package emissary.util.search;
   
   import jakarta.annotation.Nullable;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import java.io.PrintStream;
   import java.util.ArrayList;
   import java.util.Collection;
  import java.util.List;
  
  @SuppressWarnings("AvoidObjectArrays")
  public class FastBoyerMoore {
      private static final Logger logger = LoggerFactory.getLogger(FastBoyerMoore.class);
      public byte[][] keywords;
      int minKeywordLength;
      int[] lookup = new int[259];
      transient BackwardsTreeScanner scanner;
      @Nullable
      byte[] data = null;
      BackwardsTreeScanner.State root;
  
      // copy constructor
  
      private FastBoyerMoore() {}
  
      public FastBoyerMoore(final FastBoyerMoore original) {
          this();
          this.keywords = original.keywords;
          this.minKeywordLength = original.minKeywordLength;
          this.lookup = original.lookup;
          this.root = original.root;
          this.scanner = new BackwardsTreeScanner(original.scanner);
      }
  
      public FastBoyerMoore(final String[] keywordStrings) throws Exception {
          this.keywords = new byte[keywordStrings.length][];
          this.minKeywordLength = Integer.MAX_VALUE;
          for (int i = 0; i < this.keywords.length; i++) {
              this.keywords[i] = keywordStrings[i].getBytes();
              this.minKeywordLength = Math.min(this.minKeywordLength, this.keywords[i].length);
          }
          for (int i = 0; i < this.lookup.length; i++) {
              this.lookup[i] = this.minKeywordLength;
          }
          // each keyword
          for (int i = 0; i < this.keywords.length; i++) {
              final byte[] kw = this.keywords[i];
              // each keyword character
              for (int j = 0; j < kw.length - 1; j++) {
                  this.lookup[kw[j]] = Math.min(this.lookup[kw[j]], kw.length - j - 1);
              }
          }
          this.data = null;
          this.scanner = new BackwardsTreeScanner(keywordStrings);
          this.root = this.scanner.getRoot();
      }
  
      public FastBoyerMoore(final String[][] keywordStrings) throws Exception {
          this.minKeywordLength = Integer.MAX_VALUE;
          for (int i = 0; i < keywordStrings.length; i++) {
              for (int j = 0; j < keywordStrings[i].length; j++) {
                  this.minKeywordLength = Math.min(this.minKeywordLength, keywordStrings[i][j].length());
              }
          }
          for (int i = 0; i < this.lookup.length; i++) {
              this.lookup[i] = this.minKeywordLength;
          }
          // each keyword
          for (int i = 0; i < keywordStrings.length; i++) {
              for (int j = 0; j < keywordStrings[i].length; j++) {
                  final byte[] kw = keywordStrings[i][j].getBytes();
                  // each keyword character
                  for (int k = 0; k < kw.length - 1; k++) {
                      this.lookup[kw[k]] = Math.min(this.lookup[kw[k]], kw.length - k - 1);
                  }
              }
          }
          this.data = null;
          this.scanner = new BackwardsTreeScanner(keywordStrings);
          this.root = this.scanner.getRoot();
      }
  
      public void setData(final byte[] dataArg) {
          this.scanner.setData(dataArg);
          this.data = dataArg;
      }
  
      public void scan(final byte[] dataArg, final int start, final int end, final Collection<int[]> result) {
          this.data = dataArg;
          this.scanner.setData(dataArg);
          scan(start, end, result);
      }
  
      public void scan(final int start, final int end, final Collection<int[]> result) {
          final int actualEnd = Math.min(end, this.data.length);
          int pos = start;
          while (pos < actualEnd) {
              final int ch = this.data[pos] & 0x7f;
             final int jump = this.lookup[ch];
             BackwardsTreeScanner.State state = this.root.nextStates[ch];
             int curPos = pos - 1;
             while ((state != null) && (curPos >= 0)) {
                 if (state.matches != null) {
                     for (int i = 0; i < state.matches.length; i++) {
                         final int id = state.matches[i];
                         final int[] tmp = new int[3];
                         tmp[0] = curPos + 1;
                         tmp[1] = id;
                         tmp[2] = pos - curPos;
                         result.add(tmp);
                     }
                 }
                 final int ch2 = this.data[curPos] & 0x7f;
                 state = state.nextStates[ch2];
                 curPos--;
             }
             if ((state != null) && (curPos == -1)) {
                 for (int i = 0; i < state.matches.length; i++) {
                     final int id = state.matches[i];
                     final int[] tmp = new int[3];
                     tmp[0] = curPos + 1;
                     tmp[1] = id;
                     tmp[2] = pos - curPos;
                     result.add(tmp);
                 }
             }
             pos += jump;
         }
     }
 
