package edu.rice.cs.drjava.model.repl.types;

/** <p>A lightweight visitor for traversing (in depth-first order) arbitrary ASTGen-produced

* trees. Unlike the Visitor classes generated for a specific AST, implementations of

* TreeWalker are defined for all ASTs. They are more limited, having far fewer hooks

* available for manipulating the traversal process and handling different types of nodes.

* This minimal interface is enough, however, for simple visitors which aren't concerned

* with the semantic content of a tree and simply need to traverse its structure.</p>

*

* <p>When passed to a node's {@code walk()} method, a TreeWalker can expect to receive

* a specific sequence of method calls: {@link #visitNode}, then {@link #visitField}

* and a recursive invocation for each of the node's fields. "Recursive invocations"

* include additional {@code visitNode()} calls and invocations of the the other "visit"

* methods for handling Strings, lists, primitives, and objects of unrecognized type.

* (Note that the method to call is determined statically based on the field's declared

* type, not at runtime.) Clients can prevent recursion into a non-atomic element's

* children by returning {@code false} in the appropriate visit method.</p>

*/

public abstract class TreeWalker {

/** Visit an AST node. Return {@code true} to recur on each of the node's fields. */

public boolean visitNode(java.lang.Object node, java.lang.String type, int fields) { return true; }

/** Visit an AST node's field. Return {@code true} to recur on the field's value. */

public boolean visitNodeField(java.lang.String name, java.lang.Object value) { return true; }

/** Signal the end of recursion on an AST node's field. */

public void endNodeField(java.lang.String name, java.lang.Object value) {}

/** Signal the end of a sequence of node fields. */

public void endNode(java.lang.Object node, java.lang.String type, int fields) {}

/** Visit an Iterable or array. Return {@code true} to recur on each element. */

public boolean visitIterated(java.lang.Object iterable) { return true; }

/** Visit an iterated element. Return {@code true} to recur on the element value. */

public boolean visitIteratedElement(int index, java.lang.Object element) { return true; }

/** Signal the end of recursion on an iterated element. */

public void endIteratedElement(int index, java.lang.Object element) {}

/** Signal the end of a sequence of iterated elements. */

public void endIterated(java.lang.Object iterable, int size) {}

/** Visit a non-empty option-typed value. Return {@code true} to recur on the nested value. */

public boolean visitNonEmptyOption(java.lang.Object option) { return true; }

/** Signal the end of recursion on a non-empty option. */

public void endNonEmptyOption(java.lang.Object option) {}

/** Visit an empty option-typed value. */

public void visitEmptyOption(java.lang.Object option) {}

/** Visit a tuple-typed value. Return {@code true} to recur on the nested elements. */

public boolean visitTuple(java.lang.Object tuple, int arity) { return true; }

/** Visit a tuple element. Return {@code true} to recur on the element value. */

public boolean visitTupleElement(int index, java.lang.Object element) { return true; }

/** Signal the end of a tuple element. */

public void endTupleElement(int index, java.lang.Object element) {}

/** Signal the end of a sequence of tuple elements. */

public void endTuple(java.lang.Object tuple, int arity) {}

/** Visit a string value. */

public void visitString(java.lang.String s) {}

/**

* Visit an object that is not known statically to have an AST Node or

* other supported type.

*/

public void visitUnknownObject(java.lang.Object o) {}

/**

* Visit a null reference. This is called rather than {@code visitNode}, {@code visitList},

* {@code visitUnknownObject}, etc., where a field or element's value is {@code null}.

*/

public void visitNull() {}

/** Visit a boolean primitive. */

public void visitBoolean(boolean b) {}

/** Visit a char primitive. */

public void visitChar(char c) {}

/** Visit a byte primitive. */

public void visitByte(byte b) {}

/** Visit a short primitive. */

public void visitShort(short s) {}

/** Visit a int primitive. */

public void visitInt(int i) {}

/** Visit a long primitive. */

public void visitLong(long l) {}

/** Visit a float primitive. */

public void visitFloat(float f) {}

/** Visit a double primitive. */

public void visitDouble(double d) {}

}