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

struct Stack {
    int *startaddress;
    int currentsize;
    int capacity;
    int initialcap;
};

void stack_destroy(struct Stack stack_dest){
    free(stack_dest.startaddress);
}

struct Stack stack_create(int size){
    int* array;
    array = malloc (size * sizeof(int));
    struct Stack new_stack;
    new_stack.startaddress = &array[0];
    new_stack.currentsize = 0;
    new_stack.capacity = size;
    new_stack.initialcap = size;
    printf("Stack successfully created...\n");
    return new_stack;
}

/*Need to pass pointer in order to change variables outside the function, also in pop*/
void stack_push (struct Stack* ptr, int elem){
    if (ptr->currentsize >= ptr->capacity){
        printf("The stack was full, reallocating 2 times the size...\n");
        ptr->startaddress = realloc(ptr->startaddress, 2* (sizeof(int) * ptr->capacity));
        ptr->capacity *=2;
    }
    ptr->startaddress[ptr->currentsize] = elem;
    ptr->currentsize+=1;
    printf("Element added...\n");
}

int stack_pop (struct Stack* ptr){
    if(ptr->capacity > ptr->currentsize * 2 && ptr->capacity != ptr->initialcap){
        ptr->startaddress = realloc(ptr->startaddress,  sizeof(int)/ ptr->capacity / 2);
        printf("Reduced stacksize, because it was bigger than needed.\n");
    }
    ptr->currentsize--;
    return ptr->startaddress[ptr->currentsize];
}

int stack_top (struct Stack stack){
    return stack.startaddress[stack.currentsize-1];
}

void stack_print(struct Stack stack){
    if(stack.currentsize == 0){
        printf("Stack is empty!\n");
    }
    else{
    printf("Printing all elements on commandline: \n");
        for(int temp = 1; temp < stack.currentsize; temp ++){
            printf("%d ",stack.startaddress[stack.currentsize-temp]);
        }
        printf("\n");
    }
}

int main(void){
    int size = 2;
    struct Stack stack1 = stack_create(size);
    struct Stack* ptr;
    ptr = &stack1;

    stack_push(ptr, 1);
    stack_push(ptr, 2);
    stack_push(ptr, 3);
    stack_push(ptr, 4);
    stack_push(ptr, 5);
    stack_push(ptr, 6);
    stack_push(ptr, 7);

    printf("Expecting 1 through 7:\n");
    stack_print(stack1);
    printf("\n");
    printf("Expecting 7:\n");
    printf("%d\n",stack_top(stack1));
    printf("\n");
    printf("Expecting 7:\n");
    printf("%d\n",stack_pop(ptr));
    printf("\n");
    printf("Expecting 6:\n");
    printf("%d\n",stack_top(stack1));
    printf("\n");
    printf("popping elements to reduce size...\n");
    printf("%d\n",stack_pop(ptr));
    printf("%d\n",stack_pop(ptr));
    printf("%d\n",stack_pop(ptr));
    printf("%d\n",stack_pop(ptr));
    printf("%d\n",stack_pop(ptr));

    stack_destroy(stack1);
return EXIT_SUCCESS;
}