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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.rest;

import static org.apache.juneau.internal.CollectionUtils.*;
import static org.apache.juneau.internal.IOUtils.*;

import java.io.*;
import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.http.*;
import org.apache.juneau.rest.response.*;
import org.apache.juneau.svl.*;

/**
 * Represents the contents of a text file with convenience methods for resolving SVL variables and adding
 * HTTP response headers.
 * 
 * <p>
 * This class is handled special by the {@link WritableHandler} class.
 * <br>This allows these objects to be returned as responses by REST methods.
 * 
 * <p>
 * <l>ReaderResources</l> are meant to be thread-safe and reusable objects.
 * <br>The contents of the request passed into the constructor are immediately converted to read-only strings.
 * 
 * <p>
 * Instances of this class can be built using {@link ReaderResourceBuilder}.
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 *    <li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-rest-server.ReaderResource">Overview &gt; juneau-rest-server &gt; ReaderResource</a>
 * </ul>
 */
public class ReaderResource implements Writable {

   private final MediaType mediaType;
   private final String[] contents;
   private final VarResolverSession varSession;
   private final Map<String,Object> headers;
   
   /**
    * Creates a new instance of a {@link ReaderResourceBuilder}
    * 
    * @return A new instance of a {@link ReaderResourceBuilder}
    */
   public static ReaderResourceBuilder create() {
      return new ReaderResourceBuilder();
   }

   /**
    * Constructor.
    * 
    * @param mediaType The resource media type.
    * @param headers The HTTP response headers for this streamed resource.
    * @param varSession Optional variable resolver for resolving variables in the string.
    * @param contents
    *    The resource contents.
    *    <br>If multiple contents are specified, the results will be concatenated.
    *    <br>Contents can be any of the following:
    *    <ul>
    *       <li><code>InputStream</code>
    *       <li><code>Reader</code> - Converted to UTF-8 bytes.
    *       <li><code>File</code>
    *       <li><code>CharSequence</code> - Converted to UTF-8 bytes.
    *    </ul>
    * @throws IOException
    */
   public ReaderResource(MediaType mediaType, Map<String,Object> headers, VarResolverSession varSession, Object...contents) throws IOException {
      this.mediaType = mediaType;
      this.varSession = varSession;

      this.headers = immutableMap(headers);

      this.contents = new String[contents.length];
      for (int i = 0; i < contents.length; i++) {
         Object c = contents[i];
         if (c == null)
            this.contents[i] = "";
         else if (c instanceof InputStream)
            this.contents[i] = read((InputStream)c);
         else if (c instanceof File)
            this.contents[i] = read((File)c);
         else if (c instanceof Reader)
            this.contents[i] = read((Reader)c);
         else if (c instanceof CharSequence)
            this.contents[i] = ((CharSequence)c).toString();
         else
            throw new IOException("Invalid class type passed to ReaderResource: " + c.getClass().getName());
      }
   }

   /**
    * Get the HTTP response headers.
    * 
    * @return 
    *    The HTTP response headers.  
    *    <br>An unmodifiable map.  
    *    <br>Never <jk>null</jk>.
    */
   public Map<String,Object> getHeaders() {
      return headers;
   }

   @Override /* Writeable */
   public Writer writeTo(Writer w) throws IOException {
      for (String s : contents) {
         if (varSession != null)
            varSession.resolveTo(s, w);
         else
            w.write(s);
      }
      return w;
   }

   @Override /* Writeable */
   public MediaType getMediaType() {
      return mediaType;
   }

   @Override /* Object */
   public String toString() {
      if (contents.length == 1 && varSession == null)
         return contents[0];
      StringWriter sw = new StringWriter();
      for (String s : contents) {
         if (varSession != null)
            return varSession.resolve(s);
         sw.write(s);
      }
      return sw.toString();
   }

   /**
    * Same as {@link #toString()} but strips comments from the text before returning it.
    * 
    * <p>
    * Supports stripping comments from the following media types: HTML, XHTML, XML, JSON, Javascript, CSS.
    * 
    * @return The resource contents stripped of any comments.
    */
   public String toCommentStrippedString() {
      String s = toString();
      String subType = mediaType.getSubType();
      if ("html".equals(subType) || "xhtml".equals(subType) || "xml".equals(subType))
         s = s.replaceAll("(?s)<!--(.*?)-->\\s*", "");
      else if ("json".equals(subType) || "javascript".equals(subType) || "css".equals(subType))
         s = s.replaceAll("(?s)\\/\\*(.*?)\\*\\/\\s*", "");
      return s;
   }
}