angular2/ts/src/core/change_detection/coalesce.ts

Angular 2 - a web framework for modern web apps

import {isPresent, isBlank, looseIdentical} from 'angular2/src/facade/lang';
import {ListWrapper, Map} from 'angular2/src/facade/collection';
import {RecordType, ProtoRecord} from './proto_record';

/**
 * Removes "duplicate" records. It assumes that record evaluation does not have side-effects.
 *
 * Records that are not last in bindings are removed and all the indices of the records that depend
 * on them are updated.
 *
 * Records that are last in bindings CANNOT be removed, and instead are replaced with very cheap
 * SELF records.
 *
 * @internal
 */
export function coalesce(srcRecords: ProtoRecord[]): ProtoRecord[] {
  let dstRecords = [];
  let excludedIdxs = [];
  let indexMap: Map<number, number> = new Map<number, number>();
  let skipDepth = 0;
  let skipSources: ProtoRecord[] = ListWrapper.createFixedSize(srcRecords.length);

  for (let protoIndex = 0; protoIndex < srcRecords.length; protoIndex++) {
    let skipRecord = skipSources[protoIndex];
    if (isPresent(skipRecord)) {
      skipDepth--;
      skipRecord.fixedArgs[0] = dstRecords.length;
    }

    let src = srcRecords[protoIndex];
    let dst = _cloneAndUpdateIndexes(src, dstRecords, indexMap);

    if (dst.isSkipRecord()) {
      dstRecords.push(dst);
      skipDepth++;
      skipSources[dst.fixedArgs[0]] = dst;
    } else {
      let record = _mayBeAddRecord(dst, dstRecords, excludedIdxs, skipDepth > 0);
      indexMap.set(src.selfIndex, record.selfIndex);
    }
  }

  return _optimizeSkips(dstRecords);
}

/**
 * - Conditional skip of 1 record followed by an unconditional skip of N are replaced by  a
 *   conditional skip of N with the negated condition,
 * - Skips of 0 records are removed
 */
function _optimizeSkips(srcRecords: ProtoRecord[]): ProtoRecord[] {
  let dstRecords = [];
  let skipSources = ListWrapper.createFixedSize(srcRecords.length);
  let indexMap: Map<number, number> = new Map<number, number>();

  for (let protoIndex = 0; protoIndex < srcRecords.length; protoIndex++) {
    let skipRecord = skipSources[protoIndex];
    if (isPresent(skipRecord)) {
      skipRecord.fixedArgs[0] = dstRecords.length;
    }

    let src = srcRecords[protoIndex];

    if (src.isSkipRecord()) {
      if (src.isConditionalSkipRecord() && src.fixedArgs[0] === protoIndex + 2 &&
          protoIndex < srcRecords.length - 1 &&
          srcRecords[protoIndex + 1].mode === RecordType.SkipRecords) {
        src.mode = src.mode === RecordType.SkipRecordsIf ? RecordType.SkipRecordsIfNot :
                                                           RecordType.SkipRecordsIf;
        src.fixedArgs[0] = srcRecords[protoIndex + 1].fixedArgs[0];
        protoIndex++;
      }

      if (src.fixedArgs[0] > protoIndex + 1) {
        let dst = _cloneAndUpdateIndexes(src, dstRecords, indexMap);
        dstRecords.push(dst);
        skipSources[dst.fixedArgs[0]] = dst;
      }

    } else {
      let dst = _cloneAndUpdateIndexes(src, dstRecords, indexMap);
      dstRecords.push(dst);
      indexMap.set(src.selfIndex, dst.selfIndex);
    }
  }

  return dstRecords;
}

/**
 * Add a new record or re-use one of the existing records.
 */
function _mayBeAddRecord(record: ProtoRecord, dstRecords: ProtoRecord[], excludedIdxs: number[],
                         excluded: boolean): ProtoRecord {
  let match = _findFirstMatch(record, dstRecords, excludedIdxs);

  if (isPresent(match)) {
    if (record.lastInBinding) {
      dstRecords.push(_createSelfRecord(record, match.selfIndex, dstRecords.length + 1));
      match.referencedBySelf = true;
    } else {
      if (record.argumentToPureFunction) {
        match.argumentToPureFunction = true;
      }
    }

    return match;
  }

  if (excluded) {
    excludedIdxs.push(record.selfIndex);
  }

  dstRecords.push(record);
  return record;
}

/**
 * Returns the first `ProtoRecord` that matches the record.
 */
function _findFirstMatch(record: ProtoRecord, dstRecords: ProtoRecord[],
                         excludedIdxs: number[]): ProtoRecord {
  return dstRecords.find(
      // TODO(vicb): optimize excludedIdxs.indexOf (sorted array)
      rr => excludedIdxs.indexOf(rr.selfIndex) == -1 && rr.mode !== RecordType.DirectiveLifecycle &&
            _haveSameDirIndex(rr, record) && rr.mode === record.mode &&
            looseIdentical(rr.funcOrValue, record.funcOrValue) &&
            rr.contextIndex === record.contextIndex && looseIdentical(rr.name, record.name) &&
            ListWrapper.equals(rr.args, record.args));
}

/**
 * Clone the `ProtoRecord` and changes the indexes for the ones in the destination array for:
 * - the arguments,
 * - the context,
 * - self
 */
function _cloneAndUpdateIndexes(record: ProtoRecord, dstRecords: ProtoRecord[],
                                indexMap: Map<number, number>): ProtoRecord {
  let args = record.args.map(src => _srcToDstSelfIndex(indexMap, src));
  let contextIndex = _srcToDstSelfIndex(indexMap, record.contextIndex);
  let selfIndex = dstRecords.length + 1;

  return new ProtoRecord(record.mode, record.name, record.funcOrValue, args, record.fixedArgs,
                         contextIndex, record.directiveIndex, selfIndex, record.bindingRecord,
                         record.lastInBinding, record.lastInDirective,
                         record.argumentToPureFunction, record.referencedBySelf,
                         record.propertyBindingIndex);
}

/**
 * Returns the index in the destination array corresponding to the index in the src array.
 * When the element is not present in the destination array, return the source index.
 */
function _srcToDstSelfIndex(indexMap: Map<number, number>, srcIdx: number): number {
  var dstIdx = indexMap.get(srcIdx);
  return isPresent(dstIdx) ? dstIdx : srcIdx;
}

function _createSelfRecord(r: ProtoRecord, contextIndex: number, selfIndex: number): ProtoRecord {
  return new ProtoRecord(RecordType.Self, "self", null, [], r.fixedArgs, contextIndex,
                         r.directiveIndex, selfIndex, r.bindingRecord, r.lastInBinding,
                         r.lastInDirective, false, false, r.propertyBindingIndex);
}

function _haveSameDirIndex(a: ProtoRecord, b: ProtoRecord): boolean {
  var di1 = isBlank(a.directiveIndex) ? null : a.directiveIndex.directiveIndex;
  var ei1 = isBlank(a.directiveIndex) ? null : a.directiveIndex.elementIndex;

  var di2 = isBlank(b.directiveIndex) ? null : b.directiveIndex.directiveIndex;
  var ei2 = isBlank(b.directiveIndex) ? null : b.directiveIndex.elementIndex;

  return di1 === di2 && ei1 === ei2;
}