(function () {
    const LANGUAGE_KEY = "struts_lab_language";

    function getLanguage() {
        return localStorage.getItem(LANGUAGE_KEY) === "en" ? "en" : "zh";
    }

    function setLanguage(language) {
        const resolved = language === "en" ? "en" : "zh";
        localStorage.setItem(LANGUAGE_KEY, resolved);
        document.documentElement.lang = resolved === "zh" ? "zh-CN" : "en";
        return resolved;
    }

    function applyText(values) {
        Object.entries(values || {}).forEach(([id, value]) => {
            const node = document.getElementById(id);
            if (node) {
                node.textContent = value;
            }
        });
    }

    function applyHtml(values) {
        Object.entries(values || {}).forEach(([id, value]) => {
            const node = document.getElementById(id);
            if (node) {
                node.innerHTML = value;
            }
        });
    }

    function applyPlaceholders(values) {
        Object.entries(values || {}).forEach(([id, value]) => {
            const node = document.getElementById(id);
            if (node) {
                node.setAttribute("placeholder", value);
            }
        });
    }

    function mount(config) {
        const state = {
            language: setLanguage(getLanguage())
        };
        const button = document.getElementById(config.buttonId || "languageBtn");

        function messages() {
            return config.messages[state.language] || config.messages.zh || {};
        }

        function render() {
            const current = messages();
            if (current.pageTitle) {
                document.title = current.pageTitle;
            }
            applyText(current.text);
            applyHtml(current.html);
            applyPlaceholders(current.placeholders);
            if (button) {
                button.textContent = state.language === "zh" ? "EN" : "中文";
            }
            if (typeof config.render === "function") {
                config.render({
                    language: state.language,
                    messages: current,
                    setLanguage
                });
            }
        }

        if (button) {
            button.addEventListener("click", function () {
                state.language = setLanguage(state.language === "zh" ? "en" : "zh");
                render();
            });
        }

        render();
        return {
            getLanguage: function () {
                return state.language;
            }
        };
    }

    window.strutsLab = {
        mount: mount,
        getLanguage: getLanguage,
        setLanguage: setLanguage
    };
})();