package org.djutils.serialization;
   
   import java.io.IOException;
   
   import org.djunits.unit.Unit;
   import org.djunits.value.vdouble.scalar.base.DoubleScalar;
   import org.djunits.value.vfloat.scalar.base.FloatScalar;
   import org.djutils.decoderdumper.Decoder;
   import org.djutils.serialization.serializers.ArrayOrMatrixWithUnitSerializer;
  import org.djutils.serialization.serializers.BasicPrimitiveArrayOrMatrixSerializer;
  import org.djutils.serialization.serializers.FixedSizeObjectSerializer;
  import org.djutils.serialization.serializers.Pointer;
  import org.djutils.serialization.serializers.Serializer;
  import org.djutils.serialization.serializers.StringArraySerializer;
  import org.djutils.serialization.serializers.StringMatrixSerializer;
  
  /**
   * Decoder for inspection of serialized data. The SerialDataDecoder implements a state machine that processes one byte at a
   * time. Output is sent to the buffer (a StringBuilder).
   * <p>
   * Copyright (c) 2013-2025 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   */
  public class SerialDataDecoder implements Decoder
  {
      /** The endian util to use to decode multi-byte values. */
      private final EndianUtil endianUtil;
  
      /** Type of the data that is currently being decoded. */
      private byte currentFieldType;
  
      /** The serializer for the <code>currentFieldType</code>. */
      private Serializer<?> currentSerializer = null;
  
      /** Position in the dataElementBytes where the next input byte shall be store. */
      private int nextDataElementByte = -1;
  
      /** Collects the bytes that constitute the current data element. */
      private byte[] dataElementBytes = new byte[0];
  
      /** Number of rows in an array or matrix. */
      private int rowCount;
  
      /** Number of columns in a matrix. */
      private int columnCount;
  
      /** Number of characters in a string. */
      private int charCount;
  
      /** Row of matrix or array that we are now reading. */
      private int currentRow;
  
      /** Column of matrix that we are now reading. */
      private int currentColumn;
  
      /** Character in the string that we are currently reading (either 8 or 16 bits). */
      private int currentChar;
  
      /** Djunits display unit. */
      private Unit<?> displayUnit;
  
      /** Array of units for array of column vectors. */
      private Unit<?>[] columnUnits = null;
  
      /** String builder for current output line. */
      private StringBuilder buffer = new StringBuilder();
  
      /**
       * Construct a new SerialDataDecoder.
       * @param endianUtil the endian util to use to decode multi-byte values
       */
      public SerialDataDecoder(final EndianUtil endianUtil)
      {
          this.endianUtil = endianUtil;
      }
  
      @Override
      public final String getResult()
      {
          String result = this.buffer.toString();
          this.buffer.setLength(0);
          return result;
      }
  
      @Override
      public final int getMaximumWidth()
      {
          return 80;
      }
  
      /**
       * Decode one (more) byte. This method must return true when a line becomes full due to this call, otherwise this method
       * must return false.
       * @param address the address that corresponds with the byte, for printing purposes.
       * @param theByte the byte to process
       * @return true if an output line has been completed by this call; false if at least one more byte can be appended to the
      *         local accumulator before the current output line is full
      * @throws IOException when the output device throws this exception
      */
     @Override
     public final boolean append(final int address, final byte theByte) throws IOException
     {
         boolean result = false;
 
         // check if first byte to indicate the field type
         if (this.currentSerializer == null)
         {
             result = processFieldTypeByte(theByte);
             return result;
         }
 
         // add byte to data element
         if (this.nextDataElementByte < this.dataElementBytes.length)
         {
             this.dataElementBytes[this.nextDataElementByte] = theByte;
         }
         this.nextDataElementByte++;
         // if data element complete, process it, and prepare for next data element (if any in current field type)
         if (this.nextDataElementByte == this.dataElementBytes.length)
         {
             result = processDataElement();
         }
 
         // are we done?
         if (this.currentSerializer == null)
         {
             return true;
         }
         return result;
     }
 
     /**
      * Process one byte that indicates the field type.
      * @param theByte the byte to process
      * @return whether line is full
      */
     private boolean processFieldTypeByte(final byte theByte)
     {
         this.currentFieldType = (byte) (theByte & 0x7F);
         this.currentSerializer = TypedObject.PRIMITIVE_DATA_DECODERS.get(this.currentFieldType);
         if (this.currentSerializer == null)
         {
             this.buffer.append(String.format("Error: Bad field type %02x - resynchronizing", this.currentFieldType));
             return true;
         }
         this.buffer.append(this.currentSerializer.dataClassName() + (this.currentSerializer.getNumberOfDimensions() > 0
                 || this.currentSerializer.dataClassName().startsWith("Djunits") ? " " : ": "));
 
         this.columnCount = 0;
         this.rowCount = 0;
         this.displayUnit = null;
         this.columnUnits = null;
 
