var move = "✥"
var tick = "✔";
var addText = "+";
var rmText = "−";
var removebg = "#bf616a";
var hovergrn = "#a3be8c";
var hoverbg = "#434c5e";
var hoverbg2 = "#848ead";
var editMode = false;
var dragSrcEl = null;
var thumbServer = "https://www.google.com/s2/favicons?domain=";
var defaultColumns= [
      ["General",
        ["Github", "https://github.com"],
        ["Wikipedia", "https://en.wikipedia.org"],
        ["Gmail", "https://mail.google.com"]
      ],
      ["Productivity",
        ["Desmos", "https://www.desmos.com/calculator"],
        ["Wolfram", "https://wolframalpha.com"],
        ["Hacker News", "https://news.ycombinator.com"]
      ],
      ["Social",
        ["Reddit", "https://www.reddit.com"],
        ["YouTube", "https://youtube.com"],
        ["Instagram", "https://instagram.com"]
      ]
]


// --------------------------------
//
// Initialisation
//
// --------------------------------


document.addEventListener("DOMContentLoaded", loadLists);

function loadLists() {

  // Retrieve lists from storage and trigger callback to generate HTML
  
  console.log("Getting lists from storage");
  chrome.storage.sync.get({"lists": defaultColumns}, parseColumns);

  document.getElementById('edit').addEventListener('click', edit, false);
  document.getElementById('addcol').addEventListener('click', addColumn, false);

  // Set colours from preferences

  var bgCallback = function(colourPref) { document.body.style.background = colourPref["bgvalue"]; };
  var fgCallback = function(colourPref) { document.body.style.color = colourPref["fgvalue"]; };
  var hrCallback = function(colourPref) {
    document.documentElement.style.setProperty('--hover-bg', colourPref["hrvalue"]);
    hoverbg = colourPref["hrvalue"];
  };

  chrome.storage.sync.get({"bgvalue": "#2e3440"}, bgCallback);
  chrome.storage.sync.get({"fgvalue": "#d8dee9"}, fgCallback);
  chrome.storage.sync.get({"hrvalue": "#434c5e"}, hrCallback);

}


function parseColumns(config) {

  var columns = config["lists"]

  // Generate elements for each column
  for (let col of columns) {

    var ul = genColumn(col[0]);
    document.getElementById("links").appendChild(ul);

    // Iterate through links
    for(let item of col.slice(1)) {
      li = genItem(ul, item[0], item[1]);
      ul.appendChild(li);
    }

    var sortableProperties = { group: "usercolumns", animation: 150, onSort: function (evt) {saveConfig();} };
    new Sortable(ul, sortableProperties);

  }
}


function genColumn(title) {

    // Generate HTML elements for a column (without items)

    var ul = document.createElement("ul");
    ul.setAttribute("id", title);
    ul.setAttribute('draggable', 'false');

    var grip = document.createElement("span");
    grip.setAttribute("class", "grip");
    grip.addEventListener('mousedown', enableDrag);
    grip.addEventListener('mouseup', disableDrag);
    ul.appendChild(grip)

    var titleDiv = document.createElement("div");
    titleDiv.setAttribute("class", "title");

    var titleText = document.createElement("p");
    titleText.innerText = title;
    titleDiv.appendChild(titleText);

    var addBtn = document.createElement("span");
    addBtn.innerText = addText;
    addBtn.setAttribute("class", "add");
    addBtn.setAttribute("id", "add-" + title);
    addBtn.addEventListener("click", addItem);
    titleDiv.appendChild(addBtn);

    ul.appendChild(titleDiv);

    return ul;

}


function genItem(ul, nme, url) {

  // Generate HTML elements for an item

  var li = document.createElement("li");
  li.setAttribute("class", ul.id + "-" + (ul.getElementsByTagName("li").length + 1).toString() );
  li.addEventListener("mouseup", saveConfig);

  var img = requestThumbnail(url);

  var link = document.createElement("a");
  link.className = "item";
  link.href = url;

  var rmBtn = document.createElement("span");
  rmBtn.className = "remove";
  rmBtn.id = "delete-" + li.id;
  rmBtn.innerText = "-";
  rmBtn.addEventListener("click", removeItem);

  link.appendChild(img);
  link.insertAdjacentHTML("beforeend", nme);
  li.appendChild(link);
  li.appendChild(rmBtn);
  
  return li;

