/*
 * Copyright 2017 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://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.
 */

package org.jbpm.workflow.instance.node;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.drools.core.util.MVELSafeHelper;
import org.jbpm.process.core.ContextContainer;
import org.jbpm.process.core.context.variable.VariableScope;
import org.jbpm.process.instance.ContextInstance;
import org.jbpm.process.instance.context.variable.VariableScopeInstance;
import org.jbpm.workflow.core.node.ForEachNode;
import org.jbpm.workflow.core.node.ForEachNode.ForEachJoinNode;
import org.jbpm.workflow.core.node.ForEachNode.ForEachSplitNode;
import org.jbpm.workflow.instance.NodeInstance;
import org.jbpm.workflow.instance.NodeInstanceContainer;
import org.jbpm.workflow.instance.impl.NodeInstanceImpl;
import org.jbpm.workflow.instance.impl.NodeInstanceResolverFactory;
import org.kie.api.definition.process.Connection;
import org.kie.api.definition.process.Node;
import org.mvel2.integration.VariableResolver;
import org.mvel2.integration.impl.SimpleValueResolver;

/**
 * Runtime counterpart of a for each node.
 */
public class ForEachNodeInstance extends CompositeContextNodeInstance {

    private static final long serialVersionUID = 510L;

    private static final String TEMP_OUTPUT_VAR = "foreach_output";
    
    private int sequentialCounter = 0;

    public ForEachNode getForEachNode() {
        return (ForEachNode) getNode();
    }

    @Override
    public NodeInstance getNodeInstance(final Node node) {
        if (node instanceof ForEachSplitNode) {
            ForEachSplitNodeInstance nodeInstance = new ForEachSplitNodeInstance();
            nodeInstance.setNodeId(node.getId());
            nodeInstance.setNodeInstanceContainer(this);
            nodeInstance.setProcessInstance(getProcessInstance());
            String uniqueID = (String) node.getMetaData().get("UniqueId");
            if (uniqueID == null) {
                uniqueID = node.getId() + "";
            }
            int level = this.getLevelForNode(uniqueID);
            nodeInstance.setLevel(level);
            return nodeInstance;
        } else if (node instanceof ForEachJoinNode) {
            ForEachJoinNodeInstance nodeInstance = (ForEachJoinNodeInstance)
                    getFirstNodeInstance(node.getId());
            if (nodeInstance == null) {
                nodeInstance = new ForEachJoinNodeInstance();
                nodeInstance.setNodeId(node.getId());
                nodeInstance.setNodeInstanceContainer(this);
                nodeInstance.setProcessInstance(getProcessInstance());
                String uniqueID = (String) node.getMetaData().get("UniqueId");
                if (uniqueID == null) {
                    uniqueID = node.getId() + "";
                }
                int level = this.getLevelForNode(uniqueID);
                nodeInstance.setLevel(level);
            }
            return nodeInstance;
        }
        return super.getNodeInstance(node);
    }

    @Override
    public ContextContainer getContextContainer() {
        return getForEachNode().getCompositeNode();
    }

    private Collection<?> evaluateCollectionExpression(String collectionExpression) {
        Object collection;
        VariableScopeInstance variableScopeInstance = (VariableScopeInstance)
                resolveContextInstance(VariableScope.VARIABLE_SCOPE, collectionExpression);
        if (variableScopeInstance != null) {
            collection = variableScopeInstance.getVariable(collectionExpression);
        } else {
            try {
                collection = MVELSafeHelper.getEvaluator().eval(collectionExpression, new NodeInstanceResolverFactory(this));
            } catch (Throwable t) {
                throw new IllegalArgumentException(
                        "Could not find collection " + collectionExpression);
            }
        }
        if (collection == null) {
            return Collections.emptyList();
        }
        if (collection instanceof Collection<?>) {
            return (Collection<?>) collection;
        }
        if (collection.getClass().isArray()) {
            List<Object> list = new ArrayList<>();
            Collections.addAll(list, (Object[]) collection);
            return list;
        }
        throw new IllegalArgumentException(
                "Unexpected collection type: " + collection.getClass());
    }

    public class ForEachSplitNodeInstance extends NodeInstanceImpl {

        private static final long serialVersionUID = 510l;

        public ForEachSplitNode getForEachSplitNode() {
            return (ForEachSplitNode) getNode();
        }

