/*
    * 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.commons.mail2.javax;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  
  import javax.activation.DataHandler;
  import javax.activation.DataSource;
  import javax.activation.FileDataSource;
  import javax.activation.URLDataSource;
  import javax.mail.BodyPart;
  import javax.mail.MessagingException;
  import javax.mail.internet.MimeBodyPart;
  import javax.mail.internet.MimeMultipart;
  
  import org.apache.commons.mail2.core.EmailConstants;
  import org.apache.commons.mail2.core.EmailException;
  import org.apache.commons.mail2.core.EmailUtils;
  
  /**
   * An HTML multipart email.
   * <p>
   * This class is used to send HTML formatted email. A text message can also be set for HTML unaware email clients, such as text-based email clients.
   * </p>
   * <p>
   * This class also inherits from {@link MultiPartEmail}, so it is easy to add attachments to the email.
   * </p>
   * <p>
   * To send an email in HTML, one should create a {@code HtmlEmail}, then use the {@link #setFrom(String)}, {@link #addTo(String)} etc. methods. The HTML content
   * can be set with the {@link #setHtmlMsg(String)} method. The alternative text content can be set with {@link #setTextMsg(String)}.
   * </p>
   * <p>
   * Either the text or HTML can be omitted, in which case the "main" part of the multipart becomes whichever is supplied rather than a
   * {@code multipart/alternative}.
   * </p>
   * <h2>Embedding Images and Media</h2>
   * <p>
   * It is also possible to embed URLs, files, or arbitrary {@code DataSource}s directly into the body of the mail:
   * </p>
   *
   * <pre>
   * HtmlEmail he = new HtmlEmail();
   * File img = new File("my/image.gif");
   * PNGDataSource png = new PNGDataSource(decodedPNGOutputStream); // a custom class
   * StringBuffer msg = new StringBuffer();
   * msg.append("&lt;html&gt;&lt;body&gt;");
   * msg.append("&lt;img src=cid:").append(he.embed(img)).append("&gt;");
   * msg.append("&lt;img src=cid:").append(he.embed(png)).append("&gt;");
   * msg.append("&lt;/body&gt;&lt;/html&gt;");
   * he.setHtmlMsg(msg.toString());
   * // code to set the other email fields (not shown)
   * </pre>
   * <p>
   * Embedded entities are tracked by their name, which for {@code File}s is the file name itself and for {@code URL}s is the canonical path. It is an error to
   * bind the same name to more than one entity, and this class will attempt to validate that for {@code File}s and {@code URL}s. When embedding a
   * {@code DataSource}, the code uses the {@code equals()} method defined on the {@code DataSource}s to make the determination.
   * </p>
   *
   * @since 1.0
   */
  public class HtmlEmail extends MultiPartEmail {
  
      /**
       * Private bean class that encapsulates data about URL contents that are embedded in the final email.
       *
       * @since 1.1
       */
      private static final class InlineImage {
  
          /** Content id. */
          private final String cid;
  
          /** {@code DataSource} for the content. */
          private final DataSource dataSource;
  
          /** The {@code MimeBodyPart} that contains the encoded data. */
          private final MimeBodyPart mimeBodyPart;
  
         /**
          * Creates an InlineImage object to represent the specified content ID and {@code MimeBodyPart}.
          *
          * @param cid          the generated content ID, not null.
          * @param dataSource   the {@code DataSource} that represents the content, not null.
          * @param mimeBodyPart the {@code MimeBodyPart} that contains the encoded data, not null.
          */
         private InlineImage(final String cid, final DataSource dataSource, final MimeBodyPart mimeBodyPart) {
             this.cid = Objects.requireNonNull(cid, "cid");
             this.dataSource = Objects.requireNonNull(dataSource, "dataSource");
             this.mimeBodyPart = Objects.requireNonNull(mimeBodyPart, "mimeBodyPart");
         }
 
         @Override
         public boolean equals(final Object obj) {
             if (this == obj) {
                 return true;
             }
             if (!(obj instanceof InlineImage)) {
                 return false;
             }
             final InlineImage other = (InlineImage) obj;
             return Objects.equals(cid, other.cid);
         }
 
         /**
          * Returns the unique content ID of this InlineImage.
          *
          * @return the unique content ID of this InlineImage
          */
         private String getCid() {
             return cid;
         }
 
