        // ----------------------------------------------------------------------
        // spry add …
        // ----------------------------------------------------------------------

        private static int cmd_add(string[] args) throws Error, OptionError {
            if (args.length < 2) {
                print_add_usage();
                return 1;
            }
            var what = args[1];
            var rest = slice(args, 1);
            switch (what) {
                case "page":
                    return cmd_add_page(rest);
                case "action":
                    return cmd_add_action(rest);
                case "resource":
                    return cmd_add_resource(rest);
                case "login":
                    return cmd_add_login(rest);
                case "register":
                    return cmd_add_register(rest);
                case "user-management":
                    return cmd_add_user_management(rest);
                default:
                    stderr.printf("Error: Unknown add command '%s'.\n", what);
                    print_add_usage();
                    return 1;
            }
        }

        private static int cmd_add_page(string[] args) throws Error, OptionError {
            parse(args, "<name> - add a page (HTML + entrypoint + wiring)", page_options);
            if (args.length < 2) {
                stderr.printf("Error: No page name specified.\n");
                return 1;
            }
            var name = normalise(args[1]);
            if (!Generator.valid_name(name)) {
                stderr.printf("Error: '%s' is not a valid page name.\n", name);
                return 1;
            }
            var route_path = route != null ? (!)route : "/" + name;
            if (!route_path.has_prefix("/")) {
                route_path = "/" + route_path;
            }

            var app = require_app();
            add_page(app, name, Generator.pascal_case(name), route_path,
                Generator.fill(Templates.PAGE, page_vars(app, name, route_path)),
                Generator.fill(Templates.PAGE_ENTRYPOINT, page_vars(app, name, route_path)));
            stdout.printf("Added page %s at %s\n", name, route_path);
            return 0;
        }

        private static int cmd_add_action(string[] args) throws Error, OptionError {
            parse(args, "<name> - add a StatumAction skeleton", null);
            if (args.length < 2) {
                stderr.printf("Error: No action name specified.\n");
                return 1;
            }
            var name = normalise(args[1]);
            if (!Generator.valid_name(name)) {
                stderr.printf("Error: '%s' is not a valid action name.\n", name);
                return 1;
            }
            var cls = Generator.pascal_case(name);

            var app = require_app();
            var vars = app.vars;
            vars.set("CLASS", cls);

            write_new_app_file(app.dir, "src/actions/%sAction.vala".printf(cls),
                Generator.fill(Templates.ACTION, vars));
            edit_meson(app, "'src/actions/%sAction.vala',".printf(cls), MESON_SOURCES_BEGIN, MESON_SOURCES_END);
            edit_main(app, "statum.action<%sAction>();".printf(cls), VALA_ACTIONS_BEGIN, VALA_ACTIONS_END);
            stdout.printf("Added action %s\n", cls);
            return 0;
        }

        private static int cmd_add_resource(string[] args) throws Error, OptionError {
            parse(args, "<file> - embed a static resource", null);
            if (args.length < 2) {
                stderr.printf("Error: No resource file specified.\n");
                return 1;
            }
            var source = args[1];
            if (!FileUtils.test(source, FileTest.EXISTS)) {
                stderr.printf("Error: %s does not exist.\n", source);
                return 1;
            }
            var file_name = Path.get_basename(source);
            var stem = file_name.contains(".") ? file_name.substring(0, file_name.last_index_of(".")) : file_name;
            var cls = Generator.pascal_case(stem) + "Resource";
            var var_name = Generator.snake_case(stem) + "_resource";
            var content_type = content_type_for(file_name);

            var app = require_app();
            var resource_path = Path.build_filename(app.dir, "src", "resources", file_name);
            if (!FileUtils.test(resource_path, FileTest.EXISTS)) {
                Generator.write_file(resource_path, Generator.read_file(source));
            }

