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package com.backendless.persistence;

import java.io.IOException;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.StringReader;
import java.util.ArrayList;


public class WKTParser
{
  private static final String EMPTY = "EMPTY";
  private static final String COMMA = ",";
  private static final String L_PAREN = "(";
  private static final String R_PAREN = ")";
  private static final String NAN_SYMBOL = "NaN";

  private final SpatialReferenceSystemEnum srs;

  public WKTParser()
  {
    this( SpatialReferenceSystemEnum.DEFAULT );
  }

  public WKTParser( SpatialReferenceSystemEnum srs )
  {
    if( srs == null )
      throw new IllegalArgumentException( "Spatial Reference System (SRS) cannot be null." );

    this.srs = srs;
  }

  public Geometry read( String wellKnownText )
  {
    StringReader reader = new StringReader( wellKnownText );
    StreamTokenizer tokenizer = createTokenizer( reader );

    String type = getNextWord( tokenizer ).toUpperCase();
    try
    {
      return readGeometryTaggedText( tokenizer, type );
    }
    catch( IOException e )
    {
      throw new WKTParseException( e );
    }
  }

  private static StreamTokenizer createTokenizer( Reader reader )
  {
    StreamTokenizer tokenizer = new StreamTokenizer( reader );
    // set tokenizer to NOT parse numbers
    tokenizer.resetSyntax();
    tokenizer.wordChars( 'a', 'z' );
    tokenizer.wordChars( 'A', 'Z' );
    tokenizer.wordChars( 128 + 32, 255 ); // unused characters
    tokenizer.wordChars( '0', '9' );
    tokenizer.wordChars( '-', '-' );
    tokenizer.wordChars( '+', '+' );
    tokenizer.wordChars( '.', '.' );
    tokenizer.whitespaceChars( 0, ' ' ); // 0-32 whitespaces
    tokenizer.commentChar( '#' );

    return tokenizer;
  }

  private static String getNextWord( StreamTokenizer tokenizer )
  {
    try
    {
      int type = tokenizer.nextToken();
      switch( type )
      {
        case StreamTokenizer.TT_WORD:
          String word = tokenizer.sval;
          if( word.equalsIgnoreCase( EMPTY ) )
            return EMPTY;
          return word;
        case '(':
          return L_PAREN;
        case ')':
          return R_PAREN;
        case ',':
          return COMMA;
      }

      throw new WKTParseException( "Unknown type: '" + (char) type + "'" );
    }
    catch( IOException e )
    {
      throw new WKTParseException( e );
    }
  }

  private static String tokenString( StreamTokenizer tokenizer )
  {
    switch( tokenizer.ttype )
    {
      case StreamTokenizer.TT_NUMBER:
        return "";
      case StreamTokenizer.TT_EOL:
        return "End-of-Line";
      case StreamTokenizer.TT_EOF:
        return "End-of-Stream";
      case StreamTokenizer.TT_WORD:
        return "'" + tokenizer.sval + "'";
    }
    return "'" + (char) tokenizer.ttype + "'";
  }

  private static String getNextEmptyOrOpener( StreamTokenizer tokenizer )
  {
    String nextWord = getNextWord( tokenizer );
    if( nextWord.equals( EMPTY ) || nextWord.equals( L_PAREN ) )
      return nextWord;

    throw new WKTParseException( "Expected: " + EMPTY + " or " + L_PAREN );
  }

  private static String getNextCloserOrComma( StreamTokenizer tokenizer )
  {
    String nextWord = getNextWord( tokenizer );
    if( nextWord.equals( COMMA ) || nextWord.equals( R_PAREN ) )
      return nextWord;

    throw new WKTParseException( "Expected: " + COMMA + " or " + R_PAREN );
  }

  private String getNextCloser( StreamTokenizer tokenizer )
  {
    String nextWord = getNextWord( tokenizer );
    if( nextWord.equals( R_PAREN ) )
      return nextWord;

    throw new WKTParseException( "Expected: " + R_PAREN );
  }

  private static boolean isOpenerNext( StreamTokenizer tokenizer ) throws IOException
  {
    int type = tokenizer.nextToken();
    tokenizer.pushBack();
    return type == '(';
  }

  private static boolean isNumberNext( StreamTokenizer tokenizer ) throws IOException
  {
    int type = tokenizer.nextToken();
    tokenizer.pushBack();
    return type == StreamTokenizer.TT_WORD;
  }

  private double getNextNumber( StreamTokenizer tokenizer ) throws IOException
  {
    int type = tokenizer.nextToken();

    if( type == StreamTokenizer.TT_WORD )
    {
      if( tokenizer.sval.equalsIgnoreCase( NAN_SYMBOL ) )
        return Double.NaN;
      else
      {
        try
        {
          return Double.parseDouble( tokenizer.sval );
        }
        catch( NumberFormatException ex )
        {
          throw new WKTParseException( "Invalid number: " + tokenizer.sval );
        }
      }
    }

    throw new WKTParseException( "Expected: number" );
  }

  private ArrayList getCoordinateSequence( StreamTokenizer tokenizer, boolean tryParen ) throws IOException
  {
    String nextWord = getNextEmptyOrOpener( tokenizer );

    if( nextWord.equals( EMPTY ) )
      return null;

