content: package org.apache.lucene.util.fst;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import org.apache.lucene.util.ArrayUtil;
  import org.apache.lucene.util.RamUsageEstimator;
  import org.apache.lucene.util.BytesRef;
  import org.apache.lucene.util.IntsRef;
  import org.apache.lucene.util.fst.FST.INPUT_TYPE; // javadoc
  
  import java.io.IOException;
  
  /**
   * Builds a compact FST (maps an IntsRef term to an arbitrary
   * output) from pre-sorted terms with outputs (the FST
   * becomes an FSA if you use NoOutputs).  The FST is written
   * on-the-fly into a compact serialized format byte array, which can
   * be saved to / loaded from a Directory or used directly
   * for traversal.  The FST is always finite (no cycles).
   *
   * <p>NOTE: The algorithm is described at
   * http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.24.3698</p>
   *
   * If your outputs are ByteSequenceOutput then the final FST
   * will be minimal, but if you use PositiveIntOutput then
   * it's only "near minimal".  For example, aa/0, aab/1, bbb/2
   * will produce 6 states when a 5 state fst is also
   * possible.
   *
   * The parameterized type T is the output type.  See the
   * subclasses of {@link Outputs}.
   *
   * @lucene.experimental
   */
  
  public class Builder<T> {
    private final NodeHash<T> dedupHash;
    private final FST<T> fst;
    private final T NO_OUTPUT;
  
    // simplistic pruning: we prune node (and all following
    // nodes) if less than this number of terms go through it:
    private final int minSuffixCount1;
  
    // better pruning: we prune node (and all following
    // nodes) if the prior node has less than this number of
    // terms go through it:
    private final int minSuffixCount2;
  
    private final boolean doShareNonSingletonNodes;
    private final int shareMaxTailLength;
  
    private final IntsRef lastInput = new IntsRef();
  
    // NOTE: cutting this over to ArrayList instead loses ~6%
    // in build performance on 9.8M Wikipedia terms; so we
    // left this as an array:
    // current "frontier"
    private UnCompiledNode<T>[] frontier;
  
    /**
     * Instantiates an FST/FSA builder without any pruning. A shortcut
     * to {@link #Builder(FST.INPUT_TYPE, int, int, boolean, boolean, int, Outputs)} with 
     * pruning options turned off.
     */
    public Builder(FST.INPUT_TYPE inputType, Outputs<T> outputs) {
      this(inputType, 0, 0, true, true, Integer.MAX_VALUE, outputs);
    }
  
    /**
     * Instantiates an FST/FSA builder with all the possible tuning and construction
     * tweaks. Read parameter documentation carefully.
     * 
     * @param inputType 
     *    The input type (transition labels). Can be anything from {@link INPUT_TYPE}
     *    enumeration. Shorter types will consume less memory. Strings (character sequences) are 
     *    represented as {@link INPUT_TYPE#BYTE4} (full unicode codepoints). 
     *     
     * @param minSuffixCount1
     *    If pruning the input graph during construction, this threshold is used for telling
     *    if a node is kept or pruned. If transition_count(node) &gt;= minSuffixCount1, the node
     *    is kept. 
     *    
     * @param minSuffixCount2
     *    (Note: only Mike McCandless knows what this one is really doing...) 
     * 
     * @param doShareSuffix 
     *    If <code>true</code>, the shared suffixes will be compacted into unique paths.
     *    This requires an additional hash map for lookups in memory. Setting this parameter to
     *    <code>false</code> creates a single path for all input sequences. This will result in a larger
     *    graph, but may require less memory and will speed up construction.  
     *
     * @param doShareNonSingletonNodes
     *    Only used if doShareSuffix is true.  Set this to
     *    true to ensure FST is fully minimal, at cost of more
     *    CPU and more RAM during building.
     *
     * @param shareMaxTailLength
     *    Only used if doShareSuffix is true.  Set this to
     *    Integer.MAX_VALUE to ensure FST is fully minimal, at cost of more
     *    CPU and more RAM during building.
     *
     * @param outputs The output type for each input sequence. Applies only if building an FST. For
     *    FSA, use {@link NoOutputs#getSingleton()} and {@link NoOutputs#getNoOutput()} as the
     *    singleton output object.
     */
    public Builder(FST.INPUT_TYPE inputType, int minSuffixCount1, int minSuffixCount2, boolean doShareSuffix,
                   boolean doShareNonSingletonNodes, int shareMaxTailLength, Outputs<T> outputs) {
      this.minSuffixCount1 = minSuffixCount1;
      this.minSuffixCount2 = minSuffixCount2;
      this.doShareNonSingletonNodes = doShareNonSingletonNodes;
      this.shareMaxTailLength = shareMaxTailLength;
      fst = new FST<T>(inputType, outputs);
      if (doShareSuffix) {
        dedupHash = new NodeHash<T>(fst);
      } else {
        dedupHash = null;
      }
      NO_OUTPUT = outputs.getNoOutput();
  
