overleaf/services/document-updater/app/coffee/sharejs/helpers.js

/*
 * decaffeinate suggestions:
 * DS101: Remove unnecessary use of Array.from
 * DS102: Remove unnecessary code created because of implicit returns
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
// These methods let you build a transform function from a transformComponent function
// for OT types like text and JSON in which operations are lists of components
// and transforming them requires N^2 work.

// Add transform and transformX functions for an OT type which has transformComponent defined.
// transformComponent(destination array, component, other component, side)
let bootstrapTransform;
exports['_bt'] = (bootstrapTransform = function(type, transformComponent, checkValidOp, append) {
  let transformX;
  const transformComponentX = function(left, right, destLeft, destRight) {
    transformComponent(destLeft, left, right, 'left');
    return transformComponent(destRight, right, left, 'right');
  };

  // Transforms rightOp by leftOp. Returns ['rightOp', clientOp']
  type.transformX = (type['transformX'] = (transformX = function(leftOp, rightOp) {
    checkValidOp(leftOp);
    checkValidOp(rightOp);

    const newRightOp = [];

    for (let rightComponent of Array.from(rightOp)) {
      // Generate newLeftOp by composing leftOp by rightComponent
      const newLeftOp = [];

      let k = 0;
      while (k < leftOp.length) {
        var l;
        const nextC = [];
        transformComponentX(leftOp[k], rightComponent, newLeftOp, nextC);
        k++;

        if (nextC.length === 1) {
          rightComponent = nextC[0];
        } else if (nextC.length === 0) {
          for (l of Array.from(leftOp.slice(k))) { append(newLeftOp, l); }
          rightComponent = null;
          break;
        } else {
          // Recurse.
          const [l_, r_] = Array.from(transformX(leftOp.slice(k), nextC));
          for (l of Array.from(l_)) { append(newLeftOp, l); }
          for (let r of Array.from(r_)) { append(newRightOp, r); }
          rightComponent = null;
          break;
        }
      }
    
      if (rightComponent != null) { append(newRightOp, rightComponent); }
      leftOp = newLeftOp;
    }
    
    return [leftOp, newRightOp];
  }));

  // Transforms op with specified type ('left' or 'right') by otherOp.
  return type.transform = (type['transform'] = function(op, otherOp, type) {
    let _;
    if ((type !== 'left') && (type !== 'right')) { throw new Error("type must be 'left' or 'right'"); }

    if (otherOp.length === 0) { return op; }

    // TODO: Benchmark with and without this line. I _think_ it'll make a big difference...?
    if ((op.length === 1) && (otherOp.length === 1)) { return transformComponent([], op[0], otherOp[0], type); }

    if (type === 'left') {
      let left;
      [left, _] = Array.from(transformX(op, otherOp));
      return left;
    } else {
      let right;
      [_, right] = Array.from(transformX(otherOp, op));
      return right;
    }
  });
});

if (typeof WEB === 'undefined') {
  exports.bootstrapTransform = bootstrapTransform;
}