Merge Unit and Quantity drag&drop js

Closes #55

app/javascript/application.js

@@ -2,12 +2,15 @@
 // https://github.com/rails/importmap-rails
 import "@hotwired/turbo-rails"
 
+
+/* Hide page before loaded for testing purposes */
 function showPage(event) {
   document.documentElement.style.visibility="visible"
 }
 document.addEventListener('turbo:load', showPage)
 
 
+/* Turbo stream actions */
 Turbo.StreamElement.prototype.enableElement = function(element) {
     element.removeAttribute("disabled")
     element.removeAttribute("aria-disabled")
@@ -15,7 +18,6 @@ Turbo.StreamElement.prototype.enableElement = function(element) {
     element.removeAttribute("tabindex")
 }
 
-
 Turbo.StreamActions.disable = function() {
   this.targetElements.forEach((e) => {
     e.setAttribute("disabled", "disabled")
@@ -51,3 +53,89 @@ Turbo.StreamActions.close_form = function() {
     e.remove()
   })
 }
+
+
+/* Items table drag and drop support */
+function processKey(event) {
+  if (event.key == "Escape") {
+    event.currentTarget.querySelector("a[name=cancel]").click();
+  }
+}
+window.processKey = processKey;
+
+var lastEnterTime;
+function dragStart(event) {
+  lastEnterTime = event.timeStamp;
+  var row = event.currentTarget;
+  row.closest("table").querySelectorAll("thead tr").forEach((tr) => {
+    tr.toggleAttribute("hidden");
+  });
+  event.dataTransfer.setData("text/plain", row.getAttribute("data-drag-path"));
+  var rowRectangle = row.getBoundingClientRect();
+  event.dataTransfer.setDragImage(row, event.x - rowRectangle.left, event.y - rowRectangle.top);
+  event.dataTransfer.dropEffect = "move";
+}
+window.dragStart = dragStart;
+
+/*
+* Drag tracking assumptions (based on FF 122.0 experience):
+*   * Enter/Leave events at the same timeStamp may not be logically ordered
+*     (e.g. E -> E -> L, not E -> L -> E),
+*   * not every Enter event has corresponding Leave event, especially during
+*     rapid pointer moves
+* NOTE: sometimes Leave is not emitted when pointer goes fast over table
+* and outside. This should probably be fixed in browser, than patched here.
+*/
+function dragEnter(event) {
+  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id);
+  dragLeave(event);
+  lastEnterTime = event.timeStamp;
+  const id = event.currentTarget.getAttribute("data-drop-id");
+  document.getElementById(id).classList.add("dropzone");
+}
+window.dragEnter = dragEnter;
+
+function dragOver(event) {
+  event.preventDefault();
+}
+window.dragOver = dragOver;
+
+function dragLeave(event) {
+  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id);
+  // Leave has been accounted for by Enter at the same timestamp, processed earlier
+  if (event.timeStamp <= lastEnterTime) return;
+  event.currentTarget.closest("table").querySelectorAll(".dropzone").forEach((tr) => {
+    tr.classList.remove("dropzone");
+  })
+}
+window.dragLeave = dragLeave;
+
+function dragEnd(event) {
+  dragLeave(event);
+  event.currentTarget.closest("table").querySelectorAll("thead tr").forEach((tr) => {
+    tr.toggleAttribute("hidden");
+  });
+}
+window.dragEnd = dragEnd;
+
+function drop(event) {
+  event.preventDefault();
+
+  var params = new URLSearchParams();
+  var id_param = event.currentTarget.getAttribute("data-drop-id-param");
+  var id = event.currentTarget.getAttribute("data-drop-id").split("_").pop();
+  params.append(id_param, id);
+
+  fetch(event.dataTransfer.getData("text/plain"), {
+    body: params,
+    headers: {
+      "Accept": "text/vnd.turbo-stream.html",
+      "X-CSRF-Token": document.head.querySelector("meta[name=csrf-token]").content,
+      "X-Requested-With": "XMLHttpRequest"
+    },
+    method: "POST"
+  })
+  .then(response => response.text())
+  .then(html => Turbo.renderStreamMessage(html))
+}
+window.drop = drop;