/*******************************************************************************
 * Copyright (c) 2015-2018 Skymind, Inc.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Apache License, Version 2.0 which is available at
 * https://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 ******************************************************************************/

package org.deeplearning4j.nn.params;

import lombok.val;
import org.deeplearning4j.nn.api.ParamInitializer;
import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
import org.deeplearning4j.nn.conf.layers.Layer;
import org.deeplearning4j.nn.conf.layers.recurrent.SimpleRnn;
import org.deeplearning4j.nn.weights.IWeightInit;
import org.nd4j.linalg.api.ndarray.INDArray;

import java.util.*;

import static org.nd4j.linalg.indexing.NDArrayIndex.interval;
import static org.nd4j.linalg.indexing.NDArrayIndex.point;

public class SimpleRnnParamInitializer implements ParamInitializer {

    private static final SimpleRnnParamInitializer INSTANCE = new SimpleRnnParamInitializer();

    public static SimpleRnnParamInitializer getInstance(){
        return INSTANCE;
    }

    public static final String WEIGHT_KEY = DefaultParamInitializer.WEIGHT_KEY;
    public static final String RECURRENT_WEIGHT_KEY = "RW";
    public static final String BIAS_KEY = DefaultParamInitializer.BIAS_KEY;
    public static final String GAIN_KEY = DefaultParamInitializer.GAIN_KEY;

    private static final List<String> WEIGHT_KEYS = Collections.unmodifiableList(Arrays.asList(WEIGHT_KEY, RECURRENT_WEIGHT_KEY));
    private static final List<String> BIAS_KEYS = Collections.singletonList(BIAS_KEY);


    @Override
    public long numParams(NeuralNetConfiguration conf) {
        return numParams(conf.getLayer());
    }

    @Override
    public long numParams(Layer layer) {
        SimpleRnn c = (SimpleRnn)layer;
        val nIn = c.getNIn();
        val nOut = c.getNOut();
        return nIn * nOut + nOut * nOut + nOut + (hasLayerNorm(layer) ? 2 * nOut : 0);
    }

    @Override
    public List<String> paramKeys(Layer layer) {
        final ArrayList<String> keys = new ArrayList<>(3);
        keys.addAll(weightKeys(layer));
        keys.addAll(biasKeys(layer));
        return keys;
    }

    @Override
    public List<String> weightKeys(Layer layer) {
        final ArrayList<String> keys = new ArrayList<>(WEIGHT_KEYS);

        if(hasLayerNorm(layer)){
            keys.add(GAIN_KEY);
        }

        return keys;
    }

    @Override
    public List<String> biasKeys(Layer layer) {
        return BIAS_KEYS;
    }

    @Override
    public boolean isWeightParam(Layer layer, String key) {
        return WEIGHT_KEY.equals(key) || RECURRENT_WEIGHT_KEY.equals(key) || GAIN_KEY.equals(key);
    }

    @Override
    public boolean isBiasParam(Layer layer, String key) {
        return BIAS_KEY.equals(key);
    }

    @Override
    public Map<String, INDArray> init(NeuralNetConfiguration conf, INDArray paramsView, boolean initializeParams) {
        SimpleRnn c = (SimpleRnn)conf.getLayer();
        val nIn = c.getNIn();
        val nOut = c.getNOut();

        Map<String,INDArray> m;

        if (initializeParams) {
            m = getSubsets(paramsView, nIn, nOut, false, hasLayerNorm(c));
            INDArray w = c.getWeightInitFn().init(nIn, nOut, new long[]{nIn, nOut}, 'f', m.get(WEIGHT_KEY));
            m.put(WEIGHT_KEY, w);

            IWeightInit rwInit;
            if (c.getWeightInitFnRecurrent() != null) {
                rwInit = c.getWeightInitFnRecurrent();
            } else {
                rwInit = c.getWeightInitFn();
            }

            INDArray rw = rwInit.init(nOut, nOut, new long[]{nOut, nOut}, 'f', m.get(RECURRENT_WEIGHT_KEY));
            m.put(RECURRENT_WEIGHT_KEY, rw);

            m.get(BIAS_KEY).assign(c.getBiasInit());

            if(hasLayerNorm(c)){
                m.get(GAIN_KEY).assign(c.getGainInit());
            }
        } else {
            m = getSubsets(paramsView, nIn, nOut, true, hasLayerNorm(c));
        }

        conf.addVariable(WEIGHT_KEY);
        conf.addVariable(RECURRENT_WEIGHT_KEY);
        conf.addVariable(BIAS_KEY);
        if(hasLayerNorm(c)){
            conf.addVariable(GAIN_KEY);
        }

        return m;
    }

    @Override
    public Map<String, INDArray> getGradientsFromFlattened(NeuralNetConfiguration conf, INDArray gradientView) {
        SimpleRnn c = (SimpleRnn)conf.getLayer();
        val nIn = c.getNIn();
        val nOut = c.getNOut();

        return getSubsets(gradientView, nIn, nOut, true, hasLayerNorm(c));
    }

    private static Map<String,INDArray> getSubsets(INDArray in, long nIn, long nOut, boolean reshape, boolean hasLayerNorm){
        long pos = nIn * nOut;
        INDArray w = in.get(interval(0,0,true), interval(0, pos));
        INDArray rw = in.get(interval(0,0,true), interval(pos, pos + nOut * nOut));
        pos += nOut * nOut;
        INDArray b = in.get(interval(0,0,true), interval(pos, pos + nOut));

        if(reshape){
            w = w.reshape('f', nIn, nOut);
            rw = rw.reshape('f', nOut, nOut);
        }

        Map<String,INDArray> m = new LinkedHashMap<>();
        m.put(WEIGHT_KEY, w);
        m.put(RECURRENT_WEIGHT_KEY, rw);
        m.put(BIAS_KEY, b);
        if(hasLayerNorm){
            pos += nOut;
            INDArray g = in.get(interval(0,0,true), interval(pos, pos + 2 * nOut));
            m.put(GAIN_KEY, g);
        }
        return m;
    }

    protected boolean hasLayerNorm(Layer layer){
        if(layer instanceof SimpleRnn){
            return ((SimpleRnn) layer).hasLayerNorm();
        }
        return false;
    }
}
