/**
 *  Copyright (c) 2013-2014 Angelo ZERR.
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  which accompanies this distribution, and is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 *
 *  Contributors:
 *  Angelo Zerr <angelo.zerr@gmail.com> - initial API and implementation
 */
package org.eclipse.json.provisonnal.com.eclipsesource.json;

import java.io.IOException;
import java.io.Writer;


class JsonWriter {

  private static final int CONTROL_CHARACTERS_END = 0x001f;

  private static final char[] QUOT_CHARS = { '\\', '"' };
  private static final char[] BS_CHARS = { '\\', '\\' };
  private static final char[] LF_CHARS = { '\\', 'n' };
  private static final char[] CR_CHARS = { '\\', 'r' };
  private static final char[] TAB_CHARS = { '\\', 't' };
  // In JavaScript, U+2028 and U+2029 characters count as line endings and must be encoded.
  // http://stackoverflow.com/questions/2965293/javascript-parse-error-on-u2028-unicode-character
  private static final char[] UNICODE_2028_CHARS = { '\\', 'u',  '2', '0', '2', '8' };
  private static final char[] UNICODE_2029_CHARS = { '\\', 'u',  '2', '0', '2', '9' };
  private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                                             'a', 'b', 'c', 'd', 'e', 'f' };

  protected final Writer writer;

  JsonWriter( Writer writer ) {
    this.writer = writer;
  }

  protected void writeLiteral( String value ) throws IOException {
    writer.write( value );
  }

  protected void writeNumber( String string ) throws IOException {
    writer.write( string );
  }

  protected void writeString( String string ) throws IOException {
    writer.write( '"' );
    writeJsonString( string );
    writer.write( '"' );
  }

  protected void writeArrayOpen() throws IOException {
    writer.write( '[' );
  }

  protected void writeArrayClose() throws IOException {
    writer.write( ']' );
  }

  protected void writeArraySeparator() throws IOException {
    writer.write( ',' );
  }

  protected void writeObjectOpen() throws IOException {
    writer.write( '{' );
  }

  protected void writeObjectClose() throws IOException {
    writer.write( '}' );
  }

  protected void writeMemberName( String name ) throws IOException {
    writer.write( '"' );
    writeJsonString( name );
    writer.write( '"' );
  }

  protected void writeMemberSeparator() throws IOException {
    writer.write( ':' );
  }

  protected void writeObjectSeparator() throws IOException {
    writer.write( ',' );
  }

  protected void writeJsonString( String string ) throws IOException {
    int length = string.length();
    int start = 0;
    for( int index = 0; index < length; index++ ) {
      char[] replacement = getReplacementChars( string.charAt( index ) );
      if( replacement != null ) {
        writer.write( string, start, index - start );
        writer.write( replacement );
        start = index + 1;
      }
    }
    writer.write( string, start, length - start );
  }

  private static char[] getReplacementChars( char ch ) {
    if( ch > '\\' ) {
      if( ch < '\u2028' || ch > '\u2029') {
        // The lower range contains 'a' .. 'z'. Only 2 checks required.
        return null;
      }
      return ch == '\u2028' ? UNICODE_2028_CHARS : UNICODE_2029_CHARS;
    }
    if( ch == '\\' ) {
      return BS_CHARS;
    }
    if( ch > '"' ) {
      // This range contains '0' .. '9' and 'A' .. 'Z'. Need 3 checks to get here.
      return null;
    }
    if( ch == '"' ) {
      return QUOT_CHARS;
    }
    if( ch > CONTROL_CHARACTERS_END ) {
      return null;
    }
    if( ch == '\n' ) {
      return LF_CHARS;
    }
    if( ch == '\r' ) {
      return CR_CHARS;
    }
    if( ch == '\t' ) {
      return TAB_CHARS;
    }
    return new char[] { '\\', 'u', '0', '0', HEX_DIGITS[ch >> 4 & 0x000f], HEX_DIGITS[ch & 0x000f] };
  }

}