            var command = "[statum_mkres, '-o', '@OUTPUT@', '-n', '%s', '--class-name', '%s'".printf(file_name, cls);
            if (content_type != null) {
                command += ", '-c', '%s'".printf((!)content_type);
            }
            command += ", '@INPUT@']";
            var target = "%s = custom_target('%s-resource',\n".printf(var_name, Generator.snake_case(stem))
                + "    input: 'src/resources/%s',\n".printf(file_name)
                + "    output: '%s.vala',\n".printf(cls)
                + "    command: %s\n".printf(command)
                + ")";
            edit_meson(app, target, MESON_RESOURCES_BEGIN, MESON_RESOURCES_END);
            edit_meson(app, "%s,".printf(var_name), MESON_GENERATED_BEGIN, MESON_GENERATED_END);
            edit_main(app, "statum.add_resource<%s>();".printf(cls), VALA_RESOURCES_BEGIN, VALA_RESOURCES_END);
            stdout.printf("Added resource %s as %s\n", source, cls);
            return 0;
        }

        private static int cmd_add_login(string[] args) throws Error, OptionError {
            parse(args, "- add the login page", null);
            var app = require_app();
            add_page(app, "login", "Login", "/login",
                Generator.fill(Templates.LOGIN, app.vars),
                Generator.fill(Templates.LOGIN_ENTRYPOINT, app.vars));
            // Keep Spry.Actions registrations in sync with
            // SpryAuth.register_actions (Spry/src/Auth.vala), the canonical
            // list of shipped actions.
            edit_main(app, "statum.action<Spry.Actions.LoginAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_main(app, "statum.action<Spry.Actions.LogoutAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_layout(app, "<a href=\"/login\" stm-if=\"!auth\">Login</a>", NAV_BEGIN, NAV_END);
            edit_layout(app, "<button type=\"button\" stm-action=\"auth.logout\">Log out</button>", NAV_AUTH_BEGIN, NAV_AUTH_END);
            Generator.append_section(Path.build_filename(app.dir, "README.md"),
                "## Guarding pages", Generator.fill(Templates.LOGIN_README, app.vars));
            stdout.printf("Added login page at /login\n");
            return 0;
        }

        private static int cmd_add_register(string[] args) throws Error, OptionError {
            parse(args, "- add the registration page", null);
            var app = require_app();
            add_page(app, "register", "Register", "/register",
                Generator.fill(Templates.REGISTER, app.vars),
                Generator.fill(Templates.REGISTER_ENTRYPOINT, app.vars));
            edit_main(app, "statum.action<Spry.Actions.RegisterAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_layout(app, "<a href=\"/register\" stm-if=\"!auth\">Register</a>", NAV_BEGIN, NAV_END);
            stdout.printf("Added register page at /register\n");
            return 0;
        }

        private static int cmd_add_user_management(string[] args) throws Error, OptionError {
            parse(args, "- add the admin user-management page", null);
            var app = require_app();
            add_page(app, "user-management", "UserManagement", "/users",
                Generator.fill(Templates.USER_MANAGEMENT, app.vars),
                Generator.fill(Templates.USER_MANAGEMENT_ENTRYPOINT, app.vars));
            edit_main(app, "statum.action<Spry.Actions.SetUserEnabledAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_main(app, "statum.action<Spry.Actions.GrantPermissionAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_main(app, "statum.action<Spry.Actions.RevokePermissionAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_main(app, "statum.action<Spry.Actions.AlterUserAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_main(app, "statum.action<Spry.Actions.DeleteUserAction>();", VALA_AUTH_BEGIN, VALA_AUTH_END);
            edit_layout(app, "<a href=\"/users\" stm-if=\"auth && (auth.permissions.indexOf('admin') !== -1 || auth.permissions.indexOf('*') !== -1)\">Users</a>", NAV_BEGIN, NAV_END);
            stdout.printf("Added user-management page at /users\n");
            return 0;
        }

        // ----------------------------------------------------------------------
        // spry dev
        // ----------------------------------------------------------------------

        private static int cmd_dev(string[] args) throws Error, OptionError {
            parse(args, "- build, run and watch the application", dev_options);
            var app = require_app();
            return Dev.run(app.dir, app.name, dev_port, dev_fresh, dev_no_run, libdir);
        }

