var start = null;
var end = null;
var tags = new Set();
var highlight = null;

// add a cell to the given row, put link to event(id) with given content
function addCell(row,content,id){
    var a = document.createElement('a');
    if (content){
        a.onclick = e => showOverlay('/static/event?id='+id);
        a.innerHTML = content;
    }
    row.insertCell().appendChild(a);
}

// add a row to the table, fill with event data from json
function addRow(json){
    var table = element('eventlist');
    var row = table.insertRow(1);
    row.id = json.id;
    if (json.tags){
        var tagList = json.tags.join(' ');
        row.setAttribute('class',tagList);
    }
    //addCell(row,json.id,json.id);
    addCell(row,json.start,json.id);
    addCell(row,json.title,json.id);
    addCell(row,json.location,json.id);
    row.appendChild(createTags(json.tags));
}

function createNewEvent(){
    var s = '';
    var url = location.href;
    console.log(url);
    var pos = url.indexOf("?");
    if (pos>0) {
        s = url.substring(pos);
        url = url.substring(0,pos);
        console.log({url:url,search:s});
    }
    location.href = url+'static/edit'+s;

}

function createTags(tagList){
    var td = document.createElement('td');
    tagList.forEach(val => {
        var btn = document.createElement('button');
        btn.onclick = e => toggleTag(val);
        btn.appendChild(document.createTextNode(val));
        td.appendChild(btn);
        td.appendChild(document.createTextNode(' '));
    });
    return td;
}

// fetch events in the time range, then call handleEvents
function fetchEvents(start, end){
    var path = '/api/events/json';
    if (start) {
        path += '?start='+start;
        if (end) path+= '&end='+end;
    }
    fetch(path).then(handleEvents);
}

function fetchLastMonth(){
    var startDate = new Date(Date.parse(start+'-01'));
    var month = startDate.getMonth() +1;
    var year = startDate.getFullYear();
    month -= 1;
    if (month < 1) {
        year--;
        month+=12;
    }
    end = start;
    start = year + '-' + (month<10 ? '0' : '') + month;
    fetchEvents(start,end);
}

function fetchLastYear(){
    var startDate = new Date(Date.parse(start+'-01'));
    var month = startDate.getMonth() +1;
    var year = startDate.getFullYear();
    if (month <= 1) year --;
    month = 1;
    start = year + '-' + (month<10 ? '0' : '') + month;
    fetchEvents(start,end);
}

// add the events fetched with the latest request to the table
async function handleEvents(response){
    if (response.ok){
        var json = await response.json();
        json.forEach(addRow);
        updateTagVisibility();
        if (highlight){
            var row = element(highlight);
            if (row) {
                row.classList.add('highlight');
                row.scrollIntoView({behavior: 'smooth',block: 'center'});
            }
        }
    }
}

// called when page is loaded
function loadCurrentEvents(){
    let params = new URLSearchParams(location.search);
    highlight = params.get('id');
    var tagString = params.get('tags');
    if (tagString){
        tagString.split(',').forEach(t => {
            tags.add(t.trim());
        });
    }
    if (start == null){
        var now = new Date();
        var year = now.getFullYear();
        var month = now.getMonth() + 1;
        start = year + '-' + (month < 10 ? '0' : '') + month;
        fetchEvents(start,end);
    }
}

function openIcal(){
    var url = location.href;
    var query = location.search;
    var params = new URLSearchParams(query);
    var tags = params.get('tags');
    var pos = url.indexOf('?');
    if (pos>1) url = url.substring(0,pos);
    if (!url.endsWith('/')) url += '/';
    url += 'api/events/ical'+query;
    var elem = create('a');
    elem.setAttribute('href',url);
    elem.setAttribute('download',(tags?tags.replace(',','+'):'calendar')+'.ics');
    elem.click();
}

// shows the given url in an overlayed iframe
function showOverlay(url){
    var div = element('overlay');
    div.innerHTML = '';
    var iframe = document.createElement('iframe');
    iframe.src = url;
    div.appendChild(iframe);
    div.style.display = 'block';
    div.onclick = e => div.style.display = 'none';
    var closeBtn = document.createElement('div');
    closeBtn.id = 'close_overlay';
    closeBtn.innerHTML = '✖';
    closeBtn.title = 'close overlay';
    div.appendChild(closeBtn);
}

// adds or removes tag from set, updates shown tags
function toggleTag(tag){
    if (tags.has(tag)){
        tags.delete(tag);
    } else {
        tags.add(tag);
    }
    updateUrl();
    updateTagVisibility();
}

// creates a button for each tag in tags set
function updateTagVisibility(){
    var selection = document.getElementById('tag_selection');
    selection.innerHTML = 'Selected Tags: ';
    selection.style.display = tags.size > 0 ? 'block' : 'none';
    tags.forEach(tag => {
        var btn = document.createElement('button');
        btn.onclick = e => toggleTag(tag);
        btn.innerHTML = tag;
        selection.appendChild(btn);
        selection.appendChild(document.createTextNode(' '));
    });
    var table = document.getElementById('eventlist');
    for (var tr of table.getElementsByTagName('tr')){
        var classes = tr.getAttribute('class');
        if (classes =='head') continue;
        var all = true;
        tags.forEach(tag => {
            if (classes.indexOf(tag)<0) all = false;
        });
        tr.style.display = all ? 'table-row' : 'none';
    }
}

function updateUrl(){
    var url = location.href;
    var pos = url.indexOf('?');
    if (pos>0) url = url.substring(0,pos);
    var params = [];
    if (highlight) params.push('id='+highlight);
    if (start) params.push('start='+start);
    var tagString = Array.from(tags).join(',');
    if (tagString) params.push('tags='+tagString);
    var query = params.join('&');
    if (query) url += '?'+query;
    window.history.pushState(null,"",url);
}