/*

 * Copyright (c) 2010, 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 jdk.nashorn.internal.runtime;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.IOError;

import java.io.IOException;

import java.io.InputStream;

import java.io.Reader;

import java.net.MalformedURLException;

import java.net.URISyntaxException;

import java.net.URL;

import java.nio.charset.Charset;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.Arrays;

import java.util.Objects;

import jdk.nashorn.internal.parser.Token;

/**

 * Source objects track the origin of JavaScript entities.

 *

 */

public final class Source {

    /**

     * Descriptive name of the source as supplied by the user. Used for error

     * reporting to the user. For example, SyntaxError will use this to print message.

     * Used to implement __FILE__. Also used for SourceFile in .class for debugger usage.

     */

    private final String name;

    /**

     * Base directory the File or base part of the URL. Used to implement __DIR__.

     * Used to load scripts relative to the 'directory' or 'base' URL of current script.

     * This will be null when it can't be computed.

     */

    private final String base;

    /** Cached source content. */

    private final char[] content;

    /** Length of source content. */

    private final int length;

    /** Cached hash code */

    private int hash;

    private static final int BUFSIZE = 8 * 1024;

    private Source(final String name, final String base, final char[] content) {

        this.name    = name;

        this.base    = base;

        this.content = content;

        this.length  = content.length;

    }

    /**

     * Constructor

     *

     * @param name    source name

     * @param content contents as char array

     */

    public Source(final String name, final char[] content) {

        this(name, baseName(name, null), content);

    }

    /**

     * Constructor

     *

     * @param name    source name

     * @param content contents as string

     */

    public Source(final String name, final String content) {

        this(name, content.toCharArray());

    }

    /**

     * Constructor

     *

     * @param name  source name

     * @param url   url from which source can be loaded

     *

     * @throws IOException if source cannot be loaded

     */

    public Source(final String name, final URL url) throws IOException {

        this(name, baseURL(url, null), readFully(url.openStream()));

    }

    /**

     * Constructor

     *

     * @param name  source name

     * @param file  file from which source can be loaded

     *

     * @throws IOException if source cannot be loaded

     */

    public Source(final String name, final File file) throws IOException {

        this(name, dirName(file, null), readFully(file));

    }

    @Override

    public boolean equals(final Object obj) {

        if (this == obj) {

            return true;

        }

        if (!(obj instanceof Source)) {

            return false;

        }

        final Source src = (Source)obj;

        // Only compare content as a last resort measure

        return length == src.length && Objects.equals(name, src.name) && Arrays.equals(content, src.content);

    }

    @Override

    public int hashCode() {

        int h = hash;

        if (h == 0) {

            h = hash = Arrays.hashCode(content) ^ Objects.hashCode(name);

        }

        return h;

    }

    /**

     * Fetch source content.

     * @return Source content.

     */

    public String getString() {

        return new String(content, 0, length);

    }

    /**

     * Get the user supplied name of this script.

     * @return User supplied source name.

     */

    public String getName() {

        return name;

    }

    /**

     * Get the "directory" part of the file or "base" of the URL.

     * @return base of file or URL.

     */

    public String getBase() {

        return base;

    }

    /**

     * Fetch a portion of source content.

     * @param start start index in source

     * @param len length of portion

     * @return Source content portion.

     */

    public String getString(final int start, final int len) {

        return new String(content, start, len);

    }

    /**

     * Fetch a portion of source content associated with a token.

     * @param token Token descriptor.

     * @return Source content portion.

     */

    public String getString(final long token) {

        final int start = Token.descPosition(token);

        final int len = Token.descLength(token);

        return new String(content, start, len);

    }

    /**

     * Fetch a portion of source content associated with a range of tokens.

     * @param startTokenDesc Starting token descriptor.

     * @param endTokenDesc   Ending token descriptor.

     * @return Source content portion.

     */

    public String getString(final long startTokenDesc, final long endTokenDesc) {

        final int start = Token.descPosition(startTokenDesc);

        final int end   = Token.descPosition(endTokenDesc) + Token.descLength(endTokenDesc);

        return new String(content, start, end - start);

    }

    /**

     * Find the beginning of the line containing position.

     * @param position Index to offending token.

     * @return Index of first character of line.

     */

    private int findBOLN(final int position) {

        for (int i = position - 1; i > 0; i--) {

            final char ch = content[i];

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

                return i + 1;

            }

        }

        return 0;

    }

    /**

     * Find the end of the line containing position.

     * @param position Index to offending token.

     * @return Index of last character of line.

     */

    private int findEOLN(final int position) {

         for (int i = position; i < length; i++) {

            final char ch = content[i];

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

                return i - 1;

            }

        }

        return length - 1;

    }

    /**

     * Return line number of character position.

     * @param position Position of character in source content.

     * @return Line number.

     */

    public int getLine(final int position) {

        // Line count starts at 1.

        int line = 1;

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

            final char ch = content[i];

            // Works for both \n and \r\n.

            if (ch == '\n') {

                line++;

            }

        }

        return line;

    }

    /**

     * Return column number of character position.

