/**
 * @file gl-threads.c
 * @brief Glue based doubly linked-list
 * @details
 * In traditional a doubly linked-list each node will have a left and right
 * pointer and a pointer to the data, so the structure of the node will contain
 * 3 data members(next, prev, data). In Glue based doubly linked-list there will
 * only be 2 data members left and right pointers. As for the data, it will be 
 * glued on top of the node.
 *
 * Illustration
 * -------------
 * Traditional doubly linked-list:
 *                       _____________                    _____________
 *                  ___ | application |               ___| application |
 *                 |    |   data      |              |   |    data     |
 *                 |    |_____________|              |   |_____________|
 *       __________|_________              __________|_________
 *      | prev | data | next |____________| prev | data | next |
 *      |______|______|______|            |______|______|______|
 *
 *
 * Glue based doubly linked-list:
 *       _____________             _____________
 *      | application |           | application |
 *      |    data     |           |    data     |
 *      |_____________|           |_____________|
 *      | prev | next |___________| prev | next |
 *      |______|______|           |______|______|
 *
 * @author [Ashborn-SM](https://github.com/Ashborn-SM)
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define HEAD(list) (list->head)
#define OFFSETOF(structure, field) (long)&((structure*)0)->field
#define POP_FRONT(list, structure, offset){                     \
    glthread_node* _cur = HEAD(list), *temp = HEAD(list)->next; \
    structure* per = (structure*)((char*)_cur - offset);        \
    free(per);                                                  \
    HEAD(list) = temp;                                          \
}
#define ITERATE_GL_THREADS_BEGIN(lstptr, struct_type, ptr)      \
{                                                               \
    glthread_node *_glnode = NULL, *_next = NULL;               \
    for(_glnode = lstptr->head; _glnode; _glnode = _next){      \
        _next = _glnode->next;                                  \
        ptr = (struct_type *)((char *)_glnode - lstptr->offset);
#define END }}

/**
 * @struct glthread_node
 * @brief node for the glue based doubly linked list
 */
typedef struct glthread_node_{
    struct glthread_node_* next;
    struct glthread_node_* prev;
}glthread_node;

/**
 * @struct gldll
 * @brief the doubly linked-list
 */
typedef struct{
   glthread_node* head;
   unsigned int offset;
}gldll;

/**
 * @brief initialise the node
 * @details set the node members to NULL
 * @param node linked-list node
 */
void init_glthread_node(glthread_node* node){
    node->next = NULL;
    node->prev = NULL;
}

/**
 * @brief initialise the linked-list
 * @details set the head and offset
 * @param list linked-list
 * @param offset offset of the data member
 */
void init_glthread_list(gldll* list, unsigned int offset){
    list->head = NULL;
    list->offset = offset;
}

/**
 * @brief insertion of node
 * @details insert the node at the front of the list
 * @param list linked-list
 * @param node node to be inserted
 */
void glthread_pushfront(gldll* list, glthread_node* node){
    glthread_node* cur = HEAD(list);
    if(cur == NULL){
        HEAD(list) = node;
        return;
    }
    cur->prev = node;
    node->next = cur;
    HEAD(list) = node;
}

/**
 * @struct person 
 * @brief a structure with attributes of a person
 */
typedef struct{
    char name[30];
    int age, weight, height;
    glthread_node glnode;
}person;

/**
 * @brief print the details of the person
 * @param per person structure
 */
void print(person* per){
    printf("Name: %s\n", per->name);
    printf("Height: %i\n", per->height);
    printf("Age: %i\n", per->age);
    printf("Weight: %i\n", per->weight);
	printf("------------\n");
}

/**
 * @brief allocate memory
 * @returns memory with type person
 */
person* allocate(){
	person* new = malloc(sizeof(*new));
	if(new == NULL){
		printf("Allocation Failure");
		exit(0);
	}
	return new;
}

/**
 * @brief test the program
 * @param list linked-list
 */
void test(gldll* list){
	char passed[10] = "[PASSED]:\0";
	char failed[10] = "[FAILED]:\0";
	char expected[9] = "EXPECTED\0";
	char returned[9] = "RETURNED\0";
	glthread_node* cur = HEAD(list);
	person* per = NULL;
	ITERATE_GL_THREADS_BEGIN(list, person, per){
		if(strcmp(per->name, "rohit") == 0){
			printf("%s: %s -> %s, %s -> %s\n", passed, expected, "rohit",
			returned, per->name);
		}
		else{
			printf("%s: %s -> %s, %s -> %s\n", failed, expected, "rohit",
			returned, per->name);
		}
		if(per->age == 23){
			printf("%s: %s -> %i, %s -> %i\n", passed, expected, 23,
			returned, per->age);
		}
		else{
			printf("%s: %s -> %i, %s -> %i\n", failed, expected, 23,
			returned, per->age);
		}
		if(per->height == 174){
			printf("%s: %s -> %i, %s -> %i\n", passed, expected, 174,
			returned, per->height);
		}
		else{
			printf("%s: %s -> %i, %s -> %i\n", failed, expected, 174,
			returned, per->height);
		}
		if(per->weight == 67){
			printf("%s: %s -> %i, %s -> %i\n", passed, expected, 67,
			returned, per->weight);
		}
		else{
			printf("%s: %s -> %i, %s -> %i\n", failed, expected, 67,
			returned, per->weight);
		}
        break;
	}END;
}

int main(){
    gldll* list = malloc(sizeof(*list));
	if(list == NULL){
		printf("Allocation Failure");
		exit(0);
	}

    person* rahul = allocate();
    person* rohit = allocate();

    strcpy(rahul->name, "rahul");
    strcpy(rohit->name, "rohit");

    rahul->age = 19;
    rohit->age = 23;

    rahul->height = 170;
    rohit->height = 174;

    rahul->weight = 60;
    rohit->weight = 67;

    init_glthread_list(list, OFFSETOF(person, glnode));

    init_glthread_node(&(rahul->glnode));
    init_glthread_node(&(rohit->glnode));

    glthread_pushfront(list, &(rohit->glnode));
    glthread_pushfront(list, &(rahul->glnode));

    person* temp = NULL;
    ITERATE_GL_THREADS_BEGIN(list, person, temp){
        // uncomment the below line to print the details of the person
        print(temp);
    }END;
    /*
        Output:
            Name: rahul
            Height: 170
            Age:19
            Weight: 60
            -------------
            Name: rohit
            Height: 174
            Age: 23
            Weight: 77
            -------------
    */
    POP_FRONT(list, person, OFFSETOF(person, glnode));
	test(list);
}