/*
 * Copyright (C) 2015 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.voicemail.impl.mail.internet;

import android.support.annotation.Nullable;
import android.text.TextUtils;
import com.android.voicemail.impl.VvmLog;
import com.android.voicemail.impl.mail.Address;
import com.android.voicemail.impl.mail.Body;
import com.android.voicemail.impl.mail.BodyPart;
import com.android.voicemail.impl.mail.Message;
import com.android.voicemail.impl.mail.MessagingException;
import com.android.voicemail.impl.mail.Multipart;
import com.android.voicemail.impl.mail.Part;
import com.android.voicemail.impl.mail.utils.LogUtils;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Stack;
import java.util.regex.Pattern;
import org.apache.james.mime4j.MimeException;
import org.apache.james.mime4j.dom.field.DateTimeField;
import org.apache.james.mime4j.field.DefaultFieldParser;
import org.apache.james.mime4j.io.EOLConvertingInputStream;
import org.apache.james.mime4j.parser.ContentHandler;
import org.apache.james.mime4j.parser.MimeStreamParser;
import org.apache.james.mime4j.stream.BodyDescriptor;
import org.apache.james.mime4j.stream.Field;

/**
 * An implementation of Message that stores all of its metadata in RFC 822 and RFC 2045 style
 * headers.
 *
 * <p>NOTE: Automatic generation of a local message-id is becoming unwieldy and should be removed.
 * It would be better to simply do it explicitly on local creation of new outgoing messages.
 */
public class MimeMessage extends Message {
  private MimeHeader header;
  private MimeHeader extendedHeader;

  // NOTE:  The fields here are transcribed out of headers, and values stored here will supersede
  // the values found in the headers.  Use caution to prevent any out-of-phase errors.  In
  // particular, any adds/changes/deletes here must be echoed by changes in the parse() function.
  private Address[] from;
  private Address[] to;
  private Address[] cc;
  private Address[] bcc;
  private Address[] replyTo;
  private Date sentDate;
  private Body body;
  protected int size;
  private boolean inhibitLocalMessageId = false;

  // Shared random source for generating local message-id values
  private static final java.util.Random random = new java.util.Random();

  // In MIME, en_US-like date format should be used. In other words "MMM" should be encoded to
  // "Jan", not the other localized format like "Ene" (meaning January in locale es).
  // This conversion is used when generating outgoing MIME messages. Incoming MIME date
  // headers are parsed by org.apache.james.mime4j.field.DateTimeField which does not have any
  // localization code.
  private static final SimpleDateFormat DATE_FORMAT =
      new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);

  // regex that matches content id surrounded by "<>" optionally.
  private static final Pattern REMOVE_OPTIONAL_BRACKETS = Pattern.compile("^<?([^>]+)>?$");
  // regex that matches end of line.
  private static final Pattern END_OF_LINE = Pattern.compile("\r?\n");

  public MimeMessage() {
    header = null;
  }

  /**
   * Generate a local message id. This is only used when none has been assigned, and is installed
   * lazily. Any remote (typically server-assigned) message id takes precedence.
   *
   * @return a long, locally-generated message-ID value
   */
  private static String generateMessageId() {
    final StringBuilder sb = new StringBuilder();
    sb.append("<");
    for (int i = 0; i < 24; i++) {
      // We'll use a 5-bit range (0..31)
      final int value = random.nextInt() & 31;
      final char c = "0123456789abcdefghijklmnopqrstuv".charAt(value);
      sb.append(c);
    }
    sb.append(".");
    sb.append(Long.toString(System.currentTimeMillis()));
    sb.append("@email.android.com>");
    return sb.toString();
  }

