overleaf/services/document-updater/app/js/sharejs/simple.js

// TODO: This file was created by bulk-decaffeinate.
// Sanity-check the conversion and remove this comment.
/*
 * decaffeinate suggestions:
 * DS102: Remove unnecessary code created because of implicit returns
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
// This is a really simple OT type. Its not compiled with the web client, but it could be.
//
// Its mostly included for demonstration purposes and its used in a lot of unit tests.
//
// This defines a really simple text OT type which only allows inserts. (No deletes).
//
// Ops look like:
//   {position:#, text:"asdf"}
//
// Document snapshots look like:
//   {str:string}

module.exports = {
  // The name of the OT type. The type is stored in types[type.name]. The name can be
  // used in place of the actual type in all the API methods.
  name: 'simple',

  // Create a new document snapshot
  create() {
    return { str: '' }
  },

  // Apply the given op to the document snapshot. Returns the new snapshot.
  //
  // The original snapshot should not be modified.
  apply(snapshot, op) {
    if (!(op.position >= 0 && op.position <= snapshot.str.length)) {
      throw new Error('Invalid position')
    }

    let { str } = snapshot
    str = str.slice(0, op.position) + op.text + str.slice(op.position)
    return { str }
  },

  // transform op1 by op2. Return transformed version of op1.
  // sym describes the symmetry of the op. Its 'left' or 'right' depending on whether the
  // op being transformed comes from the client or the server.
  transform(op1, op2, sym) {
    let pos = op1.position
    if (op2.position < pos || (op2.position === pos && sym === 'left')) {
      pos += op2.text.length
    }

    return { position: pos, text: op1.text }
  },
}