graphql.util.TraverserContext Maven / Gradle / Ivy
package graphql.util;
import graphql.PublicApi;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* Traversal context.
*
* It is used as providing context for traversing, but also for returning an accumulate value. ({@link #setAccumulate(Object)}
*
* There is always a "fake" root context with null node, null parent, null position. See {@link #isRootContext()}
*
* @param type of tree node
*/
@PublicApi
public interface TraverserContext {
enum Phase {
LEAVE,
ENTER,
BACKREF
}
/**
* Returns current node being visited.
* Special cases:
* It is null for the root context and it is the changed node after {@link #changeNode(Object)} is called.
* Throws Exception if the node is deleted.
*
* @return current node traverser is visiting.
*
* @throws graphql.AssertException if the current node is deleted
*/
T thisNode();
/**
* Returns the original, unchanged, not deleted Node.
*
* @return the original node
*/
T originalThisNode();
/**
* Change the current node to the provided node. Only applicable in enter.
*
* Useful when the tree should be changed while traversing.
*
* Also: changing a node makes only a difference when it has different children than the current one.
*
* @param newNode the new Node
*/
void changeNode(T newNode);
/**
* Deletes the current node.
*/
void deleteNode();
/**
* @return true if the current node is deleted (by calling {@link #deleteNode()}
*/
boolean isDeleted();
/**
* @return true if the current node is changed (by calling {@link #changeNode(Object)}
*/
boolean isChanged();
/**
* Returns parent context.
* Effectively organizes Context objects in a linked list so
* by following {@link #getParentContext() } links one could obtain
* the current path as well as the variables {@link #getVar(java.lang.Class) }
* stored in every parent context.
*
* @return context associated with the node parent
*/
TraverserContext getParentContext();
/**
* The list of parent nodes starting from the current parent.
*
* @return list of parent nodes
*/
List getParentNodes();
/**
* The parent node.
*
* @return The parent node.
*/
T getParentNode();
/**
* The exact location of this node inside the tree as a list of {@link Breadcrumb}
*
* @return list of breadcrumbs. the first element is the location inside the parent.
*/
List> getBreadcrumbs();
/**
* The location of the current node regarding to the parent node.
*
* @return the position or null if this node is a root node
*/
NodeLocation getLocation();
/**
* Informs that the current node has been already "visited"
*
* @return {@code true} if a node had been already visited
*/
boolean isVisited();
/**
* Obtains all visited nodes and values received by the {@link TraverserVisitor#enter(graphql.util.TraverserContext) }
* method
*
* @return a map containg all nodes visited and values passed when visiting nodes for the first time
*/
Set visitedNodes();
/**
* Obtains a context local variable
*
* @param type of the variable
* @param key key to lookup the variable value
*
* @return a variable value or {@code null}
*/
S getVar(Class key);
/**
* Searches for a context variable starting from the parent
* up the hierarchy of contexts until the first variable is found.
*
* @param type of the variable
* @param key key to lookup the variable value
*
* @return a variable value or {@code null}
*/
S getVarFromParents(Class key);
/**
* Stores a variable in the context
*
* @param type of a varable
* @param key key to create bindings for the variable
* @param value value of variable
*
* @return this context to allow operations chaining
*/
TraverserContext setVar(Class key, S value);
/**
* Sets the new accumulate value.
*
* Can be retrieved by {@link #getNewAccumulate()}
*
* @param accumulate to set
*/
void setAccumulate(Object accumulate);
/**
* The new accumulate value, previously set by {@link #setAccumulate(Object)}
* or {@link #getCurrentAccumulate()} if {@link #setAccumulate(Object)} not invoked.
*
* @param and me
*
* @return the new accumulate value
*/
U getNewAccumulate();
/**
* The current accumulate value used as "input" for the current step.
*
* @param and me
*
* @return the current accumulate value
*/
U getCurrentAccumulate();
/**
* Used to share something across all TraverserContext.
*
* @param and me
*
* @return contextData
*/
U getSharedContextData();
/**
* Returns true for the root context, which doesn't have a node or a position.
*
* @return true for the root context, otherwise false
*/
boolean isRootContext();
/**
* In case of leave returns the children contexts, which have already been visited.
*
* @return the children contexts. If the childs are a simple list the key is null.
*/
Map>> getChildrenContexts();
/**
* @return the phase in which the node visits currently happens (Enter,Leave or BackRef)
*/
Phase getPhase();
/**
* @return true if the traversing happens in parallel (multi threaded) or not.
*/
boolean isParallel();
}