/*
 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * 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.
 *
 * Contributors:
 *     Nuxeo - initial API and implementation
 *
 * $Id$
 */

package org.nuxeo.ecm.core.api.model;

import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;

import org.nuxeo.common.utils.Path;
import org.nuxeo.ecm.core.api.Blob;
import org.nuxeo.ecm.core.api.PropertyException;
import org.nuxeo.ecm.core.api.model.resolver.PropertyObjectResolver;
import org.nuxeo.ecm.core.schema.types.ComplexType;
import org.nuxeo.ecm.core.schema.types.Field;
import org.nuxeo.ecm.core.schema.types.Schema;
import org.nuxeo.ecm.core.schema.types.Type;

/**
 * Document properties are instances of document schema fields.
 * <p>
 * You can say that a {@link Field} object is like a Java class and a Property object like a class instance. Thus,
 * schemas defines fields (or elements) which have a name and a type, and each field of a document can be instantiated
 * (if the schema permits) as a Property object.
 * <p>
 * Properties are always bound to a schema field that provides the type and constraints on the property values. An
 * exception is the root property the {@link DocumentPart} object which is not bound to a field but to a schema.
 * <p>
 * So properties are holding the actual values for each defined field.
 * <p>
 * The usual way of using properties is to get a document from the storage server then modify document properties and
 * send them back to the storage server to that modifications are be stored.
 * <p>
 * Note that the storage server can be on a remote machine so when modifying properties remotely they are serialized and
 * sent through the network between the two machines. This means properties must hold serializable values and also they
 * must store some state flags so that the storage can decide which property was modified and how in order to correctly
 * update the stored versions.
 * <p>
 * As we have seen each property may hold a serializable value which we will refer to as the <code>normalized</code>
 * property value. For each schema field type there is only one java serializable object representation that will be
 * used as the normalized value. The property API is giving you the possibility to use different compatible objects when
 * setting or getting property values. Each property implementation will automatically convert the given value into a
 * normalized one; so internally only the normalized value is stored.
 * <p>
 * For example, for date properties you may use either <code>Date</code> or <code>Calendar</code> when setting or
 * retrieving a property value, but the normalized value will be the <code>Calendar</code> one.
 * <p>
 * As we have seen, properties keep some state flags. Property flags can be divided in two groups:
 * <ul>
 * <li>Dirty Flags - that reflect the public status of the document
 * <li>Internal Flags - that reflect some internal state
 * </ul>
 * <p>
 * Property Types:
 * <p>
 * Before going deeper in property flags, we will talk first about property types. There are several types of properties
 * that are very closed on the type of fields they are bound onto.
 * <ul>
 * <li>Root Property (or <code>DocumentPart</code>) - this is a special property that is bound to a schema instead of a
 * field And it is the root of the property tree.
 * <li>Complex Properties - container properties that are bound to complex field types that can be represented as java
 * <code>Map</code> objects. These properties contains a set of schema defined properties. You cannot add new child
 * properties. You can only modify existing child properties. Complex property values are expressed as java
 * <code>Map</code> objects.
 * <ul>
 * <li>Structured Properties - this is a special case of complex properties. The difference is that structured property
 * values are expressed as <i>scalar</i> java objects instead of java maps. By scalar java objects we mean any well
 * structured object which is not a container like a <code>Map</code> or a <code>Collection</code>. These objects are
 * usually as scalar values - it doesn't make sense for example to set only some parts of that objects without creating
 * the object completely. An example of usage are Blob properties that use {@link Blob} values.
 * </ul>
 * <li>List Properties - container properties that are bound to list field types.
 * <li>Scalar Properties - atomic properties that are bound to scalar field types and that are using as values scalar or
 * primitive java objects like arrays, primitives, String, Date etc.
 * </ul>
 * <p>
 * As we've seen there are 2 categories of properties: container properties and scalar properties Complex and list
 * properties are container properties while structured and scalar properties are scalar.
 * <p>
 * Dirty Flags:
 * <p>
 * Dirty flags are used to keep track of the dirty state of a property. The following flags are supported:
 * <ul>
 * <li> <code>IS_PHANTOM</code> - whether the property is existing in the storage (was explicitly set by the user) or it
 * was dynamically generated using the default value by the implementation to fulfill schema definition. This applies to
 * all property types
 * <li> <code>IS_MODIFIED</code> - whether the property value was modified. This applies to all property types.
 * <li> <code>IS_NEW</code> - whether the property is a new property that was added to a parent list property This
 * applies only to properties that are children of a list property.
 * <li> <code>IS_REMOVED</code> - whether a property was removed. A removed property will be removed from the storage and
 * the next time you access the property it will be a <code>phantom</code> one. This applies only to properties that are
 * children of a complex property.
 * <li> <code>IS_MOVED</code> - whether the property was moved on another position inside the container list. This
 * applies only to properties that are children of a list property.
 * </ul>
 * <p>
 * There are several constraints on how property flags may change. This is a list of all changes that may occur over
 * dirty flags:
 * <ul>
 * <li>NONE + MODIFIED =&gt; MODFIED
 * <li>NONE + REMOVED =&gt; REMOVED
 * <li>NONE + MOVED =&gt; MOVED
 * <li>PHANTOM + MODIFIED =&gt; MODIFIED
 * <li>NEW + MODIFIED =&gt; NEW | MODIFIED
 * <li>NEW + MOVED =&gt; NEW | MOVED
 * <li>MODIFIED + REMOVED =&gt; REMOVED
 * <li>MODIFIED + MOVED =&gt; MODIFIED | MOVED
 * <li>MODIFIED + MODIFIED =&gt; MODIFIED
 * </ul>
 * <p>
 * The combinations not listed above are not permitted.
 * <p>
 * In case of list items, the REMOVED flag is not used since the property will be physically removed from the property
 * tree.
 * <p>
 * Also when the dirty flag of a children property changes, its parent is informed to update its MODIFIED flag if
 * needed. This way a modification on a children property is propagated to parents in the form of a MODIFIED flag.
 * <p>
 * Internal Flags:
 * <p>
 * Internal flags are used by the implementation to keep some internal state. For these flags you should look into the
 * implementation
 * <p>
 * Apart flags properties can also hold some random user data using {@link Property#setData(Object)} and
 * {@link Property#getData()} methods. This can be used for example to keep a context attached to a property. But be
 * aware when using this you should provide serializable objects as the data you are attaching otherwise if properties
 * are serialized / unserialized this will generate errors. The API is not forcing you to use serializable values since
 * you can also use this feature to store temporary context data that will not be sent over the network.
 *
 * @see <code>TestPropertyModel</code> for usage of property API
 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
 */
public interface Property extends Cloneable, Serializable, Iterable<Property> {