         /**
          * Returns the {@code DataSource} that represents the encoded content.
          *
          * @return the {@code DataSource} representing the encoded content
          */
         private DataSource getDataSource() {
             return dataSource;
         }
 
         /**
          * Returns the {@code MimeBodyPart} that contains the encoded InlineImage data.
          *
          * @return the {@code MimeBodyPart} containing the encoded InlineImage data
          */
         private MimeBodyPart getMimeBodyPart() {
             return mimeBodyPart;
         }
 
         @Override
         public int hashCode() {
             return Objects.hash(cid);
         }
     }
 
     /** Definition of the length of generated CID's. */
     public static final int CID_LENGTH = 10;
 
     /** Prefix for default HTML mail. */
     private static final String HTML_MESSAGE_START = "<html><body><pre>";
 
     /** Suffix for default HTML mail. */
     private static final String HTML_MESSAGE_END = "</pre></body></html>";
 
     /**
      * Text part of the message. This will be used as alternative text if the email client does not support HTML messages.
      */
     private String text;
 
     /**
      * HTML part of the message.
      */
     private String html;
 
     /**
      * Embedded images Map&lt;String, InlineImage&gt; where the key is the user-defined image name.
      */
     private final Map<String, InlineImage> inlineEmbeds = new HashMap<>();
 
     /**
      * Constructs a new instance.
      */
     public HtmlEmail() {
         // empty
     }
 
     /**
      * @throws EmailException     EmailException
      * @throws MessagingException MessagingException
      */
     private void build() throws MessagingException, EmailException {
         final MimeMultipart rootContainer = getContainer();
         MimeMultipart bodyEmbedsContainer = rootContainer;
         MimeMultipart bodyContainer = rootContainer;
         MimeBodyPart msgHtml = null;
         MimeBodyPart msgText = null;
 
         rootContainer.setSubType("mixed");
 
         // determine how to form multiparts of email
 
         if (EmailUtils.isNotEmpty(html) && !EmailUtils.isEmpty(inlineEmbeds)) {
             // If HTML body and embeds are used, create a related container and add it to the root container
             bodyEmbedsContainer = new MimeMultipart("related");
             bodyContainer = bodyEmbedsContainer;
             addPart(bodyEmbedsContainer, 0);
 
             // If TEXT body was specified, create a alternative container and add it to the embeds container
             if (EmailUtils.isNotEmpty(text)) {
                 bodyContainer = new MimeMultipart("alternative");
                 final BodyPart bodyPart = createBodyPart();
                 try {
                     bodyPart.setContent(bodyContainer);
                     bodyEmbedsContainer.addBodyPart(bodyPart, 0);
                 } catch (final MessagingException e) {
                     throw new EmailException(e);
                 }
             }
         } else if (EmailUtils.isNotEmpty(text) && EmailUtils.isNotEmpty(html)) {
             // EMAIL-142: if we have both an HTML and TEXT body, but no attachments or
             // inline images, the root container should have mimetype
             // "multipart/alternative".
             // reference: https://tools.ietf.org/html/rfc2046#section-5.1.4
             if (!EmailUtils.isEmpty(inlineEmbeds) || isBoolHasAttachments()) {
                 // If both HTML and TEXT bodies are provided, create an alternative
                 // container and add it to the root container
                 bodyContainer = new MimeMultipart("alternative");
                 this.addPart(bodyContainer, 0);
             } else {
                 // no attachments or embedded images present, change the mimetype
                 // of the root container (= body container)
                 rootContainer.setSubType("alternative");
             }
         }
 
         if (EmailUtils.isNotEmpty(html)) {
             msgHtml = new MimeBodyPart();
             bodyContainer.addBodyPart(msgHtml, 0);
 
             // EMAIL-104: call explicitly setText to use default mime charset
             // (property "mail.mime.charset") in case none has been set
             msgHtml.setText(html, getCharsetName(), EmailConstants.TEXT_SUBTYPE_HTML);
 