      @SuppressWarnings("unchecked") final UnCompiledNode<T>[] f = (UnCompiledNode<T>[]) new UnCompiledNode[10];
      frontier = f;
      for(int idx=0;idx<frontier.length;idx++) {
        frontier[idx] = new UnCompiledNode<T>(this, idx);
      }
    }
  
    public int getTotStateCount() {
      return fst.nodeCount;
    }
  
    public long getTermCount() {
      return frontier[0].inputCount;
    }
  
    public int getMappedStateCount() {
      return dedupHash == null ? 0 : fst.nodeCount;
    }
  
    private CompiledNode compileNode(UnCompiledNode<T> n, int tailLength) throws IOException {
      final int address;
      if (dedupHash != null && (doShareNonSingletonNodes || n.numArcs <= 1) && tailLength <= shareMaxTailLength) {
        if (n.numArcs == 0) {
          address = fst.addNode(n);
        } else {
          address = dedupHash.add(n);
        }
      } else {
        address = fst.addNode(n);
      }
      assert address != -2;
  
      n.clear();
  
      final CompiledNode fn = new CompiledNode();
      fn.address = address;
      return fn;
    }
  
    private void compilePrevTail(int prefixLenPlus1) throws IOException {
      assert prefixLenPlus1 >= 1;
      //System.out.println("  compileTail " + prefixLenPlus1);
      for(int idx=lastInput.length; idx >= prefixLenPlus1; idx--) {
        boolean doPrune = false;
        boolean doCompile = false;
  
        final UnCompiledNode<T> node = frontier[idx];
        final UnCompiledNode<T> parent = frontier[idx-1];
  
        if (node.inputCount < minSuffixCount1) {
          doPrune = true;
          doCompile = true;
        } else if (idx > prefixLenPlus1) {
          // prune if parent's inputCount is less than suffixMinCount2
          if (parent.inputCount < minSuffixCount2 || minSuffixCount2 == 1 && parent.inputCount == 1) {
            // my parent, about to be compiled, doesn't make the cut, so
            // I'm definitely pruned 
  
            // if pruneCount2 is 1, we keep only up
            // until the 'distinguished edge', ie we keep only the
            // 'divergent' part of the FST. if my parent, about to be
            // compiled, has inputCount 1 then we are already past the
            // distinguished edge.  NOTE: this only works if
            // the FST outputs are not "compressible" (simple
            // ords ARE compressible).
            doPrune = true;
          } else {
            // my parent, about to be compiled, does make the cut, so
            // I'm definitely not pruned 
            doPrune = false;
          }
          doCompile = true;
        } else {
          // if pruning is disabled (count is 0) we can always
          // compile current node
          doCompile = minSuffixCount2 == 0;
        }
  
        //System.out.println("    label=" + ((char) lastInput.ints[lastInput.offset+idx-1]) + " idx=" + idx + " inputCount=" + frontier[idx].inputCount + " doCompile=" + doCompile + " doPrune=" + doPrune);
  
        if (node.inputCount < minSuffixCount2 || minSuffixCount2 == 1 && node.inputCount == 1) {
          // drop all arcs
          for(int arcIdx=0;arcIdx<node.numArcs;arcIdx++) {
            @SuppressWarnings("unchecked") final UnCompiledNode<T> target = (UnCompiledNode<T>) node.arcs[arcIdx].target;
            target.clear();
          }
          node.numArcs = 0;
        }
  
        if (doPrune) {
          // this node doesn't make it -- deref it
          node.clear();
          parent.deleteLast(lastInput.ints[lastInput.offset+idx-1], node);
        } else {
  
          if (minSuffixCount2 != 0) {
            compileAllTargets(node, lastInput.length-idx);
          }
          final T nextFinalOutput = node.output;
  
