/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.databoard.util;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

/**
 * <a href="http://www.simantics.org/wiki/index.php/URI">Simantics URI and identifier escape specification.
 * 
 * @author Hannu Niemist&ouml;
 */
public final class URIUtil {

    static final Charset UTF8        = Charset.forName("UTF-8");

    static final byte[]  encodeTable = new byte[128];
    static final byte[]  encodeTable2 = new byte[128]; // for non-bijection filenames

    static {
        for (int i = 0; i < 128; ++i) {
            char c = (char) i;
            if (c == ' ')
                encodeTable[i] = '_';
            
            else if (Character.isJavaIdentifierPart(c) && c != '_' && c != '$') {
                encodeTable[i] = (byte) i;
            } else
                encodeTable[i] = -1;
        }
        
        for (int i = 0; i < 128; ++i) {
            char c = (char) i;
            if (c == ' ' || c == '_' || c == '(' || c== ')')
                encodeTable2[i] = (byte) i;
            else if (c == '/')
                encodeTable2[i] = (byte) '-';
            else if (c == ' ')
                encodeTable2[i] = (byte) '_';
            else if (c == '-' || c == '.')
                encodeTable2[i] = (byte) i;
            else if (Character.isJavaIdentifierPart(c) && c != '_' && c != '$') {
                encodeTable2[i] = (byte) i;
            } else
                encodeTable2[i] = -1;
        }
        
    }

    public static byte[] encode(String str, byte escapeChar, boolean identifier) throws UnsupportedEncodingException {
        byte[] bytes = str.getBytes(UTF8);

        boolean prefixWithUnderscore = identifier && bytes.length > 0 && (bytes[0] == '_' || Character.isDigit(bytes[0]));

        // First calculate the length
        int length = bytes.length;
        for (byte b : bytes) {
            if (b < 0 || encodeTable[b] == -1)
                length += 2;
        }
        if (prefixWithUnderscore)
            length += 1;

        // Then encode
        if (length == bytes.length) {
            for (int i = 0; i < length; ++i)
                bytes[i] = encodeTable[bytes[i]];
            return bytes;
        } else {
            byte[] result = new byte[length];
            int pos = 0;
            if (prefixWithUnderscore) {
                result[pos++] = '_';
            }
            for (byte b : bytes) {
                int ib = (int) b;
                if (ib >= 0) {
                    byte eb = encodeTable[ib];
                    if (eb >= 0) {
                        result[pos++] = eb;
                        continue;
                    }
                } else
                    ib += 256;

                result[pos++] = escapeChar;
                result[pos++] = (byte) Character.forDigit(ib >> 4, 16);
                result[pos++] = (byte) Character.forDigit(ib & 15, 16);
            }
            return result;
        }
    }
    
    public static byte[] encodeFilename(String str, byte escapeChar, boolean identifier) throws UnsupportedEncodingException {
        byte[] bytes = str.getBytes(UTF8);

        boolean prefixWithUnderscore = identifier && bytes.length > 0 && (bytes[0] == '_' || Character.isDigit(bytes[0]));

        // First calculate the length
        int length = bytes.length;
        for (byte b : bytes) {
            if (b < 0 || encodeTable2[b] == -1)
                length += 2;
        }
        if (prefixWithUnderscore)
            length += 1;

        // Then encode
        if (length == bytes.length) {
            for (int i = 0; i < length; ++i)
                bytes[i] = encodeTable2[bytes[i]];
            return bytes;
        } else {
            byte[] result = new byte[length];
            int pos = 0;
            if (prefixWithUnderscore) {
                result[pos++] = '_';
            }
            for (byte b : bytes) {
                int ib = (int) b;
                if (ib >= 0) {
                    byte eb = encodeTable2[ib];
                    if (eb >= 0) {
                        result[pos++] = eb;
                        continue;
                    }
                } else
                    ib += 256;

                result[pos++] = escapeChar;
                result[pos++] = (byte) Character.forDigit(ib >> 4, 16);
                result[pos++] = (byte) Character.forDigit(ib & 15, 16);
            }
            return result;
        }
    }
    
    public static String encodeFilename(String str) {
        try {
            byte[] result = encodeFilename(str, (byte) '%', false);
            return new String(result, 0, result.length);
        } catch (UnsupportedEncodingException e) {
            // Should never happen when using UTF-8
            throw new Error(e);
        }

    }

    public static String encodeURI(String str) {
        try {
            byte[] result = encode(str, (byte) '%', false);
            return new String(result, 0, result.length);
        } catch (UnsupportedEncodingException e) {
            // Should never happen when using UTF-8
            throw new Error(e);
        }

    }

    public static String encodeIdentifier(String str) {
        try {
            byte[] result = encode(str, (byte) '$', true);
            return new String(result, 0, result.length);
        } catch (UnsupportedEncodingException e) {
            // Should never happen when using UTF-8
            throw new Error(e);
        }

    }

    public static String decode(byte[] bytes, byte escapeChar, boolean identifier) {
        int length = 0;
        int startPos = 0;
        {
            int i = 0;
            // Skip '_' prefix if necessary
            if (identifier && bytes.length > 0 && bytes[0] == '_') {
                startPos = 1;
                i = 1;
            }
            for (; i < bytes.length; ++i) {
                byte b = bytes[i];
                if (b == escapeChar)
                    i += 2;
                ++length;
            }
        }
        int pos = 0;
        byte[] result = new byte[length];
        for (int i = startPos; i < bytes.length; ++i) {
            byte b = bytes[i];
            if (b == escapeChar) {
                int c = Character.digit((char) bytes[++i], 16);
                c *= 16;
                c += Character.digit((char) bytes[++i], 16);
                result[pos] = (byte) c;
            } else {
                if (b == '_')
                    result[pos] = ' ';
                else
                    result[pos] = b;
            }
            ++pos;
        }
        return new String(result, UTF8);
    }

    public static String decodeURI(String str) {
        return decode(str.getBytes(), (byte) '%', false);
    }

    public static String decodeIdentifier(String str) {
        return decode(str.getBytes(), (byte) '$', true);
    }
    
}