/*

 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.util.Iterator;

import java.util.Locale;

import java.util.NoSuchElementException;

/* This is useful for the nightmare of parsing multi-part HTTP/RFC822 headers

 * sensibly:

 * From a String like: 'timeout=15, max=5'

 * create an array of Strings:

 * { {"timeout", "15"},

 *   {"max", "5"}

 * }

 * From one like: 'Basic Realm="FuzzFace" Foo="Biz Bar Baz"'

 * create one like (no quotes in literal):

 * { {"basic", null},

 *   {"realm", "FuzzFace"}

 *   {"foo", "Biz Bar Baz"}

 * }

 * keys are converted to lower case, vals are left as is....

 */

class HeaderParser {

    /* table of key/val pairs */

    String raw;

    String[][] tab;

    int nkeys;

    int asize = 10; // initial size of array is 10

    public HeaderParser(String raw) {

        this.raw = raw;

        tab = new String[asize][2];

        parse();

    }

//    private HeaderParser () { }

//    /**

//     * Creates a new HeaderParser from this, whose keys (and corresponding

//     * values) range from "start" to "end-1"

//     */

//    public HeaderParser subsequence(int start, int end) {

//        if (start == 0 && end == nkeys) {

//            return this;

//        }

//        if (start < 0 || start >= end || end > nkeys) {

//            throw new IllegalArgumentException("invalid start or end");

//        }

//        HeaderParser n = new HeaderParser();

//        n.tab = new String [asize][2];

//        n.asize = asize;

//        System.arraycopy (tab, start, n.tab, 0, (end-start));

//        n.nkeys= (end-start);

//        return n;

//    }

    private void parse() {

        if (raw != null) {

            raw = raw.trim();

            char[] ca = raw.toCharArray();

            int beg = 0, end = 0, i = 0;

            boolean inKey = true;

            boolean inQuote = false;

            int len = ca.length;

            while (end < len) {

                char c = ca[end];

                if ((c == '=') && !inQuote) { // end of a key

                    tab[i][0] = new String(ca, beg, end-beg).toLowerCase(Locale.US);

                    inKey = false;

                    end++;

                    beg = end;

                } else if (c == '\"') {

                    if (inQuote) {

                        tab[i++][1]= new String(ca, beg, end-beg);

                        inQuote=false;

                        do {

                            end++;

                        } while (end < len && (ca[end] == ' ' || ca[end] == ','));

                        inKey=true;

                        beg=end;

                    } else {

                        inQuote=true;

                        end++;

                        beg=end;

                    }

                } else if (c == ' ' || c == ',') { // end key/val, of whatever we're in

                    if (inQuote) {

                        end++;

                        continue;

                    } else if (inKey) {

                        tab[i++][0] = (new String(ca, beg, end-beg)).toLowerCase(Locale.US);

                    } else {

                        tab[i++][1] = (new String(ca, beg, end-beg));

                    }

                    while (end < len && (ca[end] == ' ' || ca[end] == ',')) {

                        end++;

                    }

                    inKey = true;

                    beg = end;

                } else {

                    end++;

                }

                if (i == asize) {

                    asize = asize * 2;

                    String[][] ntab = new String[asize][2];

                    System.arraycopy (tab, 0, ntab, 0, tab.length);

                    tab = ntab;

                }

            }

            // get last key/val, if any

            if (--end > beg) {

                if (!inKey) {

                    if (ca[end] == '\"') {

                        tab[i++][1] = (new String(ca, beg, end-beg));

                    } else {

                        tab[i++][1] = (new String(ca, beg, end-beg+1));

                    }

                } else {

                    tab[i++][0] = (new String(ca, beg, end-beg+1)).toLowerCase();

                }

            } else if (end == beg) {

                if (!inKey) {

                    if (ca[end] == '\"') {

                        tab[i++][1] = String.valueOf(ca[end-1]);

                    } else {

                        tab[i++][1] = String.valueOf(ca[end]);

                    }

                } else {

                    tab[i++][0] = String.valueOf(ca[end]).toLowerCase();

                }

            }

            nkeys=i;

        }

    }

    public String findKey(int i) {

        if (i < 0 || i > asize) {

            return null;

        }

        return tab[i][0];

    }

    public String findValue(int i) {

        if (i < 0 || i > asize) {

            return null;

        }

        return tab[i][1];

    }

    public String findValue(String key) {

        return findValue(key, null);

    }

    public String findValue(String k, String Default) {

        if (k == null) {

            return Default;

        }

        k = k.toLowerCase(Locale.US);

        for (int i = 0; i < asize; ++i) {

            if (tab[i][0] == null) {

                return Default;

            } else if (k.equals(tab[i][0])) {

                return tab[i][1];

            }

        }

        return Default;

    }

    class ParserIterator implements Iterator<String> {

        int index;

        boolean returnsValue; // or key

        ParserIterator (boolean returnValue) {

            returnsValue = returnValue;

        }

        @Override

        public boolean hasNext () {

            return index<nkeys;

        }

        @Override

        public String next () {

            if (index >= nkeys) {

                throw new NoSuchElementException();

            }

            return tab[index++][returnsValue?1:0];

        }

    }

    public Iterator<String> keys () {

        return new ParserIterator (false);

    }

//    public Iterator<String> values () {

//        return new ParserIterator (true);

//    }

    @Override

    public String toString () {

        Iterator<String> k = keys();

        StringBuilder sb = new StringBuilder();

        sb.append("{size=").append(asize).append(" nkeys=").append(nkeys)

                .append(' ');

        for (int i=0; k.hasNext(); i++) {

            String key = k.next();

            String val = findValue (i);

            if (val != null && "".equals (val)) {

                val = null;

            }

            sb.append(" {").append(key).append(val == null ? "" : "," + val)

                    .append('}');

            if (k.hasNext()) {

                sb.append (',');

            }

        }

        sb.append (" }");

        return sb.toString();

    }

//    public int findInt(String k, int Default) {

//        try {

//            return Integer.parseInt(findValue(k, String.valueOf(Default)));

//        } catch (Throwable t) {

//            return Default;

//        }

//    }

}