          // We "fake" the node as being final if it has no
          // outgoing arcs; in theory we could leave it
          // as non-final (the FST can represent this), but
          // FSTEnum, Util, etc., have trouble w/ non-final
          // dead-end states:
          final boolean isFinal = node.isFinal || node.numArcs == 0;
  
          if (doCompile) {
            // this node makes it and we now compile it.  first,
            // compile any targets that were previously
            // undecided:
            parent.replaceLast(lastInput.ints[lastInput.offset + idx-1],
                               compileNode(node, 1+lastInput.length-idx),
                               nextFinalOutput,
                               isFinal);
          } else {
            // replaceLast just to install
            // nextFinalOutput/isFinal onto the arc
            parent.replaceLast(lastInput.ints[lastInput.offset + idx-1],
                               node,
                               nextFinalOutput,
                               isFinal);
            // this node will stay in play for now, since we are
            // undecided on whether to prune it.  later, it
            // will be either compiled or pruned, so we must
            // allocate a new node:
            frontier[idx] = new UnCompiledNode<T>(this, idx);
          }
        }
      }
    }
  
    private final IntsRef scratchIntsRef = new IntsRef(10);
  
    public void add(BytesRef input, T output) throws IOException {
      assert fst.getInputType() == FST.INPUT_TYPE.BYTE1;
      scratchIntsRef.grow(input.length);
      for(int i=0;i<input.length;i++) {
        scratchIntsRef.ints[i] = input.bytes[i+input.offset] & 0xFF;
      }
      scratchIntsRef.length = input.length;
      add(scratchIntsRef, output);
    }
  
    /** Sugar: adds the UTF32 codepoints from char[] slice.  FST
     *  must be FST.INPUT_TYPE.BYTE4! */
    public void add(char[] s, int offset, int length, T output) throws IOException {
      assert fst.getInputType() == FST.INPUT_TYPE.BYTE4;
      int charIdx = offset;
      int intIdx = 0;
      final int charLimit = offset + length;
      while(charIdx < charLimit) {
        scratchIntsRef.grow(intIdx+1);
        final int utf32 = Character.codePointAt(s, charIdx);
        scratchIntsRef.ints[intIdx] = utf32;
        charIdx += Character.charCount(utf32);
        intIdx++;
      }
      scratchIntsRef.length = intIdx;
      add(scratchIntsRef, output);
    }
  
    /** Sugar: adds the UTF32 codepoints from CharSequence.  FST
     *  must be FST.INPUT_TYPE.BYTE4! */
    public void add(CharSequence s, T output) throws IOException {
      assert fst.getInputType() == FST.INPUT_TYPE.BYTE4;
      int charIdx = 0;
      int intIdx = 0;
      final int charLimit = s.length();
      while(charIdx < charLimit) {
        scratchIntsRef.grow(intIdx+1);
        final int utf32 = Character.codePointAt(s, charIdx);
        scratchIntsRef.ints[intIdx] = utf32;
        charIdx += Character.charCount(utf32);
        intIdx++;
      }
      scratchIntsRef.length = intIdx;
      add(scratchIntsRef, output);
    }
  
    /** It's OK to add the same input twice in a row with
     *  different outputs, as long as outputs impls the merge
     *  method. */
    public void add(IntsRef input, T output) throws IOException {
      //System.out.println("\nFST ADD: input=" + input + " output=" + fst.outputs.outputToString(output));
      assert lastInput.length == 0 || input.compareTo(lastInput) >= 0: "inputs are added out of order lastInput=" + lastInput + " vs input=" + input;
      assert validOutput(output);
  
      //System.out.println("\nadd: " + input);
      if (input.length == 0) {
        // empty input: only allowed as first input.  we have
        // to special case this because the packed FST
        // format cannot represent the empty input since
        // 'finalness' is stored on the incoming arc, not on
        // the node
        frontier[0].inputCount++;
        frontier[0].isFinal = true;
        fst.setEmptyOutput(output);
        return;
      }
  
      // compare shared prefix length
      int pos1 = 0;
      int pos2 = input.offset;
      final int pos1Stop = Math.min(lastInput.length, input.length);
      while(true) {
        //System.out.println("  incr " + pos1);
        frontier[pos1].inputCount++;
        if (pos1 >= pos1Stop || lastInput.ints[pos1] != input.ints[pos2]) {
          break;
        }
        pos1++;
        pos2++;
      }
      final int prefixLenPlus1 = pos1+1;
        
      if (frontier.length < input.length+1) {
        @SuppressWarnings("unchecked") final UnCompiledNode<T>[] next =
          new UnCompiledNode[ArrayUtil.oversize(input.length+1, RamUsageEstimator.NUM_BYTES_OBJECT_REF)];
        System.arraycopy(frontier, 0, next, 0, frontier.length);
        for(int idx=frontier.length;idx<next.length;idx++) {
          next[idx] = new UnCompiledNode<T>(this, idx);
        }
        frontier = next;
      }
  
