// This Source Code is in the Public Domain per: http://unlicense.org
package org.litesoft.core.util;

import org.litesoft.commonfoundation.base.*;
import org.litesoft.commonfoundation.charstreams.*;

public class UtilsCommon {
    protected UtilsCommon() {
    }

    /**
     * @param pText !null
     */
    public static void formatToJavaSourceString( StringBuilder pSB, String pText ) {
        LowLevelEncode( pSB, new CharSourceFromSequence( pText ), true );
    }

    public static String encodeToConstrainedASCII( String pText ) {
        if ( Currently.isNullOrEmpty( pText ) ) {
            return pText;
        }
        return LowLevelEncode( new StringBuilder(), new CharSourceFromSequence( pText, 0 ), true ).toString();
    }

    public static String decodeFromConstrainedASCII( String pText ) {
        if ( Currently.isNullOrEmpty( pText ) ) {
            return pText;
        }
        return LowLevelDecode( new StringBuilder(), new CharSourceFromSequence( pText, 0 ), false ).toString();
    }

    private static StringBuilder LowLevelEncode( StringBuilder pSB, CharSource pSource, boolean pDoubleQuoteSpecial ) {
        for ( int c; -1 != (c = pSource.get()); ) {
            if ( pDoubleQuoteSpecial && (c == '"') ) {
                pSB.append( '\\' );
                pSB.append( (char) c );
            } else {
                switch ( c ) {
                    case '\\':
                        pSB.append( '\\' );
                        pSB.append( '\\' );
                        break;
                    case '\n':
                        pSB.append( '\\' );
                        pSB.append( 'n' );
                        break;
                    case '\r':
                        pSB.append( '\\' );
                        pSB.append( 'r' );
                        break;
                    case '\t':
                        pSB.append( '\\' );
                        pSB.append( 't' );
                        break;
                    default:
                        if ( (' ' <= c) && (c < 127) ) {
                            pSB.append( (char) c );
                            break;
                        }
                        pSB.append( '\\' );
                        pSB.append( 'x' );
                        pSB.append( Hex.toChar( c >> 24 ) );
                        pSB.append( Hex.toChar( c >> 16 ) );
                        pSB.append( Hex.toChar( c >> 8 ) );
                        pSB.append( Hex.toChar( c ) );
                        break;
                }
            }
        }
        return pSB;
    }

    private static StringBuilder LowLevelDecode( StringBuilder pSB, CharSource pSource, boolean pDoubleQuoteSpecial ) {
        for ( int c; -1 != (c = pSource.get()); ) {
            if ( (c < ' ') || (127 <= c) ) {
                throw new IllegalArgumentException( "Decoding Error: Char[" + pSource.getLastOffset() + "] Not between ' ' & Ascii 126 (inclusive)" );
            }
            if ( c != '\\' ) {
                pSB.append( (char) c );
                continue;
            }
            if ( -1 == (c = pSource.get()) ) {
                throw new IllegalArgumentException( "Decoding Error: No Char after escape \\" );
            }
            if ( pDoubleQuoteSpecial && (c == '"') ) {
                pSB.append( (char) c );
            } else {
                switch ( c ) {
                    case '\\':
                        pSB.append( (char) c );
                        break;
                    case 'n':
                        pSB.append( '\n' );
                        break;
                    case 'r':
                        pSB.append( '\r' );
                        break;
                    case 't':
                        pSB.append( '\t' );
                        break;
                    case 'x':
                        int c1 = pSource.get();
                        int c2 = pSource.get();
                        int c3 = pSource.get();
                        int c4 = pSource.get();
                        if ( c4 == -1 ) {
                            throw new IllegalArgumentException( "Decoding Error: Not enough Chars after \\x" );
                        }
                        try {
                            int zChar = (Hex.fromCharChecked( (char) c1 ) << 24) + //
                                        (Hex.fromCharChecked( (char) c2 ) << 16) + //
                                        (Hex.fromCharChecked( (char) c3 ) << 8) + //
                                        Hex.fromCharChecked( (char) c4 );
                            pSB.append( (char) zChar );
                        }
                        catch ( IllegalArgumentException e ) {
                            throw new IllegalArgumentException( "Decoding Error: After \\x expected 4 hex digits: " + e.getMessage() );
                        }
                        break;
                    default:
                        throw new IllegalArgumentException( "Decoding Error: Invalid Char '" + c + "' after escape \\" );
                }
            }
        }
        return pSB;
    }
}