}


function requestThumbnail(imageUrl) {
  // Get thumbnail from Google's favicon server
  var img = document.createElement("img");
  var xhr = new XMLHttpRequest();
  xhr.open('GET', thumbServer + imageUrl);
  xhr.responseType = "blob";
  xhr.onload = function() {
    img.setAttribute("data-src", thumbServer + imageUrl);
    img.className = "icon";
    var objUrl = URL.createObjectURL(xhr.response);
    img.setAttribute("src", objUrl);
  }.bind(this);
  xhr.send();
  return img;
}


// --------------------------------
//
// Edit mode
//
// --------------------------------


function edit(event) {
  
  // Enter/exit edit mode
  
  if (editMode == true) {
    console.log("Exited edit mode");
    closeEdit(this);
    return false;
  }

  console.log("Entered edit mode");

  this.style.background = hovergrn;
  this.innerText = tick;
  addBtn= document.getElementById("addcol");
  addBtn.style.display = "flex";
  var cols = document.getElementsByTagName("ul");

  for (let col of cols) {
    
    var titleDiv = col.getElementsByClassName("title")[0];
    titleDiv.getElementsByClassName("add")[0].style.display = "flex";

    col.style.bottom = "26px";
    col.getElementsByClassName("grip")[0].style.display = "inline-block";

    var rmColBtn = document.createElement("span"); 
    rmColBtn.className = "rmcol";
    rmColBtn.id = "rmcol-" + col.id;
    rmColBtn.innerText = rmText;
    titleDiv.appendChild(rmColBtn);

    var titleStatic = titleDiv.getElementsByTagName("p")[0];
    var titleInput = document.createElement("input");
    titleInput.type = "text";
    titleInput.className = "colname";
    titleInput.placeholder = titleStatic.innerText;
    titleInput.value = titleStatic.innerText;
    titleDiv.insertBefore(titleInput, titleStatic);
    titleStatic.remove();

  }

  updateListeners();
  editMode = true;
}

function closeEdit(editBtn) {

  // Exit edit mode and clean up elements

  editMode = false;
  editBtn.style.background = "";
  editBtn.innerText = move;

  var addBtn = document.getElementById("addcol");
  addBtn.style.display = "none";

  var cols = document.getElementsByTagName("ul");

  for (let col of cols) {

    col.style.bottom = "0";
    col.getElementsByClassName("grip")[0].style.display = "none";

    var rmColBtn = col.getElementsByClassName("title")[0].getElementsByClassName("rmcol")[0];
    rmColBtn.remove();

    var titleDiv = col.getElementsByClassName("title")[0];
    titleDiv.getElementsByClassName("add")[0].style.display = "";

    titleInput = titleDiv.getElementsByClassName("colname")[0];
    titleStatic = document.createElement("p");
    titleStatic.innerText = titleInput.value;
    if (titleStatic.innerText == "") {
      titleStatic.innerText = titleInput.placeholder;
    }
    titleInput.remove();
    titleDiv.appendChild(titleStatic);

  }

  saveConfig();

}

function addColumn(event) {

  // Create a new column from Edit mode

  var ul = document.createElement("ul");

  // Make sure columns do not share an id
  var ex = document.querySelectorAll('[id^="new "]'); // existing "new" columns
  if (ex.length > 0) {
    indices = []
    for (let i of ex) {
     indices.push(Number(i.id.split(" ")[1])); 
    }
    ul.setAttribute("id", "new " + (Math.max.apply(Math, indices)+1).toString());
  }
  else {
    ul.setAttribute("id", "new 1");
  }
  ul.setAttribute('draggable', 'false');

  var grip = document.createElement("span");
  grip.setAttribute("class", "grip");
  grip.addEventListener("mousedown", enableDrag);
  grip.addEventListener("mouseup", disableDrag);
  grip.style.display = "inline-block";
  ul.style.bottom = "26px";
  ul.appendChild(grip)

