/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */
package org.antlr.v4.runtime.dfa;

import org.antlr.v4.runtime.Parser;
import org.antlr.v4.runtime.Vocabulary;
import org.antlr.v4.runtime.VocabularyImpl;
import org.antlr.v4.runtime.atn.ATNConfigSet;
import org.antlr.v4.runtime.atn.DecisionState;
import org.antlr.v4.runtime.atn.StarLoopEntryState;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class DFA {
	
A set of all DFA states. Use Map so we can get old state back (Set only allows you to see if it's there). /** A set of all DFA states. Use {@link Map} so we can get old state back
	 *  ({@link Set} only allows you to see if it's there).
     */

	public final Map<DFAState, DFAState> states = new HashMap<DFAState, DFAState>();

	public volatile DFAState s0;

	public final int decision;

	
From which ATN state did we create this DFA? /** From which ATN state did we create this DFA? */

	public final DecisionState atnStartState;

	
true if this DFA is for a precedence decision; otherwise, false. This is the backing field for isPrecedenceDfa. /**
	 * {@code true} if this DFA is for a precedence decision; otherwise,
	 * {@code false}. This is the backing field for {@link #isPrecedenceDfa}.
	 */
	private final boolean precedenceDfa;

	public DFA(DecisionState atnStartState) {
		this(atnStartState, 0);
	}

	public DFA(DecisionState atnStartState, int decision) {
		this.atnStartState = atnStartState;
		this.decision = decision;

		boolean precedenceDfa = false;
		if (atnStartState instanceof StarLoopEntryState) {
			if (((StarLoopEntryState)atnStartState).isPrecedenceDecision) {
				precedenceDfa = true;
				DFAState precedenceState = new DFAState(new ATNConfigSet());
				precedenceState.edges = new DFAState[0];
				precedenceState.isAcceptState = false;
				precedenceState.requiresFullContext = false;
				this.s0 = precedenceState;
			}
		}

		this.precedenceDfa = precedenceDfa;
	}

	
Gets whether this DFA is a precedence DFA. Precedence DFAs use a special start state s0 which is not stored in states. The DFAState.edges array for this start state contains outgoing edges supplying individual start states corresponding to specific precedence values. 
See Also:
Parser.getPrecedence()
Returns:
true if this is a precedence DFA; otherwise, false./**
	 * Gets whether this DFA is a precedence DFA. Precedence DFAs use a special
	 * start state {@link #s0} which is not stored in {@link #states}. The
	 * {@link DFAState#edges} array for this start state contains outgoing edges
	 * supplying individual start states corresponding to specific precedence
	 * values.
	 *
	 * @return {@code true} if this is a precedence DFA; otherwise,
	 * {@code false}.
	 * @see Parser#getPrecedence()
	 */
	public final boolean isPrecedenceDfa() {
		return precedenceDfa;
	}

	
Get the start state for a specific precedence value.
Params:
precedence – The current precedence.
Throws:
IllegalStateException – if this is not a precedence DFA.
See Also:
isPrecedenceDfa()
Returns:
The start state corresponding to the specified precedence, or null if no start state exists for the specified precedence./**
	 * Get the start state for a specific precedence value.
	 *
	 * @param precedence The current precedence.
	 * @return The start state corresponding to the specified precedence, or
	 * {@code null} if no start state exists for the specified precedence.
	 *
	 * @throws IllegalStateException if this is not a precedence DFA.
	 * @see #isPrecedenceDfa()
	 */
	@SuppressWarnings("null")
	public final DFAState getPrecedenceStartState(int precedence) {
		if (!isPrecedenceDfa()) {
			throw new IllegalStateException("Only precedence DFAs may contain a precedence start state.");
		}

		// s0.edges is never null for a precedence DFA
		if (precedence < 0 || precedence >= s0.edges.length) {
			return null;
		}

		return s0.edges[precedence];
	}

	
Set the start state for a specific precedence value.
Params:
precedence – The current precedence.
startState – The start state corresponding to the specified
precedence.
Throws:
IllegalStateException – if this is not a precedence DFA.
See Also:
isPrecedenceDfa()/**
	 * Set the start state for a specific precedence value.
	 *
	 * @param precedence The current precedence.
	 * @param startState The start state corresponding to the specified
	 * precedence.
	 *
	 * @throws IllegalStateException if this is not a precedence DFA.
	 * @see #isPrecedenceDfa()
	 */
	@SuppressWarnings({"SynchronizeOnNonFinalField", "null"})
	public final void setPrecedenceStartState(int precedence, DFAState startState) {
		if (!isPrecedenceDfa()) {
			throw new IllegalStateException("Only precedence DFAs may contain a precedence start state.");
		}

		if (precedence < 0) {
			return;
		}

		// synchronization on s0 here is ok. when the DFA is turned into a
		// precedence DFA, s0 will be initialized once and not updated again
		synchronized (s0) {
			// s0.edges is never null for a precedence DFA
			if (precedence >= s0.edges.length) {
				s0.edges = Arrays.copyOf(s0.edges, precedence + 1);
			}

			s0.edges[precedence] = startState;
		}
	}

	
Sets whether this is a precedence DFA.
Params:
precedenceDfa – true if this is a precedence DFA; otherwise, false
Throws:
UnsupportedOperationException – if precedenceDfa does not match the value of isPrecedenceDfa for the current DFA.
Deprecated:
This method no longer performs any action./**
	 * Sets whether this is a precedence DFA.
	 *
	 * @param precedenceDfa {@code true} if this is a precedence DFA; otherwise,
	 * {@code false}
	 *
	 * @throws UnsupportedOperationException if {@code precedenceDfa} does not
	 * match the value of {@link #isPrecedenceDfa} for the current DFA.
	 *
	 * @deprecated This method no longer performs any action.
	 */
	@Deprecated
	public final void setPrecedenceDfa(boolean precedenceDfa) {
		if (precedenceDfa != isPrecedenceDfa()) {
			throw new UnsupportedOperationException("The precedenceDfa field cannot change after a DFA is constructed.");
		}
	}

	
Return a list of all states in this DFA, ordered by state number.
/**
	 * Return a list of all states in this DFA, ordered by state number.
	 */

	public List<DFAState> getStates() {
		List<DFAState> result = new ArrayList<DFAState>(states.keySet());
		Collections.sort(result, new Comparator<DFAState>() {
			@Override
			public int compare(DFAState o1, DFAState o2) {
				return o1.stateNumber - o2.stateNumber;
			}
		});

		return result;
	}

	@Override
	public String toString() { return toString(VocabularyImpl.EMPTY_VOCABULARY); }

	
Deprecated:
Use toString(Vocabulary) instead./**
	 * @deprecated Use {@link #toString(Vocabulary)} instead.
	 */
	@Deprecated
	public String toString(String[] tokenNames) {
		if ( s0==null ) return "";
		DFASerializer serializer = new DFASerializer(this,tokenNames);
		return serializer.toString();
	}

	public String toString(Vocabulary vocabulary) {
		if (s0 == null) {
			return "";
		}

		DFASerializer serializer = new DFASerializer(this, vocabulary);
		return serializer.toString();
	}

	public String toLexerString() {
		if ( s0==null ) return "";
		DFASerializer serializer = new LexerDFASerializer(this);
		return serializer.toString();
	}

}