         // check the type and prepare for what is expected; primitive types
         if (this.currentSerializer instanceof FixedSizeObjectSerializer<?>)
         {
             var fsoe = (FixedSizeObjectSerializer<?>) this.currentSerializer;
             int size = fsoe.size(null);
             prepareForDataElement(size);
             return false;
         }
 
         // array or matrix type: next variable to expect is one or more ints (rows/cols)
         if (this.currentSerializer.getNumberOfDimensions() > 0)
         {
             int size = this.currentSerializer.getNumberOfDimensions() * 4;
             prepareForDataElement(size);
             return false;
         }
 
         // regular string type, next is an int for length
         if (this.currentFieldType == 9 || this.currentFieldType == 10)
         {
             prepareForDataElement(4);
             return false;
         }
 
         // djunits scalar type, next is quantity type and unit
         if (this.currentFieldType == 25 || this.currentFieldType == 26)
         {
             prepareForDataElement(2);
             return false;
         }
 
         this.buffer
                 .append(String.format("Error: No field type handler for type %02x - resynchronizing", this.currentFieldType));
         return true;
     }
 
     /**
      * Process a completed data element. If the current data type has more elements, prepare for the next data element.
      * @return whether the line is full or not
      */
     private boolean processDataElement()
     {
         boolean result = false;
 
         // primitive types
         if (this.currentSerializer instanceof FixedSizeObjectSerializer<?>)
         {
             result = appendFixedSizeObject();
             done();
             return result;
         }
 
         // regular string type
         if (this.currentFieldType == 9 || this.currentFieldType == 10)
         {
             appendString();
             if (this.currentChar >= this.charCount)
             {
                 done();
             }
             return false;
         }
 
         // processing of vector array type before array or matrix type
         if (this.currentFieldType == 31 || this.currentFieldType == 32)
         {
             if (this.rowCount == 0)
             {
                 processRowsCols();
                 prepareForDataElement(2 * this.columnCount); // unit type and display type for every column
                 return false;
             }
             if (this.columnUnits == null)
             {
                 return fillDjunitsVectorArrayColumnUnits();
             }
             return appendDjunitsVectorArrayElement();
         }
 
         // array or matrix type
         if (this.currentSerializer.getNumberOfDimensions() > 0)
         {
             if (this.rowCount == 0)
             {
                 processRowsCols();
                 if (this.currentSerializer.hasUnit())
                 {
                     prepareForDataElement(2); // unit type and display type
                 }
                 else if (this.currentSerializer instanceof BasicPrimitiveArrayOrMatrixSerializer<?>)
                 {
                     var bpams = (BasicPrimitiveArrayOrMatrixSerializer<?>) this.currentSerializer;
                     prepareForDataElement(bpams.getElementSize());
                 }
                 else if (this.currentSerializer instanceof StringArraySerializer
                         || this.currentSerializer instanceof StringMatrixSerializer)
                 {
                     prepareForDataElement(4);
                 }
                 return false;
             }
             if (this.currentSerializer.hasUnit())
             {
                 if (this.displayUnit == null)
                 {
                     result = processUnit();
                     prepareForDataElement(((ArrayOrMatrixWithUnitSerializer<?, ?>) this.currentSerializer).getElementSize());
                     return result;
                 }
                 result = appendDjunitsElement();
                 prepareForDataElement(this.dataElementBytes.length);
                 incColumnCount();
                 return result;
             }
             if (this.currentSerializer instanceof StringArraySerializer
                     || this.currentSerializer instanceof StringMatrixSerializer)
             {
                 processStringElement();
                 return false;
             }
             result = appendPrimitiveElement();
             prepareForDataElement(this.dataElementBytes.length);
             incColumnCount();
             return result;
         }
 
         // djunits scalar type
         if (this.currentFieldType == 25 || this.currentFieldType == 26)
         {
             if (this.displayUnit == null)
             {
                 result = processUnit();
                 prepareForDataElement(getSize() - 2); // subtract unit bytes
                 return result;
             }
             result = appendDjunitsElement();
             done();
             return result;
         }
 
         // any leftovers?
         System.err.println("Did not process type " + this.currentFieldType);
         return true;
     }
 
     /**
      * Return the size of the encoding for a fixed size data element.
      * @return the encoding size of an element
      */
     private int getSize()
     {
         try
         {
             return this.currentSerializer.size(null);
         }
         catch (SerializationException e)
         {
             System.err.println("Could not determine size of element for field type " + this.currentFieldType);
             return 1;
         }
     }
 