        @Override
        public void internalTrigger(org.kie.api.runtime.process.NodeInstance fromm, String type) {
            String collectionExpression = getForEachNode().getCollectionExpression();
            Collection<?> collection = evaluateCollectionExpression(collectionExpression);
            ((NodeInstanceContainer) getNodeInstanceContainer()).removeNodeInstance(this);
            if (collection.isEmpty()) {
                ForEachNodeInstance.this.triggerCompleted(org.jbpm.workflow.core.Node.CONNECTION_DEFAULT_TYPE, true);
            } else {
            	List<NodeInstance> nodeInstances = new ArrayList<>();
            	
            	for (Object o: collection) {
            		String variableName = getForEachNode().getVariableName();
            		NodeInstance nodeInstance =
            		((NodeInstanceContainer) getNodeInstanceContainer()).getNodeInstance(getForEachSplitNode().getTo().getTo());
            		VariableScopeInstance variableScopeInstance = (VariableScopeInstance)
            			nodeInstance.resolveContextInstance(VariableScope.VARIABLE_SCOPE, variableName);
            		variableScopeInstance.getVariableScope().validateVariable(getProcessInstance().getProcessName(), variableName, o);
            		variableScopeInstance.setVariable(variableName, o);
            		nodeInstances.add(nodeInstance);
            		
            		if (getForEachNode().isSequential()) {
            		    // for sequential mode trigger only first item from the list
            		    sequentialCounter++;
            		    break;
            		}
            	}
            	for (NodeInstance nodeInstance: nodeInstances) {
            	    logger.debug( "Triggering [{}] in multi-instance loop.", nodeInstance.getNodeId() );
            		nodeInstance.trigger(this, getForEachSplitNode().getTo().getToType());
            	}
	            if (!getForEachNode().isWaitForCompletion()) {
	            	ForEachNodeInstance.this.triggerCompleted(org.jbpm.workflow.core.Node.CONNECTION_DEFAULT_TYPE, false);
	            }
            }
        }
    }

    public class ForEachJoinNodeInstance extends NodeInstanceImpl {

        private static final long serialVersionUID = 510l;

        public ForEachJoinNode getForEachJoinNode() {
            return (ForEachJoinNode) getNode();
        }

        @Override
        @SuppressWarnings({"unchecked", "rawtypes"})
        public void internalTrigger(org.kie.api.runtime.process.NodeInstance from, String type) {
        	Map<String, Object> tempVariables = new HashMap<>();
            VariableScopeInstance subprocessVariableScopeInstance = null;
            if (getForEachNode().getOutputVariableName() != null) {
                subprocessVariableScopeInstance = (VariableScopeInstance) getContextInstance(VariableScope.VARIABLE_SCOPE);

                Collection<Object> outputCollection = (Collection<Object>) subprocessVariableScopeInstance.getVariable(TEMP_OUTPUT_VAR);
                if (outputCollection == null) {
                    outputCollection = new ArrayList<>();
                }

                VariableScopeInstance variableScopeInstance = (VariableScopeInstance)
                        ((NodeInstanceImpl) from).resolveContextInstance(VariableScope.VARIABLE_SCOPE, getForEachNode().getOutputVariableName());
                Object outputVariable = null;
                if (variableScopeInstance != null) {
                    outputVariable = variableScopeInstance.getVariable(getForEachNode().getOutputVariableName());
                }
                outputCollection.add(outputVariable);

                subprocessVariableScopeInstance.setVariable(TEMP_OUTPUT_VAR, outputCollection);
                // add temp collection under actual mi output name for completion condition evaluation
                tempVariables.put(getForEachNode().getOutputVariableName(), outputVariable);
                String outputCollectionName = getForEachNode().getOutputCollectionExpression();
                tempVariables.put(outputCollectionName, outputCollection);
            }
            boolean isCompletionConditionMet = evaluateCompletionCondition(getForEachNode().getCompletionConditionExpression(), tempVariables);
            

            if (getForEachNode().isSequential() && !isCompletionConditionMet) {
                String collectionExpression = getForEachNode().getCollectionExpression();
                Collection<?> collection = evaluateCollectionExpression(collectionExpression);
                
