/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.
 */
/**
 * @file
 *  
 * The file contains description of public component manager handles
 * and interfaces for initialization and dynamic linking of VM components.
 */
    
#ifndef _OPEN_COMPMGR_H
#define _OPEN_COMPMGR_H

#include <apr_pools.h>

#ifdef __cplusplus
extern "C"
{
#endif

/**
 * The <code>_OpenInterface</code> structure represents
 * a virtual table of interface functions. An interface 
 * contains function pointers:
 * <pre>
 *    void* func1;
 *    void* func2;
 *    void* func3;
 * </pre>
 */
union _OpenInterface;

/**
 * @name Handles
 * Handles are opaque for an interface user. The user
 * operates with handles by means of interface functions.
 */

/**
 * @ingroup Handles
 * The handle of the abstract component interface.
 */
typedef const union _OpenInterface* OpenInterfaceHandle;

/**
 * Default component interface. Each component must
 * provide implementation of the functions from this
 * interface.
 */
struct _OpenComponent
{
    /**
     * Returns a component name.
     */
    const char* (*GetName) ();
    /**
     * Returns a component version which is numbers separated with dots.
     * Implementors must check a major version number for compatibility.
     */
    const char* (*GetVersion) ();
    /**
     * Returns human-readable description of the component.
     */
    const char* (*GetDescription) ();
    /**
     * Returns the human-readable vendor string, e.&nbsp;g.,
     * name of the organization which provides this component.
     */
    const char* (*GetVendor) ();
    /**
     * Queries optional properties.
     * @param key property name
     * @return a string, true/false for boolean properties
     */
    const char* (*GetProperty) (const char* key);

    /**
     * Exposes a NULL terminated list of component-specific
     * interface names for the given component.
     *
     * This default component interface is not included.
     * @return a pointer to an internal component manager structure,
     * which should not be modified or freed.
     */
    const char** (*ListInterfaceNames) ();

    /**
     * Exposes a component interface.
     * @param[out] p_intf on return, points to an interface handle
     * @param intf_name an interface name
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*GetInterface) (OpenInterfaceHandle* p_intf,
            const char* intf_name);

    /**
     * The call to this function frees all component resources.
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*Free) ();
};
/**
 * @ingroup Handles
 * The handle of the open component.
 */
typedef const struct _OpenComponent* OpenComponentHandle;

/**
 * The generic component instance. It contains several interfacec tables and
 * other data.
 * <pre>
 *      OpenInterfaceHandle intf1;
 *      OpenInterfaceHandle intf2;
 *      void* data1;
 *      void* data2;
 * </pre>
 */
union _OpenInstance;

/**
 * @ingroup Handles
 * The handle of the open instance.
 */
typedef const union _OpenInstance* OpenInstanceHandle;

/**
 * The private component interface used by a component manager to allocate
 * and dispose instances.
 */
struct _OpenInstanceAllocator {
    /**
     * The component provides a constructor-like method for instance
     * initialization which is called by component manager when a
     * new instance is created.
     *
     * @param[out] p_instance on return, points to handle of a new instance
     * @param pool created by a component manager for a lifetime of
     * the instance, the component could use the pool for allocation
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*CreateInstance) (OpenInstanceHandle* p_instance,
                           apr_pool_t* pool);

    /**
     * Free memory and other resources for a given instance.
     * @param instance a handle of an instance to free
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*FreeInstance) (OpenInstanceHandle instance);
};
/**
 * @ingroup Handles
 * The handle of the instance allocator interface.
 */
typedef const struct _OpenInstanceAllocator* OpenInstanceAllocatorHandle;

/**
 * The virtual table which contains public component manager
 * interface. The interface allows accessing components by name
 * and operating with component instances.
 *
 * It is safe to call these functions from multiple threads.
 */
struct _OpenComponentManager
{

    /**
     * Gets a default interface of a registered component by name.
     * @param[out] p_component on return, points to
     * a handle of the default component interface
     * @param name the component name
     * @return APR_SUCCESS if successful, APR_NOTFOUND if a component with
     * the given name cannot be found, or another non-zero error code
     */
    int (*GetComponent) (OpenComponentHandle* p_component,
            const char* name);

    /**
     * Gets a default interface of a component instance.
     * @param[out] p_component on return, points to
     * a handle of the default component interface
     * @param instance the instance handle
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*GetComponentByInstance) (OpenComponentHandle* p_component,
            OpenInstanceHandle instance);


    /**
     * Creates a new component instance and register it in
     * a component manager.
     * @param[out] p_instance on return, points to a handle of a newly
     * created instance
     * @param name the component name
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*CreateInstance) (OpenInstanceHandle* p_instance,
            const char* name);

    /**
     * Unregisters the instance in a component manager,
     * frees memory and other resources held by the instance.
     * @param instance a handle to the instance to Free
     * @return APR_SUCCESS if successful, otherwise a non-zero error code
     */
    int (*FreeInstance) (OpenInstanceHandle instance);

    /**
     * Fills a pre-allocated buffer with instances of the component.
     * @param[in,out] a pointer to the given buffer which is preallocated by
     * a caller and filled with component instances on return
     * @param buf_len the length of the buffer
     * @param[out] len an actual number of instances
     * @param name a component name
     * @return APR_SUCCESS if successful, APR_NOTFOUND if a component with
     * the given name cannot be found, or another non-zero error code
     */
    int (*GetInstances) (OpenInstanceHandle* p_instance, int buf_len, int* len,
            const char* name);
};
/**
 * @ingroup Handles
 * The handle of the component manager interface.
 */
typedef const struct _OpenComponentManager* OpenComponentManagerHandle;

/**
 * The generic component initialization function type.
 * @param[out] p_component on return, points to a handle of a default
 * component interface
 * @param[out] p_allocator on return, points to a handle of a private
 * instance allocation interface
 * @param pool a memory pool with the component lifetime
 * @return APR_SUCCESS if successful, otherwise a non-zero error code
 */
typedef int
(*OpenComponentInitializer) (OpenComponentHandle* p_component,
                             OpenInstanceAllocatorHandle* p_allocator,
                             apr_pool_t* pool);

#ifdef __cplusplus
}
#endif

#endif                          /* _OPEN_COMPMGR_H */