        // ----------------------------------------------------------------------
        // spry keys / spry deploy
        // ----------------------------------------------------------------------

        private static int cmd_keys(string[] args) throws Error, OptionError {
            parse(args, "- generate and merge static keys into web-config.json", keys_options);
            Keys.run(out_path ?? "web-config.json", tools_dir, libdir);
            return 0;
        }

        private static int cmd_deploy(string[] args) throws Error, OptionError {
            string[] repositories;
            string[] remaining;
            extract_repositories(args, out repositories, out remaining);
            parse(remaining, "- build the USM container image via usm manifest deploy", deploy_options);
            var app = require_app();
            return Deploy.run(app.dir, app.name, usm, deploy_exec, deploy_base,
                repositories, deploy_installer_url, deploy_no_build, deploy_verbose);
        }

        /**
         * Collects repeatable `--repository FILE` / `--repository=FILE`
         * arguments into {@link repositories}, leaving the rest in
         * {@link remaining} so the GLib option context (whose string-array
         * capture is unreliable here) never sees them.
         */
        private static void extract_repositories(string[] args, out string[] repositories, out string[] remaining) {
            var found = new string[0];
            var rest = new string[args.length];
            rest[0] = args[0];
            int out_index = 1;
            for (int i = 1; i < args.length; i++) {
                if (args[i] == "--repository" && i + 1 < args.length) {
                    found += args[++i];
                }
                else if (args[i].has_prefix("--repository=")) {
                    found += args[i].substring("--repository=".length);
                }
                else {
                    rest[out_index++] = args[i];
                }
            }
            rest.length = out_index;
            repositories = found;
            remaining = rest;
        }

        // ----------------------------------------------------------------------
        // Shared helpers
        // ----------------------------------------------------------------------

        /**
         * The surrounding spry application: the current directory, the app
         * name (directory basename) and the namespace its generated pages
         * use (read back from meson.build, falling back to the directory
         * name).
         */
        private class AppContext {
            public string dir;
            public string name;
            public string ns;
            public HashTable<string, string> vars;

            public AppContext(string dir, string name, string ns) {
                this.dir = dir;
                this.name = name;
                this.ns = ns;
                this.vars = new HashTable<string, string>(str_hash, str_equal);
                this.vars.insert("APP_NAME", name);
                this.vars.insert("NS", ns);
            }
        }

        private static AppContext require_app() throws Error {
            var cwd = Environment.get_current_dir();
            if (!FileUtils.test(Path.build_filename(cwd, "meson.build"), FileTest.EXISTS)
                || !FileUtils.test(Path.build_filename(cwd, "src", "main.vala"), FileTest.EXISTS)) {
                throw Generator.cli_error("not a spry application directory (run from the project root)");
            }

            var name = Path.get_basename(cwd);
            var ns = detect_ns(Generator.read_file(Path.build_filename(cwd, "meson.build")));
            if (ns.length == 0) {
                ns = Generator.pascal_case(name);
            }
            return new AppContext(cwd, name, ns);
        }

        private static string detect_ns(string meson) {
            var marker = "'--ns', '";
            var index = meson.index_of(marker);
            if (index < 0) {
                return "";
            }
            var start = index + marker.length;
            var stop = meson.index_of("'", start);
            return stop > start ? meson.substring(start, stop - start) : "";
        }

        private static HashTable<string, string> base_vars(string name) {
            var vars = new HashTable<string, string>(str_hash, str_equal);
            vars.insert("APP_NAME", name);
            vars.insert("NS", Generator.pascal_case(name));
            return vars;
        }

        private static HashTable<string, string> page_vars(AppContext app, string name, string route_path) {
            app.vars.set("CLASS", Generator.pascal_case(name));
            app.vars.set("ROUTE", route_path);
            return app.vars;
        }

        private static void add_page(AppContext app, string name, string cls, string route_path,
                string html, string entrypoint) throws Error {
            write_new_app_file(app.dir, "src/pages/%s.html".printf(name), html);
            write_new_app_file(app.dir, "src/entrypoints/%sEntrypoint.vala".printf(cls), entrypoint);

