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'use strict';
// --------------------------------------------------------------------// Private stuff// --------------------------------------------------------------------
function PosInfo() {  this.applicationMemoKeyStack = []; // active applications at this position  this.memo = {};  this.maxExaminedLength = 0;  this.maxRightmostFailureOffset = -1;  this.currentLeftRecursion = undefined;}
PosInfo.prototype = {  isActive(application) {    return this.applicationMemoKeyStack.indexOf(application.toMemoKey()) >= 0;  },
  enter(application) {    this.applicationMemoKeyStack.push(application.toMemoKey());  },
  exit() {    this.applicationMemoKeyStack.pop();  },
  startLeftRecursion(headApplication, memoRec) {    memoRec.isLeftRecursion = true;    memoRec.headApplication = headApplication;    memoRec.nextLeftRecursion = this.currentLeftRecursion;    this.currentLeftRecursion = memoRec;
    const {applicationMemoKeyStack} = this;    const indexOfFirstInvolvedRule =      applicationMemoKeyStack.indexOf(headApplication.toMemoKey()) + 1;    const involvedApplicationMemoKeys = applicationMemoKeyStack.slice(        indexOfFirstInvolvedRule    );
    memoRec.isInvolved = function(applicationMemoKey) {      return involvedApplicationMemoKeys.indexOf(applicationMemoKey) >= 0;    };
    memoRec.updateInvolvedApplicationMemoKeys = function() {      for (let idx = indexOfFirstInvolvedRule; idx < applicationMemoKeyStack.length; idx++) {        const applicationMemoKey = applicationMemoKeyStack[idx];        if (!this.isInvolved(applicationMemoKey)) {          involvedApplicationMemoKeys.push(applicationMemoKey);        }      }    };  },
  endLeftRecursion() {    this.currentLeftRecursion = this.currentLeftRecursion.nextLeftRecursion;  },
  // Note: this method doesn't get called for the "head" of a left recursion -- for LR heads,  // the memoized result (which starts out being a failure) is always used.  shouldUseMemoizedResult(memoRec) {    if (!memoRec.isLeftRecursion) {      return true;    }    const {applicationMemoKeyStack} = this;    for (let idx = 0; idx < applicationMemoKeyStack.length; idx++) {      const applicationMemoKey = applicationMemoKeyStack[idx];      if (memoRec.isInvolved(applicationMemoKey)) {        return false;      }    }    return true;  },
  memoize(memoKey, memoRec) {    this.memo[memoKey] = memoRec;    this.maxExaminedLength = Math.max(this.maxExaminedLength, memoRec.examinedLength);    this.maxRightmostFailureOffset = Math.max(        this.maxRightmostFailureOffset,        memoRec.rightmostFailureOffset    );    return memoRec;  },
  clearObsoleteEntries(pos, invalidatedIdx) {    if (pos + this.maxExaminedLength <= invalidatedIdx) {      // Optimization: none of the rule applications that were memoized here examined the      // interval of the input that changed, so nothing has to be invalidated.      return;    }
    const {memo} = this;    this.maxExaminedLength = 0;    this.maxRightmostFailureOffset = -1;    Object.keys(memo).forEach(k => {      const memoRec = memo[k];      if (pos + memoRec.examinedLength > invalidatedIdx) {        delete memo[k];      } else {        this.maxExaminedLength = Math.max(this.maxExaminedLength, memoRec.examinedLength);        this.maxRightmostFailureOffset = Math.max(            this.maxRightmostFailureOffset,            memoRec.rightmostFailureOffset        );      }    });  },};
// --------------------------------------------------------------------// Exports// --------------------------------------------------------------------
module.exports = PosInfo;