// Where the caret and the selection go when another changes the open file's
// text (textBinding.ts): moved by what was inserted or deleted before them,
// left before what another inserts just at them — the deltas as Yjs gives them.

import { describe, expect, it } from 'vitest';
import * as Y from 'yjs';
import { mapIndex, type TextDelta } from '../src/desktop/textBinding.js';

/** The delta of a change to a text that held `before`. */
function deltaOf(before: string, change: (text: Y.Text) => void): TextDelta {
  const doc = new Y.Doc();
  const text = doc.getText('t');
  text.insert(0, before);
  let delta: TextDelta = [];
  text.observe((event) => (delta = event.delta as TextDelta));
  change(text);
  return delta;
}

describe('a place in the text after another’s change', () => {
  it('moves by what was inserted before it, not by what came after it or just at it', () => {
    const insert = deltaOf('Hallo Welt', (text) => text.insert(6, 'schöne '));
    expect([0, 5, 6, 7, 10].map((index) => mapIndex(index, insert))).toEqual([0, 5, 6, 14, 17]);
    expect(
      mapIndex(
        3,
        deltaOf('abc', (text) => text.insert(0, 'xy')),
      ),
    ).toBe(5);
    expect(
      mapIndex(
        0,
        deltaOf('abc', (text) => text.insert(0, 'xy')),
      ),
    ).toBe(0);
  });

  it('moves back by what was deleted before it, to where the deletion began when it lay inside', () => {
    const removed = deltaOf('Hallo schöne Welt', (text) => text.delete(6, 7));
    expect([0, 6, 9, 13, 17].map((index) => mapIndex(index, removed))).toEqual([0, 6, 6, 6, 10]);
  });

  it('takes a replacement as its deletion and then its insertion: a place at the end of what was replaced stays before the new text', () => {
    const replaced = deltaOf('Erster Stand', (text) => {
      text.doc!.transact(() => {
        text.delete(0, 6);
        text.insert(0, 'Zweiter');
      });
    });
    expect(replaced).toEqual([{ delete: 6 }, { insert: 'Zweiter' }]);
    expect([0, 3, 6, 7, 12].map((index) => mapIndex(index, replaced))).toEqual([0, 0, 0, 8, 13]);
    // An embedded object counts as one place.
    expect(mapIndex(2, [{ insert: { image: 'x' } }])).toBe(3);
    expect(mapIndex(2, [{ retain: 2 }, { insert: { image: 'x' } }])).toBe(2);
  });
});