            var var_name = Generator.snake_case(name) + "_page";
            var target = "%s = custom_target('%s-page',\n".printf(var_name, Generator.snake_case(name))
                + "    input: 'src/pages/%s.html',\n".printf(name)
                + "    output: '%sPage.vala',\n".printf(cls)
                + "    command: [statum_mkpstm, '-o', '@OUTPUT@', '-n', '%sPage', '--ns', '%s', '@INPUT@'],\n".printf(cls, app.ns)
                + "    depend_files: files('src/pages/main.html')\n"
                + ")";
            edit_meson(app, target, MESON_PAGES_BEGIN, MESON_PAGES_END);
            edit_meson(app, "'src/entrypoints/%sEntrypoint.vala',".printf(cls), MESON_SOURCES_BEGIN, MESON_SOURCES_END);
            edit_meson(app, "%s,".printf(var_name), MESON_GENERATED_BEGIN, MESON_GENERATED_END);
            edit_main(app, "statum.add_page<%sPage, %sEntrypoint>();".printf(cls, cls), VALA_PAGES_BEGIN, VALA_PAGES_END);
        }

        private static void edit_meson(AppContext app, string snippet, string begin, string end) throws Error {
            var path = Path.build_filename(app.dir, "meson.build");
            Generator.write_file(path, Generator.insert_marked(Generator.read_file(path), begin, end, snippet));
        }

        private static void edit_main(AppContext app, string snippet, string begin, string end) throws Error {
            var path = Path.build_filename(app.dir, "src", "main.vala");
            Generator.write_file(path, Generator.insert_marked(Generator.read_file(path), begin, end, snippet));
        }

        private static void edit_layout(AppContext app, string snippet, string begin, string end) throws Error {
            var path = Path.build_filename(app.dir, "src", "pages", "main.html");
            Generator.write_file(path, Generator.insert_marked(Generator.read_file(path), begin, end, snippet));
        }

        private static void write_app_file(string app_dir, string relative, string contents, uint32 mode = 0644) throws Error {
            Generator.write_file(Path.build_filename(app_dir, relative), contents, mode);
        }

        /**
         * Writes a scaffolded file only when it does not exist yet, so
         * re-running `add` commands never clobbers user edits.
         */
        private static void write_new_app_file(string app_dir, string relative, string contents) throws Error {
            var path = Path.build_filename(app_dir, relative);
            if (FileUtils.test(path, FileTest.EXISTS)) {
                stdout.printf("%s already exists — left untouched\n", path);
                return;
            }
            Generator.write_file(path, contents);
        }

        private static string normalise(string name) {
            return name.down();
        }

        private static string? content_type_for(string filename) {
            var extension = filename.contains(".") ? filename.substring(filename.last_index_of(".") + 1).down() : "";
            switch (extension) {
                case "css":
                    return "text/css";
                case "js":
                case "mjs":
                    return "application/javascript";
                case "png":
                    return "image/png";
                case "svg":
                    return "image/svg+xml";
                case "jpg":
                case "jpeg":
                    return "image/jpeg";
                case "ico":
                    return "image/x-icon";
                case "woff2":
                    return "font/woff2";
                case "woff":
                    return "font/woff";
                default:
                    return null;
            }
        }

        private static void parse(string[] args, string summary, OptionEntry[]? extra) throws OptionError {
            var context = new OptionContext(summary);
            context.add_main_entries(global_options, null);
            if (extra != null) {
                context.add_main_entries((!)extra, null);
            }
            context.parse(ref args);
        }

        /** Drops `skip` positional words after `args[0]`, keeping `args[0]`. */
        private static string[] slice(string[] args, int skip) {
            var rest = new string[int.max(1, args.length - skip)];
            rest[0] = args[0];
            for (int i = skip + 1; i < args.length; i++) {
                rest[i - skip] = args[i];
            }
            return rest;
        }
    }
}