  var titleDiv = document.createElement("div");
  titleDiv.setAttribute("class", "title");

  var titleInput = document.createElement("input");
  titleInput.type = "text";
  titleInput.className = "colname";
  titleInput.placeholder = ul.id;
  titleDiv.appendChild(titleInput);

  var addBtn = document.createElement("span");
  addBtn.style.display = "flex";
  addBtn.innerText = addText;
  addBtn.setAttribute("class", "add");
  addBtn.setAttribute("id", "add-" + ul.id);
  addBtn.addEventListener("click", addItem);
  titleDiv.appendChild(addBtn);

  var rmColBtn = document.createElement("span"); 
  rmColBtn.className = "rmcol";
  rmColBtn.id = "rmcol-" + ul.id;
  rmColBtn.innerText = rmText;
  titleDiv.appendChild(rmColBtn);

  ul.appendChild(titleDiv);

  document.getElementById("links").appendChild(ul);
  saveConfig();
  updateListeners();
  titleInput.focus();

}


function removeColumn(event) {

  // Delete column in edit mode
  
  this.parentNode.parentNode.remove();
  saveConfig();

}


function removeItem(event) {

  // Remove link in edit or normal mode
  
  this.parentNode.outerHTML = "";
  delete this.parentNode;
  saveConfig();

}


function addItem(event) {

  // Interface for adding a new list item to an existing category

  var ul = this.parentNode.parentNode;
  var id = ul.id;

  // Check if a form has already been generated for this column
  existing = ul.getElementsByClassName("new");
  if (existing.length > 0) {
    existing[0].getElementsByClassName("name")[0].focus();
    return false;
  }

  var li = document.createElement("li");
  li.setAttribute("class", "new");
  li.addEventListener("keyup", formKeys); 

  var saveBtn = document.createElement("span");
  saveBtn.className = "save";
  saveBtn.tabIndex = "3";
  saveBtn.id = "save-" + ul.id;
  saveBtn.innerText = tick;
  saveBtn.addEventListener("click", saveItem);
  saveBtn.addEventListener("mouseover", saveMouseOver);
  saveBtn.addEventListener("mouseout", saveMouseOut);
  li.appendChild(saveBtn);

  var nameInput = document.createElement("input");
  nameInput.type = "text";
  nameInput.className = "name";
  nameInput.placeholder = "name";
  nameInput.tabIndex = "1";
  li.appendChild(nameInput);

  var urlInput = document.createElement("input");
  urlInput.type = "url";
  urlInput.className = "url";
  urlInput.placeholder = "url";
  urlInput.tabIndex = "2";
  urlInput.spellcheck = "false";
  li.appendChild(urlInput);

  ul.appendChild(li);
  updateListeners();
  nameInput.focus();

}


function saveItem(event) {

  // Add new item to a column after pressing the save button in form

  var li = this.parentNode;
  var ul = this.parentNode.parentNode;
  var nameField = li.getElementsByClassName("name")[0];
  var urlField = li.getElementsByClassName("url")[0];

  if (nameField.value != "" && urlField.value != "" && urlField.validity.typeMismatch== false) {

    var newli = genItem(ul, nameField.value, urlField.value);
    li.remove();
    delete li;

    ul.appendChild(newli);
    saveConfig();

  }
  else {

    if (nameField.value == "" && urlField.value == "") {
      console.log("No data supplied, deleting form");
      li.remove();
    }
    else {
      console.log("Missing data, press Esc to delete form");
    }

  }

}


// --------------------------------
//
// UI event listeners
//
// --------------------------------


function updateListeners() {

  // Update event listeners for interface elements, since listeners are tied DOM objects which are lost on dataTransfer operations

  var addBtns = document.getElementsByClassName("add");
  for (let addBtn of addBtns) {
    addBtn.addEventListener("click", addItem);
  }

  var rmBtns = document.getElementsByClassName("rm");
  for (let rmBtn of rmBtns) {
    rmBtn.addEventListener("click", removeItem);
  }

  var rmColBtns = document.getElementsByClassName("rmcol");
  for (let rmColBtn of rmColBtns) {
    rmColBtn.addEventListener("click", removeColumn); 
  }

  var saveBtns = document.getElementsByClassName("save");
  for (let saveBtn of saveBtns) {
    saveBtn.addEventListener("click", saveItem);
    saveBtn.addEventListener("mouseover", saveMouseOver);
    saveBtn.addEventListener("mouseout", saveMouseOut);
  }