  /**
   * Parse the given InputStream using Apache Mime4J to build a MimeMessage.
   *
   * @param in InputStream providing message content
   * @throws IOException
   * @throws MessagingException
   */
  public MimeMessage(InputStream in) throws IOException, MessagingException, MimeException {
    parse(in);
  }

  private MimeStreamParser init() {
    // Before parsing the input stream, clear all local fields that may be superceded by
    // the new incoming message.
    getMimeHeaders().clear();
    inhibitLocalMessageId = true;
    from = null;
    to = null;
    cc = null;
    bcc = null;
    replyTo = null;
    sentDate = null;
    body = null;

    final MimeStreamParser parser = new MimeStreamParser();
    parser.setContentHandler(new MimeMessageBuilder());
    return parser;
  }

  public void parse(InputStream in) throws IOException, MessagingException, MimeException {
    final MimeStreamParser parser = init();
    parser.parse(new EOLConvertingInputStream(in));
  }

  /**
   * Return the internal mHeader value, with very lazy initialization. The goal is to save memory by
   * not creating the headers until needed.
   */
  private MimeHeader getMimeHeaders() {
    if (header == null) {
      header = new MimeHeader();
    }
    return header;
  }

  @Override
  public Date getReceivedDate() throws MessagingException {
    return null;
  }

  @Override
  public Date getSentDate() throws MessagingException {
    if (sentDate == null) {
      try {
        DateTimeField field =
            (DateTimeField)
                DefaultFieldParser.parse(
                    "Date: " + MimeUtility.unfoldAndDecode(getFirstHeader("Date")));
        sentDate = field.getDate();
        // TODO: We should make it more clear what exceptions can be thrown here,
        // and whether they reflect a normal or error condition.
      } catch (Exception e) {
        LogUtils.v(LogUtils.TAG, "Message missing Date header");
      }
    }
    if (sentDate == null) {
      // If we still don't have a date, fall back to "Delivery-date"
      try {
        DateTimeField field =
            (DateTimeField)
                DefaultFieldParser.parse(
                    "Date: " + MimeUtility.unfoldAndDecode(getFirstHeader("Delivery-date")));
        sentDate = field.getDate();
        // TODO: We should make it more clear what exceptions can be thrown here,
        // and whether they reflect a normal or error condition.
      } catch (Exception e) {
        LogUtils.v(LogUtils.TAG, "Message also missing Delivery-Date header");
      }
    }
    return sentDate;
  }

  @Override
  public void setSentDate(Date sentDate) throws MessagingException {
    setHeader("Date", DATE_FORMAT.format(sentDate));
    this.sentDate = sentDate;
  }

  @Override
  @Nullable
  public Long getDuration() {
    String durationHeader = null;
    try {
      durationHeader = getFirstHeader(MimeHeader.HEADER_CONTENT_DURATION);
    } catch (MessagingException e) {
      VvmLog.e("MimeMessage.getDuration", "cannot retrieve header: ", e);
      return null;
    }
    if (durationHeader == null) {
      VvmLog.w("MimeMessage.getDuration", "message missing Content-Duration header");
      return null;
    }
    try {
      return Long.valueOf(durationHeader);
    } catch (NumberFormatException e) {
      VvmLog.w("MimeMessage.getDuration", "cannot parse duration " + durationHeader);
      return null;
    }
  }

  @Override
  public String getContentType() throws MessagingException {
    final String contentType = getFirstHeader(MimeHeader.HEADER_CONTENT_TYPE);
    if (contentType == null) {
      return "text/plain";
    } else {
      return contentType;
    }
  }

  @Override
  public String getDisposition() throws MessagingException {
    return getFirstHeader(MimeHeader.HEADER_CONTENT_DISPOSITION);
  }

  @Override
  public String getContentId() throws MessagingException {
    final String contentId = getFirstHeader(MimeHeader.HEADER_CONTENT_ID);
    if (contentId == null) {
      return null;
    } else {
      // remove optionally surrounding brackets.
      return REMOVE_OPTIONAL_BRACKETS.matcher(contentId).replaceAll("$1");
    }
  }

  @Override
  public String getMimeType() throws MessagingException {
    return MimeUtility.getHeaderParameter(getContentType(), null);
  }