             // EMAIL-147: work-around for buggy JavaMail implementations;
             // in case setText(...) does not set the correct content type,
             // use the setContent() method instead.
             final String contentType = msgHtml.getContentType();
             if (contentType == null || !contentType.equals(EmailConstants.TEXT_HTML)) {
                 // apply default charset if one has been set
                 if (EmailUtils.isNotEmpty(getCharsetName())) {
                     msgHtml.setContent(html, EmailConstants.TEXT_HTML + "; charset=" + getCharsetName());
                 } else {
                     // unfortunately, MimeUtility.getDefaultMIMECharset() is package private
                     // and thus can not be used to set the default system charset in case
                     // no charset has been provided by the user
                     msgHtml.setContent(html, EmailConstants.TEXT_HTML);
                 }
             }
 
             for (final InlineImage image : inlineEmbeds.values()) {
                 bodyEmbedsContainer.addBodyPart(image.getMimeBodyPart());
             }
         }
 
         if (EmailUtils.isNotEmpty(text)) {
             msgText = new MimeBodyPart();
             bodyContainer.addBodyPart(msgText, 0);
 
             // EMAIL-104: call explicitly setText to use default mime charset
             // (property "mail.mime.charset") in case none has been set
             msgText.setText(text, getCharsetName());
         }
     }
 
     /**
      * Builds the MimeMessage. Please note that a user rarely calls this method directly and only if he/she is interested in the sending the underlying
      * MimeMessage without commons-email.
      *
      * @throws EmailException if there was an error.
      * @since 1.0
      */
     @Override
     public void buildMimeMessage() throws EmailException {
         try {
             build();
         } catch (final MessagingException e) {
             throw new EmailException(e);
         }
         super.buildMimeMessage();
     }
 
     /**
      * Embeds the specified {@code DataSource} in the HTML using a randomly generated Content-ID. Returns the generated Content-ID string.
      *
      * @param dataSource the {@code DataSource} to embed
      * @param name       the name that will be set in the file name header field
      * @return the generated Content-ID for this {@code DataSource}
      * @throws EmailException if the embedding fails or if {@code name} is null or empty
      * @see #embed(DataSource, String, String)
      * @since 1.1
      */
     public String embed(final DataSource dataSource, final String name) throws EmailException {
         // check if the DataSource has already been attached;
         // if so, return the cached CID value.
         final InlineImage inlineImage = inlineEmbeds.get(name);
         if (inlineImage != null) {
             // make sure the supplied URL points to the same thing
             // as the one already associated with this name.
             if (dataSource.equals(inlineImage.getDataSource())) {
                 return inlineImage.getCid();
             }
             throw new EmailException("embedded DataSource '" + name + "' is already bound to name " + inlineImage.getDataSource().toString()
                     + "; existing names cannot be rebound");
         }
 
         final String cid = EmailUtils.toLower(EmailUtils.randomAlphabetic(CID_LENGTH));
         return embed(dataSource, name, cid);
     }
 
     /**
      * Embeds the specified {@code DataSource} in the HTML using the specified Content-ID. Returns the specified Content-ID string.
      *
      * @param dataSource the {@code DataSource} to embed
      * @param name       the name that will be set in the file name header field
      * @param cid        the Content-ID to use for this {@code DataSource}
      * @return the URL encoded Content-ID for this {@code DataSource}
      * @throws EmailException if the embedding fails or if {@code name} is null or empty
      * @since 1.1
      */
     public String embed(final DataSource dataSource, final String name, final String cid) throws EmailException {
         EmailException.checkNonEmpty(name, () -> "Name cannot be null or empty");
         final MimeBodyPart mbp = new MimeBodyPart();
         try {
             // URL encode the cid according to RFC 2392
             final String encodedCid = EmailUtils.encodeUrl(cid);
             mbp.setDataHandler(new DataHandler(dataSource));
             mbp.setFileName(name);
             mbp.setDisposition(EmailAttachment.INLINE);
             mbp.setContentID("<" + encodedCid + ">");
             this.inlineEmbeds.put(name, new InlineImage(encodedCid, dataSource, mbp));
             return encodedCid;
         } catch (final MessagingException e) {
             throw new EmailException(e);
         }
     }
 
