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Morfologik Finite State Automata Builder
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package morfologik.fsa.builders;

import java.util.BitSet;

import morfologik.fsa.FSA;
import morfologik.fsa.FSA5;

import com.carrotsearch.hppc.IntIntHashMap;

/**
 * Compute additional information about an FSA: number of arcs, nodes, etc.
 */
public final class FSAInfo {
  /**
   * Computes the exact number of states and nodes by recursively traversing the FSA.
   */
  private static class NodeVisitor {
    final BitSet visitedArcs = new BitSet();
    final BitSet visitedNodes = new BitSet();

    int nodes;
    int arcs;
    int totalArcs;

    private final FSA fsa;

    NodeVisitor(FSA fsa) {
      this.fsa = fsa;
    }

    public void visitNode(final int node) {
      if (visitedNodes.get(node)) {
        return;
      }
      visitedNodes.set(node);

      nodes++;
      for (int arc = fsa.getFirstArc(node); arc != 0; arc = fsa.getNextArc(arc)) {
        if (!visitedArcs.get(arc)) {
          arcs++;
        }
        totalArcs++;
        visitedArcs.set(arc);

        if (!fsa.isArcTerminal(arc)) {
          visitNode(fsa.getEndNode(arc));
        }
      }
    }
  }

  /**
   * Computes the exact number of final states.
   */
  private static class FinalStateVisitor {
    final IntIntHashMap visitedNodes = new IntIntHashMap();

    private final FSA fsa;

    FinalStateVisitor(FSA fsa) {
      this.fsa = fsa;
    }

    public int visitNode(int node) {
      int index = visitedNodes.indexOf(node);
      if (index >= 0) {
        return visitedNodes.indexGet(index);
      }

      int fromHere = 0;
      for (int arc = fsa.getFirstArc(node); arc != 0; arc = fsa.getNextArc(arc)) {
        if (fsa.isArcFinal(arc))
          fromHere++;

        if (!fsa.isArcTerminal(arc)) {
          fromHere += visitNode(fsa.getEndNode(arc));
        }
      }
      visitedNodes.put(node, fromHere);
      return fromHere;
    }
  }

  /**
   * Number of nodes in the automaton.
   */
  public final int nodeCount;

  /**
   * Number of arcs in the automaton, excluding an arcs from the zero node (initial) and an arc from the start node to
   * the root node.
   */
  public final int arcsCount;

  /**
   * Total number of arcs, counting arcs that physically overlap due to merging.
   */
  public final int arcsCountTotal;

  /**
   * Number of final states (number of input sequences stored in the automaton).
   */
  public final int finalStatesCount;

  /**
   * Arcs size (in serialized form).
   */
  public final int size;

  /*
	 * 
	 */
  public FSAInfo(FSA fsa) {
    final NodeVisitor w = new NodeVisitor(fsa);
    int root = fsa.getRootNode();
    if (root > 0) {
      w.visitNode(root);
    }

    this.nodeCount = 1 + w.nodes;
    this.arcsCount = 1 + w.arcs;
    this.arcsCountTotal = 1 + w.totalArcs;

    final FinalStateVisitor fsv = new FinalStateVisitor(fsa);
    this.finalStatesCount = fsv.visitNode(fsa.getRootNode());

    if (fsa instanceof FSA5) {
      this.size = ((FSA5) fsa).arcs.length;
    } else {
      this.size = 0;
    }
  }

  /*
	 * 
	 */
  public FSAInfo(int nodeCount, int arcsCount, int arcsCountTotal, int finalStatesCount) {
    this.nodeCount = nodeCount;
    this.arcsCount = arcsCount;
    this.arcsCountTotal = arcsCountTotal;
    this.finalStatesCount = finalStatesCount;
    this.size = 0;
  }

  /*
	 * 
	 */
  @Override
  public String toString() {
    return "Nodes: " + nodeCount + ", arcs visited: " + arcsCount + ", arcs total: " + arcsCountTotal
        + ", final states: " + finalStatesCount + ", size: " + size;
  }
}