MediaType.java

package org.yamcs.api;

import java.util.HashMap;
import java.util.Map;

import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpRequest;

/**
 * Syntactic sugar around a media type string. Contains predefined ones, but is
 * open-ended for when we support dynamic rest handlers better.
 */
public final class MediaType {
    static final Map<String, MediaType> knownTypes = new HashMap<>();
    public static final MediaType OCTET_STREAM = new MediaType("application/octet-stream");
    public static final MediaType CSV = new MediaType("text/csv");
    public static final MediaType JAVA_SERIALIZED_OBJECT = new MediaType("application/x-java-serialized-object");
    public static final MediaType JSON = new MediaType("application/json");
    public static final MediaType PROTOBUF = new MediaType("application/protobuf");
    public static final MediaType PLAIN_TEXT = new MediaType("plain/text");
    public static final MediaType ANY = new MediaType("*/*");

    private final String typeString;
    
    private MediaType(String typeString) {
        if (typeString == null) {
            throw new NullPointerException("typeString must not be null");
        }
        this.typeString = typeString;
        knownTypes.put(typeString, this);
    }
    
    public boolean is(String typeString) {
        return typeString != null && this.typeString.equals(typeString);
    }
    
    @Override
    public boolean equals(Object obj) {
        if (obj == null || !(obj instanceof MediaType)) return false;
        return typeString.equals(((MediaType) obj).typeString);
    }
    
    @Override
    public int hashCode() {
        return typeString.hashCode();
    }
    
    @Override
    public String toString() {
        return typeString;
    }
    
    /**
     * Returns one  of the static members (OCTET_STREAM, CSV, etc)  if this is a known type or a new object if the type is unknown.
     * 
     * @param typeString
     * @return the MediaType object corresponding to the type string
     */
    public static MediaType from(String typeString) {
        MediaType mt = knownTypes.get(typeString);
        if(mt!=null) return mt;
        return new MediaType(typeString);
    }

    /**
     * @param req
     * @return the Content-Type header if present or JSON by default if the Content-Type header is not present.
     */
    public static MediaType getContentType(HttpRequest req) {
        String declaredContentType = req.headers().get(HttpHeaderNames.CONTENT_TYPE);
        if(declaredContentType!=null) {
            return MediaType.from(declaredContentType);
        }
        return MediaType.JSON;
    }
    
    /**
     * @param req
     * @return the Accept header if present and not set to ANY or Content-Type header if present or JSON if none of the headers is present or the Accept is present and set to ANY.
     */
    public static MediaType getAcceptType(HttpRequest req) {
        String acceptType = req.headers().get(HttpHeaderNames.ACCEPT);
        if(acceptType!=null) {
            MediaType r =  MediaType.from(acceptType);
            if(r==MediaType.ANY) {
                return getContentType(req); 
            } else {
                return r;
            }
        } else {
            return getContentType(req); 
        }
    }
}