     * @param position Position of character in source content.

     * @return Column number.

     */

    public int getColumn(final int position) {

        // TODO - column needs to account for tabs.

        return position - findBOLN(position);

    }

    /**

     * Return line text including character position.

     * @param position Position of character in source content.

     * @return Line text.

     */

    public String getSourceLine(final int position) {

        // Find end of previous line.

        final int first = findBOLN(position);

        // Find end of this line.

        final int last = findEOLN(position);

        return new String(content, first, last - first + 1);

    }

    /**

     * Get the content of this source as a char array

     * @return content

     */

    public char[] getContent() {

        return content;

    }

    /**

     * Get the length in chars for this source

     * @return length

     */

    public int getLength() {

        return length;

    }

    /**

     * Read all of the source until end of file. Return it as char array

     *

     * @param reader  reader opened to source stream

     * @return source as content

     *

     * @throws IOException if source could not be read

     */

    public static char[] readFully(final Reader reader) throws IOException {

        final char[]        arr = new char[BUFSIZE];

        final StringBuilder sb  = new StringBuilder();

        try {

            int numChars;

            while ((numChars = reader.read(arr, 0, arr.length)) > 0) {

                sb.append(arr, 0, numChars);

            }

        } finally {

            reader.close();

        }

        return sb.toString().toCharArray();

    }

    /**

     * Read all of the source until end of file. Return it as char array

     *

     * @param file  source file

     * @return source as content

     *

     * @throws IOException if source could not be read

     */

    public static char[] readFully(final File file) throws IOException {

        if (!file.isFile()) {

            throw new IOException(file + " is not a file"); //TODO localize?

        }

        return byteToCharArray(Files.readAllBytes(file.toPath()));

    }

    /**

     * Get the base url. This is currently used for testing only

     * @param url a URL

     * @return base URL for url

     */

    public static String baseURL(final URL url) {

        return baseURL(url, null);

    }

    private static String baseURL(final URL url, final String defaultValue) {

        if (url.getProtocol().equals("file")) {

            try {

                final Path path = Paths.get(url.toURI());

                final Path parent = path.getParent();

                return (parent != null) ? (parent + File.separator) : defaultValue;

            } catch (final SecurityException | URISyntaxException | IOError e) {

                return defaultValue;

            }

        }

        // FIXME: is there a better way to find 'base' URL of a given URL?

        String path = url.getPath();

        if (path.isEmpty()) {

            return defaultValue;

        }

        path = path.substring(0, path.lastIndexOf('/') + 1);

        final int port = url.getPort();

        try {

            return new URL(url.getProtocol(), url.getHost(), port, path).toString();

        } catch (final MalformedURLException e) {

            return defaultValue;

        }

    }

    private static String dirName(final File file, final String defaultValue) {

        final String res = file.getParent();

        return (res != null)? (res + File.separator) : defaultValue;

    }

    // fake directory like name

    private static String baseName(final String name, final String defaultValue) {

        int idx = name.lastIndexOf('/');

        if (idx == -1) {

            idx = name.lastIndexOf('\\');

        }

        return (idx != -1)? name.substring(0, idx + 1) : defaultValue;

    }

    private static char[] readFully(final InputStream is) throws IOException {

        return byteToCharArray(readBytes(is));

    }

    private static char[] byteToCharArray(final byte[] bytes) {

        Charset cs = StandardCharsets.UTF_8;

        int start = 0;

        // BOM detection.

        if (bytes.length > 1 && bytes[0] == (byte)0xFE && bytes[1] == (byte)0xFF) {

            start = 2;

            cs = StandardCharsets.UTF_16BE;

        } else if (bytes.length > 1 && bytes[0] == (byte)0xFF && bytes[1] == (byte)0xFE) {

            start = 2;

            cs = StandardCharsets.UTF_16LE;

        } else if (bytes.length > 2 && bytes[0] == (byte)0xEF && bytes[1] == (byte)0xBB && bytes[2] == (byte)0xBF) {

            start = 3;

            cs = StandardCharsets.UTF_8;

        } else if (bytes.length > 3 && bytes[0] == (byte)0xFF && bytes[1] == (byte)0xFE && bytes[2] == 0 && bytes[3] == 0) {

            start = 4;

            cs = Charset.forName("UTF-32LE");

        } else if (bytes.length > 3 && bytes[0] == 0 && bytes[1] == 0 && bytes[2] == (byte)0xFE && bytes[3] == (byte)0xFF) {

            start = 4;

            cs = Charset.forName("UTF-32BE");

        }

        return new String(bytes, start, bytes.length - start, cs).toCharArray();

    }

    static byte[] readBytes(final InputStream is) throws IOException {

        final byte[] arr = new byte[BUFSIZE];

        try {

            try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {

                int numBytes;

                while ((numBytes = is.read(arr, 0, arr.length)) > 0) {

                    buf.write(arr, 0, numBytes);

                }

                return buf.toByteArray();

            }

        } finally {

            is.close();

        }

    }

    @Override

    public String toString() {

        return getName();

    }

}