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import {deepEqual} from '../json.js';import type {ReadonlyEntry} from './node';
export type Splice = [at: number, removed: number, added: number, from: number];
const SPLICE_UNASSIGNED = -1;export const SPLICE_AT = 0;export const SPLICE_REMOVED = 1;export const SPLICE_ADDED = 2;export const SPLICE_FROM = 3;
const KEY = 0;const VALUE = 1;
export function* computeSplices<T>(  previous: readonly ReadonlyEntry<T>[],  current: readonly ReadonlyEntry<T>[],): Generator<Splice, void> {  let previousIndex = 0;  let currentIndex = 0;  let splice: Splice | undefined;
  function ensureAssigned(splice: Splice, index: number): void {    if (splice[SPLICE_FROM] === SPLICE_UNASSIGNED) {      splice[SPLICE_FROM] = index;    }  }
  function newSplice(): Splice {    return [previousIndex, 0, 0, SPLICE_UNASSIGNED];  }
  while (previousIndex < previous.length && currentIndex < current.length) {    if (previous[previousIndex][KEY] === current[currentIndex][KEY]) {      if (        deepEqual(previous[previousIndex][VALUE], current[currentIndex][VALUE])      ) {        if (splice) {          ensureAssigned(splice, 0);          yield splice;          splice = undefined;        }      } else {        if (!splice) {          splice = newSplice();        }        splice[SPLICE_ADDED]++;        splice[SPLICE_REMOVED]++;        ensureAssigned(splice, currentIndex);      }      previousIndex++;      currentIndex++;    } else if (previous[previousIndex][KEY] < current[currentIndex][KEY]) {      // previous was removed      if (!splice) {        splice = newSplice();      }      splice[SPLICE_REMOVED]++;
      previousIndex++;    } else {      // current was added      if (!splice) {        splice = newSplice();      }      splice[SPLICE_ADDED]++;      ensureAssigned(splice, currentIndex);
      currentIndex++;    }  }
  if (currentIndex < current.length) {    if (!splice) {      splice = newSplice();    }    splice[SPLICE_ADDED] += current.length - currentIndex;    ensureAssigned(splice, currentIndex);  }
  if (previousIndex < previous.length) {    if (!splice) {      splice = newSplice();    }    splice[SPLICE_REMOVED] += previous.length - previousIndex;  }
  if (splice) {    ensureAssigned(splice, 0);    yield splice;  }}