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

// create the linked list structure of the memory block
struct MemoryBlock {
    int beginAddr;
    int endAddr;
    int hole;
    int Pro_ID;
    struct MemoryBlock* next;
};
typedef struct MemoryBlock node;

// declare the starting pointer of the linked list as NULL
node* start = NULL;

//initialize and return a free memory block/node
node* createNode(int beginAddr, int endAddr)
{ //takes the starting address and the ending address as input
    node* temp = (node*)malloc(sizeof(node)); //allocate memory using malloc() function
    temp->beginAddr = beginAddr;
    temp->endAddr = endAddr;
    temp->hole = 1; //hole
    temp->Pro_ID = -1; //means there's no process going on
    return temp; //returns the
}

//if the size of the memory block/node >= the size of the process, a process is assigned to the block
void addProcess(int size, int pid) {
    node* ptr = start;
    while(ptr != NULL) {
        if ((ptr->endAddr - ptr->beginAddr) >= size && ptr->hole==1)
		{
            node* new_node = createNode(ptr->beginAddr + size, ptr->endAddr);
            ptr->endAddr = (ptr->beginAddr + size-1);
            ptr->hole = 0; //Memory block is occupied
            ptr->Pro_ID = pid; //the Process id of the Process occupied
            new_node->next = ptr->next;
            ptr->next = new_node; // points to the next node/block
            break;
        }
        ptr = ptr->next;
    }
}

//aadds the created node to the list
void addNode(node* new_node) {
    if (start == NULL) {
        start = new_node;
    }
	else
	{
        node* ptr = start;
        while (ptr->next != NULL) {
            ptr = ptr->next;
        }
        ptr->next = new_node;
    }
}

int deleteProcess(node *start, int del_pid)
{
	node* prePtr = start;
    node* ptr = start;
	if(del_pid<0)
	{
        printf("Invalid Process ID!\n");
        return 0;
    }

    while(ptr != NULL)
	{
        if (ptr->Pro_ID == del_pid)
		{
            ptr->hole = 1;
            ptr->Pro_ID = -1;
			if(ptr==prePtr)
			{
				return 1;
			}
			if(ptr->next == NULL)
			{
				return 1;
			}

            return 1;
        }
        prePtr = ptr;
        ptr = ptr->next;
    }
    printf("No match for Process ID %d\n", del_pid);
    return 0;

}

//Snapshot of the current memory blocks
void printSnapshot(node *start){
	node* temp = start;
	int size;
    printf("Process ID\tSize\tBegin Address\t\tEnd Address\tHole\n");
    printf("-----------------------------------------------------------------------\n");
    	printf("OS\t\t"); //ProcessID of the node
    	printf("400\t\t");
        printf("0\t\t"); //Starting address of the node
        printf("399\t\t");
        printf("0\t\n");
    while(temp != NULL) //while the node is not empty
	{
        printf("%d\t\t", temp->Pro_ID); //ProcessID of the node
        printf("%d\t\t", temp->endAddr - (temp->beginAddr - 1)); //Size of the node
        printf("%d\t\t", temp->beginAddr);
        printf("%d\t\t", temp->endAddr);
        printf("%d\t\t\n", temp->hole);

        temp = temp->next;
    }
}


int main(){
    int choice;
	int pid, size;
    int del_pid;

    node* tmp=createNode(400, 2560); //Initialize memory block
    addNode(tmp);

	//printSnapshot(start);
	addProcess(600,1);
	//printSnapshot(start);
	addProcess(200,2);
	printSnapshot(start);
	//deleteProcess(start,1);
	//printSnapshot(start);
	//addProcess(700,3);
	//printSnapshot(start);
	//deleteProcess(start,1);
	//printSnapshot(start);
    printf("\n\n");

	return 0;
    }