#include "date_time_handling.h"
#include "string_handling.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

// buffer needs to contain a string with a strlen of 15 (format: "xxxxxxxxTxxxxxx")
// or a strlen of 16 (format: "YYYYmmddTHHMMSSZ")
void get_date(char buffer[]) {
	// add 1 because strlen does not include the null character
	size_t buffer_size = strlen(buffer) + 1;
	time_t my_unix_ts = time(NULL);
	struct tm* my_tm_local = localtime(&my_unix_ts);
	if (strlen(buffer) == 15) {
		strftime(buffer, buffer_size, "%Y%m%dT%H%M%S", my_tm_local);
	} else if (strlen(buffer) == 16) {
		strftime(buffer, buffer_size, "%Y%m%dT%H%M%SZ", my_tm_local);
	}
}

// 20230823T194138 -> 2023-08-23 19:41:38
void pretty_print_date_time(char date_time[]) {
	char *date = strtok(date_time, "T");
	char *time = strtok(NULL, "T");
	if (date == NULL) {
		printf ("\nError: date points to NULL!\n");
		exit(1);
	}
	printf ("%c%c%c%c-", date[0], date[1], date[2], date[3]);
	printf ("%c%c-", date[4], date[5]);
	printf ("%c%c", date[6], date[7]);
	
	if (time != NULL) {
		printf (" %c%c:", time[0], time[1]);
		printf ("%c%c:", time[2], time[3]);
		printf ("%c%c", time[4], time[5]);
	}
}

void marshall_date_time(char date_time[]) {
	char transformed_string[strlen(date_time)];
	int j = 0;
	remove_nl_and_cr(date_time);
	for (int i = 0; i<=strlen(date_time); i++) {
		if (date_time[i] != ':' && date_time[i] != '-') {
			if (date_time[i] == ' ') {
				transformed_string[j] = 'T';
			} else {
				transformed_string[j] = date_time[i];
			}
			
			j++;
		}
	
	}
	memset(date_time, '\0', strlen(date_time));
	strcpy(date_time, transformed_string);
}

void print_end_date(char end_date[], char start_date[]) {
	time_t start_uts = transform_date_to_unix_ts(start_date);
	time_t end_uts = transform_date_to_unix_ts(end_date);
	double time_difference = difftime(end_uts, start_uts);

	// end_date is all day event
	if (strlen(end_date) == 8) {
		if (time_difference == 86400) {
			return;
		} else {
			printf (" - ");
			end_uts -= 86400;
			char *end_date_minus_one = transform_unix_ts_to_date(end_uts);
			pretty_print_date_time(end_date_minus_one);
			free(end_date_minus_one);
			return;
		}
	} else {
		// end_date is not an all day event

		char *end_date_chunk = strtok(end_date, "T");
		char *end_time_chunk = strtok(NULL, "T");
		char *start_date_chunk = strtok(start_date, "T");

		printf (" - ");

		// only print the end date if it is not the same as the start date
		if (strcmp(start_date_chunk, end_date_chunk) != 0) {
			printf("%c%c%c%c-", end_date_chunk[0], end_date_chunk[1], \
			end_date_chunk[2], end_date_chunk[3]);
			printf("%c%c-", end_date_chunk[4], end_date_chunk[5]);
			printf("%c%c ", end_date_chunk[6], end_date_chunk[7]);
		}
		
		printf ("%c%c:", end_time_chunk[0], end_time_chunk[1]);
		printf ("%c%c:", end_time_chunk[2], end_time_chunk[3]);
		printf ("%c%c", end_time_chunk[4], end_time_chunk[5]);
	}
}

// YYYYmmdd -> unix timestamp
time_t transform_date_to_unix_ts(char date_str[]) {
	time_t unix_stamp = 0;
	int date_only = atoi(date_str);
	struct tm my_tm = {0};
	my_tm.tm_year = date_only / 10000 - 1900;
	my_tm.tm_mon = (date_only % 10000) / 100 - 1;
	my_tm.tm_mday = date_only % 100;

	unix_stamp = mktime(&my_tm);

	return unix_stamp;
}

// unix timestamp -> YYYYmmdd
// make sure to free the returned buffer
char *transform_unix_ts_to_date(time_t unix_ts) {
	char *date_buffer = malloc(9);
	struct tm *my_tm;
	my_tm = localtime(&unix_ts);
	strftime(date_buffer, 9, "%Y%m%d", my_tm);

	return date_buffer;
}

char *get_tz() {
	char *timezone_path = malloc(256);
	ssize_t bytes_read = readlink("/etc/localtime", timezone_path, 255);

	if (bytes_read != -1) {
		// Null-terminate the string
    	timezone_path[bytes_read] = '\0';
	} else {
		perror("readlink");
		exit(1);
	}

	return timezone_path;
}