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

#define LINESIZE 1024
#define BUFSIZE 512
#define NAMESIZE 20
#define BLOCK 2

typedef struct
{
    char last[NAMESIZE]; /* last name; 1 (non-empty) word */
    char first[NAMESIZE]; /* first name; 1 (non-empty) word */
} name;

typedef struct
{
    int id; /* student ID; between 1000000 & 9999999 inclusive */
    name name; /* name of student */
    int score; /* between 0 & 100 inclusive */
} record;

typedef struct{
    record **data; /*points to dynamic array of pointers */
    size_t nalloc; /*number of pointers allocated */
    size_t nused; /*number of pointers in use */
} record_list;

/*Function to get input*/
int getInput(char a[LINESIZE])
{
    char input[LINESIZE];
    if (!fgets(input, LINESIZE, stdin))
    {
        clearerr(stdin);
        return 0;
    }
    strcpy(a, input);
    return 1;
}

/*Comparison function to compare IDs in ascending order*/
int cmpID(const void *p, const void *q)
{
    const record *pp = p;
    const record *qq = q;
    return (pp->id - qq->id);
}

/*Comparison function to compare name in ascending order*/
int cmpName(const void *p, const void *q)
{
    int n = 0;
    record *pp = *(record**)p;
    record *qq = *(record**)q;
    /*if last names are equal, compare the first names*/
    if ((n = (strcmp(pp->name.last, qq->name.last))) == 0)
    {
        /*if first names are not equal return the value of strcmp*/
        if ((n = (strcmp(pp->name.first, qq->name.first))) != 0)
        {
            return n;
        }
    }
    /*return value of strcmp if names are not equal*/
    return strcmp(pp->name.last, qq->name.last);
}

/*Validate id*/
int validateID(int *id)
{
    if (*id < 1000000 || *id > 9999999)
    {
        return 0;
    }
    if (*id == 0)
    {
        return 2;
    }
    return 1;
}

/*Validate score*/
int validateScore(int *grade)
{
    if (*grade < 0 || *grade >= 100)
    {
        return 0;
    }
    return 1;
}

/*Validate name*/
int validateName(char a[])
{
    if (strlen(a) == 0)
    {
        return 0;
    }
    return 1;
}

/*Get ID*/
int getID(int n)
{
    char line[BUFSIZE];
    while (1)
    {
        fprintf(stderr, "Enter a student id:\n");
        if (!getInput(line))
        {
            break;
        }
        if (sscanf(line, "%d\n", &n) == 1)
        {
            if (n == 0)
            {
                break;
            }
            if (validateID(&n) == 1)
            {
                return 1;
            }
        }

    }
    return 0;
}

/*Get fname*/
int getfName(char *fname)
{
    char line[BUFSIZE];
    while(1)
    {
        fprintf(stderr,"Enter in student's first name:\n");
        if (!getInput(line))
        {
            break;
        }
        if (sscanf(line, "%s\n", fname) == 1)
        {
            if (validateName(fname) == 1)
            {
                return 1;
            }
        }
    }
    return 0;
}

/*Get lname*/
int getlName(char *lname)
{
    char line[BUFSIZE];
    while (1)
    {
        fprintf(stderr, "Enter in student's last name:\n");
        if (!getInput(line))
        {
            break;
        }
        if (sscanf(line, "%s\n", lname) == 1)
        {
            if (validateName(lname) == 1)
            {
                return 1;
            }
        }
    }
    return 0;
}

/*Get score*/
int getScore(int score)
{
    char line[BUFSIZE];
    while (1)
    {
        fprintf(stderr, "Enter in student's score:\n");
        if (!getInput(line))
        {
            break;
        }
        if (sscanf(line, "%d\n", &score) == 1)
        {
            if (validateScore(&score) == 1)
            {
                return 1;
            }
        }
    }
    return 0;
}

/*initialize the list */
void list_init(record_list *list)
{
     list->data = 0;
     list->nalloc = 0;
     list->nused = 0;
}

