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//
// $Id: Resulting.java 6702 2011-09-27 04:58:08Z ray $

package com.threerings.util;

import com.google.common.base.Function;
import com.google.common.base.Objects;

import com.samskivert.util.ArrayUtil;
import com.samskivert.util.IntResultListener;
import com.samskivert.util.Invoker;
import com.samskivert.util.Logger;
import com.samskivert.util.ResultListener;

import com.threerings.presents.client.InvocationService;
import com.threerings.presents.data.InvocationCodes;
import com.threerings.presents.server.InvocationException;

import static com.threerings.NaryaLog.log;

/**
 * A chainable ResultListener, InvocationListener, and Invoker.Unit all in one.
 *
 * TODO: add some examples of different usages.
 */
public class Resulting extends Invoker.Unit
    implements ResultListener,
        InvocationService.ConfirmListener, InvocationService.ResultListener
{
    /** A handy Object->Void function for when you wish to chain to a ResultListener. */
    public static final Function TO_VOID =
        new Function() {
            public Void apply (Object o) {
                return null;
            }
        };

    public Resulting (String name)
    {
        super(name);
    }

    public Resulting (String name, Resulting chain)
    {
        this(name, (ResultListener)chain);
    }

    public Resulting (Resulting chain)
    {
        this(chain.toString(), chain);
    }

    public Resulting (String name, ResultListener chain)
    {
        this(name);
        _chain = chain;
    }

    public Resulting (ResultListener chain)
    {
        this(chain.toString(), chain);
    }

    public Resulting (String name, InvocationService.InvocationListener chain)
    {
        this(name);
        _invChain = chain;
    }

    public Resulting (InvocationService.InvocationListener chain)
    {
        this(chain.toString(), chain);
    }

    public  Resulting (
        String name, final ResultListener chain, final Function xform)
    {
        this(name, new ResultListener() {
            public void requestCompleted (T result) {
                chain.requestCompleted(xform.apply(result));
            }
            public void requestFailed (Exception cause) {
                chain.requestFailed(cause);
            }
        });
    }

    public  Resulting (ResultListener chain, Function xform)
    {
        this(chain.toString(), chain, xform);
    }

    public Resulting (String name, Logger log, Object... logArgs)
    {
        this(name);
        _log = log;
        _logArgs = logArgs;
    }

    /**
     * Construct your Resulting, overriding what you need to,
     * then call this to adapt it.
     */
    public final IntResultListener asIntResultListener ()
    {
        return new IntResultListener() {
            public void requestCompleted (int result) {
                // call the invocation method and it will do the unsafe cast for us.
                Resulting.this.requestProcessed((Object)result);
            }
            public void requestFailed (Exception cause) {
                Resulting.this.requestFailed(cause);
            }
        };
    }

// TODO: Maybe we don't extend Invoker.Unit
//    public Invoker.Unit asUnit (Callable callable)
//    {
//    }
//
//    public Invoker.Unit asUnit ()
//    {
//    }
//
    /**
     * Override this if you are using a Resulting as an Invoker unit.
     */
    public T invokePersist ()
        throws Exception
    {
        // please to be overriding
        return null;
    }

    @Override
    public final boolean invoke ()
    {
        try {
            _result = invokePersist();

        } catch (StopException se) {
            return false;

        } catch (Exception e) {
            _error = e;
        }
        return true;
    }

    /**
     * Call this from your invokePersist() to suppress returning to the dobj thread.
     * @throws StopException every time.
     */
    protected final T stop ()
        throws StopException
    {
        throw STOP.get();
    }

    @Override
    public final void handleResult ()
    {
        if (_error != null) {
            requestFailed(_error);
        } else {
            requestCompleted(_result);
        }
    }

    // from InvocationService.InvocationListener
    public final void requestFailed (String error)
    {
        requestFailed(INV_EX.get().setMessage(error));
    }

    // from InvocationService.ConfirmListener
    public final void requestProcessed ()
    {
        requestCompleted(null);
    }

    // from InvocationService.ResultListener
    public final void requestProcessed (Object result)
    {
        @SuppressWarnings("unchecked") T casted = (T)result;
        requestCompleted(casted);
    }

    /**
     * Override this to handle a request failed in your own way.
     */
    public void requestFailed (Exception cause)
    {
        if (_chain != null) {
            _chain.requestFailed(cause);

        } else if (_invChain != null) {
            _invChain.requestFailed((cause instanceof InvocationException)
                ? cause.getMessage()
                : InvocationCodes.INTERNAL_ERROR);

        } else {
            Object[] logArgs = Objects.firstNonNull(_logArgs, ArrayUtil.EMPTY_OBJECT);
            Object[] args;
            if (cause instanceof InvocationException) {
                args = new Object[logArgs.length + 4];
                args[args.length - 2] = "error";
                args[args.length - 1] = cause.getMessage();

            } else {
                args = new Object[logArgs.length + 3];
                args[args.length - 1] = cause;
            }
            args[0] = "Resulting";
            args[1] = this;
            System.arraycopy(logArgs, 0, args, 2, logArgs.length);
            Objects.firstNonNull(_log, log).warning("Request failed", args);
        }
    }

    /**
     * Override this to handle a request completion in your own way.
     */
    public void requestCompleted (T result)
    {
        if (_chain != null) {
            _chain.requestCompleted(result);

        } else if (_invChain instanceof InvocationService.ResultListener) {
            ((InvocationService.ResultListener)_invChain).requestProcessed(result);

        } else if (_invChain instanceof InvocationService.ConfirmListener) {
            ((InvocationService.ConfirmListener)_invChain).requestProcessed();
        }
    }

    /** Our invocation chain, if any. */
    protected InvocationService.InvocationListener _invChain;

    protected ResultListener _chain;

    protected Logger _log;

    protected Object[] _logArgs;

    protected T _result;

    protected Exception _error;

    protected static final ThreadLocal INV_EX =
        new ThreadLocal() {
            @Override protected ReusableInvocationException initialValue () {
                return new ReusableInvocationException();
            }
        };

    protected static class ReusableInvocationException extends InvocationException
    {
        public ReusableInvocationException ()
        {
            super("");
        }

        public ReusableInvocationException setMessage (String msg)
        {
            _msg = msg;
            return this;
        }

        @Override public String getMessage ()
        {
            return _msg;
        }

        protected String _msg;
    }

    protected static final ThreadLocal STOP =
        new ThreadLocal() {
            @Override protected StopException initialValue () {
                return new StopException();
            }
        };

    protected static class StopException extends RuntimeException
    {
    }
}