    ArrayList coordinates = new ArrayList<>();
    do
    {
      coordinates.add( getCoordinate( tokenizer, tryParen ) );
    }
    while( getNextCloserOrComma( tokenizer ).equals( COMMA ) );

    return coordinates;
  }

  private double[] getCoordinate( StreamTokenizer tokenizer, boolean tryParen ) throws IOException
  {
    boolean opened;

    if( opened = tryParen && isOpenerNext( tokenizer ) )
      tokenizer.nextToken();

    double[] sequence = new double[ 2 ];
    sequence[ 0 ] = getNextNumber( tokenizer );
    sequence[ 1 ] = getNextNumber( tokenizer );

    // read close token if it was opened here
    if( opened )
      getNextCloser( tokenizer );

    return sequence;
  }

  private Geometry readGeometryTaggedText( StreamTokenizer tokenizer, String type ) throws IOException
  {
    if( type.startsWith( Point.WKT_TYPE ) )
    {
      return readPointText( tokenizer );
    }
    else if( type.startsWith( LineString.WKT_TYPE ) )
    {
      return readLineStringText( tokenizer );
    }
    else if( type.startsWith( Polygon.WKT_TYPE ) )
    {
      return readPolygonText( tokenizer );
    }

/*
    else if (type.startsWith("MULTIPOINT")) {
      return readMultiPointText(tokenizer, ordinateFlags);
    }
    else if (type.startsWith("MULTILINESTRING")) {
      return readMultiLineStringText(tokenizer, ordinateFlags);
    }
    else if (type.startsWith("MULTIPOLYGON")) {
      return readMultiPolygonText(tokenizer, ordinateFlags);
    }
    else if (type.startsWith("GEOMETRYCOLLECTION")) {
      return readGeometryCollectionText(tokenizer, ordinateFlags);
    }
*/

    throw new WKTParseException( "Unknown geometry type: '" + type + "'" );
  }

  private Point readPointText( StreamTokenizer tokenizer ) throws IOException
  {
    ArrayList coordinateSiequence = getCoordinateSequence( tokenizer, false );
    if( coordinateSiequence == null )
      return null;

    return new Point( this.srs ).setX( coordinateSiequence.get( 0 )[ 0 ] ).setY( coordinateSiequence.get( 0 )[ 1 ] );
  }

  private LineString readLineStringText( StreamTokenizer tokenizer ) throws IOException
  {
    ArrayList coordinateSiequence = getCoordinateSequence( tokenizer, false );
    if( coordinateSiequence == null )
      return null;

    ArrayList points = new ArrayList<>();
    for( double[] coordinates : coordinateSiequence )
      points.add( new Point( srs ).setX( coordinates[ 0 ] ).setY( coordinates[ 1 ] ) );

    return new LineString( points, this.srs );
  }

  private Polygon readPolygonText( StreamTokenizer tokenizer ) throws IOException
  {
    String nextToken = getNextEmptyOrOpener( tokenizer );
    if( nextToken.equals( EMPTY ) )
      return null;

    LineString shell = readLineStringText( tokenizer );

    ArrayList holes = new ArrayList<>();
    nextToken = getNextCloserOrComma( tokenizer );
    while( nextToken.equals( COMMA ) )
    {
      LineString hole = readLineStringText( tokenizer );
      holes.add( hole );
      nextToken = getNextCloserOrComma( tokenizer );
    }

    return new Polygon( shell, holes, srs );
  }

/*
  private MultiPoint readMultiPointText( StreamTokenizer tokenizer )
  {

    return null;
  }

  private MultiLineString readMultiLineStringText( StreamTokenizer tokenizer )
  {

    return null;
  }

  private MultiPolygon readMultiPolygonText( StreamTokenizer tokenizer )
  {

    return null;
  }

  private List readGeometryCollectionText( StreamTokenizer tokenizer )
  {

    return null;
  }
*/

  public static class WKTParseException extends RuntimeException
  {
    public WKTParseException( String message )
    {
      super( message );
    }

    public WKTParseException( Throwable cause )
    {
      super( cause );
    }

    public WKTParseException( String message, Throwable cause )
    {
      super( message, cause );
    }
  }
}