     public int staticSingleScan(final byte[] dataArg, final int start, final int end, final Collection<int[]> result) {
         final int actualEnd = Math.min(end, dataArg.length);
         boolean found = false;
         int pos = start;
         while ((pos < actualEnd) && !found) {
             final int ch = dataArg[pos] & 0x7f;
             final int jump = this.lookup[ch];
             BackwardsTreeScanner.State state = this.root.nextStates[ch];
             int curPos = pos - 1;
             while ((state != null) && (curPos >= 0)) {
                 if (state.matches != null) {
                     for (int i = 0; i < state.matches.length; i++) {
                         final int id = state.matches[i];
                         final int[] tmp = new int[3];
                         tmp[0] = curPos + 1;
                         tmp[1] = id;
                         tmp[2] = pos - curPos;
                         result.add(tmp);
                         found = true;
                     }
                 }
                 final int ch2 = dataArg[curPos] & 0x7f;
                 state = state.nextStates[ch2];
                 curPos--;
             }
             if ((state != null) && (state.matches != null) && (curPos == -1)) {
                 for (int i = 0; i < state.matches.length; i++) {
                     final int id = state.matches[i];
                     final int[] tmp = new int[3];
                     tmp[0] = curPos + 1;
                     tmp[1] = id;
                     tmp[2] = pos - curPos;
                     result.add(tmp);
                     found = true;
                 }
             }
             pos += jump;
         }
         return pos;
     }
 
     public static final int ID = 1;
     public static final int LOC = 0;
     public static final int LENGTH = 2;
 
     public static void main(final String[] args) {
         try {
             // a list of interesting keywords. */
             final String[][] keys = {{"\nABCD"}, // 0,1,2,3,4
                     {"\nABC"}, // 5 6 7 8
                     {"\nAB"}, // 9 10 11
                     {"\n//xyz//"}, // 12 13 14 15 16 17 18 19
                     {"\nxxxxx"}, // 20 21 22 23 24 25
                     {"\nabcdefghi"}, // 26 27 28 29 30 31 32 33 34 35
                     {"\nabcde", "\nabcdefg"}}; // 36 37 38 39 41 41 42 43 44 45
             // A string for holding the test data to be searched
             final StringBuilder dataString = new StringBuilder();
             // The thing we are testing
             final FastBoyerMoore scanner = new FastBoyerMoore(keys);
             // Make up an interesting string. The second half should never match.
             for (int i = 0; i < keys.length; i++) {
                 for (int j = 0; j < keys[i].length; j++) {
                     dataString.append(keys[i][j]);
                 }
             }
             // for (int i = 0;i<keys.length;i++)dataString +=keys[i].toString().substring(0,2);
             // A byte array version of the data.
             final byte[] dataBytes = dataString.toString().getBytes();
 
             // A vector for holding the results.
             final List<int[]> result = new ArrayList<>();
             scanner.setData(dataBytes);
             scanner.scan(0, dataBytes.length, result);
             for (int i = 0; i < result.size(); i++) {
                 final int[] tmp = result.get(i);
                 logger.info("Hit At: {} id: {} l: {}", tmp[0], tmp[1], tmp[2]);
             }
         } catch (Exception e) {
             logger.error("Exception in test", e);
         }
     }
 
     /**
      * This class implements a tree state machine scanner that searches text backwards starting from the end. A list of
      * strings is provided as the keywords to be searched. This class is usefull for a relatively small set of keywords.
      * Larger keyword lists can be used if you have memory!
      *
      * @author ce
      * @version 1.0
      */
     public static class BackwardsTreeScanner {
         /** Original list of keywords storred in byte array form. */
         // byte[][] keywords;
         /** Root node of tree state diagram. Always start a search from here! */
         State root = new State((byte) 0);
         @Nullable
         byte[] data = null;
 
         public BackwardsTreeScanner(final BackwardsTreeScanner o) {
             this.root = o.root;
         }
 
