import * as Automerge from '@automerge/automerge';
import { describe, expect, it } from 'vitest';

import { readDocContent, spliceText, updateTextContent } from './text-diff';

type Doc = { content: string };

describe('updateTextContent', () => {
  it('merges concurrent character-level edits without clobbering', () => {
    const base = Automerge.from<Doc>({ content: 'hello world' });

    // Two actors fork from the same base and edit different regions.
    let a = Automerge.clone(base, { actor: 'aaaaaaaaaaaaaaaa' });
    let b = Automerge.clone(base, { actor: 'bbbbbbbbbbbbbbbb' });

    a = Automerge.change(a, (d) =>
      updateTextContent(d, ['content'], 'HELLO world'),
    );
    b = Automerge.change(b, (d) =>
      updateTextContent(d, ['content'], 'hello WORLD'),
    );

    const merged = Automerge.merge(a, b);

    // Character-level splices merge: both edits survive (a wholesale write
    // would have kept only one side).
    expect(readDocContent(merged.content)).toBe('HELLO WORLD');
  });

  it('replaces content for a single editor', () => {
    let doc = Automerge.from<Doc>({ content: 'v1' });
    doc = Automerge.change(doc, (d) =>
      updateTextContent(d, ['content'], 'v2 longer text'),
    );
    expect(readDocContent(doc.content)).toBe('v2 longer text');
  });

  it('assigns into an empty field', () => {
    let doc = Automerge.from<Doc>({ content: '' });
    doc = Automerge.change(doc, (d) =>
      updateTextContent(d, ['content'], 'fresh'),
    );
    expect(readDocContent(doc.content)).toBe('fresh');
  });
});

describe('spliceText', () => {
  it('applies minimal character-level edits', () => {
    let doc = Automerge.from<Doc>({ content: 'the quick brown fox' });
    doc = Automerge.change(doc, (d) =>
      spliceText(d, ['content'], 'the quick brown fox', 'the slow brown fox'),
    );
    expect(readDocContent(doc.content)).toBe('the slow brown fox');
  });
});

describe('readDocContent', () => {
  it('returns plain strings as-is', () => {
    expect(readDocContent('hello')).toBe('hello');
  });

  it('passes through binary content', () => {
    const bytes = new Uint8Array([1, 2, 3]);
    expect(readDocContent(bytes)).toBe(bytes);
  });

  it('returns null for null/undefined', () => {
    expect(readDocContent(null)).toBeNull();
    expect(readDocContent(undefined)).toBeNull();
  });
});