     /**
      * Embeds a file in the HTML. This implementation delegates to {@link #embed(File, String)}.
      *
      * @param file The {@code File} object to embed
      * @return A String with the Content-ID of the file.
      * @throws EmailException when the supplied {@code File} cannot be used; also see {@link javax.mail.internet.MimeBodyPart} for definitions
      *
      * @see #embed(File, String)
      * @since 1.1
      */
     public String embed(final File file) throws EmailException {
         return embed(file, EmailUtils.toLower(EmailUtils.randomAlphabetic(CID_LENGTH)));
     }
 
     /**
      * Embeds a file in the HTML.
      *
      * <p>
      * This method embeds a file located by an URL into the mail body. It allows, for instance, to add inline images to the email. Inline files may be
      * referenced with a {@code cid:xxxxxx} URL, where xxxxxx is the Content-ID returned by the embed function. Files are bound to their names, which is the
      * value returned by {@link java.io.File#getName()}. If the same file is embedded multiple times, the same CID is guaranteed to be returned.
      *
      * <p>
      * While functionally the same as passing {@code FileDataSource} to {@link #embed(DataSource, String, String)}, this method attempts to validate the file
      * before embedding it in the message and will throw {@code EmailException} if the validation fails. In this case, the {@code HtmlEmail} object will not be
      * changed.
      *
      * @param file The {@code File} to embed
      * @param cid  the Content-ID to use for the embedded {@code File}
      * @return A String with the Content-ID of the file.
      * @throws EmailException when the supplied {@code File} cannot be used or if the file has already been embedded; also see
      *                        {@link javax.mail.internet.MimeBodyPart} for definitions
      * @since 1.1
      */
     public String embed(final File file, final String cid) throws EmailException {
         EmailException.checkNonEmpty(file.getName(), () -> "File name cannot be null or empty");
 
         // verify that the File can provide a canonical path
         String filePath = null;
         try {
             filePath = file.getCanonicalPath();
         } catch (final IOException e) {
             throw new EmailException("couldn't get canonical path for " + file.getName(), e);
         }
 
         // check if a FileDataSource for this name has already been attached;
         // if so, return the cached CID value.
         final InlineImage inlineImage = inlineEmbeds.get(file.getName());
         if (inlineImage != null) {
             final FileDataSource fileDataSource = (FileDataSource) inlineImage.getDataSource();
             // make sure the supplied file has the same canonical path
             // as the one already associated with this name.
             String existingFilePath = null;
             try {
                 existingFilePath = fileDataSource.getFile().getCanonicalPath();
             } catch (final IOException e) {
                 throw new EmailException("couldn't get canonical path for file " + fileDataSource.getFile().getName() + "which has already been embedded", e);
             }
             if (filePath.equals(existingFilePath)) {
                 return inlineImage.getCid();
             }
             throw new EmailException(
                     "embedded name '" + file.getName() + "' is already bound to file " + existingFilePath + "; existing names cannot be rebound");
         }
 
         // verify that the file is valid
         if (!file.exists()) {
             throw new EmailException("file " + filePath + " doesn't exist");
         }
         if (!file.isFile()) {
             throw new EmailException("file " + filePath + " isn't a normal file");
         }
         if (!file.canRead()) {
             throw new EmailException("file " + filePath + " isn't readable");
         }
 
         return embed(new FileDataSource(file), file.getName(), cid);
     }
 
     /**
      * Parses the specified {@code String} as a URL that will then be embedded in the message.
      *
      * @param urlString String representation of the URL.
      * @param name      The name that will be set in the file name header field.
      * @return A String with the Content-ID of the URL.
      * @throws EmailException when URL supplied is invalid or if {@code name} is null or empty; also see {@link javax.mail.internet.MimeBodyPart} for
      *                        definitions
      *
      * @see #embed(URL, String)
      * @since 1.1
      */
     public String embed(final String urlString, final String name) throws EmailException {
         try {
             return embed(new URL(urlString), name);
         } catch (final MalformedURLException e) {
             throw new EmailException("Invalid URL", e);
         }
     }
 
