// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.restapi;

import com.yahoo.container.jdisc.HttpRequest;
import com.yahoo.container.jdisc.HttpResponse;
import com.yahoo.container.jdisc.RequestView;
import com.yahoo.container.jdisc.ThreadedHttpRequestHandler;
import com.yahoo.container.jdisc.RequestHandlerSpec;
import com.yahoo.container.jdisc.utils.CapabilityRequiringRequestHandler;
import com.yahoo.jdisc.Metric;
import com.yahoo.security.tls.CapabilitySet;

import java.util.concurrent.Executor;

/**
 * @author bjorncs
 */
public abstract class RestApiRequestHandler<T extends RestApiRequestHandler<T>> extends ThreadedHttpRequestHandler
        implements CapabilityRequiringRequestHandler {

    private final RestApi restApi;

    @FunctionalInterface public interface RestApiProvider<T> { RestApi createRestApi(T self); }

    /**
     * RestApi will usually refer to handler methods of subclass, which are not accessible before super constructor has completed.
     * This is hack to leak reference to subclass instance's "this" reference.
     * Caller must ensure that provider instance does not try to access any uninitialized fields.
     */
    @SuppressWarnings("unchecked")
    protected RestApiRequestHandler(ThreadedHttpRequestHandler.Context context, RestApiProvider<T> provider) {
        super(context);
        this.restApi = provider.createRestApi((T)this);
    }

    /**
     * @see #RestApiRequestHandler(Context, RestApiProvider)
     */
    @SuppressWarnings("unchecked")
    protected RestApiRequestHandler(Executor executor, Metric metric, RestApiProvider<T> provider) {
        super(executor, metric);
        this.restApi = provider.createRestApi((T)this);
    }

    protected RestApiRequestHandler(ThreadedHttpRequestHandler.Context context, RestApi restApi) {
        super(context);
        this.restApi = restApi;
    }

    protected RestApiRequestHandler(Executor executor, Metric metric, RestApi restApi) {
        super(executor, metric);
        this.restApi = restApi;
    }

    @Override public final HttpResponse handle(HttpRequest request) { return restApi.handleRequest(request); }
    @Override public RequestHandlerSpec requestHandlerSpec() { return restApi.requestHandlerSpec(); }
    @Override public CapabilitySet requiredCapabilities(RequestView req) { return restApi.requiredCapabilities(req); }

    public RestApi restApi() { return restApi; }
}