    /**
     * No dirty flags set.
     */
    int NONE = 0;

    /**
     * Flag used to mark a property as new. Property was added to a list.
     */
    int IS_NEW = 1;

    /**
     * Flag used to mark a property as dirty. Property value was modified.
     */
    int IS_MODIFIED = 2;

    /**
     * Flag used to mark a property as dirty. Property was removed.
     */
    int IS_REMOVED = 4;

    /**
     * Flag used to mark a property as dirty. Property was moved to another index.
     */
    int IS_MOVED = 8;

    /**
     * Flag used to mark a property as phantom.
     */
    int IS_PHANTOM = 16;

    /**
     * A mask for the first 4 flags: NEW, REMOVED, MODIFIED, MOVED.
     */
    int IS_DIRTY = IS_NEW | IS_REMOVED | IS_MOVED | IS_MODIFIED;

    /**
     * A mask for public flags.
     */
    int DIRTY_MASK = IS_PHANTOM | IS_DIRTY;

    /**
     * Tests if this property is new (just created but not yet stored).
     * <p>
     * A property is new when added to a collection. This is the typical state for a new property added to a list
     *
     * @return true if this property is new, false otherwise
     */
    boolean isNew();

    /**
     * Tests if a property is flagged as removed. Removed properties are child property that were removed from their
     * container.
     *
     * @return if the property was removed, false otherwise
     */
    boolean isRemoved();

    /**
     * Tests if a property value was modified.
     *
     * @return if the property was removed, false otherwise
     */
    boolean isModified();

    /**
     * Tests if a property value was moved to another index in the parent list if any.
     *
     * @return if the property was removed, false otherwise
     */
    boolean isMoved();

    /**
     * Tests if the property is a phantom. This means it doesn't exists yet in the storage and it is not a new property.
     * This is a placeholder for a property that is defined by the schema but was not yet set.
     *
     * @return true if a phantom false otherwise
     */
    boolean isPhantom();

    /**
     * Tests whether a property is dirty.
     * <p>
     * This tests whether or not a dirty flag is set on the property.
     *
     * @return true if the property changed or is new
     */
    boolean isDirty();

    /**
     * only for SimpleDocumentModel
     */
    boolean isForceDirty();

    /**
     * only for SimpleDocumentModel
     */
    void setForceDirty(boolean forceDirty);

