import * as Automerge from '@automerge/automerge';

import type { FileDocument } from '../types';

/**
 * Splice text into an Automerge document at a given path.
 * Wraps Automerge.splice() for the vault document shape.
 *
 * Only works when the target field is an Automerge text object.
 * For plain strings, use updateTextContent instead.
 */
export function spliceText<T extends FileDocument>(
  doc: Automerge.Doc<T>,
  path: readonly string[],
  index: number,
  deleteCount: number,
  insert: string,
): Automerge.Doc<T> {
  return Automerge.change(doc, (d) => {
    Automerge.splice(d, path as any, index, deleteCount, insert);
  });
}

/**
 * Update the `content` field of a FileDocument to match `newContent`.
 *
 * For regular strings: assigns directly (plain strings in Automerge are
 * replaced wholesale; this is the correct path for the PushworkFileDocument
 * schema which stores content as `string | Uint8Array`).
 *
 * For legacy immutable strings (RawString / ImmutableString): assigns directly.
 * For Automerge text objects: uses Automerge.updateText for efficient
 * character-level diffing.
 */
export function updateTextContent<T extends FileDocument>(
  doc: Automerge.Doc<T>,
  newContent: string,
): Automerge.Doc<T> {
  const current = readDocContent(doc);
  if (current === newContent) return doc;

  return Automerge.change(doc, (d) => {
    const content = d.content as unknown;
    if (typeof content === 'string') {
      // Plain string: direct assignment
      d.content = newContent as unknown as T['content'];
    } else if (Automerge.isImmutableString(content)) {
      // ImmutableString / RawString: direct assignment
      d.content = newContent as unknown as T['content'];
    } else {
      // Assume it's an Automerge text object
      Automerge.updateText(d, ['content'] as any, newContent);
    }
  });
}

/**
 * Read the `content` field from a FileDocument, normalizing RawString to plain string.
 */
export function readDocContent<T extends FileDocument>(doc: Automerge.Doc<T>): string {
  const content = doc.content as unknown;
  if (typeof content === 'string') return content;
  if (content instanceof Uint8Array) return '';
  // RawString / ImmutableString fallback
  if (Automerge.isImmutableString(content)) {
    return content.val;
  }
  return '';
}