}


function saveMouseOver(event) {
  nameField = this.parentNode.getElementsByClassName("name")[0];
  urlField = this.parentNode.getElementsByClassName("url")[0];
  if (nameField.value === ''  || urlField.value === '' || urlField.validity.typeMismatch == true) {
    this.style.background = removebg;
  }
  else {
    this.style.background = hovergrn; 
  }
}


function saveMouseOut(event) {
  this.style.background = hoverbg2;
}


function enableDrag() {
  // Enable drag & drop when grip is grabbed (otherwise any mouse click triggers dragStart)
  console.log("Drag started");
  uls = document.getElementsByTagName("ul");
  for (let ul of uls) {
    ul.setAttribute("draggable", "true");
    ul.addEventListener('dragstart', dragStart, false);
    ul.addEventListener('dragover', dragOver, false);
    ul.addEventListener('drop', drop, false);
  }
}


function disableDrag() {
  // Disable drag after grip has been released
  console.log("Drag ended");
  uls = document.getElementsByTagName("ul");
  for (let ul of uls) {
    ul.setAttribute("draggable", "false");
    ul.removeEventListener('dragstart');
    ul.removeEventListener('dragover');
    ul.removeEventListener('drop');
  }
}


function dragStart(e) {
  dragSrcEl = this;
  e.dataTransfer.effectAllowed = 'move';
  e.dataTransfer.setData('text/html', this.innerHTML);
}


function dragOver(e) {
  if (e.preventDefault) {
    e.preventDefault();
  }
  e.dataTransfer.dropEffect = 'move';
  return false;
}


function drop(e) {
  if (e.stopPropagation); {
    e.stopPropagation();
  }
  if (dragSrcEl != this) {
    var srcTitleInput = dragSrcEl.getElementsByClassName("colname")[0].value;
    var destTitleInput = this.getElementsByClassName("colname")[0].value;
    dragSrcEl.innerHTML = this.innerHTML;
    dragSrcEl.getElementsByClassName("colname")[0].value = destTitleInput;
    this.innerHTML = e.dataTransfer.getData('text/html');
    this.getElementsByClassName("colname")[0].value = srcTitleInput;
    saveConfig();
    updateListeners();
  }
  return false;
}


function formKeys(e) {
  var focus = document.activeElement;
  if (focus.parentNode.className != "new") {
    return false;
  }
  switch (e.which) {
    case 27: // escape
      focus.parentNode.remove();
      break;
    case 13: // enter
      focus.parentNode.getElementsByClassName("save")[0].click();
      break;
  }
}


// --------------------------------
//
// Configuration management
//
// --------------------------------


function saveConfig() {
  
  // Save current DOM structure as JSON data

  console.log("Saving settings");
  data = []
  for (let ul of document.getElementsByTagName("ul")) {
    data.push(columnToArray(ul, true));
  }
  chrome.storage.sync.set( {"lists": data} );

}


function columnToArray(ul, title = false) {

  // Convert a column of data (ul) to a 2D array, optionally including the title

  var data = [];
  var items = ul.getElementsByClassName("item");

  if (title == true && editMode == true) {
    data[0] = ul.getElementsByClassName("title")[0].getElementsByTagName("input")[0].value;
    if (data[0] == "" || data[0] == null) {
      console.log("Using default category name since input was empty");
      data[0] = ul.getElementsByClassName("title")[0].getElementsByTagName("input")[0].placeholder;
    }
  }
  else if (title == true) {
    data[0] = ul.getElementsByClassName('title')[0].getElementsByTagName("p")[0].textContent;
  }

  for (let li of items) {
    if (li.class == "new" || li.class == "title") {
      continue; // Ignore input forms and titles (already handled)
    }
    else {
      data.push([li.innerText, li.getAttribute("href")]);
    }
  }

  return data;

}