         public BackwardsTreeScanner(final String[][] keywordStrings) throws Exception {
             for (int i = 0; i < keywordStrings.length; i++) {
                 for (int j = 0; j < keywordStrings[i].length; j++) {
                     this.root.learn(keywordStrings[i][j].getBytes(), i);
                 }
             }
             // this.root.print(System.out);
         }
 
         public BackwardsTreeScanner(final String[] keywordStrings) throws Exception {
             // make byte arrays
             final byte[][] keywords = new byte[keywordStrings.length][];
             // and learn them
             for (int i = 0; i < keywords.length; i++) {
                 keywords[i] = keywordStrings[i].getBytes();
                 this.root.learn(keywordStrings[i].getBytes(), i);
             }
             // this.root.print(System.out);
         }
 
         public static void main(final String[] args) {
             try {
                 // a list of interesting keywords. */
                 final String[][] keys = {{"\nABCD", "\nABC", "\nAB", "\n//xyz//", "\nxxxxx", "\nabcdefghi"}, {"\nabcde", "\nabcdefg"}};
 
                 // The thing we are testing
                 final BackwardsTreeScanner scanner = new BackwardsTreeScanner(keys);
                 // A string for holding the test data to be searched
                 final StringBuilder dataString = new StringBuilder();
                 // Make up an interesting string. The second half should never match.
                 for (int i = 0; i < keys.length; i++) {
                     for (int j = 0; j < keys[i].length; j++) {
                         dataString.append(keys[i][j]);
                     }
                 }
                 // for (int i = 0;i<keys.length;i++)dataString +=keys[i].toString().substring(0,2);
                 // A byte array version of the data.
                 final byte[] dataBytes = dataString.toString().getBytes();
 
                 // A vector for holding the results.
                 final List<int[]> hits = new ArrayList<>();
                 /*
                  * loop through the data from beginint to end calling scan at each position. This shows how to use scan(), but in
                  * general this should be used more effediently (with a boyer more algorithm or something.
                  */
                 for (int pos = 1; pos < dataBytes.length; pos++) {
                     scanner.scan(dataBytes, pos, hits);
                     for (int i = 0; i < hits.size(); i++) {
                         final int[] tmp = hits.get(i);
                         logger.info("Hit At: {} id: {} l: {}", tmp[0], tmp[1], tmp[2]);
                     }
                     hits.clear();
                 }
             } catch (Exception e) {
                 logger.error("Exception in test", e);
             }
         }
 
         public static void main2(final String[] args) {
             try {
                 // a list of interesting keywords. */
                 final String[] keys = {"\nABCD", "\nABC", "\nAB", "\n//xyz//", "\nxxxxx", "\nabcdefghi", "\nabcde", "\nabcdefg"};
                 // A string for holding the test data to be searched
                 final StringBuilder dataString = new StringBuilder();
                 // The thing we are testing
                 final BackwardsTreeScanner scanner = new BackwardsTreeScanner(keys);
                 // Make up an interesting string. The second half should never match.
                 for (int i = 0; i < keys.length; i++) {
                     dataString.append(keys[i]);
                 }
                 // for (int i = 0;i<keys.length;i++)dataString +=keys[i].toString().substring(0,2);
                 // A byte array version of the data.
                 final byte[] dataBytes = dataString.toString().getBytes();
 
                 // A vector for holding the results.
                 final List<int[]> hits = new ArrayList<>();
                 /*
                  * loop through the data from beginint to end calling scan at each position. This shows how to use scan(), but in
                  * general this should be used more effediently (with a boyer more algorithm or something.
                  */
                 for (int pos = 1; pos < dataBytes.length; pos++) {
                     scanner.scan(dataBytes, pos, hits);
                     for (int i = 0; i < hits.size(); i++) {
                         final int[] tmp = hits.get(i);
                         logger.info("Hit At: {} id: {}", tmp[0], tmp[1]);
                     }
                     hits.clear();
                 }
             } catch (Exception e) {
                 logger.error("Exception in test", e);
             }
         }
 
         public synchronized State getRoot() {
             return this.root;
         }
 
         public synchronized void setData(final byte[] dataArg) {
             this.data = dataArg;
         }
 
