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#ifndef GRPC_SUPPORT_AVL_H
#define GRPC_SUPPORT_AVL_H

#include <grpc/support/sync.h>

/** internal node of an AVL tree */
typedef struct gpr_avl_node {
  gpr_refcount refs;
  void *key;
  void *value;
  struct gpr_avl_node *left;
  struct gpr_avl_node *right;
  long height;
} gpr_avl_node;

typedef struct gpr_avl_vtable {
  /** destroy a key */
  void (*destroy_key)(void *key);
  /** copy a key, returning new value */
  void *(*copy_key)(void *key);
  /** compare key1, key2; return <0 if key1 < key2,
      >0 if key1 > key2, 0 if key1 == key2 */
  long (*compare_keys)(void *key1, void *key2);
  /** destroy a value */
  void (*destroy_value)(void *value);
  /** copy a value */
  void *(*copy_value)(void *value);
} gpr_avl_vtable;

/** "pointer" to an AVL tree - this is a reference
    counted object - use gpr_avl_ref to add a reference,
    gpr_avl_unref when done with a reference */
typedef struct gpr_avl {
  const gpr_avl_vtable *vtable;
  gpr_avl_node *root;
} gpr_avl;

/** create an immutable AVL tree */
GPR_API gpr_avl gpr_avl_create(const gpr_avl_vtable *vtable);
/** add a reference to an existing tree - returns
    the tree as a convenience */
GPR_API gpr_avl gpr_avl_ref(gpr_avl avl);
/** remove a reference to a tree - destroying it if there
    are no references left */
GPR_API void gpr_avl_unref(gpr_avl avl);
/** return a new tree with (key, value) added to avl.
    implicitly unrefs avl to allow easy chaining.
    if key exists in avl, the new tree's key entry updated
    (i.e. a duplicate is not created) */
GPR_API gpr_avl gpr_avl_add(gpr_avl avl, void *key, void *value);
/** return a new tree with key deleted */
GPR_API gpr_avl gpr_avl_remove(gpr_avl avl, void *key);
/** lookup key, and return the associated value.
    does not mutate avl.
    returns NULL if key is not found. */
GPR_API void *gpr_avl_get(gpr_avl avl, void *key);

#endif
