package org.simantics.scl.compiler.markdown.internal;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;

import gnu.trove.map.hash.TCharObjectHashMap;

public class HtmlEscape {

    private static final Charset UTF8 = Charset.forName("UTF-8");
    
    private static final TCharObjectHashMap<String> ESCAPED_CHARS = new TCharObjectHashMap<String>();
    static {
        ESCAPED_CHARS.put('<', "&lt;");
        ESCAPED_CHARS.put('>', "&gt;");
        ESCAPED_CHARS.put('"', "&quot;");
        ESCAPED_CHARS.put('&', "&amp;");
    }
    
    public static CharSequence escape(CharSequence text) {
        int length = text.length();
        for(int i=0;i<length;++i) {
            char c = text.charAt(i);
            String esc = ESCAPED_CHARS.get(c);
            if(esc != null) {
                StringBuilder b = new StringBuilder(length+16);
                b.append(text, 0, i);
                b.append(esc);
                for(++i;i<length;++i) {
                    c = text.charAt(i);
                    esc = ESCAPED_CHARS.get(c);
                    if(esc != null)
                        b.append(esc);
                    else
                        b.append(c);
                }
                return b.toString();
            }
        }
        return text;
    }       
    
    public static StringBuilder escapeURL(CharSequence str) {
        StringBuilder result = new StringBuilder();
        for(int i=0;i<str.length();++i) {
            char c = str.charAt(i);
            if(c < 0 || c >= 128) {
                ByteBuffer bs = UTF8.encode(CharBuffer.wrap(new char[] {c}));
                for(int j=0;j<bs.limit();++j)
                    result.append(percentEncode(bs.get()));
            }
            else if(URL_CAN_CONTAIN[(int)c])
                result.append(c);
            else if(c == '&')
                result.append("&amp;");
            else
                result.append(percentEncode(c));
        }
        return result;
    }
    
    private static String percentEncode(int c) {
        if(c < 0)
            c += 256;
        String hex = Integer.toHexString(c).toUpperCase();
        if(hex.length() == 1)
            return "%0" + hex;
        else
            return "%" + hex;
    }
    
    private static final boolean[] URL_CAN_CONTAIN = new boolean[] {
        false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
        false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
        false, true, false, true, true, true, false, false, true, true, true, true, true, true, true, true,
        true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, true,
        true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true,
        true, true, true, true, true, true, true, true, true, true, true, false, false, false, false, true,
        false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true,
        true, true, true, true, true, true, true, true, true, true, true, false, false, false, false, false,
    };
}