    /**
     * Get the dirty flags that are set on this property.
     *
     * @return the dirty flags mask
     */
    int getDirtyFlags();

    /**
     * Notify the property that its changes was stored so it can safely remove dirty flags.
     * <p>
     * Dirty flags are removed according to the type of the modifications. This way if the property was REMOVED it
     * becomes a PHANTOM otherwise all dirty flags are cleared.
     * <p>
     * This method should be used by storage implementors to notify the property it should reset its dirty flags. Note
     * that clearing dirty flags is not propagated to the parent property or to children. You need to clear dirty flags
     * explicitly for each property.
     */
    void clearDirtyFlags();

    /**
     * Whether the property is read only.
     *
     * @return true if read only false otherwise
     */
    boolean isReadOnly();

    /**
     * Sets the read only flag.
     *
     * @param value true to set this property read only false otherwise
     */
    void setReadOnly(boolean value);

    /**
     * Tests whether this property is of a map (complex) type.
     *
     * @return true if the property is of map type, false otherwise
     */
    boolean isComplex();

    /**
     * Tests whether this property is of a list type.
     *
     * @return true if the property is of list type, false otherwise
     */
    boolean isList();

    /**
     * Tests whether this property is of a scalar type.
     *
     * @return true if the property is of a scalar type, false otherwise
     */
    boolean isScalar();

    /**
     * Whether this property is a container - this means the property value is a map or a list.
     * <p>
     * Container properties don't have a scalar values. Container values are computed each time they are requested - by
     * calling on of the <code>getValue</code> methods - by collecting the values of the child properties.
     *
     * @return true if scalar false otherwise
     */
    boolean isContainer();

    /**
     * Gets the property name.
     *
     * @return the property name
     */
    String getName();

    /**
     * Gets the xpath of this property.
     * <p>
     * The xpath is of the form {@code pref:foo/mylist/123/elem}, of note:
     * <ul>
     * <li>there is no initial {@code /}
     * <li>the schema prefix is only present if a prefix is configured for the base property's schema
     * <li>list elements indexes start at 0
     * <li>list elements aren't using the old syntax {@code foo/bar[123]/baz} but the new syntax {@code foo/123/baz}
     * </ul>
     *
     * @return the xpath
     * @since 9.1
     */
    String getXPath();

    /**
     * Gets the path of this property relative to the owner document.
     * <p>
     * The path for top level properties is the same to the property name.
     * <p>
     * NOTE the path returned contains an initial {@code /} and expresses list indexes using an old syntax
     *
     * @return the path
     * @deprecated since 9.1 as it's cumbersome to use; use {@link #getXPath} instead
     */
    @Deprecated
    String getPath();

    /**
     * Get the type of the field corresponding to this property.
     *
     * @return the property type
     */
    Type getType();

    /**
     * Gets the field corresponding to this property.
     * <p>
     * The field is the object defining the property. You can see the field as a java class and the property as a class
     * instance
     *
     * @return
     */
    Field getField();

    /**
     * Gets the property parent.
     *
     * @return the property parent for sub properties or null for top level properties
     */
    Property getParent();

    /**
     * Gets the document schema defining the property tree from which the property belongs.
     *
     * @return the document schema owning the field corresponding to the property
     */
    Schema getSchema();

    /**
     * Gets the root property.
     *
     * @return the root property
     */
    DocumentPart getRoot();

    /**
     * Initializes the property with the given normalized value.
     * <p>
     * The given value must be normalized - note that no check is done on that.
     * <p>
     * The phantom flag is unset by this operation.
     * <p>
     * This method should be used to initialize properties.
     *
     * @param value the normalized value to set
     */
    void init(Serializable value) throws PropertyException;

    /**
     * Sets this property value. The value will be first normalized and then set.
     * <p>
     * For complex or list properties the value will be set recursively (as a map or list value).
     *
     * @param value the value to set
     * @throws {@link InvalidPropertyValueException} if the given value type is not compatible with the expected value
     *         type
     */
    void setValue(Object value) throws PropertyException;

    /**
     * Gets the property normalized value.
     * <p>
     * Normalized values are of the java type that correspond to the field type.
     *
     * @return the property value, which may be null
     */
    Serializable getValue() throws PropertyException;

    /**
     * Gets the property normalized value for write.
     * <p>
     * Can be different fropm {@link #getValue()} in cases where the property adapts the value it is given to store.
     *
     * @return the property value to use for write, which may be null
     * @since 5.2.1
     */
    Serializable getValueForWrite() throws PropertyException;

