/*
 * Copyright (c) 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 sun.nio.fs;

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Map;
import java.util.HashMap;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.List;

/**
 * File type detector that uses a file extension to look up its MIME type
 * by checking the mappings recorded in a mime.types file.
 */

class MimeTypesFileTypeDetector extends AbstractFileTypeDetector {

    private Map<String, String> mimeTypeMap;

    private final Path mimeTypesFile;

    public MimeTypesFileTypeDetector(final Path filePath) {
        mimeTypesFile = filePath;
    }

    @Override
    protected String implProbeContentType(final Path file) {
        if (file == null || file.getFileName() == null) {
            return null;
        }

        final String extension = getExtension(file.getFileName().toString());
        if (extension.isEmpty()) {
            return null;
        }

        loadMimeTypes();
        if (mimeTypeMap == null || mimeTypeMap.isEmpty()) {
            return null;
        }

        String mimeType = null;
        // Case-sensitive search
        String ext = extension;
        do {
            mimeType = mimeTypeMap.get(ext);
            if (mimeType == null) {
                ext = getExtension(ext);
            }
        } while (mimeType == null && !ext.isEmpty());

        // Case-insensitive search if no mime type is found
        if (mimeType == null) {
            ext = extension;
            do {
                for (String key : mimeTypeMap.keySet()) {
                    if (ext.equalsIgnoreCase(key)) {
                        mimeType = mimeTypeMap.get(key);
                        break;
                    }
                }
                if (mimeType == null) {
                    ext = getExtension(ext);
                }
            } while (mimeType == null && !ext.isEmpty());
        }

        return mimeType;
    }

    // Get the extension of a file name.
    private static String getExtension(final String name) {
        String ext = "";
        if (name != null && !name.isEmpty()) {
            int dot = name.indexOf('.');
            if ((dot >= 0) && (dot < name.length() - 1)) {
                ext = name.substring(dot + 1);
            }
        }
        return ext;
    }

    // Parse the mime types file, and store the type-extension
    // mappings into mimeTypeMap.
    private void loadMimeTypes() {
        if (mimeTypeMap != null || mimeTypesFile == null || 
                !mimeTypesFile.toFile().isFile())
        {
            return;
        }

        List<String> lines = null;
        try {
            lines = Files.readAllLines(mimeTypesFile, Charset.defaultCharset());
        } catch (IOException|SecurityException ex) {
        }

        if (lines != null && !lines.isEmpty()) {
            mimeTypeMap = new HashMap<>(lines.size());
            String command = "";
            for (String line : lines) {
                command += line;
                if (command.endsWith("\\")) {
                    command = command.substring(0, command.length() - 1);
                    continue;
                }
                parseMimeCommand(command);
                command = "";
            }
            if (!command.isEmpty()) {
                parseMimeCommand(command);
            }
        }
    }

    /*
     * Parse a mime-types command, which can have the following formats:
     * 1) Simple space-delimited format
     * image/jpeg   jpeg jpg jpe JPG
     *
     * 2) Netscape key-value format
     * type=application/x-java-jnlp-file desc="Java Web Start" exts="jnlp"
     * or
     * type=text/html exts=htm,html
     */
    private void parseMimeCommand(String command) {
        command = command.trim();
        if (command.isEmpty() || command.charAt(0) == '#') {
            return;
        }

        command = command.replaceAll("\\s*#.*", "");
        int equalIdx = command.indexOf('=');
        if (equalIdx > 0) {
            // Parse a mime-types command having the key-value format
            final String TypeSign = "type=";
            String typeRegex = "\\b" + TypeSign +
                    "(\"\\p{Graph}+?/\\p{Graph}+?\"|\\p{Graph}+/\\p{Graph}+\\b)";
            Pattern typePattern = Pattern.compile(typeRegex);
            Matcher typeMatcher = typePattern.matcher(command);

            if (typeMatcher.find()) {
                String type = typeMatcher.group().substring(TypeSign.length());
                if (type.charAt(0) == '"') {
                    type = type.substring(1, type.length() - 1);
                }

                final String ExtSign = "exts=";
                String extRegex = "\\b" + ExtSign +
                        "(\"[\\p{Graph}|\\p{Blank}]+?\"|\\p{Graph}+\\b)";
                Pattern extPattern = Pattern.compile(extRegex);
                Matcher extMatcher = extPattern.matcher(command);

                if (extMatcher.find()) {
                    String exts = extMatcher.group().substring(ExtSign.length());
                    if (exts.charAt(0) == '"') {
                        exts = exts.substring(1, exts.length() - 1);
                    }
                    String[] extList = exts.split("[\\p{Blank}|\\p{Punct}]+");
                    for (String ext : extList) {
                        putIfAbsent(ext, type);
                    }
                }
            }
        } else {
            // Parse a mime-types command having the space-delimited format
            String[] elements = command.split("\\s+");
            int i = 1;
            while (i < elements.length) {
                putIfAbsent(elements[i++], elements[0]);
            }
        }
    }

    private void putIfAbsent(String key, String value) {
        if (key != null && !key.isEmpty() &&
                value != null && !value.isEmpty() &&
                !mimeTypeMap.containsKey(key))
        {
            mimeTypeMap.put(key, value);
        }
    }
}