/*

 * 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.io.IOException;

import java.lang.ref.SoftReference;

import java.nio.CharBuffer;

import javax.tools.JavaFileObject;

import com.sun.tools.javac.file.JavacFileManager;

import com.sun.tools.javac.tree.EndPosTable;

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

/**

 * A simple abstraction of a source file, as needed for use in a diagnostic message.

 * Provides access to the line and position in a line for any given character offset.

 *

 *  <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 DiagnosticSource {

    /* constant DiagnosticSource to be used when sourcefile is missing */

    public static final DiagnosticSource NO_SOURCE = new DiagnosticSource() {

        @Override

        protected boolean findLine(int pos) {

            return false;

        }

    };

    public DiagnosticSource(JavaFileObject fo, AbstractLog log) {

        this.fileObject = fo;

        this.log = log;

    }

    private DiagnosticSource() {}

    /** Return the underlying file object handled by this

     *  DiagnosticSource object.

     */

    public JavaFileObject getFile() {

        return fileObject;

    }

    /** Return the one-based line number associated with a given pos

     * for the current source file.  Zero is returned if no line exists

     * for the given position.

     */

    public int getLineNumber(int pos) {

        try {

            if (findLine(pos)) {

                return line;

            }

            return 0;

        } finally {

            buf = null;

        }

    }

    /** Return the one-based column number associated with a given pos

     * for the current source file.  Zero is returned if no column exists

     * for the given position.

     */

    public int getColumnNumber(int pos, boolean expandTabs) {

        try {

            if (findLine(pos)) {

                int column = 0;

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

                    if (bp >= bufLen) {

                        return 0;

                    }

                    if (buf[bp] == '\t' && expandTabs) {

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

                    } else {

                        column++;

                    }

                }

                return column + 1; // positions are one-based

            }

            return 0;

        } finally {

            buf = null;

        }

    }

    /** Return the content of the line containing a given pos.

     */

    public String getLine(int pos) {

        try {

            if (!findLine(pos))

                return null;

            int lineEnd = lineStart;

            while (lineEnd < bufLen && buf[lineEnd] != CR && buf[lineEnd] != LF)

                lineEnd++;

            if (lineEnd - lineStart == 0)

                return null;

            return new String(buf, lineStart, lineEnd - lineStart);

        } finally {

            buf = null;

        }

    }

    public EndPosTable getEndPosTable() {

        return endPosTable;

    }

    public void setEndPosTable(EndPosTable t) {

        if (endPosTable != null && endPosTable != t)

            throw new IllegalStateException("endPosTable already set");

        endPosTable = t;

    }

    /** Find the line in the buffer that contains the current position

     * @param pos      Character offset into the buffer

     */

    protected boolean findLine(int pos) {

        if (pos == Position.NOPOS)

            return false;

        try {

            // try and recover buffer from soft reference cache

            if (buf == null && refBuf != null)

                buf = refBuf.get();

            if (buf == null) {

                buf = initBuf(fileObject);

                lineStart = 0;

                line = 1;

            } else if (lineStart > pos) { // messages don't come in order

                lineStart = 0;

                line = 1;

            }

            int bp = lineStart;

            while (bp < bufLen && bp < pos) {

                switch (buf[bp++]) {

                case CR:

                    if (bp < bufLen && buf[bp] == LF) bp++;

                    line++;

                    lineStart = bp;

                    break;

                case LF:

                    line++;

                    lineStart = bp;

                    break;

                }

            }

            return bp <= bufLen;

        } catch (IOException e) {

            log.directError("source.unavailable");

            buf = new char[0];

            return false;

        }

    }

    protected char[] initBuf(JavaFileObject fileObject) throws IOException {

        char[] buf;

        CharSequence cs = fileObject.getCharContent(true);

        if (cs instanceof CharBuffer) {

            CharBuffer cb = (CharBuffer) cs;

            buf = JavacFileManager.toArray(cb);

            bufLen = cb.limit();

        } else {

            buf = cs.toString().toCharArray();

            bufLen = buf.length;

        }

        refBuf = new SoftReference<char[]>(buf);

        return buf;

    }

    /** The underlying file object. */

    protected JavaFileObject fileObject;

    protected EndPosTable endPosTable;

    /** A soft reference to the content of the file object. */

    protected SoftReference<char[]> refBuf;

    /** A temporary hard reference to the content of the file object. */

    protected char[] buf;

    /** The length of the content. */

    protected int bufLen;

    /** The start of a line found by findLine. */

    protected int lineStart;

    /** The line number of a line found by findLine. */

    protected int line;

    /** A log for reporting errors, such as errors accessing the content. */

    protected AbstractLog log;

}