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astyanax-entity-mapper
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package com.netflix.astyanax.entitystore;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.PersistenceException;

import org.apache.commons.lang.StringUtils;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.netflix.astyanax.ColumnListMutation;
import com.netflix.astyanax.MutationBatch;
import com.netflix.astyanax.model.ColumnFamily;
import com.netflix.astyanax.model.ColumnList;

/**
 * utility class to map btw root Entity and cassandra data model
 * @param  entity type 
 * @param  rowKey type
 */
public class EntityMapper {

	private final Class clazz;
	private final Integer ttl;
	private final Method ttlMethod;
	private final Field idField;
	private final Map columnList;
	private final ColumnMapper uniqueColumn;
	private final String entityName;
	
	/**
	 * 
	 * @param clazz
	 * @throws IllegalArgumentException 
	 * 		if clazz is NOT annotated with @Entity
	 * 		if column name contains illegal char (like dot)
	 */
	public EntityMapper(Class clazz, Integer ttl) {
		this.clazz = clazz;
		
		// clazz should be annotated with @Entity
		Entity entityAnnotation = clazz.getAnnotation(Entity.class);
		if(entityAnnotation == null)
			throw new IllegalArgumentException("class is NOT annotated with @javax.persistence.Entity: " + clazz.getName());
		
		entityName = MappingUtils.getEntityName(entityAnnotation, clazz);
		
		// TTL value from constructor or class-level annotation
		Integer tmpTtlValue = ttl;
		if(tmpTtlValue == null) {
			// constructor value has higher priority
			// try @TTL annotation at entity/class level.
			// it doesn't make sense to support @TTL annotation at individual column level.
			TTL ttlAnnotation = clazz.getAnnotation(TTL.class);
			if(ttlAnnotation != null) {
				int ttlAnnotationValue = ttlAnnotation.value();
				Preconditions.checkState(ttlAnnotationValue > 0, "cannot define non-positive value for TTL annotation at class level: " + ttlAnnotationValue);
				tmpTtlValue = ttlAnnotationValue;
			}
		}
		this.ttl = tmpTtlValue;

		// TTL method
		Method tmpTtlMethod = null;
		for (Method method : this.clazz.getDeclaredMethods()) {
			if (method.isAnnotationPresent(TTL.class)) {
				Preconditions.checkState(tmpTtlMethod == null, "Duplicate TTL method annotation on " + method.getName());
				tmpTtlMethod = method;
				tmpTtlMethod.setAccessible(true);
			}
		}
		this.ttlMethod = tmpTtlMethod;

		Field[] declaredFields = clazz.getDeclaredFields();
		columnList = Maps.newHashMapWithExpectedSize(declaredFields.length);
		Set usedColumnNames = Sets.newHashSet();
		Field tmpIdField = null;
		ColumnMapper tempUniqueMapper = null;
		for (Field field : declaredFields) {
			Id idAnnotation = field.getAnnotation(Id.class);
			if(idAnnotation != null) {
				Preconditions.checkArgument(tmpIdField == null, "there are multiple fields with @Id annotation");
				field.setAccessible(true);
				tmpIdField = field;
			}
			Column columnAnnotation = field.getAnnotation(Column.class);
			if ((columnAnnotation != null)) {
				field.setAccessible(true);
				ColumnMapper columnMapper = null;
				Entity compositeAnnotation = field.getType().getAnnotation(Entity.class);
			    if (Map.class.isAssignableFrom(field.getType())) {
                    columnMapper = new MapColumnMapper(field);
                } else if (Set.class.isAssignableFrom(field.getType())) {
                    columnMapper = new SetColumnMapper(field);
                } else if(compositeAnnotation == null) {
                    if (columnAnnotation.unique()) {
                        Preconditions.checkArgument(tempUniqueMapper == null, "can't have multiple unique columns '" + field.getName() + "'");
                        tempUniqueMapper = new LeafColumnMapper(field);
                    }
                    else {
                        columnMapper = new LeafColumnMapper(field);
                    }
				} else {
	                columnMapper = new CompositeColumnMapper(field);
				}
				Preconditions.checkArgument(!usedColumnNames.contains(columnMapper.getColumnName()), 
						String.format("duplicate case-insensitive column name: %s", columnMapper.getColumnName().toLowerCase()));
				columnList.put(columnMapper.getColumnName(), columnMapper);
				usedColumnNames.add(columnMapper.getColumnName().toLowerCase());
			}
		}
		Preconditions.checkNotNull(tmpIdField, "there are no field with @Id annotation");
		//Preconditions.checkArgument(tmpIdField.getClass().equals(K.getClass()), String.format("@Id field type (%s) doesn't match generic type K (%s)", tmpIdField.getClass(), K.getClass()));
		idField = tmpIdField;
		uniqueColumn = tempUniqueMapper;
	}

    public void fillMutationBatch(MutationBatch mb, ColumnFamily columnFamily, T entity) {
		try {
			@SuppressWarnings("unchecked")
			K rowKey = (K) idField.get(entity);
			ColumnListMutation clm = mb.withRow(columnFamily, rowKey);
			clm.setDefaultTtl(getTtl(entity));
			
			for (ColumnMapper mapper : columnList.values()) {
				mapper.fillMutationBatch(entity, clm, "");
			}
		} catch(Exception e) {
			throw new PersistenceException("failed to fill mutation batch", e);
		}
	}
    
    private Integer getTtl(T entity) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
    	Integer retTtl = this.ttl;
    	// TTL method has higher priority
    	if(ttlMethod != null) {
    		Object retobj = ttlMethod.invoke(entity);
    		retTtl = (Integer) retobj;
    	}
    	return retTtl;
    }

	public T constructEntity(K id, ColumnList cl) {
		try {
		    T entity = clazz.newInstance();
			idField.set(entity, id);
			
			for (com.netflix.astyanax.model.Column column : cl) {
			    List name = Lists.newArrayList(StringUtils.split(column.getName(), "."));
			    setField(entity, name.iterator(), column);
			}
			
			for (ColumnMapper column : columnList.values()) {
			    column.validate(entity);
			}
			return entity;
		} catch(Exception e) {
			throw new PersistenceException("failed to construct entity", e);
		}
	}
	
	void setField(T entity, Iterator name, com.netflix.astyanax.model.Column column) throws Exception {
	    String fieldName = name.next();
	    ColumnMapper mapper = this.columnList.get(fieldName);
        if (mapper != null)
            mapper.setField(entity, name, column);
	}
	
	@SuppressWarnings("unchecked")
	public K getEntityId(T entity) throws Exception {
	    return (K)idField.get(entity);
	}
	
	@VisibleForTesting
	Field getId() {
		return idField;
	}
	
	@VisibleForTesting
	Collection getColumnList() {
		return columnList.values();
	}

	public String getEntityName() {
	    return entityName;
	}
	
	@Override
	public String toString() {
		return String.format("EntityMapper(%s)", clazz);
	}
}