                if (collection.size() > sequentialCounter) {
                                       
                    String variableName = getForEachNode().getVariableName();
                    NodeInstance nodeInstance = (NodeInstance)
                    ((NodeInstanceContainer) getNodeInstanceContainer()).getNodeInstance(getForEachNode().getForEachSplitNode().getTo().getTo());
                    VariableScopeInstance variableScopeInstance = (VariableScopeInstance)
                        nodeInstance.resolveContextInstance(VariableScope.VARIABLE_SCOPE, variableName);
                    variableScopeInstance.setVariable(variableName, new ArrayList<>(collection).get(sequentialCounter));                        
                    sequentialCounter++;                    
                                
                    logger.debug( "Triggering [{}] in multi-instance loop.", ((NodeInstanceImpl) nodeInstance).getNodeId() );
                    ((org.jbpm.workflow.instance.NodeInstance) nodeInstance).trigger(null, getForEachNode().getForEachSplitNode().getTo().getToType());
                
                }
            }
            
            if (getNodeInstanceContainer().getNodeInstances().size() == 1 || isCompletionConditionMet) {
                String outputCollection = getForEachNode().getOutputCollectionExpression();
                if (outputCollection != null) {
                    VariableScopeInstance variableScopeInstance = (VariableScopeInstance) resolveContextInstance(VariableScope.VARIABLE_SCOPE, outputCollection);
                    Collection<?> outputVariable = (Collection<?>) variableScopeInstance.getVariable(outputCollection);
                    if (outputVariable != null) {
                        outputVariable.addAll((Collection) subprocessVariableScopeInstance.getVariable(TEMP_OUTPUT_VAR));
                    } else {
                        outputVariable = (Collection<Object>) subprocessVariableScopeInstance.getVariable(TEMP_OUTPUT_VAR);
                    }
                    variableScopeInstance.setVariable(outputCollection, outputVariable);
                }
                ((NodeInstanceContainer) getNodeInstanceContainer()).removeNodeInstance(this);
                if (getForEachNode().isWaitForCompletion()) {

                    if (!"true".equals(System.getProperty("jbpm.enable.multi.con"))) {

                        triggerConnection(getForEachJoinNode().getTo());
                    } else {

                        List<Connection> connections = getForEachJoinNode().getOutgoingConnections(org.jbpm.workflow.core.Node.CONNECTION_DEFAULT_TYPE);
                        for (Connection connection : connections) {
                            triggerConnection(connection);
                        }
                    }
                }
            }
            
        }

        private boolean evaluateCompletionCondition(String expression, Map<String, Object> tempVariables) {
            if (expression == null || expression.isEmpty()) {
                return false;
            }
            try {
                Object result = MVELSafeHelper.getEvaluator().eval(expression, new ForEachNodeInstanceResolverFactory(this, tempVariables));
                if (!(result instanceof Boolean)) {
                    throw new RuntimeException("Completion condition expression must return boolean values: " + result
                                                       + " for expression " + expression);
                }
                return ((Boolean) result).booleanValue();
            } catch (Throwable t) {
                throw new IllegalArgumentException("Could not evaluate completion condition  " + expression, t);
            }
        }
    }

    @Override
    public ContextInstance getContextInstance(String contextId) {
        ContextInstance contextInstance = super.getContextInstance(contextId);
        if (contextInstance == null) {
            contextInstance = resolveContextInstance(contextId, TEMP_OUTPUT_VAR);
            setContextInstance(contextId, contextInstance);
        }

        return contextInstance;
    }

    @Override
    public int getLevelForNode(String uniqueID) {
        // always 1 for for each
        return 1;
    }

    public void setInternalSequentialCounter(int counter) {
        this.sequentialCounter = counter;
    }
    
    public int getSequentialCounter() {
        return this.sequentialCounter;
    }
    
    private class ForEachNodeInstanceResolverFactory extends NodeInstanceResolverFactory {

        private static final long serialVersionUID = -8856846610671009685L;

        private Map<String, Object> tempVariables;

        public ForEachNodeInstanceResolverFactory(NodeInstance nodeInstance, Map<String, Object> tempVariables) {
            super(nodeInstance);
            this.tempVariables = tempVariables;
        }

        @Override
        public boolean isResolveable(String name) {
            boolean result = tempVariables.containsKey(name);
            if (result) {
                return result;
            }
            return super.isResolveable(name);
        }

        @Override
        public VariableResolver getVariableResolver(String name) {
            if (tempVariables.containsKey(name)) {
                return new SimpleValueResolver(tempVariables.get(name));
            }
            return super.getVariableResolver(name);
        }
    }
}