     /**
      * Append a fixed size object (i.e., primitive type) to the buffer.
      * @return whether the line is full or not
      */
     private boolean appendFixedSizeObject()
     {
         try
         {
             Object value = this.currentSerializer.deSerialize(this.dataElementBytes, new Pointer(), this.endianUtil);
             this.buffer.append(value.toString());
         }
         catch (SerializationException e)
         {
             this.buffer.append("Error deserializing data");
             return true;
         }
         return false;
     }
 
     /**
      * Append a character of a string to the buffer.
      */
     private void appendString()
     {
         int elementSize = this.currentSerializer.dataClassName().contains("8") ? 1 : 2;
         if (this.charCount == 0)
         {
             this.charCount = this.endianUtil.decodeInt(this.dataElementBytes, 0);
             this.currentChar = 0;
             prepareForDataElement(elementSize);
         }
         else
         {
             if (elementSize == 1)
             {
                 if (this.dataElementBytes[0] > 32 && this.dataElementBytes[0] < 127)
                 {
                     this.buffer.append((char) this.dataElementBytes[0]); // safe to print
                 }
                 else
                 {
                     this.buffer.append("."); // not safe to print
                 }
             }
             else
             {
                 char character = this.endianUtil.decodeChar(this.dataElementBytes, 0);
                 if (Character.isAlphabetic(character))
                 {
                     this.buffer.append(character); // safe to print
                 }
                 else
                 {
                     this.buffer.append("."); // not safe to print
                 }
             }
             this.currentChar++;
         }
         this.nextDataElementByte = 0;
     }
 
     /**
      * Process a string element in a string array or string matrix.
      */
     private void processStringElement()
     {
         appendString();
         if (this.currentChar >= this.charCount)
         {
             incColumnCount();
             this.charCount = 0;
             prepareForDataElement(4);
         }
     }
 
     /**
      * Process the height and width of a matrix, or length of an array.
      */
     private void processRowsCols()
     {
         this.currentRow = 0;
         this.currentColumn = 0;
         if (this.dataElementBytes.length == 8)
         {
             this.rowCount = this.endianUtil.decodeInt(this.dataElementBytes, 0);
             this.columnCount = this.endianUtil.decodeInt(this.dataElementBytes, 4);
             this.buffer.append(String.format("height %d, width %d: ", this.rowCount, this.columnCount));
         }
         else
         {
             this.columnCount = this.endianUtil.decodeInt(this.dataElementBytes, 0);
             this.rowCount = 1;
             this.buffer.append(String.format("length %d: ", this.columnCount));
         }
     }
 
     /**
      * Fill the unit type for the columns of this special type.
      * @return whether line is full or not.
      */
     private boolean fillDjunitsVectorArrayColumnUnits()
     {
         boolean result = false;
         this.columnUnits = new Unit<?>[this.columnCount];
         for (int i = 0; i < this.columnCount; i++)
         {
             byte unitTypeCode = this.dataElementBytes[2 * i];
             byte displayUnitCode = this.dataElementBytes[2 * i + 1];
             this.columnUnits[i] = DisplayType.getUnit(unitTypeCode, displayUnitCode);
             if (this.columnUnits[i] == null && !result)
             {
                 this.buffer.append(
                         String.format("Error: Could not find unit type %d, display unit %d", unitTypeCode, displayUnitCode));
                 result = true;
             }
         }
         prepareForDataElement(this.currentFieldType == 31 ? 4 : 8);
         return result;
     }
 
     /**
      * Append one (row) element in an array of (column) vectors.
      * @return whether the line is full or not
      * @param <U> the unit type
      * @param <FS> the float scalar type
      * @param <DS> the double scalar type
      */
     @SuppressWarnings("unchecked")
     private <U extends Unit<U>, FS extends FloatScalar<U, FS>,
             DS extends DoubleScalar<U, DS>> boolean appendDjunitsVectorArrayElement()
     {
         boolean result = false;
         try
         {
             U unit = (U) this.columnUnits[this.currentColumn];
             if (this.currentFieldType == 31)
             {
                 float f = this.endianUtil.decodeFloat(this.dataElementBytes, 0);
                 FloatScalar<U, FS> afs = FloatScalar.instantiateAnonymous(f, unit.getStandardUnit());
                 afs.setDisplayUnit(unit);
                 this.buffer.append(afs.toDisplayString().replace(" ", "") + " ");
             }
             else
             {
                 double d = this.endianUtil.decodeDouble(this.dataElementBytes, 0);
                 DoubleScalar<U, DS> ads = DoubleScalar.instantiateAnonymous(d, unit.getStandardUnit());
                 ads.setDisplayUnit(unit);
                 this.buffer.append(ads.toDisplayString().replace(" ", "") + " ");
             }
         }
         catch (Exception e)
         {
             this.buffer.append("Error: Illegal element in vector array -- could not parse");
             result = true;
         }
         prepareForDataElement(this.dataElementBytes.length);
         incColumnCount();
         return result;
     }
 
