(core) move client code to core

Summary:
This moves all client code to core, and makes minimal fix-ups to
get grist and grist-core to compile correctly.  The client works
in core, but I'm leaving clean-up around the build and bundles to
follow-up.

Test Plan: existing tests pass; server-dev bundle looks sane

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2627

app/client/ui/transientInput.ts

@@ -0,0 +1,50 @@
+/**
+ * This is a temporary <input> element. The intended usage is to create is when needed (e.g. when
+ * some "rename" option is chosen), and provide methods to save and to close.
+ *
+ * It calls save() on Enter and on blur, which should return a Promise. On successful save, and on
+ * Escape, it calls close(), which should destroy the <input>.
+ */
+
+import {reportError} from 'app/client/models/AppModel';
+import {dom, DomArg} from 'grainjs';
+
+export interface ITransientInputOptions {
+  initialValue: string;
+  save(value: string): Promise<void>|any;
+  close(): void;
+}
+
+export function transientInput({initialValue, save, close}: ITransientInputOptions,
+                               ...args: Array<DomArg<HTMLInputElement>>) {
+  let lastSave: string = initialValue;
+
+  async function onSave(explicitSave: boolean) {
+    try {
+      if (explicitSave || input.value !== lastSave) {
+        lastSave = input.value;
+        await save(input.value);
+      }
+      close();
+    } catch (err) {
+      reportError(err);
+      delayedFocus();
+    }
+  }
+
+  function delayedFocus() {
+    setTimeout(() => { input.focus(); input.select(); }, 10);
+  }
+
+  const input = dom('input', {type: 'text', placeholder: 'Enter name'},
+    dom.prop('value', initialValue),
+    dom.on('blur', () => onSave(false)),
+    dom.onKeyDown({
+      Enter: () => onSave(true),
+      Escape: () => close(),
+    }),
+    ...args,
+  );
+  delayedFocus();
+  return input;
+}