  @Override
  public int getSize() throws MessagingException {
    return size;
  }

  /**
   * Returns a list of the given recipient type from this message. If no addresses are found the
   * method returns an empty array.
   */
  @Override
  public Address[] getRecipients(String type) throws MessagingException {
    if (type == RECIPIENT_TYPE_TO) {
      if (to == null) {
        to = Address.parse(MimeUtility.unfold(getFirstHeader("To")));
      }
      return to;
    } else if (type == RECIPIENT_TYPE_CC) {
      if (cc == null) {
        cc = Address.parse(MimeUtility.unfold(getFirstHeader("CC")));
      }
      return cc;
    } else if (type == RECIPIENT_TYPE_BCC) {
      if (bcc == null) {
        bcc = Address.parse(MimeUtility.unfold(getFirstHeader("BCC")));
      }
      return bcc;
    } else {
      throw new MessagingException("Unrecognized recipient type.");
    }
  }

  @Override
  public void setRecipients(String type, Address[] addresses) throws MessagingException {
    final int toLength = 4; // "To: "
    final int ccLength = 4; // "Cc: "
    final int bccLength = 5; // "Bcc: "
    if (type == RECIPIENT_TYPE_TO) {
      if (addresses == null || addresses.length == 0) {
        removeHeader("To");
        this.to = null;
      } else {
        setHeader("To", MimeUtility.fold(Address.toHeader(addresses), toLength));
        this.to = addresses;
      }
    } else if (type == RECIPIENT_TYPE_CC) {
      if (addresses == null || addresses.length == 0) {
        removeHeader("CC");
        this.cc = null;
      } else {
        setHeader("CC", MimeUtility.fold(Address.toHeader(addresses), ccLength));
        this.cc = addresses;
      }
    } else if (type == RECIPIENT_TYPE_BCC) {
      if (addresses == null || addresses.length == 0) {
        removeHeader("BCC");
        this.bcc = null;
      } else {
        setHeader("BCC", MimeUtility.fold(Address.toHeader(addresses), bccLength));
        this.bcc = addresses;
      }
    } else {
      throw new MessagingException("Unrecognized recipient type.");
    }
  }

  /** Returns the unfolded, decoded value of the Subject header. */
  @Override
  public String getSubject() throws MessagingException {
    return MimeUtility.unfoldAndDecode(getFirstHeader("Subject"));
  }

  @Override
  public void setSubject(String subject) throws MessagingException {
    final int headerNameLength = 9; // "Subject: "
    setHeader("Subject", MimeUtility.foldAndEncode2(subject, headerNameLength));
  }

  @Override
  public Address[] getFrom() throws MessagingException {
    if (from == null) {
      String list = MimeUtility.unfold(getFirstHeader("From"));
      if (list == null || list.length() == 0) {
        list = MimeUtility.unfold(getFirstHeader("Sender"));
      }
      from = Address.parse(list);
    }
    return from;
  }

  @Override
  public void setFrom(Address from) throws MessagingException {
    final int fromLength = 6; // "From: "
    if (from != null) {
      setHeader("From", MimeUtility.fold(from.toHeader(), fromLength));
      this.from = new Address[] {from};
    } else {
      this.from = null;
    }
  }

  @Override
  public Address[] getReplyTo() throws MessagingException {
    if (replyTo == null) {
      replyTo = Address.parse(MimeUtility.unfold(getFirstHeader("Reply-to")));
    }
    return replyTo;
  }

  @Override
  public void setReplyTo(Address[] replyTo) throws MessagingException {
    final int replyToLength = 10; // "Reply-to: "
    if (replyTo == null || replyTo.length == 0) {
      removeHeader("Reply-to");
      this.replyTo = null;
    } else {
      setHeader("Reply-to", MimeUtility.fold(Address.toHeader(replyTo), replyToLength));
      this.replyTo = replyTo;
    }
  }