      // minimize/compile states from previous input's
      // orphan'd suffix
      compilePrevTail(prefixLenPlus1);
  
      // init tail states for current input
      for(int idx=prefixLenPlus1;idx<=input.length;idx++) {
        frontier[idx-1].addArc(input.ints[input.offset + idx - 1],
                               frontier[idx]);
        //System.out.println("  incr tail " + idx);
        frontier[idx].inputCount++;
      }
  
      final UnCompiledNode<T> lastNode = frontier[input.length];
      lastNode.isFinal = true;
      lastNode.output = NO_OUTPUT;
  
      // push conflicting outputs forward, only as far as
      // needed
      for(int idx=1;idx<prefixLenPlus1;idx++) {
        final UnCompiledNode<T> node = frontier[idx];
        final UnCompiledNode<T> parentNode = frontier[idx-1];
  
        final T lastOutput = parentNode.getLastOutput(input.ints[input.offset + idx - 1]);
        assert validOutput(lastOutput);
  
        final T commonOutputPrefix;
        final T wordSuffix;
  
        if (lastOutput != NO_OUTPUT) {
          commonOutputPrefix = fst.outputs.common(output, lastOutput);
          assert validOutput(commonOutputPrefix);
          wordSuffix = fst.outputs.subtract(lastOutput, commonOutputPrefix);
          assert validOutput(wordSuffix);
          parentNode.setLastOutput(input.ints[input.offset + idx - 1], commonOutputPrefix);
          node.prependOutput(wordSuffix);
        } else {
          commonOutputPrefix = wordSuffix = NO_OUTPUT;
        }
  
        output = fst.outputs.subtract(output, commonOutputPrefix);
        assert validOutput(output);
      }
  
      if (lastInput.length == input.length && prefixLenPlus1 == 1+input.length) {
        // same input more than 1 time in a row, mapping to
        // multiple outputs
        lastNode.output = fst.outputs.merge(lastNode.output, output);
      } else {
        // this new arc is private to this new input; set its
        // arc output to the leftover output:
        frontier[prefixLenPlus1-1].setLastOutput(input.ints[input.offset + prefixLenPlus1-1], output);
      }
  
      // save last input
      lastInput.copy(input);
  
      //System.out.println("  count[0]=" + frontier[0].inputCount);
    }
  
    private boolean validOutput(T output) {
      return output == NO_OUTPUT || !output.equals(NO_OUTPUT);
    }
  
    /** Returns final FST.  NOTE: this will return null if
     *  nothing is accepted by the FST. */
    public FST<T> finish() throws IOException {
  
      // minimize nodes in the last word's suffix
      compilePrevTail(1);
      //System.out.println("finish: inputCount=" + frontier[0].inputCount);
      if (frontier[0].inputCount < minSuffixCount1 || frontier[0].inputCount < minSuffixCount2 || frontier[0].numArcs == 0) {
        if (fst.emptyOutput == null) {
          return null;
        } else if (minSuffixCount1 > 0 || minSuffixCount2 > 0) {
          // empty string got pruned
          return null;
        } else {
          fst.finish(compileNode(frontier[0], lastInput.length).address);
          //System.out.println("compile addr = " + fst.getStartNode());
          return fst;
        }
      } else {
        if (minSuffixCount2 != 0) {
          compileAllTargets(frontier[0], lastInput.length);
        }
        //System.out.println("NOW: " + frontier[0].numArcs);
        fst.finish(compileNode(frontier[0], lastInput.length).address);
      }
  
      /*
      if (dedupHash != null) {
        System.out.println("NH: " + dedupHash.count()); 
      }
      */
      
      return fst;
    }
  
    private void compileAllTargets(UnCompiledNode<T> node, int tailLength) throws IOException {
      for(int arcIdx=0;arcIdx<node.numArcs;arcIdx++) {
        final Arc<T> arc = node.arcs[arcIdx];
        if (!arc.target.isCompiled()) {
          // not yet compiled
          @SuppressWarnings("unchecked") final UnCompiledNode<T> n = (UnCompiledNode<T>) arc.target;
          if (n.numArcs == 0) {
            //System.out.println("seg=" + segment + "        FORCE final arc=" + (char) arc.label);
            arc.isFinal = n.isFinal = true;
          }
          arc.target = compileNode(n, tailLength-1);
        }
      }
    }
  
    static class Arc<T> {
      public int label;                             // really an "unsigned" byte
      public Node target;
      public boolean isFinal;
      public T output;
      public T nextFinalOutput;
    }
  
