server.c

// Implemented by Rakim

#ifndef SERVER
#define SERVER

#include <stdio.h>
#include <stdlib.h>
#include "log.c"
#include "student.h"
#include "main_memory.c"
#include "tuple.h"
#include "generate_students.c"


// Functional Prototypes
void server();
void registerStudent();

void delete(int id, node* head);
void printFile(char* filename);

void server()
{
    node *head = NULL;
    char op_id = 0; // OPERATION ID, 0->registration, 1-> search, 2-> update, 3-> delete.
    int st_id = 0;

    FILE *waitingQueue = fopen("waiting_queue", "r");
    tuple temp;
    int count = 0;
    double time = GetTime();
    // int sum = 0;
    while (fread(&temp, 1, sizeof(tuple), waitingQueue) == sizeof(tuple))
    {
        //fputs("> ", stdout);
        //scanf("%c", &op_id);
        //op_id = '1';
        st_id = temp.stdID;
        op_id = '0'+temp.opID;
        int newRoomNumber = temp.roomNo;
        // if (op_id == '2')
        // {
        //     printf("%c %d %d\n", op_id, st_id, temp.roomNo);
        // }
        // else
        // {
        //     printf("%c %d\n", op_id, st_id);
        // }
        switch(op_id)
        {
            case '0':
                registerStudent();
                break;

            case '1':
                //scanf("%d", &st_id);
                search(&head, st_id);
                break;

            case '2':
                //scanf("%d", &st_id);
                //scanf("%d\n", &newRoomNumber);
                update(&head, st_id, newRoomNumber);
                break;
                
            case'3':
                //scanf("%d", &st_id);
                delete(st_id, head);
                //printFile("disk.tmp");
                break;
            case '4':
                printFile("disk");
                break;
        }
        count++;
        if (GetTime()-time >= 1)
        {
            printf("Throughput: %d\n", count);
            count = 0;
            time = GetTime();
        }
    }

    while (head != NULL)
    {
        removeHeadNode(&head, 1);
    }
    printf("Mean Response Time: %lf\n", (GetTime()-time)/(1.0*count));
    printf("Throughput: %lf\n", (1.0*count)/(GetTime()-time));
}

// Register a user and update the file accordingly
// First get the last roll no. used and then use generate_student(id) to write it to the file.
// Use printFile to see if the file is updated.
void registerStudent()
{
    writeTwo();
    FILE* db = fopen("disk", "r+");
    if (db == NULL) 
    {
        perror("Error opening database file");
        exit(0);
    }
    struct Student temp;
    int id = 0;

    while(fread(&temp, 1, sizeof(struct Student), db) && sizeof(temp) == sizeof(struct Student))
    {
        id = temp.id;
    }

    struct Student s;
    id++;
    s = generateStudent(id);
    fwrite(&s, 1, sizeof(struct Student), db);
    fclose(db);
}

// Delete a line from the file 

void delete(int id, node* head)
{
    /* 
     *
     *  Implement the logic for deleting here.
     *
     *  First search file, but instead of returning a number, get the line number.
     *  Now make a new copy of the file and copy all the lines except that one.
     *  Delete the original file and rename the current file to disk.
     *
     *  refer https://www.w3resource.com/c-programming-exercises/file-handling/c-file-handling-exercise-8.php
     *
     */
    FILE* db = fopen("disk", "r");
    FILE* dbTemp = fopen("disk.tmp", "w");
    writeTwo();

    if (db == NULL) 
    {
        perror("Error opening database file");
        exit(0);
    }
    if (dbTemp == NULL) 
    {
        perror("Error opening database file");
        exit(0);
    }

    struct Student temp;
    while(fread(&temp, 1, sizeof(struct Student), db) && sizeof(temp) == sizeof(struct Student))
    {
        if (temp.id != id)
        {
            fwrite(&temp, 1, sizeof(struct Student), dbTemp);
        }
    }

    fclose(db);
    fclose(dbTemp);
    remove("disk");
    rename("disk.tmp", "disk");
    
    if (head != NULL)
    {
        if (head->student.id != id)
        {
            removeHeadNode(&head, 1);
        }
        else
        {
            removeHeadNode(&head, 0);
        }
    }
    return;
}

void printFile(char* filename)
{
    FILE* db = fopen(filename, "r");
    if (db == NULL) 
    {
        perror("Error opening database file");
        exit(0);
    }
    struct Student temp;
    while(fread(&temp, 1, sizeof(struct Student), db) && sizeof(temp) == sizeof(struct Student))
    {
        printf("%d: %s\n", temp.id, temp.name);
    }
    fclose(db);
}
#endif