  /**
   * Set the mime "Message-ID" header
   *
   * @param messageId the new Message-ID value
   * @throws MessagingException
   */
  @Override
  public void setMessageId(String messageId) throws MessagingException {
    setHeader("Message-ID", messageId);
  }

  /**
   * Get the mime "Message-ID" header. This value will be preloaded with a locally-generated random
   * ID, if the value has not previously been set. Local generation can be inhibited/ overridden by
   * explicitly clearing the headers, removing the message-id header, etc.
   *
   * @return the Message-ID header string, or null if explicitly has been set to null
   */
  @Override
  public String getMessageId() throws MessagingException {
    String messageId = getFirstHeader("Message-ID");
    if (messageId == null && !inhibitLocalMessageId) {
      messageId = generateMessageId();
      setMessageId(messageId);
    }
    return messageId;
  }

  @Override
  public void saveChanges() throws MessagingException {
    throw new MessagingException("saveChanges not yet implemented");
  }

  @Override
  public Body getBody() throws MessagingException {
    return body;
  }

  @Override
  public void setBody(Body body) throws MessagingException {
    this.body = body;
    if (body instanceof Multipart) {
      final Multipart multipart = ((Multipart) body);
      multipart.setParent(this);
      setHeader(MimeHeader.HEADER_CONTENT_TYPE, multipart.getContentType());
      setHeader("MIME-Version", "1.0");
    } else if (body instanceof TextBody) {
      setHeader(
          MimeHeader.HEADER_CONTENT_TYPE, String.format("%s;\n charset=utf-8", getMimeType()));
      setHeader(MimeHeader.HEADER_CONTENT_TRANSFER_ENCODING, "base64");
    }
  }

  protected String getFirstHeader(String name) throws MessagingException {
    return getMimeHeaders().getFirstHeader(name);
  }

  @Override
  public void addHeader(String name, String value) throws MessagingException {
    getMimeHeaders().addHeader(name, value);
  }

  @Override
  public void setHeader(String name, String value) throws MessagingException {
    getMimeHeaders().setHeader(name, value);
  }

  @Override
  public String[] getHeader(String name) throws MessagingException {
    return getMimeHeaders().getHeader(name);
  }

  @Override
  public void removeHeader(String name) throws MessagingException {
    getMimeHeaders().removeHeader(name);
    if ("Message-ID".equalsIgnoreCase(name)) {
      inhibitLocalMessageId = true;
    }
  }

  /**
   * Set extended header
   *
   * @param name Extended header name
   * @param value header value - flattened by removing CR-NL if any remove header if value is null
   * @throws MessagingException
   */
  @Override
  public void setExtendedHeader(String name, String value) throws MessagingException {
    if (value == null) {
      if (extendedHeader != null) {
        extendedHeader.removeHeader(name);
      }
      return;
    }
    if (extendedHeader == null) {
      extendedHeader = new MimeHeader();
    }
    extendedHeader.setHeader(name, END_OF_LINE.matcher(value).replaceAll(""));
  }

  /**
   * Get extended header
   *
   * @param name Extended header name
   * @return header value - null if header does not exist
   * @throws MessagingException
   */
  @Override
  public String getExtendedHeader(String name) throws MessagingException {
    if (extendedHeader == null) {
      return null;
    }
    return extendedHeader.getFirstHeader(name);
  }

  /**
   * Set entire extended headers from String
   *
   * @param headers Extended header and its value - "CR-NL-separated pairs if null or empty, remove
   *     entire extended headers
   * @throws MessagingException
   */
  public void setExtendedHeaders(String headers) throws MessagingException {
    if (TextUtils.isEmpty(headers)) {
      extendedHeader = null;
    } else {
      extendedHeader = new MimeHeader();
      for (final String header : END_OF_LINE.split(headers)) {
        final String[] tokens = header.split(":", 2);
        if (tokens.length != 2) {
          throw new MessagingException("Illegal extended headers: " + headers);
        }
        extendedHeader.setHeader(tokens[0].trim(), tokens[1].trim());
      }
    }
  }