    /**
     * Gets the property value as the given type.
     * <p>
     * The value is converted using the registered converter to the given type.
     * <p>
     * If conversion is not supported a runtime exception will be triggered.
     *
     * @return the property value, which may be null
     */
    <T> T getValue(Class<T> type) throws PropertyException;

    /**
     * Removes this property from the tree.
     * <p>
     * This method marks the property as dirty and sets its value to null.
     *
     * @return the old property value
     */
    Serializable remove() throws PropertyException;

    /**
     * Gets the child property having the given name.
     * <p>
     * If the property is a scalar, this will return always null.
     * <p>
     * The given name should be the full name (i.e. prefixed name if any prefix exists).
     * <p>
     * If a non prefixed name is given, the first child property having the given local name will be returned.
     * <p>
     * Relative paths are not resolved. THis method is intended to lookup direct children. For path lookups use
     * {@link Property#resolvePath(String)} instead.
     *
     * @param name the child property name (the full name including the prefix if any)
     * @return the child property if any null if no child property with that name is found or if the property is a
     *         scalar
     * @throws {@link UnsupportedOperationException} if the property is a scalar property (doesn't have children)
     * @throws {@link PropertyNotFoundException} if the child property is not found in the type definition
     */
    Property get(String name) throws PropertyNotFoundException;

    /**
     * Get the child property given it's index. This operation is mandatory for List properties.
     * <p>
     * If this method is not supported an {@link UnsupportedOperationException} must be thrown
     * <p>
     * Relative paths are not resolved. THis method is intended to lookup direct chilren. For path lookups, use
     * {@link Property#resolvePath(String)} instead.
     *
     * @param index
     * @return the child property if any null if no child property with that name is found or if the property is a
     *         scalar
     * @throws {@link UnsupportedOperationException} if the property is a scalar property (doesn't have children)
     * @throws {@link PropertyNotFoundException} if the child property is not found in the type definition
     */
    Property get(int index) throws PropertyNotFoundException;

    /**
     * Sets a child property value given its index. This method is required only for List properties.
     * <p>
     * If this method is not supported, an {@link UnsupportedOperationException} must be thrown.
     * <p>
     * This method will mark the child value as dirty for existing values and in the case of map properties it will mark
     * phantom properties as new properties.
     *
     * @param index
     * @param value the new value
     * @throws {@link UnsupportedOperationException} if the property is a scalar property (doesn't have children)
     * @throws {@link PropertyNotFoundException} if the child property is not found in the type definition
     */
    void setValue(int index, Object value) throws PropertyException;

    /**
     * Get a collection over the children properties. This includes all children including phantom ones (those who are
     * not yet set by the user).
     * <p>
     * The returned collection is ordered for list properties, and unordered for complex properties
     * <p>
     * Be aware that this method is creating phantom child properties for all schema fields that are not yet set.
     *
     * @return the children properties
     */
    Collection<Property> getChildren();

    /**
     * Get the count of the children properties. This includes phantom properties. So the returned size will be equal to
     * the one returned by the property {@link ComplexType#getFieldsCount()}.
     *
     * @return the children properties count
     */
    int size();

    /**
     * Appends a new value to the list. A new property will be created to store the given value and appended to the
     * children list.
     * <p>
     * The created property will be marked as {@link Property#isNew()}.
     *
     * @param value
     * @return the added property
     */
    Property addValue(Object value) throws PropertyException;

    /**
     * Inserts at the given position a new value to the list. A new property will be created to store the given value
     * and appended to the children list.
     * <p>
     * The created property will be marked as {@link Property#isNew()}.
     *
     * @param value
     * @param index the position to insert the value
     * @return the added property
     */
    Property addValue(int index, Object value) throws PropertyException;

    /**
     * Creates an empty child property and adds it as a property to the list container.
     * <p>
     * This method is useful to construct lists.
     *
     * @return the created property
     * @throws PropertyException
     */
    Property addEmpty() throws PropertyException;

    /**
     * Moves a property position into the parent container list.
     * <p>
     * This method applies only for list item properties. The given index includes removed properties.
     *
     * @param index the position in the parent container to move this property
     * @throws UnsupportedOperationException if the operation is not supported by the target property
     */
    void moveTo(int index);

    /**
     * Same as {@link Property#resolvePath(Path)} but with a string path as argument. This is the same as calling
     * <code>resolvePath(new Path(path))</code>.
     *
     * @param path the string path to resolve.
     * @return the resolved property
     * @throws PropertyNotFoundException if the path cannot be resolved
     */
    Property resolvePath(String path) throws PropertyNotFoundException;

