All files / src/core/nfa fragment.js

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function fragmentState( transitions, index ) {
  return {
    transitions: transitions === null ? [] : transitions,
    index: index || null,
  };
}
 
function fragmentTransition( clause, target ) {
  return {
    clause: clause,
    target: target,
  };
}
 
function fragment( head, tails ) {
  return {
    head: head,
    tails: tails,
  }
}
 
function namedFragment( name, head, tails ) {
  var f = fragment( head, tails );
  f.name = name;
  return f;
}
 
function patch( tails, state ) {
  tails.forEach( ( tail ) => {
    tail.target = state;
  } );
}
 
function epsilonState() {
  return {
    isEpsilon: true,
  };
}
 
function namedEpsilonState( dir, name, op, group ) {
  var s = epsilonState();
  s.name = name;
  s.op = op;
  s.group = group;
  s.dir = dir;
  return s;
}
 
function frontWithState( state, f ) {
  var transIn = fragmentTransition( state, f.head );
  var newHead = fragmentState( [ transIn ] );
  var newF = fragment( newHead, f.tails );
  return newF;
}
 
function rearWithState( state, f ) {
  var newTrans = fragmentTransition( state, null );
  var newS = fragmentState( [ newTrans ], null )
  patch( f.tails, newS );
  var r = fragment( f.head, [ newTrans ] );
  return r;
}
 
var build = {};
 
build.PRED = function PRED( clause ) {
  var trans = fragmentTransition( clause, null );
  var head = fragmentState( [ trans ], null );
  var tails = [ trans ];
  var f = fragment( head, tails );
  return f;
};
 
 
build.OR = function OR( frags ) {
  frags = frags.map( ( f ) => {
    var outState = namedEpsilonState( 'out', f.name, 'OR' );
    var trans = fragmentTransition( outState, null );
    var nameOutState = fragmentState( [ trans ] );
    patch( f.tails, nameOutState );
    var transIn = fragmentTransition( namedEpsilonState( 'in', f.name, 'OR' ), f.head );
    var newHead = fragmentState( [ transIn ] );
    var newF = namedFragment( f.name, newHead, [ trans ] );
    return newF;
  } );
  var binaryAlt = function( frag1, frag2 ) {
    var combinedTransitions = frag1.head.transitions.concat( frag2.head.transitions );
    var head = fragmentState( combinedTransitions );
    var tails = frag1.tails.concat( frag2.tails );
    var acc = namedFragment( frag1.name, head, tails );
    return acc;
  };
 
  var newF = frags.reduce( binaryAlt );
  newF = frontWithState( namedEpsilonState( 'enter', null, 'OR', 'para_in' ), newF );
  newF = rearWithState( namedEpsilonState( 'exit', null, 'OR', 'para_out' ), newF );
 
  return newF;
};
 
build.CAT = function CAT( frags ) {
 
  var binaryConcat = function( frag1, currFrag ) {
    patch( frag1.tails, currFrag.head );
    var head = frag1.head;
    var tails = currFrag.tails;
    var newF = fragment( head, tails );
    return newF;
  };
 
  frags = frags.map( function addEpsilonState( f ) {
    var trans = fragmentTransition(
      namedEpsilonState( 'maybe_out', f.name, 'CAT' ), null );
    var nameOutState = fragmentState( [ trans ] );
    patch( f.tails, nameOutState );
 
    var nameInTranstions = f.head.transitions.map( ( t ) => {
      var s = fragmentState( [ t ] );
      var namedInTrans = fragmentTransition(
        namedEpsilonState( 'maybe_in', f.name, 'CAT' ), s );
      return namedInTrans;
    } );
    var newHead = fragmentState( nameInTranstions );
 
    var newF = namedFragment( f.name, newHead, [ trans ] );
    return newF;
  } );
  var r;
  if ( frags.length > 0 ) {
    r = frags.reduce( binaryConcat );
  } else {
    var s = epsilonState();
    var t = fragmentTransition( s, null );
    var ss = fragmentState( [ t ] );
    r = fragment( ss, [ t ] );
  }
  r = frontWithState( namedEpsilonState( 'maybe_enter', null, 'CAT', 'in' ), r );
  r = rearWithState( namedEpsilonState( 'maybe_exit', null, 'CAT', 'out' ), r );
  return r;
};
 
build.Z_OR_M = function Z_OR_M( frag ) {
  var l = 'Z_OR_M';
  var loopTrans = fragmentTransition( namedEpsilonState( 'loop', null, l ), frag.head );
  var breakTrans = fragmentTransition( epsilonState(), null );
  var head = fragmentState( [ loopTrans, breakTrans ] );
  patch( frag.tails, head );
  var newF = fragment( head, [ breakTrans ] );
 
  var nameInTranstions = newF.head.transitions.map( ( t ) => {
    var s = fragmentState( [ t ] );
    var namedInTrans = fragmentTransition( epsilonState(), s );
    return namedInTrans;
  } );
  var newHead = fragmentState( nameInTranstions );
 
  newF = fragment( newHead, newF.tails );
  newF = frontWithState( namedEpsilonState( 'maybe_enter', null, l, 'in' ), newF );
  newF = rearWithState( namedEpsilonState( 'maybe_exit', null, l, 'out' ), newF );
 
  return newF;
};
 
build.O_OR_M = function O_OR_M( frag ) {
  var l = 'O_OR_M';
  var loopTrans = fragmentTransition( namedEpsilonState( 'loop', null, l ), frag.head );
  var breakTrans = fragmentTransition( epsilonState(), null );
  var state = fragmentState( [ loopTrans, breakTrans ] );
  patch( frag.tails, state );
 
  var newF = fragment( frag.head, [ breakTrans ] );
  newF = frontWithState( namedEpsilonState( 'maybe_enter', null, l, 'in' ), newF );
  newF = rearWithState( namedEpsilonState( 'maybe_exit', null, l, 'out' ), newF );
 
  return newF;
};
 
build.Z_OR_O = function Z_OR_O( frag ) {
  var l = 'Z_OR_O';
  var matchTrans = fragmentTransition( namedEpsilonState( 'loop', null, l ), frag.head );
  var skipTrans = fragmentTransition( epsilonState(), null );
  var head = fragmentState( [ matchTrans, skipTrans ] );
  var tails = frag.tails.concat( [ skipTrans ] );
 
  var newF = fragment( head, tails );
  newF = frontWithState( namedEpsilonState( 'maybe_single_enter', null, l, 'in' ), newF );
  newF = rearWithState( namedEpsilonState( 'maybe_single_exit', null, l, 'out' ), newF );
 
  return newF;
};
 
build.ROOT = function ROOT( frag ) {
  var finalState = fragmentState( null, null );
  patch( frag.tails, finalState );
  return fragment( frag.head, [] );
};
 
module.exports = build;