(function () {
    const reply_control = document.querySelector("#reply-control");
    // watch for inner html change
    reply_control.addEventListener("DOMSubtreeModified", function () {
        // find tedxtarea
        const textarea = reply_control.querySelector("textarea.ember-text-area");
        if (textarea) {
            if (document.querySelector("#mars-btn")) {
                return;
            }
            if (!reply_control.querySelector("div.save-or-cancel")) {
                return;
            }
            const button = document.createElement("button");
            button.className = "btn btn-icon-text btn-primary";
            button.innerText = "火星文";
            button.id = "mars-btn";
            button.addEventListener("click", function () {
                textarea.value = "火星文";
                // do some stuff here...
                textarea.dispatchEvent(new Event('change'));
            });
            reply_control.querySelector("div.save-or-cancel").appendChild(button);
        }
    });
})()