df

function solve(e) {
    const [lectNameField, dateField] = document.querySelectorAll(`input`);
    const moduleNameField = document.getElementsByTagName('select')[0];
    const modules = document.getElementsByClassName('modules')[0];
    document.querySelector('button').addEventListener('click', addLecture);

    function lectureTemplate(date, lectureName) {
        const li = document.createElement('li');
        li.className = 'flex';
        li.innerHTML = `<h4>${lectureName} - ${date}</h4>
        <button class='red'>Del</button>`;
        li.querySelector('button').addEventListener('click', dellLecture);
        li.date = date;

        return li;
    }

    function moduleTemplate(moduleName, date, lectureName) {
        const moduleDiv = document.createElement('div');
        moduleDiv.className = 'module';
        moduleDiv.innerHTML = `<h3>${moduleName}</h3>`;
        const moduleLectures = document.createElement('ul');
        moduleLectures.appendChild(lectureTemplate(date, lectureName));
        moduleDiv.appendChild(moduleLectures);

        return moduleDiv;
    }

    const helpers = {fDate: (s) => s.replaceAll('-', '/').replace('T', ' - '),
                    fName: (n) => `${n.toLocaleUpperCase()}-MODULE`}

    function addLecture(e) {
        e.preventDefault();
        const [lectureName, date, moduleName] = [lectNameField.value, helpers.fDate(dateField.value), helpers.fName(moduleNameField.value)];

        if (lectureName !== '' && date !== '' && moduleName !== 'Select module') {
            const sameModule = Array.from(modules.children)
                .find(x => x.children[0].innerHTML === moduleName);
            if (sameModule) {
                const trainings = sameModule.children[1];
                const lectures = Array.from(trainings.children);
                lectures.push(lectureTemplate(date, lectureName));
                lectures.sort((a, b) => a.date.localeCompare(b.date));
                lectures.forEach(lecture => trainings.appendChild(lecture));
            } else {
                modules.appendChild(moduleTemplate(moduleName, date, lectureName));
            }
        lectNameField.value = '';
        dateField.value = '';
        moduleNameField.value = 'Select module';
        }
    }

    function dellLecture(e) {
        const moduleSection = e.target.parentElement.parentElement.parentElement;
        e.target.parentElement.remove();
        if (moduleSection.children[1].children.length === 0) {
            moduleSection.remove()
        }
    }
}