Class {
	#name : 'PEGFsaAbstractDeterminizator',
	#superclass : 'Object',
	#instVars : [
		'fsa',
		'joinDictionary'
	],
	#category : 'PetitCompiler-FSA'
}

{ #category : 'as yet unclassified' }
PEGFsaAbstractDeterminizator class >> new [
	^ self basicNew initialize
]

{ #category : 'determinization' }
PEGFsaAbstractDeterminizator >> determinize [
	| states |
"	fsa checkSanity."
	fsa removeEpsilons.
	fsa removeUnreachableStates.
	fsa mergeTransitions.
	
	states := fsa topologicalOrder asOrderedCollection.
	states do: [ :state |
		self determinizeState: state
	].

	fsa states:	fsa startState reachableStates.
	
	fsa removeUnreachableStates.
	fsa mergeTransitions.
]

{ #category : 'determinization' }
PEGFsaAbstractDeterminizator >> determinize: anFsa [
	fsa := anFsa.
	joinDictionary := Dictionary new.
	
	self determinize.
	^ fsa
]

{ #category : 'determinization' }
PEGFsaAbstractDeterminizator >> determinizeOverlap: t1 second: t2 state: state [
	|  t1Prime t2Prime tIntersection |
	self assert: (state transitions includes: t1).
	self assert: (state transitions includes: t2).
	
	tIntersection := self joinTransition: t1 with: t2.

	t1Prime := PEGFsaCharacterTransition new
					destination: t1 destination;
					characterSet: (t1 complement: t2);
					yourself.
	t2Prime := PEGFsaCharacterTransition new
					destination: t2 destination;
					characterSet: (t2 complement: t1);
					yourself.					
									
								
	state removeTransition: t1.
	state removeTransition: t2.
	
	tIntersection isEmpty ifFalse: [ state addTransition: tIntersection  ].
	t1Prime isEmpty ifFalse: [ state addTransition: t1Prime ].
	t2Prime isEmpty ifFalse: [ state addTransition: t2Prime ].
]

{ #category : 'determinization' }
PEGFsaAbstractDeterminizator >> determinizeState: state [
	| pairs |

	pairs := state transitionPairs asOrderedCollection.

	[pairs isEmpty] whileFalse: [ 
		| pair |
		
		(joinDictionary size > 100) ifTrue: [ self error: 'Oh man, this is really big FSA. Are you sure you want to continue?' ].
		
		pair := pairs removeFirst.
		self assert:((pair first destination = pair second destination) not 
					or: [pair first isPredicateTransition not 
					or: [pair second isPredicateTransition not ] ]).
				
		self assert: (pair contains: #isEpsilon) not.		
				
		(pair first overlapsWith: pair second) ifTrue: [ 
			self determinizeOverlap: pair first second: pair second state: state.
			"recompute pairs after the determinization"
			pairs := state transitionPairs asOrderedCollection.
		]
	].
]

{ #category : 'initialization' }
PEGFsaAbstractDeterminizator >> initialize [
	super initialize.
	joinDictionary := Dictionary new
]

{ #category : 'accessing - keys' }
PEGFsaAbstractDeterminizator >> joinKey: key with: anotherKey [
	^ Set new
		addAll: key;
		addAll: anotherKey;
		yourself.

]

{ #category : 'joining' }
PEGFsaAbstractDeterminizator >> joinName: state with: anotherState into: newState [
	newState name: state name asString, '_', anotherState name asString.

]

{ #category : 'joining' }
PEGFsaAbstractDeterminizator >> joinState: state with: anotherState [
	| key newState |
	key := self keyFor: state and: anotherState.
	(joinDictionary includesKey: key) ifTrue: [ ^ joinDictionary at: key ].
	
	newState := PEGFsaState new.
	joinDictionary at: key put: newState.

	self joinRetval: state with: anotherState into: newState.
	self joinInfo: state with: anotherState into: newState.
	self joinName: state with: anotherState into: newState.
	self joinTransitions: state with: anotherState into: newState.	

	self determinizeState: newState.
	
	self assert: ((joinDictionary at: key) == newState).
	^ newState
]

{ #category : 'joining' }
PEGFsaAbstractDeterminizator >> joinTransition: t1 with: t2 [
	| newDestination newTransition |
	self assert: t1 isCharacterTransition.
	self assert: t2 isCharacterTransition.
	
	newDestination := self joinState: t1 destination with: t2 destination.
	
	newTransition := PEGFsaCharacterTransition new.
	newTransition destination: newDestination.
	newTransition characterSet: (t1 intersection: t2).
	newTransition priority: (t1 priority max: t2 priority).
	
	^ newTransition 
]

{ #category : 'accessing - keys' }
PEGFsaAbstractDeterminizator >> keyFor: state [
	^ joinDictionary keyAtIdentityValue: state ifAbsent: [ Set with: state ]
]

{ #category : 'accessing - keys' }
PEGFsaAbstractDeterminizator >> keyFor: state and: anotherState [
	| key anotherKey |
	key := self keyFor: state.
	anotherKey := self keyFor: anotherState.
	
	^ self joinKey: key with: anotherKey
]