/***********************************************************************
 *
 * Multiplication Tables Trainer: practice multiplication tables 
 * and beat your best time.
 *
 * Program.......: mt_trainer
 * Date..........: August 30, 2022
 * Author........: yetimach
 *
 * **********************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <time.h>
#include <sys/stat.h>
#include <sys/types.h>

#define MAX_UN 20
#define MAX_FN 30
#define TABLE_SIZE 13
#define MAX_ANSWER_LEN 4
	

// swap int element with last element in array 
void swap_with_last(int *arr, int size, int elem){
	int temp = arr[size - 1];
	arr[size - 1] = arr[elem];
	arr[elem] = temp;
}

void shuffle_int_arr(int *arr, int size){
	int num, temp_arr[size], pos = 0, i;
	srand(time(0));
	while (size > 0){
		num = (rand() % size);
		temp_arr[pos++] = arr[num];
		swap_with_last(arr, size, num);
		--size;
	}
	for (i = 0; i < pos; i++)
		arr[i] = temp_arr[i];
}

// check if user answer is the correct answer
int match(int ca, int ua){
	return (ca == ua) ?  1 : 0;
}

// read a positive int    
int read_int(){    
    int num = 0, si = 0, ch;    
    char string[MAX_ANSWER_LEN];    
	while (!isdigit(ch = getchar()))
		;
	string[si++] = ch;
    while ((ch = getchar()) != '\n'){    
        if (si < MAX_ANSWER_LEN - 1)    
			if (isdigit(ch))    
				string[si++] = ch;    
    }    
	string[si] = '\0';    
    num = atoi(string);    
	return num;	 
}

void print_time(long int t){
	if (t > 60)
		printf("%ld min %ld sec", t / 60, t % 60);
	else
		printf("%ld sec", t);
}

void practice_table(int *nums, time_t *tt){
    int	i, t = 0;
	do {
		if (t > TABLE_SIZE - 1)
			printf("\n\t%d is invalid.", t);
		printf("\n\tTable to practice: "); 
		t = read_int();
	} while (t > TABLE_SIZE - 1);
	shuffle_int_arr(nums, TABLE_SIZE);
	printf("\n\t%d Table\n", t);
	long int best_time = tt[t];
	if (best_time > 0){
		printf("\n\tThe time to beat is ");
		print_time(best_time);
		printf(".\n");
	}
	printf("\n\tPress enter to begin ");
	time_t start = time(NULL);
	while (getchar() != '\n')
		;
	printf("\n\tGo!\n\n");
	for (i = 0; i < TABLE_SIZE;){
		printf("\t%2d  x %2d  = ", t, nums[i]);
		while (match((t * nums[i]), read_int()) == 0){
			printf("\tSorry, try again.");
			printf("\n\t%2d  x %2d  = ", t, nums[i]);
		}
		++i;
	}
	time_t finish = time(NULL);
	long int current_time = finish - start;
	if (current_time < best_time || best_time == 0){
		printf("\n\t");
		print_time(current_time);
		putchar('\n');
		printf("\n\tA new record!\n");
		tt[t] = current_time;
	}else{
		printf("\n\t");
		print_time(current_time);
		printf("\n\tKeep practicing!\n");
	}
}

int read_username(char *un){
	int success = 0, ch, count = 0;
	while ((!isalpha(ch = getchar())))
			; //read to a letter
	un[count++] = ch;
	while ((isalpha(ch = getchar())) && ch != ' ' && ch != '\n' 
			&& ch != '\t' && count <  MAX_UN - 1)
		un[count++] = ch;
	if (count > 1)
		success = 1;
	if (ch != '\n')
		while ((ch = getchar() != '\n'))
			; // read to newline
	un[count] = '\0';
	return success;
}

void make_record(FILE *uf, char *file_name, time_t *tt){
	int i;
	uf = fopen(file_name, "w");
	for (i = 0; i < TABLE_SIZE; i++)
		fprintf(uf, "%ld\n", tt[i]);
	fclose(uf);
}

void read_record(FILE *uf, char *file_name, time_t *tt){
	int i;
	uf = fopen(file_name, "r");
	for (i = 0; i < TABLE_SIZE; i++)
		fscanf(uf, "%ld\n", &tt[i]);
	fclose(uf);
}

int read_option(void){
	int opt;
	while ((tolower(opt = getchar())) != 'v' && opt != 'p' && opt != 'q'){
		if (opt != '\n')
			printf("\n\tInvalid input. Tray again: ");
	}
	while (getchar() != '\n')
		; // read to newline
	return opt;
}

void view_table(void){
	int i, t;
	printf("\n\tTable to view: ");
	t = read_int();
	putchar('\n');
	for (i = 0; i < TABLE_SIZE; i++)
		printf("\n\t%2d  x  %2d  = %3d", t, i, t*i);
	putchar('\n');
}

int print_and_process_opts(time_t *tt){
	int i, numbers[TABLE_SIZE];
	for (i = 0; i < TABLE_SIZE; i++)
		numbers[i] = i;
	printf("\n\t'v' view table, 'p' practice table, 'q' quit: ");
	int option = read_option();
	if (option == 'q')
		return 0;
	else if (option == 'v')
		view_table();
	else if (option == 'p')
		practice_table(numbers, tt);
	return 1;
}

int main(void)
{
	FILE *user_file;
	time_t table_times[TABLE_SIZE];
	// check for users directory; create it if none.
	struct stat st = {0};
	if (stat("users", &st) == -1) 
		mkdir("users", 0751);
	char username[MAX_UN];
		printf("\n\tMultiplication Tables Trainer\n"
		   "\n\tPractice the multiplication tables and try to beat"
		   "\n\tyour best time. Enter existing username to access"
		   "\n\tan account or enter a new username to create one."
		   "\n\t(letters only--at least two)\n"
		   "\n\tEnter username: ");
	while ((read_username(username) == 0))
			printf("\n\tInvalid username. Try again: ");
	char user_file_name[MAX_FN] = "";
	strcpy(user_file_name, "users/");
	strcat(user_file_name, username);
	strcat(user_file_name, "_records.txt");
	if( access( user_file_name, F_OK ) != -1 ) {
		read_record(user_file, user_file_name, table_times);
	}else{
		int i;
		for (i = 0; i < TABLE_SIZE; i++)
			table_times[i] = 0;
		make_record(user_file, user_file_name, table_times);
		printf("\n\tAccount created for %s.", username);
	}
	printf("\n\n\tWelcome, %s!\n", username);
	//print and process options
	while (print_and_process_opts(table_times))
		;
	make_record(user_file, user_file_name, table_times);	
	printf("\n\tGoodbye\n\n");
	return 0;
}