#include <stdio.h>   
#ifndef _LINKEDLIST_H_
#define _LINKEDLIST_H_
#ifndef _POLYGONSTRUCT_H_
#define _POLYGONSTRUCT_H_
#include <GL/gl.h>   
#define MAXVERTS 32   


typedef struct poly_struct {
    int type;         /* E.g., 0=SQUARE, 1=POLY, 2=RECT, ... */
    GLint numVerts;      /* # of vertices in polygon */
    GLdouble v[MAXVERTS][2];   /* Polygon's vertex array:       */
            /* v[i][0] = vertex i's x-coord; */
            /* v[i][1] = vertex i's y-coord  */
    GLdouble center[2];      /* Polygon's "center" point, for use in */
            /* rotating polygon                     */
    GLdouble rot_angle;      /* Rotation angle for polygon (degrees) */
    GLdouble rgb[3];      /* Polygon's color: 0.0=off, 1.0=max; */
            /* rgb[0]=red, [1]=green, [2]=blue    */
} Polygon;
#endif



typedef struct polygon_list_struct {
    Polygon p;
    struct polygon_list_struct *next,   /* Pointers to next, prev polygons */
                               *prev;   /* in the doubly-linked list */
} Polygon_list_node;


#endif

/*
* Global pointers for the linked list:
*/
Polygon_list_node *head = NULL,   /* Pointer to the head of the list */
                  *curr = NULL,   /* Pointer to the currently selected node */
                  *tail = NULL;   /* Pointer to the tail of the list */

void InsertAfter(Polygon_list_node *item, Polygon_list_node *afterMe) {
   /*
    * Inserts *item after *afterMe in the linked list:
    */
    if (afterMe == NULL) {
        if (head == NULL && tail == NULL) {   /* empty list */
            head = tail = item;
            item->prev = item->next = NULL;
        }
        else
            fprintf(stderr,"InsertAfter: cannot insert after a NULL ptr\n");
        return;
    }
    item->prev = afterMe;
    if (afterMe == tail) {
        tail = item;
        item->next = NULL;
    }
    else {
        item->next = afterMe->next;
        item->next->prev = item;
    }
    afterMe->next = item;
}

void InsertBefore(Polygon_list_node *item, Polygon_list_node *beforeMe) {
   /*
    * Inserts *item before *beforeMe in the linked list:
    */
    if (beforeMe == NULL) {
        if (head == NULL && tail == NULL) {   /* empty list */
            head = tail = item;
            item->prev = item->next = NULL;
        }
        else
            fprintf(stderr,"InsertBefore: cannot insert before a NULL ptr\n");
        return;
    }
    item->next = beforeMe;
    if (beforeMe == head) {
        head = item;
        item->prev = NULL;
    }
    else {
        item->prev = beforeMe->prev;
        item->prev->next = item;
    }
    beforeMe->prev = item;
}

void RemoveItem(Polygon_list_node *item) {
   /*
    * Removes *item from the linked list (but doesn't free() it):
    */
    if (item == NULL)      /* Should print out an error message */
        return;
    if (item == head && item == tail) {   /* Only one element in the list */
        head = tail = NULL;
    }
    else if (item == head) {
        item->next->prev = NULL;
        head = item->next;
    }
    else if (item == tail) {
        item->prev->next = NULL;
        tail = item->prev;
    }
    else {
        item->prev->next = item->next;
        item->next->prev = item->prev;
    }
    item->prev = item->next = NULL;
}

/* Aqui van los includes */

/* Aqui van los typedefs, structs, macros, etc. */

/* Primero declaras las funciones que vas a utilizar antes de main */
void InsertAfter(Polygon_list_node *item, Polygon_list_node *afterMe); /* Fijate que la declaracion lleva un ; al final */
void InsertBefore(Polygon_list_node *item, Polygon_list_node *beforeMe);
void RemoveItem(Polygon_list_node *item);

int main ( int argc, char **argv )
{
    /* Aqui haces lo que quieras con las funciones*/
    InsertAfter(/* parametros de la funcion */);
    InsertBefore(/* parametros de la funcion */);
    RemoveItem(/* parametros de la funcion */);

    return 0;
}

/* Y abajo de main se definen las funciones */
void InsertAfter(Polygon_list_node *item, Polygon_list_node *afterMe)
{
    /* Codigo de la funcion */
}

void InsertBefore(Polygon_list_node *item, Polygon_list_node *beforeMe)
{
    /* Codigo de la funcion */
}

void RemoveItem(Polygon_list_node *item)
{
    /* Codigo de la funcion */
}