     /**
      * Embeds an URL in the HTML.
      *
      * <p>
      * This method embeds a file located by an URL into the mail body. It allows, for instance, to add inline images to the email. Inline files may be
      * referenced with a {@code cid:xxxxxx} URL, where xxxxxx is the Content-ID returned by the embed function. It is an error to bind the same name to more
      * than one URL; if the same URL is embedded multiple times, the same Content-ID is guaranteed to be returned.
      * </p>
      * <p>
      * While functionally the same as passing {@code URLDataSource} to {@link #embed(DataSource, String, String)}, this method attempts to validate the URL
      * before embedding it in the message and will throw {@code EmailException} if the validation fails. In this case, the {@code HtmlEmail} object will not be
      * changed.
      * </p>
      * <p>
      * NOTE: Clients should take care to ensure that different URLs are bound to different names. This implementation tries to detect this and throw
      * {@code EmailException}. However, it is not guaranteed to catch all cases, especially when the URL refers to a remote HTTP host that may be part of a
      * virtual host cluster.
      * </p>
      *
      * @param url  The URL of the file.
      * @param name The name that will be set in the file name header field.
      * @return A String with the Content-ID of the file.
      * @throws EmailException when URL supplied is invalid or if {@code name} is null or empty; also see {@link javax.mail.internet.MimeBodyPart} for
      *                        definitions
      * @since 1.0
      */
     public String embed(final URL url, final String name) throws EmailException {
         EmailException.checkNonEmpty(name, () -> "Name cannot be null or empty");
         // check if a URLDataSource for this name has already been attached;
         // if so, return the cached CID value.
         final InlineImage inlineImage = inlineEmbeds.get(name);
         if (inlineImage != null) {
             final URLDataSource urlDataSource = (URLDataSource) inlineImage.getDataSource();
             // make sure the supplied URL points to the same thing
             // as the one already associated with this name.
             // NOTE: Comparing URLs with URL.equals() is a blocking operation
             // in the case of a network failure therefore we use
             // url.toExternalForm().equals() here.
             if (url.toExternalForm().equals(urlDataSource.getURL().toExternalForm())) {
                 return inlineImage.getCid();
             }
             throw new EmailException("embedded name '" + name + "' is already bound to URL " + urlDataSource.getURL() + "; existing names cannot be rebound");
         }
         // verify that the URL is valid
         try (InputStream inputStream = url.openStream()) {
             // Make sure we can read.
             inputStream.read();
         } catch (final IOException e) {
             throw new EmailException("Invalid URL", e);
         }
         return embed(new URLDataSource(url), name);
     }
 
     /**
      * Gets the HTML content.
      *
      * @return the HTML content.
      * @since 1.6.0
      */
     public String getHtml() {
         return html;
     }
 
     /**
      * Gets the message text.
      *
      * @return the message text.
      * @since 1.6.0
      */
     public String getText() {
         return text;
     }
 
     /**
      * Sets the HTML content.
      *
      * @param html A String.
      * @return An HtmlEmail.
      * @throws EmailException see javax.mail.internet.MimeBodyPart for definitions
      * @since 1.0
      */
     public HtmlEmail setHtmlMsg(final String html) throws EmailException {
         this.html = EmailException.checkNonEmpty(html, () -> "Invalid message.");
         return this;
     }
 
     /**
      * Sets the message.
      *
      * <p>
      * This method overrides {@link MultiPartEmail#setMsg(String)} in order to send an HTML message instead of a plain text message in the mail body. The
      * message is formatted in HTML for the HTML part of the message; it is left as is in the alternate text part.
      * </p>
      *
      * @param msg the message text to use
      * @return this {@code HtmlEmail}
      * @throws EmailException if msg is null or empty; see javax.mail.internet.MimeBodyPart for definitions
      * @since 1.0
      */
     @Override
     public Email setMsg(final String msg) throws EmailException {
         setTextMsg(msg);
         final StringBuilder htmlMsgBuf = new StringBuilder(msg.length() + HTML_MESSAGE_START.length() + HTML_MESSAGE_END.length());
         htmlMsgBuf.append(HTML_MESSAGE_START).append(msg).append(HTML_MESSAGE_END);
         setHtmlMsg(htmlMsgBuf.toString());
         return this;
     }
 
     /**
      * Sets the text content.
      *
      * @param text A String.
      * @return An HtmlEmail.
      * @throws EmailException see javax.mail.internet.MimeBodyPart for definitions
      * @since 1.0
      */
     public HtmlEmail setTextMsg(final String text) throws EmailException {
         this.text = EmailException.checkNonEmpty(text, () -> "Invalid message.");
         return this;
     }
 }