/****************************************************************
 * Licensed to the Apache Software Foundation (ASF) under one   *
 * or more contributor license agreements.  See the NOTICE file *
 * distributed with this work for additional information        *
 * regarding copyright ownership.  The ASF licenses this file   *
 * to you 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 org.apache.james.mime4j.message;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Stack;

import org.apache.james.mime4j.BodyDescriptor;
import org.apache.james.mime4j.ContentHandler;
import org.apache.james.mime4j.MimeStreamParser;
import org.apache.james.mime4j.decoder.Base64InputStream;
import org.apache.james.mime4j.decoder.QuotedPrintableInputStream;
import org.apache.james.mime4j.field.Field;
import org.apache.james.mime4j.field.UnstructuredField;


/**
 * Represents a MIME message. The following code parses a stream into a
 * <code>Message</code> object.
 *
 * <pre>
 *      Message msg = new Message(new BufferedInputStream(
 *                                      new FileInputStream("mime.msg")));
 * </pre>
 *
 *
 *
 * @version $Id: Message.java,v 1.3 2004/10/02 12:41:11 ntherning Exp $
 */
public class Message extends Entity implements Body {

    /**
     * Creates a new empty <code>Message</code>.
     */
    public Message() {
    }

    /**
     * Parses the specified MIME message stream into a <code>Message</code>
     * instance.
     *
     * @param is the stream to parse.
     * @throws IOException on I/O errors.
     */
    public Message(InputStream is) throws IOException {
        MimeStreamParser parser = new MimeStreamParser();
        parser.setContentHandler(new MessageBuilder());
        parser.parse(is);
    }


    /**
     * Gets the <code>Subject</code> field.
     *
     * @return the <code>Subject</code> field or <code>null</code> if it
     *         doesn't exist.
     */
    public UnstructuredField getSubject() {
        return (UnstructuredField) getHeader().getField(Field.SUBJECT);
    }

    /**
     *
     * @see org.apache.james.mime4j.message.Entity#writeTo(java.io.OutputStream)
     */
    @Override
    public void writeTo(OutputStream out) throws IOException {
        getHeader().writeTo(out);

        Body body = getBody();
        if (body instanceof Multipart) {
            Multipart mp = (Multipart) body;
            mp.writeTo(out);
        } else {
            body.writeTo(out);
        }
    }


    private class MessageBuilder implements ContentHandler {
        private Stack<Object> stack = new Stack<Object>();

        public MessageBuilder() {
        }

        private void expect(Class c) {
            if (!c.isInstance(stack.peek())) {
                throw new IllegalStateException("Internal stack error: "
                        + "Expected '" + c.getName() + "' found '"
                        + stack.peek().getClass().getName() + "'");
            }
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#startMessage()
         */
        public void startMessage() {
            if (stack.isEmpty()) {
                stack.push(Message.this);
            } else {
                expect(Entity.class);
                Message m = new Message();
                ((Entity) stack.peek()).setBody(m);
                stack.push(m);
            }
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#endMessage()
         */
        public void endMessage() {
            expect(Message.class);
            stack.pop();
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#startHeader()
         */
        public void startHeader() {
            stack.push(new Header());
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#field(java.lang.String)
         */
        public void field(String fieldData) {
            expect(Header.class);
            ((Header) stack.peek()).addField(Field.parse(fieldData));
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#endHeader()
         */
        public void endHeader() {
            expect(Header.class);
            Header h = (Header) stack.pop();
            expect(Entity.class);
            ((Entity) stack.peek()).setHeader(h);
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#startMultipart(org.apache.james.mime4j.BodyDescriptor)
         */
        public void startMultipart(BodyDescriptor bd) {
            expect(Entity.class);

            Entity e = (Entity) stack.peek();
            Multipart multiPart = new Multipart();
            e.setBody(multiPart);
            stack.push(multiPart);
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#body(org.apache.james.mime4j.BodyDescriptor, java.io.InputStream)
         */
        public void body(BodyDescriptor bd, InputStream is) throws IOException {
            expect(Entity.class);

            String enc = bd.getTransferEncoding();
            if ("base64".equals(enc)) {
                is = new Base64InputStream(is);
            } else if ("quoted-printable".equals(enc)) {
                is = new QuotedPrintableInputStream(is);
            }

            Body body = null;
            if (bd.getMimeType().startsWith("text/")) {
                body = new MemoryTextBody(is, bd.getCharset());
            } else {
                body = new MemoryBinaryBody(is);
            }

            ((Entity) stack.peek()).setBody(body);
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#endMultipart()
         */
        public void endMultipart() {
            stack.pop();
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#startBodyPart()
         */
        public void startBodyPart() {
            expect(Multipart.class);

            BodyPart bodyPart = new BodyPart();
            ((Multipart) stack.peek()).addBodyPart(bodyPart);
            stack.push(bodyPart);
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#endBodyPart()
         */
        public void endBodyPart() {
            expect(BodyPart.class);
            stack.pop();
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#epilogue(java.io.InputStream)
         */
        public void epilogue(InputStream is) throws IOException {
            expect(Multipart.class);
            StringBuffer sb = new StringBuffer();
            int b;
            while ((b = is.read()) != -1) {
                sb.append((char) b);
            }
            ((Multipart) stack.peek()).setEpilogue(sb.toString());
        }

        /**
         * @see org.apache.james.mime4j.ContentHandler#preamble(java.io.InputStream)
         */
        public void preamble(InputStream is) throws IOException {
            expect(Multipart.class);
            StringBuffer sb = new StringBuffer();
            int b;
            while ((b = is.read()) != -1) {
                sb.append((char) b);
            }
            ((Multipart) stack.peek()).setPreamble(sb.toString());
        }

        /**
         * TODO: Implement me
         *
         * @see org.apache.james.mime4j.ContentHandler#raw(java.io.InputStream)
         */
        public void raw(InputStream is) throws IOException {
            throw new UnsupportedOperationException("Not supported");
        }

    }
}