    /**
     * Resolves the given path relative to the current property and return the property if any is found otherwise throws
     * an exception.
     * <p>
     * The path format is a subset of XPath. Thus, / is used as path element separator, [n] for list element indexes.
     * Attribute separator '@' are not supported since all properties are assumed to be elements. Also you .. and . can
     * be used as element names.
     * <p>
     * Example of paths:
     * <ul>
     * <li><code>dc:title</code>
     * <li><code>attachments/item[2]/mimeType</code>
     * <li><code>../dc:title</code>
     * </ul>
     *
     * @param path the path to resolve.
     * @return the resolved property
     * @throws PropertyNotFoundException if the path cannot be resolved
     */
    Property resolvePath(Path path) throws PropertyNotFoundException;

    /**
     * Gets the value of the property resolved using the given path.
     * <p>
     * This method is a shortcut for: <code>resolvePath(path).getValue()</code>.
     *
     * @param path the path to the property
     * @return the property value
     */
    Serializable getValue(String path) throws PropertyException;

    /**
     * Gets the value of the property resolved using the given path.
     * <p>
     * The value will be converted to the given type if possible, otherwise an exception will be thrown.
     * <p>
     * This method is a shortcut for: <code>resolvePath(path).getValue(type)</code>.
     *
     * @param <T> The type of the value to return
     * @param type the class of the value
     * @param path the java path of the property value
     * @return the value
     * @throws PropertyException
     */
    <T> T getValue(Class<T> type, String path) throws PropertyException;

    /**
     * Sets the value of the property resolved using the given path.
     * <p>
     * This method is a shortcut for: <code>resolvePath(path).setValue(value)</code>.
     *
     * @param path the property path
     * @param value the value
     * @throws PropertyException
     */
    void setValue(String path, Object value) throws PropertyException;

    /**
     * Normalizes the given value as dictated by the property type.
     * <p>
     * Normalized values are the ones that are used for transportation over the net and that are given to the storage
     * implementation to be stored in the repository
     * <p>
     * Normalized values must be {@link Serializable}
     * <p>
     * If the given value is already normalized it will be returned back.
     *
     * @param value the value to normalize according to the property type
     * @return the normalized value
     */
    Serializable normalize(Object value) throws PropertyConversionException;

    /**
     * Checks if the given value is a normalized one. This means the value has a type that is normalized.
     * <p>
     * Null values are considered as normalized.
     *
     * @param value the value to check
     * @return true if the value is normalized false otherwise
     */
    boolean isNormalized(Object value);

    /**
     * Converts the given normalized value to the given type.
     * <p>
     * If the value has already the given type it will be returned back.
     *
     * @param value the normalized value to convert
     * @param toType the conversion type
     * @return the converted value, which may be null
     * @throws PropertyConversionException if the conversion cannot be made because of type incompatibilities
     */
    <T> T convertTo(Serializable value, Class<T> toType) throws PropertyConversionException;

    /**
     * Validates the given value type.
     * <p>
     * Tests if the given value type can be converted to a normalized type and thus a value of this type can be set to
     * that property.
     *
     * @param type the type to validate
     * @return true if the type is valid, false otherwise
     */
    boolean validateType(Class<?> type);

    /**
     * Creates a new and empty instance of a normalized value.
     * <p>
     * Empty is used in the sense of a value that has not been initialized or can be considered as an empty value. For
     * example for the {@link String} type the empty value will be the empty string ""
     *
     * @return the empty instance the empty instance, or null for some implementations
     */
    Object newInstance();

    /**
     * Method that implement the visitor pattern.
     * <p>
     * The visitor must return null to stop visiting children otherwise a context object that will be passed as the arg
     * argument to children
     *
     * @param visitor the visitor to accept
     * @param arg an argument passed to the visitor. This should be used by the visitor to carry on the visiting
     *            context.
     */
    void accept(PropertyVisitor visitor, Object arg) throws PropertyException;

    /**
     * Compare the two properties by content.
     *
     * @param property
     * @return true If the properties have a similar content, otherwise false
     * @throws PropertyException
     */
    boolean isSameAs(Property property) throws PropertyException;

    /**
     * Gets an iterator over the dirty children properties.
     *
     * @return the iterator
     */
    Iterator<Property> getDirtyChildren();

    /**
     * @return A {@link PropertyObjectResolver} to manage this property reference to external entities, null if this
     *         property's type has no resolver.
     * @since 7.1
     */
    PropertyObjectResolver getObjectResolver();

}