/*

 * Copyright (c) 1999, 2012, 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.

 */

package com.sun.tools.javac.util;

import java.util.BitSet;

import static com.sun.tools.javac.util.LayoutCharacters.*;

/** A class that defines source code positions as simple character

 *  offsets from the beginning of the file. The first character

 *  is at position 0.

 *

 *  Support is also provided for (line,column) coordinates, but tab

 *  expansion is optional and no Unicode excape translation is considered.

 *  The first character is at location (1,1).

 *

 *  <p><b>This is NOT part of any supported API.

 *  If you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class Position {

    public static final int NOPOS        = -1;

    public static final int FIRSTPOS     = 0;

    public static final int FIRSTLINE    = 1;

    public static final int FIRSTCOLUMN  = 1;

    public static final int LINESHIFT    = 10;

    public static final int MAXCOLUMN    = (1<<LINESHIFT) - 1;

    public static final int MAXLINE      = (1<<(Integer.SIZE-LINESHIFT)) - 1;

    public static final int MAXPOS       = Integer.MAX_VALUE;

    /**

     * This is class is not supposed to be instantiated.

     */

    private Position() {}

    /** A two-way map between line/column numbers and positions,

     *  derived from a scan done at creation time.  Tab expansion is

     *  optionally supported via a character map.  Text content

     *  is not retained.

     *<p>

     *  Notes:  The first character position FIRSTPOS is at

     *  (FIRSTLINE,FIRSTCOLUMN).  No account is taken of Unicode escapes.

     *

     * @param   src         Source characters

     * @param   max         Number of characters to read

     * @param   expandTabs  If true, expand tabs when calculating columns

     */

    public static LineMap makeLineMap(char[] src, int max, boolean expandTabs) {

        LineMapImpl lineMap = expandTabs ?

            new LineTabMapImpl(max) : new LineMapImpl();

        lineMap.build(src, max);

        return lineMap;

    }

    /** Encode line and column numbers in an integer as:

     *  {@code line-number << LINESHIFT + column-number }.

     *  {@link Position#NOPOS} represents an undefined position.

     *

     * @param  line  number of line (first is 1)

     * @param  col   number of character on line (first is 1)

     * @return       an encoded position or {@link Position#NOPOS}

     *               if the line or column number is too big to

     *               represent in the encoded format

     * @throws IllegalArgumentException if line or col is less than 1

     */

    public static int encodePosition(int line, int col) {

        if (line < 1)

            throw new IllegalArgumentException("line must be greater than 0");

        if (col < 1)

            throw new IllegalArgumentException("column must be greater than 0");

        if (line > MAXLINE || col > MAXCOLUMN) {

            return NOPOS;

        }

        return (line << LINESHIFT) + col;

    }

    public static interface LineMap extends com.sun.source.tree.LineMap {

        /** Find the start position of a line.

         *

         * @param line number of line (first is 1)

         * @return     position of first character in line

         * @throws  ArrayIndexOutOfBoundsException

         *           if {@code lineNumber < 1}

         *           if {@code lineNumber > no. of lines}

         */

        int getStartPosition(int line);

        /** Find the position corresponding to a (line,column).

         *

         * @param   line    number of line (first is 1)

         * @param   column  number of character on line (first is 1)

         *

         * @return  position of character

         * @throws  ArrayIndexOutOfBoundsException

         *           if {@code line < 1}

         *           if {@code line > no. of lines}

         */

        int getPosition(int line, int column);

        /** Find the line containing a position; a line termination

         * character is on the line it terminates.

         *

         * @param   pos  character offset of the position

         * @return the line number on which pos occurs (first line is 1)

         */

        int getLineNumber(int pos);

        /** Find the column for a character position.

         *  Note:  this method does not handle tab expansion.

         *  If tab expansion is needed, use a LineTabMap instead.

         *

         * @param  pos   character offset of the position

         * @return       the column number at which pos occurs

         */

        int getColumnNumber(int pos);

    }

    static class LineMapImpl implements LineMap {

        protected int[] startPosition; // start position of each line

        protected LineMapImpl() {}

        protected void build(char[] src, int max) {

            int c = 0;

            int i = 0;

            int[] linebuf = new int[max];

            while (i < max) {

                linebuf[c++] = i;

                do {

                    char ch = src[i];

                    if (ch == '\r' || ch == '\n') {

                        if (ch == '\r' && (i+1) < max && src[i+1] == '\n')

                            i += 2;

                        else

                            ++i;

                        break;

                    }

                    else if (ch == '\t')

                        setTabPosition(i);

                } while (++i < max);

            }

            this.startPosition = new int[c];

            System.arraycopy(linebuf, 0, startPosition, 0, c);

        }

        public int getStartPosition(int line) {

            return startPosition[line - FIRSTLINE];

        }

        public long getStartPosition(long line) {

            return getStartPosition(longToInt(line));

        }

        public int getPosition(int line, int column) {

            return startPosition[line - FIRSTLINE] + column - FIRSTCOLUMN;

        }

        public long getPosition(long line, long column) {

            return getPosition(longToInt(line), longToInt(column));

        }

        // Cache of last line number lookup

        private int lastPosition = Position.FIRSTPOS;

        private int lastLine = Position.FIRSTLINE;

        public int getLineNumber(int pos) {

            if (pos == lastPosition) {

                return lastLine;

            }

            lastPosition = pos;

            int low = 0;

            int high = startPosition.length-1;

            while (low <= high) {

                int mid = (low + high) >> 1;

                int midVal = startPosition[mid];

                if (midVal < pos)

                    low = mid + 1;

                else if (midVal > pos)

                    high = mid - 1;

                else {

                    lastLine = mid + 1; // pos is at beginning of this line

                    return lastLine;

                }

            }

            lastLine = low;

            return lastLine;  // pos is on this line

        }

        public long getLineNumber(long pos) {

            return getLineNumber(longToInt(pos));

        }

        public int getColumnNumber(int pos) {

            return pos - startPosition[getLineNumber(pos) - FIRSTLINE] + FIRSTCOLUMN;

        }

        public long getColumnNumber(long pos) {

            return getColumnNumber(longToInt(pos));

        }

        private static int longToInt(long longValue) {

            int intValue = (int)longValue;

            if (intValue != longValue)

                throw new IndexOutOfBoundsException();

            return intValue;

        }

        protected void setTabPosition(int offset) {}

    }

    /**

     * A LineMap that handles tab expansion correctly.  The cost is

     * an additional bit per character in the source array.

     */

    public static class LineTabMapImpl extends LineMapImpl {

        private BitSet tabMap;       // bits set for tab positions.

        public LineTabMapImpl(int max) {

            super();

            tabMap = new BitSet(max);

        }

        protected void setTabPosition(int offset) {

            tabMap.set(offset);

        }

        public int getColumnNumber(int pos) {

            int lineStart = startPosition[getLineNumber(pos) - FIRSTLINE];

            int column = 0;

            for (int bp = lineStart; bp < pos; bp++) {

                if (tabMap.get(bp))

                    column = (column / TabInc * TabInc) + TabInc;

                else

                    column++;

            }

            return column + FIRSTCOLUMN;

        }

        public int getPosition(int line, int column) {

            int pos = startPosition[line - FIRSTLINE];

            column -= FIRSTCOLUMN;

            int col = 0;

            while (col < column) {

                pos++;

                if (tabMap.get(pos))

                    col = (col / TabInc * TabInc) + TabInc;

                else

                    col++;

            }

            return pos;

        }

    }

}