/*initialize the record */
void record_init(record *p)
{
    p->id = 0;
    strcpy(p->name.first, "");
    strcpy(p->name.last, "");
    p->score = 0;
}

/*Function to store the grade */
int store_record(record *p, int *id, char *first,
        char *last, int *score)
{
    p->id = *id;
    strcpy(p->name.first, first);
    strcpy(p->name.last, last);
    p->score = *score;
    return 1;
}

/*Function to print out records*/
void print_grade(const record *p)
{
    printf("%d %s, %s: %d\n", p->id, p->name.first, p->name.last, p->score);
}

/*Function to go through and print records */
void show_byID(record_list *list)
{
    size_t n = 0;
    qsort(list->data,list->nused,sizeof(record*),cmpID);
    for (n = 0; n < list->nused; n++)
    {
        print_grade(list->data[n]);
    }
}

void show_byName(record_list *list)
{
    size_t n = 0;
    qsort(list->data,list->nused, sizeof(record*),cmpName);
    for  (n = 0; n < list->nused; n++)
    {
        print_grade(list->data[n]);
    }
}

/*function to insert records */
int insert_record(record_list *list, const record *rec)
{
    void *tmp = 0;
    if (list->nalloc == list->nused)
    {
        tmp = realloc(list->data, (list->nalloc + BLOCK * sizeof(record)));
        if (tmp == 0)
        {
            fprintf(stderr, "Memory reallocation failed");
            return 0;
        }
        list->data = tmp;
        list->nalloc += BLOCK;
    }
    list->data[list->nused] = malloc(sizeof(record));
    if (list->data[list->nused] == 0)
    {
        fprintf(stderr, "Memory allocation failed");
        return 0;
    }
    *list->data[list->nused] = *rec;
    list->nused++;
    return 1;
}

/*go through and delete every single record*/
int delete_records(record_list *list)
{
    size_t n = 0;
    for (n = 0; n < list->nalloc; n++)
    {
        free(list->data[n]);
    }
    list_init(list);
    return 1;
}

/*get the ID, name, score to store into a record
to insert into the list */
int getRecord(int *id, int *score, char fname[BUFSIZE],
         char lname[BUFSIZE], record *p, record_list *list)
{
    int result = 0;
    while(1)
    {
        result = getID(*id);
        if ((result == 0) || (result == 2))
        {
            return 0;
        }
        if (getfName(fname) == 0)
        {
            return 0;
        }
        if (getlName(lname) == 0)
        {
            return 0;
        }
        if (getScore(*score) == 0)
        {
            return 0;
        }
        if (store_record(p,id,fname,lname,score) == 1)
        {
            if (insert_record(list, p) == 1)
            {
                fprintf(stderr,"Record successfully inserted\n");
            }
        }
    }
    return 0;
}


/* Display the menu and prompt for actions*/
void menu_display()
{
    fprintf(stderr, "1. Enter records\n");
    fprintf(stderr, "2. Sort by ID\n");
    fprintf(stderr, "3. Sort by name\n");
    fprintf(stderr, "4. Quit\n");
}

/*Verify menu prompt*/
int menu()
{
    char line[LINESIZE] = "";
    int n = 0;
    while (1)
    {
        menu_display();
        getInput(line);
        if (sscanf(line, "%d\n", &n) == 1)
        {
            if ((n < 5) && (n > 0))
            {
                return n;
            }
        }
    }
}

int main(void)
{
    /*initializing variables */
    int option = 0;
    record_list list;
    record p;
    int id = 0;
    int score = 0;
    char fname[BUFSIZE];
    char lname[BUFSIZE];

    list_init(&list);
    record_init(&p);

    /*program starts*/
    while (1)
    {
        option = menu();
        if (option == 1)
        {
            getRecord(&id, &score, fname, lname, &p, &list);
        }
        if (option == 2)
        {
            show_byID(&list);
            continue;
        }
        if (option == 3)
        {
            show_byName(&list);
            continue;
        }
        if (option == 4)
        {
            delete_records(&list);
            return 0;
        }
    }
    return 0;
}