         /**
          * This scans the byte array backwards from the offset. Each hit is added to the result vector. We stop when all
          * posibilities are found
          */
         public synchronized int scan(final byte[] dataArg, final int offset, final Collection<int[]> result) {
             this.data = dataArg;
             return scan(offset, result);
         }
 
         public synchronized int scan(final int curPosArg, final Collection<int[]> result) {
             if (!(curPosArg < this.data.length)) {
                 return curPosArg;
             }
             State state = this.root;
             int length = 0;
             int curPos = curPosArg;
             while ((state != null) && (curPos >= 0)) {
                 if (curPos > this.data.length || curPos < 0) {
                     return curPos;
                 }
                 int ch = this.data[curPos];
                 if (ch < 0) {
                     ch += Byte.MAX_VALUE - Byte.MIN_VALUE;
                 }
                 state = state.nextStates[ch];
                 length++;
                 if (state != null && state.matches != null) {
                     for (int i = 0; i < state.matches.length; i++) {
                         final int id = state.matches[i];
                         final int[] tmp = new int[3];
                         tmp[0] = curPos;
                         tmp[1] = id;
                         tmp[2] = length;
                         result.add(tmp);
                     }
                 }
                 curPos--;
             }
             return curPos;
         }
 
         /*
          * This class implements a state machine that can learn character sequences.
          */
         public class State {
 
             // Each state has 256 transitions leaving it to new states based
             // on a single ascii character. If there is no next state for a
             // character, then the next state will be null.
             public State[] nextStates = new State[256];
 
             // Each state can be visited by a single character. This is it!
             public int gotHereBy;
 
             // A list of keyword ids that are matched at this state.
             @Nullable
             public int[] matches = null;
 
             // constructor
             public State(final int gotHereBy) {
                 this.gotHereBy = gotHereBy;
             }
 
             public void learn(final byte[] word, final int id) throws Exception {
                 learn(word, word.length - 1, id);
             }
 
             /**
              * Walk throught he keyword backwards. Adding states to the root (or current state) when they don't exists. At the end,
              * record the keyowrd id in the ending state.
              *
              * Warning this is recursive, but thats OK for small keywords.
              */
             public void learn(final byte[] word, final int wordLoc, final int id) throws Exception {
                 if (word == null) {
                     throw new Exception("null keyword in BackwardsTreeScanner.learn()");
                 }
                 if (wordLoc >= word.length) {
                     throw new Exception("char pos > word length:" + wordLoc + ">" + word.length);
                 }
                 if (wordLoc < 0) {
                     // we are finished because this is the first character,
                     // so save the id in this state. We want the matches to be
                     // in an array so this is a little harder than a vector thing.
                     if (this.matches == null) {
                         this.matches = new int[0];
                     }
                     final int[] newMatches = new int[this.matches.length + 1];
                     System.arraycopy(this.matches, 0, newMatches, 0, this.matches.length);
                     this.matches = newMatches;
                     this.matches[this.matches.length - 1] = id;
                 } else {
                     // Get the next character in the word
                     int nextChar = word[wordLoc];
                     if (nextChar < 0) {
                         nextChar += Byte.MAX_VALUE - Byte.MIN_VALUE;
                     }
 
                     // See if the state already exists
                     State nextState = this.nextStates[nextChar];
                     if (nextState == null) {
                         // Make a new state because it isn't there yet.
                         nextState = this.nextStates[nextChar] = new State(nextChar);
                     }
                     // Learn the rest of the keyword in the new state.
                     nextState.learn(word, wordLoc - 1, id);
                 }
             }
 
             public void print(final PrintStream out) {
                 print(out, "root:");
             }
 
             // Make a pretty picture.
             public void print(final PrintStream out, final String prefix) {
                 if ((this.gotHereBy < ' ') || (this.gotHereBy > '~')) {
                     out.println(prefix + "-> " + "(byte)" + this.gotHereBy);
                 } else {
                     out.println(prefix + "-> " + (char) this.gotHereBy);
                 }
                 if (this.matches != null) {
                     out.print(prefix + "ids [");
                     for (int i = 0; i < this.matches.length; i++) {
                         out.print(" " + this.matches[i]);
                     }
                     out.println(" ]");
                 }
                 for (int i = 0; i < this.nextStates.length; i++) {
                     if (this.nextStates[i] != null) {
                         this.nextStates[i].print(out, prefix + "  ");
                     }
                 }
             }
         }
     }
 }