  /**
   * Get entire extended headers as String
   *
   * @return "CR-NL-separated extended headers - null if extended header does not exist
   */
  public String getExtendedHeaders() {
    if (extendedHeader != null) {
      return extendedHeader.writeToString();
    }
    return null;
  }

  /**
   * Write message header and body to output stream
   *
   * @param out Output steam to write message header and body.
   */
  @Override
  public void writeTo(OutputStream out) throws IOException, MessagingException {
    final BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out), 1024);
    // Force creation of local message-id
    getMessageId();
    getMimeHeaders().writeTo(out);
    // mExtendedHeader will not be write out to external output stream,
    // because it is intended to internal use.
    writer.write("\r\n");
    writer.flush();
    if (body != null) {
      body.writeTo(out);
    }
  }

  @Override
  public InputStream getInputStream() throws MessagingException {
    return null;
  }

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

    public MimeMessageBuilder() {}

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

    @Override
    public void startMessage() {
      if (stack.isEmpty()) {
        stack.push(MimeMessage.this);
      } else {
        expect(Part.class);
        try {
          final MimeMessage m = new MimeMessage();
          ((Part) stack.peek()).setBody(m);
          stack.push(m);
        } catch (MessagingException me) {
          throw new Error(me);
        }
      }
    }

    @Override
    public void endMessage() {
      expect(MimeMessage.class);
      stack.pop();
    }

    @Override
    public void startHeader() {
      expect(Part.class);
    }

    @Override
    public void field(Field rawField) {
      expect(Part.class);
      try {
        final String[] tokens = rawField.getRaw().toString().split(":", 2);
        ((Part) stack.peek()).addHeader(tokens[0], tokens[1].trim());
      } catch (MessagingException me) {
        throw new Error(me);
      }
    }

    @Override
    public void endHeader() {
      expect(Part.class);
    }

    @Override
    public void startMultipart(BodyDescriptor bd) {
      expect(Part.class);

      final Part e = (Part) stack.peek();
      try {
        final MimeMultipart multiPart = new MimeMultipart(e.getContentType());
        e.setBody(multiPart);
        stack.push(multiPart);
      } catch (MessagingException me) {
        throw new Error(me);
      }
    }

    @Override
    public void body(BodyDescriptor bd, InputStream in) throws IOException {
      expect(Part.class);
      final Body body = MimeUtility.decodeBody(in, bd.getTransferEncoding());
      try {
        ((Part) stack.peek()).setBody(body);
      } catch (MessagingException me) {
        throw new Error(me);
      }
    }

    @Override
    public void endMultipart() {
      stack.pop();
    }

    @Override
    public void startBodyPart() {
      expect(MimeMultipart.class);

      try {
        final MimeBodyPart bodyPart = new MimeBodyPart();
        ((MimeMultipart) stack.peek()).addBodyPart(bodyPart);
        stack.push(bodyPart);
      } catch (MessagingException me) {
        throw new Error(me);
      }
    }

    @Override
    public void endBodyPart() {
      expect(BodyPart.class);
      stack.pop();
    }

    @Override
    public void epilogue(InputStream is) throws IOException {
      expect(MimeMultipart.class);
      final StringBuilder sb = new StringBuilder();
      int b;
      while ((b = is.read()) != -1) {
        sb.append((char) b);
      }
      // TODO: why is this commented out?
      // ((Multipart) stack.peek()).setEpilogue(sb.toString());
    }

    @Override
    public void preamble(InputStream is) throws IOException {
      expect(MimeMultipart.class);
      final StringBuilder sb = new StringBuilder();
      int b;
      while ((b = is.read()) != -1) {
        sb.append((char) b);
      }
      try {
        ((MimeMultipart) stack.peek()).setPreamble(sb.toString());
      } catch (MessagingException me) {
        throw new Error(me);
      }
    }

    @Override
    public void raw(InputStream is) throws IOException {
      throw new UnsupportedOperationException("Not supported");
    }
  }
}