/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.email.mail.internet;

import com.android.email.Email;
import com.android.email.mail.Body;
import com.android.email.mail.BodyPart;
import com.android.email.mail.Message;
import com.android.email.mail.MessagingException;
import com.android.email.mail.Multipart;
import com.android.email.mail.Part;

import org.apache.commons.io.IOUtils;
import org.apache.james.mime4j.decoder.Base64InputStream;
import org.apache.james.mime4j.decoder.DecoderUtil;
import org.apache.james.mime4j.decoder.QuotedPrintableInputStream;
import org.apache.james.mime4j.util.CharsetUtil;

import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.regex.Pattern;

public class MimeUtility {
    public static String unfold(String s) {
        if (s == null) {
            return null;
        }
        return s.replaceAll("\r|\n", "");
    }

    public static String decode(String s) {
        if (s == null) {
            return null;
        }
        return DecoderUtil.decodeEncodedWords(s);
    }

    public static String unfoldAndDecode(String s) {
        return decode(unfold(s));
    }

    // TODO implement proper foldAndEncode
    public static String foldAndEncode(String s) {
        return s;
    }

    /**
     * Returns the named parameter of a header field. If name is null the first
     * parameter is returned, or if there are no additional parameters in the
     * field the entire field is returned. Otherwise the named parameter is
     * searched for in a case insensitive fashion and returned. If the parameter
     * cannot be found the method returns null.
     *
     * @param header
     * @param name
     * @return
     */
    public static String getHeaderParameter(String header, String name) {
        if (header == null) {
            return null;
        }
        header = header.replaceAll("\r|\n", "");
        String[] parts = header.split(";");
        if (name == null) {
            return parts[0];
        }
        for (String part : parts) {
            if (part.trim().toLowerCase().startsWith(name.toLowerCase())) {
                String parameter = part.split("=", 2)[1].trim();
                if (parameter.startsWith("\"") && parameter.endsWith("\"")) {
                    return parameter.substring(1, parameter.length() - 1);
                }
                else {
                    return parameter;
                }
            }
        }
        return null;
    }

    public static Part findFirstPartByMimeType(Part part, String mimeType)
            throws MessagingException {
        if (part.getBody() instanceof Multipart) {
            Multipart multipart = (Multipart)part.getBody();
            for (int i = 0, count = multipart.getCount(); i < count; i++) {
                BodyPart bodyPart = multipart.getBodyPart(i);
                Part ret = findFirstPartByMimeType(bodyPart, mimeType);
                if (ret != null) {
                    return ret;
                }
            }
        }
        else if (part.getMimeType().equalsIgnoreCase(mimeType)) {
            return part;
        }
        return null;
    }

    public static Part findPartByContentId(Part part, String contentId) throws Exception {
        if (part.getBody() instanceof Multipart) {
            Multipart multipart = (Multipart)part.getBody();
            for (int i = 0, count = multipart.getCount(); i < count; i++) {
                BodyPart bodyPart = multipart.getBodyPart(i);
                Part ret = findPartByContentId(bodyPart, contentId);
                if (ret != null) {
                    return ret;
                }
            }
        }
        String cid = part.getContentId();
        if (contentId.equals(cid)) {
            return part;
        }
        return null;
    }

    /**
     * Reads the Part's body and returns a String based on any charset conversion that needed
     * to be done.
     * @param part
     * @return
     * @throws IOException
     */
    public static String getTextFromPart(Part part) {
        try {
            if (part != null && part.getBody() != null) {
                InputStream in = part.getBody().getInputStream();
                String mimeType = part.getMimeType();
                if (mimeType != null && MimeUtility.mimeTypeMatches(mimeType, "text/*")) {
                    /*
                     * Now we read the part into a buffer for further processing. Because
                     * the stream is now wrapped we'll remove any transfer encoding at this point.
                     */
                    ByteArrayOutputStream out = new ByteArrayOutputStream();
                    IOUtils.copy(in, out);

                    byte[] bytes = out.toByteArray();
                    in.close();
                    out.close();

                    String charset = getHeaderParameter(part.getContentType(), "charset");
                    /*
                     * We've got a text part, so let's see if it needs to be processed further.
                     */
                    if (charset != null) {
                        /*
                         * See if there is conversion from the MIME charset to the Java one.
                         */
                        charset = CharsetUtil.toJavaCharset(charset);
                    }
                    if (charset != null) {
                        /*
                         * We've got a charset encoding, so decode using it.
                         */
                        return new String(bytes, 0, bytes.length, charset);
                    }
                    else {
                        /*
                         * No encoding, so use us-ascii, which is the standard.
                         */
                        return new String(bytes, 0, bytes.length, "ASCII");
                    }
                }
            }

