#include "../include/quiz.h"
#include "../include/utils.h"
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>

#define INPUT_BUFFER_SIZE 64
#define QUIZ_DATA_DIRECTORY "data"
#define QUESTIONS_FILE_NAME "questions.txt"
#define RESULTS_FILE_NAME "results.csv"
#define CSV_TIMESTAMP_BUFFER 32
#define FILE_PATH_BUFFER 256
#define PERMISSIONS_DATA_DIRECTORY 0755
#define TIME_UNLIMITED 0
#define BASE_VALUE 10

static const char* START_PROMPT = "Press ENTER to start...";
static const char* DONE_PROMPT = "Press ENTER when done...";
static const char* TIME_LIMIT_PROMPT = "Time limit (sec, 0 = unlimited): ";
static const char* CORRECT_PROMPT = "Correct? (y/n): ";
static const char* NEXT_QUESTION_PROMPT = "Next? (y/n): ";
static const char* TIME_EXCEEDED_MESSAGE = "Time exceeded!\n";
static const char* CSV_OPEN_ERROR_MESSAGE = "CSV open";
static const char* QUESTIONS_LOAD_ERROR = "Error: cannot load questions file\n";
static const char* DATA_DIR_ERROR = "Error: cannot create data directory\n";

static bool ensure_data_directory_exists(void)
{
	struct stat st = {0};
	if (stat(QUIZ_DATA_DIRECTORY, &st) == -1) {
#ifdef _WIN32
		return _mkdir(QUIZ_DATA_DIRECTORY) == 0;
#else
		return mkdir(QUIZ_DATA_DIRECTORY, PERMISSIONS_DATA_DIRECTORY)
		       == 0;
#endif
	}
	return true;
}

static int read_time_limit(void)
{
	char buffer[INPUT_BUFFER_SIZE];
	printf("%s", TIME_LIMIT_PROMPT);

	if (!fgets(buffer, sizeof buffer, stdin))
		return TIME_UNLIMITED;

	errno = 0;
	char* end = NULL;
	long value = strtol(buffer, &end, BASE_VALUE);

	if (errno == ERANGE || end == buffer)
		return TIME_UNLIMITED;
	if (value < 0)
		value = 0;
	if (value > INT_MAX)
		value = INT_MAX;

	return (int)value;
}

static void write_csv_result(FILE* csv,
			     const char* timestamp,
			     const char* general_q,
			     const char* major_q,
			     const bool correct_answer,
			     const double duration)
{
	static const char* CSV_FORMAT = "\"%s\",\"%s\",\"%s\",%c,%.0f\n";
	fprintf(csv,
		CSV_FORMAT,
		timestamp,
		general_q,
		major_q,
		correct_answer ? 'y' : 'n',
		duration);
}

void print_score(const size_t correct, size_t total)
{
	double percentage = 0.0;
	if (total != 0)
		percentage = (double)correct / total * PERCENT_MULTIPLIER;

	printf(SCORE_FORMAT, correct, total, percentage);
}

void print_final_score(const QuizSession* session)
{
	double final_percentage = 0.0;
	if (session->total_answered > 0)
		final_percentage = (double)session->total_correct
				   / session->total_answered
				   * PERCENT_MULTIPLIER;

	printf("\nSession score: %.1f%%\n", final_percentage);
}

// ------------------------
// Initialization & Cleanup
// ------------------------
bool initialize_quiz_session(QuizSession* session)
{
	session->seed = (unsigned int)time(NULL);
	srand(session->seed);

	if (!ensure_data_directory_exists()) {
		fprintf(stderr, "%s", DATA_DIR_ERROR);
		return false;
	}

	char questions_path[FILE_PATH_BUFFER];
	snprintf(questions_path,
		 sizeof questions_path,
		 "%s/%s",
		 QUIZ_DATA_DIRECTORY,
		 QUESTIONS_FILE_NAME);

	char results_path[FILE_PATH_BUFFER];
	snprintf(results_path,
		 sizeof results_path,
		 "%s/%s",
		 QUIZ_DATA_DIRECTORY,
		 RESULTS_FILE_NAME);

	if (load_questions(questions_path, &session->questions)
	    != EXIT_SUCCESS) {
		fprintf(stderr, "%s", QUESTIONS_LOAD_ERROR);
		return false;
	}

	session->csv = fopen(results_path, "a");
	if (!session->csv) {
		perror(CSV_OPEN_ERROR_MESSAGE);
		free_questions(&session->questions);
		return false;
	}

	session->total_answered = 0;
	session->total_correct = 0;
	session->time_limit = read_time_limit();

	return true;
}

void cleanup_session(QuizSession* session)
{
	fclose(session->csv);
	free_questions(&session->questions);
}

// ------------------------
// Single Quiz Iteration
// ------------------------
bool quiz_iteration(QuizSession* session)
{
	const size_t general_index = get_random_question_index(
	    &session->seed, session->questions.general_count);
	const size_t major_index = get_random_question_index(
	    &session->seed, session->questions.major_count);

	const char* general_question =
	    session->questions.general[general_index];
	const char* major_question = session->questions.major[major_index];

	print_line();
	printf(
	    "GENERAL:\n%s\n\nMAJOR:\n%s\n", general_question, major_question);
	print_line();

	wait_for_enter(START_PROMPT);
	const time_t start_time = time(NULL);

	wait_for_enter(DONE_PROMPT);
	const double duration_seconds = difftime(time(NULL), start_time);

	if (session->time_limit > 0 && duration_seconds > session->time_limit)
		printf("%s", TIME_EXCEEDED_MESSAGE);

	const bool correct = ask_yes_no(CORRECT_PROMPT);
	if (correct)
		session->total_correct++;
	session->total_answered++;

	char timestamp[CSV_TIMESTAMP_BUFFER];
	get_answer_timestamp(timestamp, sizeof timestamp);

	write_csv_result(session->csv,
			 timestamp,
			 general_question,
			 major_question,
			 correct,
			 duration_seconds);

	print_score(session->total_correct, session->total_answered);

	return ask_yes_no(NEXT_QUESTION_PROMPT);
}