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package net.sf.javaprinciples.resource;

import java.io.IOException;
import java.io.InputStream;

/**
 * The Resource object encapsulates the content.
 * It is flexible on whether the content is stored in memory or on disk.
 * The resource support a window of time for when the resource is valid.
 * 
 * @author wslade
 * @param  - resource type
 *
 */
public interface Resource
{
    /**
     * A resource may be valid from a point in time.
     * This typically will be the time the resource was created. It may not be the
     * time the resource was first served.
     * @return A time in milliseconds since 1970 relative to UTC.
     */
    public long getValidFrom();
    
    /**
     * A resource may be valid only up to a point in time.
     * This typically will be the time the resource may be updated.
     * @return A time in milliseconds since 1970 relative to UTC.
     */
    public long getValidUntil();

    /**
     * Each resource holds content of a specific type.
     * @return The mime type of the content.  
     */
    public String getMimeType();

    /**
     * The resource may have a specific encoding.
     * @return A standard encoding, may be null
     */
    public String getEncoding();

    /**
     * The length of the resource in bytes
     */
    public long getResourceLength();

    /**
     * Apply content to the resource.
     * @param content May be the content itself or a reference such as a file url.
     */
    public void setContent(T content);
    
    /**
     * Get content of the resource.
     * @return content of resource. 
     */
    public T getContent();
    
    /**
     * 
     * @return A stream to the content. May be null if the content is no longer present.
     * @throws IOException If a problem occurs opening the stream. Retrying wont help.
     */
    InputStream getInputStream() throws IOException;
}