        }
        catch (Exception e) {
            /*
             * If we are not able to process the body there's nothing we can do about it. Return
             * null and let the upper layers handle the missing content.
             */
            Log.e(Email.LOG_TAG, "Unable to getTextFromPart", e);
        }
        return null;
    }

    /**
     * Returns true if the given mimeType matches the matchAgainst specification.  The comparison
     * ignores case and the matchAgainst string may include "*" for a wildcard (e.g. "image/*").
     * 
     * @param mimeType A MIME type to check.
     * @param matchAgainst A MIME type to check against. May include wildcards.
     * @return true if the mimeType matches
     */
    public static boolean mimeTypeMatches(String mimeType, String matchAgainst) {
        Pattern p = Pattern.compile(matchAgainst.replaceAll("\\*", "\\.\\*"), 
                Pattern.CASE_INSENSITIVE);
        return p.matcher(mimeType).matches();
    }

    /**
     * Returns true if the given mimeType matches any of the matchAgainst specifications.  The 
     * comparison ignores case and the matchAgainst strings may include "*" for a wildcard 
     * (e.g. "image/*").
     * 
     * @param mimeType A MIME type to check.
     * @param matchAgainst An array of MIME types to check against. May include wildcards.
     * @return true if the mimeType matches any of the matchAgainst strings
     */
    public static boolean mimeTypeMatches(String mimeType, String[] matchAgainst) {
        for (String matchType : matchAgainst) {
            if (mimeTypeMatches(mimeType, matchType)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Removes any content transfer encoding from the stream and returns a Body.
     */
    public static Body decodeBody(InputStream in, String contentTransferEncoding)
            throws IOException {
        /*
         * We'll remove any transfer encoding by wrapping the stream.
         */
        if (contentTransferEncoding != null) {
            contentTransferEncoding =
                MimeUtility.getHeaderParameter(contentTransferEncoding, null);
            if ("quoted-printable".equalsIgnoreCase(contentTransferEncoding)) {
                in = new QuotedPrintableInputStream(in);
            }
            else if ("base64".equalsIgnoreCase(contentTransferEncoding)) {
                in = new Base64InputStream(in);
            }
        }

        BinaryTempFileBody tempBody = new BinaryTempFileBody();
        OutputStream out = tempBody.getOutputStream();
        IOUtils.copy(in, out);
        out.close();
        return tempBody;
    }

    /**
     * An unfortunately named method that makes decisions about a Part (usually a Message)
     * as to which of it's children will be "viewable" and which will be attachments.
     * The method recursively sorts the viewables and attachments into seperate
     * lists for further processing.
     * @param part
     * @param viewables
     * @param attachments
     * @throws MessagingException
     */
    public static void collectParts(Part part, ArrayList<Part> viewables,
            ArrayList<Part> attachments) throws MessagingException {
        String disposition = part.getDisposition();
        String dispositionType = null;
        String dispositionFilename = null;
        if (disposition != null) {
            dispositionType = MimeUtility.getHeaderParameter(disposition, null);
            dispositionFilename = MimeUtility.getHeaderParameter(disposition, "filename");
        }

        /*
         * A best guess that this part is intended to be an attachment and not inline.
         */
        boolean attachment = ("attachment".equalsIgnoreCase(dispositionType))
                || (dispositionFilename != null)
                && (!"inline".equalsIgnoreCase(dispositionType));

        /*
         * If the part is Multipart but not alternative it's either mixed or
         * something we don't know about, which means we treat it as mixed
         * per the spec. We just process it's pieces recursively.
         */
        if (part.getBody() instanceof Multipart) {
            Multipart mp = (Multipart)part.getBody();
            for (int i = 0; i < mp.getCount(); i++) {
                collectParts(mp.getBodyPart(i), viewables, attachments);
            }
        }
        /*
         * If the part is an embedded message we just continue to process
         * it, pulling any viewables or attachments into the running list.
         */
        else if (part.getBody() instanceof Message) {
            Message message = (Message)part.getBody();
            collectParts(message, viewables, attachments);
        }
        /*
         * If the part is HTML and it got this far it's part of a mixed (et
         * al) and should be rendered inline.
         */
        else if ((!attachment) && (part.getMimeType().equalsIgnoreCase("text/html"))) {
            viewables.add(part);
        }
        /*
         * If the part is plain text and it got this far it's part of a
         * mixed (et al) and should be rendered inline.
         */
        else if ((!attachment) && (part.getMimeType().equalsIgnoreCase("text/plain"))) {
            viewables.add(part);
        }
        /*
         * Finally, if it's nothing else we will include it as an attachment.
         */
        else {
            attachments.add(part);
        }
    }
}