    // NOTE: not many instances of Node or CompiledNode are in
    // memory while the FST is being built; it's only the
    // current "frontier":
  
    static interface Node {
      boolean isCompiled();
    }
  
    static final class CompiledNode implements Node {
      int address;
      public boolean isCompiled() {
        return true;
      }
    }
  
    static final class UnCompiledNode<T> implements Node {
      final Builder<T> owner;
      int numArcs;
      Arc<T>[] arcs;
      T output;
      boolean isFinal;
      long inputCount;
  
      /** This node's depth, starting from the automaton root. */
      final int depth;
  
      /**
       * @param depth
       *          The node's depth starting from the automaton root. Needed for
       *          LUCENE-2934 (node expansion based on conditions other than the
       *          fanout size).
       */
      @SuppressWarnings("unchecked")
      public UnCompiledNode(Builder<T> owner, int depth) {
        this.owner = owner;
        arcs = (Arc<T>[]) new Arc[1];
        arcs[0] = new Arc<T>();
        output = owner.NO_OUTPUT;
        this.depth = depth;
      }
  
      public boolean isCompiled() {
        return false;
      }
  
      public void clear() {
        numArcs = 0;
        isFinal = false;
        output = owner.NO_OUTPUT;
        inputCount = 0;
  
        // We don't clear the depth here because it never changes 
        // for nodes on the frontier (even when reused).
      }
  
      public T getLastOutput(int labelToMatch) {
        assert numArcs > 0;
        assert arcs[numArcs-1].label == labelToMatch;
        return arcs[numArcs-1].output;
      }
  
      public void addArc(int label, Node target) {
        assert label >= 0;
        assert numArcs == 0 || label > arcs[numArcs-1].label: "arc[-1].label=" + arcs[numArcs-1].label + " new label=" + label + " numArcs=" + numArcs;
        if (numArcs == arcs.length) {
          @SuppressWarnings("unchecked") final Arc<T>[] newArcs =
            new Arc[ArrayUtil.oversize(numArcs+1, RamUsageEstimator.NUM_BYTES_OBJECT_REF)];
          System.arraycopy(arcs, 0, newArcs, 0, arcs.length);
          for(int arcIdx=numArcs;arcIdx<newArcs.length;arcIdx++) {
            newArcs[arcIdx] = new Arc<T>();
          }
          arcs = newArcs;
        }
        final Arc<T> arc = arcs[numArcs++];
        arc.label = label;
        arc.target = target;
        arc.output = arc.nextFinalOutput = owner.NO_OUTPUT;
        arc.isFinal = false;
      }
  
      public void replaceLast(int labelToMatch, Node target, T nextFinalOutput, boolean isFinal) {
        assert numArcs > 0;
        final Arc<T> arc = arcs[numArcs-1];
        assert arc.label == labelToMatch: "arc.label=" + arc.label + " vs " + labelToMatch;
        arc.target = target;
        //assert target.address != -2;
        arc.nextFinalOutput = nextFinalOutput;
        arc.isFinal = isFinal;
      }
  
      public void deleteLast(int label, Node target) {
        assert numArcs > 0;
        assert label == arcs[numArcs-1].label;
        assert target == arcs[numArcs-1].target;
        numArcs--;
      }
  
      public void setLastOutput(int labelToMatch, T newOutput) {
        assert owner.validOutput(newOutput);
        assert numArcs > 0;
        final Arc<T> arc = arcs[numArcs-1];
        assert arc.label == labelToMatch;
        arc.output = newOutput;
      }
  
      // pushes an output prefix forward onto all arcs
      public void prependOutput(T outputPrefix) {
        assert owner.validOutput(outputPrefix);
  
        for(int arcIdx=0;arcIdx<numArcs;arcIdx++) {
          arcs[arcIdx].output = owner.fst.outputs.add(outputPrefix, arcs[arcIdx].output);
          assert owner.validOutput(arcs[arcIdx].output);
        }
  
        if (isFinal) {
          output = owner.fst.outputs.add(outputPrefix, output);
          assert owner.validOutput(output);
        }
      }
    }
  }
  