(function () {
    var textarea = document.getElementById('editor');
    if (!textarea) return;

    function wrap(before, after, placeholder) {
        var start = textarea.selectionStart;
        var end = textarea.selectionEnd;
        var selected = textarea.value.slice(start, end) || placeholder;
        var replacement = before + selected + after;
        textarea.value = textarea.value.slice(0, start) + replacement + textarea.value.slice(end);
        if (selected === placeholder) {
            textarea.selectionStart = start + before.length;
            textarea.selectionEnd = start + before.length + placeholder.length;
        } else {
            textarea.selectionStart = start + replacement.length;
            textarea.selectionEnd = start + replacement.length;
        }
        textarea.focus();
    }

    function linePrefix(prefix) {
        var start = textarea.selectionStart;
        var lineStart = textarea.value.lastIndexOf('\n', start - 1) + 1;
        textarea.value = textarea.value.slice(0, lineStart) + prefix + textarea.value.slice(lineStart);
        textarea.selectionStart = textarea.selectionEnd = start + prefix.length;
        textarea.focus();
    }

    var actions = {
        bold:      function () { wrap('**', '**', 'bold text'); },
        italic:    function () { wrap('*', '*', 'italic text'); },
        h1:        function () { linePrefix('# '); },
        h2:        function () { linePrefix('## '); },
        h3:        function () { linePrefix('### '); },
        code:      function () { wrap('`', '`', 'code'); },
        codeblock: function () { wrap('```\n', '\n```', 'code'); },
        quote:     function () { linePrefix('> '); },
        link:      function () { wrap('[', '](url)', 'link text'); },
        ul:        function () { linePrefix('- '); },
        ol:        function () { linePrefix('1. '); },
        hr:        function () { wrap('\n\n---\n\n', '', ''); },
    };

    document.querySelectorAll('[data-action]').forEach(function (btn) {
        btn.addEventListener('click', function () {
            var action = actions[btn.dataset.action];
            if (action) action();
        });
    });
})();