     /**
      * Process a unit (2 bytes).
      * @return whether the line is full or not
      */
     private boolean processUnit()
     {
         byte unitTypeCode = this.dataElementBytes[0];
         byte displayUnitCode = this.dataElementBytes[1];
         this.displayUnit = DisplayType.getUnit(unitTypeCode, displayUnitCode);
         if (this.displayUnit == null)
         {
             this.buffer
                     .append(String.format("Error: Could not find unit ype %d, display unit %d", unitTypeCode, displayUnitCode));
             return true;
         }
         return false;
     }
 
     /**
      * Process one element of a djunits vector or array.
      * @return whether the line is full or not
      * @param <U> the unit type
      * @param <FS> the float scalar type
      * @param <DS> the double scalar type
      */
     @SuppressWarnings("unchecked")
     private <U extends Unit<U>, FS extends FloatScalar<U, FS>, DS extends DoubleScalar<U, DS>> boolean appendDjunitsElement()
     {
         boolean result = false;
         try
         {
             if (this.dataElementBytes.length == 4)
             {
                 float f = this.endianUtil.decodeFloat(this.dataElementBytes, 0);
                 FloatScalar<U, FS> afs = FloatScalar.instantiateAnonymous(f, this.displayUnit.getStandardUnit());
                 afs.setDisplayUnit((U) this.displayUnit);
                 this.buffer.append(afs.toDisplayString().replace(" ", "") + " ");
             }
             else
             {
                 double d = this.endianUtil.decodeDouble(this.dataElementBytes, 0);
                 DoubleScalar<U, DS> ads = DoubleScalar.instantiateAnonymous(d, this.displayUnit.getStandardUnit());
                 ads.setDisplayUnit((U) this.displayUnit);
                 this.buffer.append(ads.toDisplayString().replace(" ", "") + " ");
             }
         }
         catch (Exception e)
         {
             this.buffer.append("Error: Could not instantiate djunits element");
             result = true;
         }
         return result;
     }
 
     /**
      * Append a primitive element to the buffer.
      * @return whether the line is full or not.
      */
     private boolean appendPrimitiveElement()
     {
         boolean result = false;
         this.buffer.append(switch (this.currentSerializer.fieldType())
         {
             // @formatter:off
             case FieldTypes.BYTE_8_ARRAY, FieldTypes.BYTE_8_MATRIX -> 
                 String.format("%02x ", this.dataElementBytes[0]);
             case FieldTypes.SHORT_16_ARRAY, FieldTypes.SHORT_16_MATRIX -> 
                 String.format("%d ", this.endianUtil.decodeShort(this.dataElementBytes, 0));
             case FieldTypes.INT_32_ARRAY, FieldTypes.INT_32_MATRIX -> 
                 String.format("%d ", this.endianUtil.decodeInt(this.dataElementBytes, 0));
             case FieldTypes.LONG_64_ARRAY, FieldTypes.LONG_64_MATRIX -> 
                 String.format("%d ", this.endianUtil.decodeLong(this.dataElementBytes, 0));
             case FieldTypes.FLOAT_32_ARRAY, FieldTypes.FLOAT_32_MATRIX -> 
                 String.format("%f ", this.endianUtil.decodeFloat(this.dataElementBytes, 0));
             case FieldTypes.DOUBLE_64_ARRAY, FieldTypes.DOUBLE_64_MATRIX -> 
                 String.format("%f ", this.endianUtil.decodeDouble(this.dataElementBytes, 0));
             case FieldTypes.BOOLEAN_8_ARRAY, FieldTypes.BOOLEAN_8_MATRIX -> 
                 this.dataElementBytes[0] == 0 ? "false " : "true ";
             // @formatter:on
             default -> "Error: Unhandled type of basicPrimitiveArraySerializer: " + this.currentSerializer.fieldType();
         });
         return result;
     }
 
     /**
      * Increase the column count and possibly row count. Reset when complete.
      */
     private void incColumnCount()
     {
         this.currentColumn++;
         if (this.currentColumn >= this.columnCount)
         {
             this.currentColumn = 0;
             this.currentRow++;
             if (this.currentRow >= this.rowCount)
             {
                 done();
             }
         }
     }
 
     /**
      * Reset the state when done with the current variable.
      */
     private void done()
     {
         this.currentSerializer = null;
         this.rowCount = 0;
         this.columnCount = 0;
         this.charCount = 0;
     }
 
     /**
      * Allocate a buffer for the next data element (or two).
      * @param dataElementSize size of the buffer
      */
     private void prepareForDataElement(final int dataElementSize)
     {
         this.dataElementBytes = new byte[dataElementSize];
         this.nextDataElementByte = 0;
     }
 
     @Override
     public final boolean ignoreForIdenticalOutputCheck()
     {
         return false;
     }
 
 }