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


#define BUFFER_SIZE 1024
#define	NUM_DAYS	7
#define ASCII_ZERO	48


static char time_string[50];


enum { MONDAY = 0, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY };


struct building_info {
	char name[100];
	char day_string[NUM_DAYS][50]; //Day of the week letter + 48 '@' or '_' + NULL terminator
	struct building_info* next;
	int hall_number; //not really sure yet, but I feel like this will be useful later with a more interactive app with a map
};


//negative in start_time means that the building is closed on that day
//in military time xxxx with leading 0s as needed
struct converted_time {
	int start_time; 
	int end_time;
};


void parse_time(char* buf, struct building_info* building_struct);


void print_linked_list(struct building_info* first_building);


int main(void)
{
	FILE* fptr = fopen("times.txt" , "r");
	if (fptr == NULL) { fprintf(stderr, "Problem reading file times.txt!\n"); exit(-1);}

	char buffer[BUFFER_SIZE];
	struct building_info* current_building = calloc(1, sizeof(struct building_info));
	struct building_info* first_node = current_building; //passed to print_linked_list to print all of them in the end
	int num_halls = 0;

	while (fgets(buffer, BUFFER_SIZE, fptr) != NULL) { //while reading the file
		if (strstr(buffer, "Monday")) { //parse the times and put them in the struct
			parse_time(buffer, current_building);
		} else if (buffer[0] >= 'A' && buffer[0] <= 'z') { //new hall, create new node (except for first node) and set name
			++num_halls;
			if (current_building->name[0] != 0) { //not first in linked list, have to create a new node
				struct building_info* new_building = calloc(1, sizeof(struct building_info));
				current_building->next = new_building;
				current_building = new_building;
			}
			current_building->hall_number = num_halls;
			char* name_buffer = (char*) calloc(100, sizeof(char));
			strncpy(name_buffer,buffer, 100);
			strncpy(current_building->name,  name_buffer, 100);
		}
	}
	print_linked_list(first_node);
	return 0;
}


//XX:XX [AP]M (can only occur when the [2] index is ':')
//X:XX [AP]M
//XX [AP]M (can only occur when the first X is a 1) (the second X can only be a 0, 1, or 2)
//X [AP]M (X can never be a 0 or a 1)
//need to catch 12 [AP]M - 12:59 [AP]M quirk
int convert_time(char* str, struct converted_time* conv_times) {
	int i = 0;
	if (str[0] == 'O') {
		if (strstr(str, "Open 24 hours") != NULL) {
			conv_times->start_time = 0;
			conv_times->end_time = 2359;
			return 0;
		}
	}
	if (str[0] == 'C') {
		conv_times->start_time = -1;
		conv_times->end_time = -1;
	} else {
		for (; i < 2; ++i) {
			if (i == 1) {
				str = strstr(str, "-");
				str += 2;
				if (str == NULL) {
					fprintf(stderr, "couldn't find the -\n");
					exit(-1);
				}
				//handle Noon exception
				if ((str[0] == 'N' || str[0] == 'n') && (strstr(str, "Noon") != NULL || strstr(str, "noon") != NULL)) {
					conv_times->end_time = 1200;
					continue;
				}
				//Midnight exception
				if ((str[0] == 'M' || str[0] == 'm') && (strstr(str, "Midnight") != NULL || strstr(str, "midnight") != NULL)) {
					conv_times->end_time = 2359;
					continue;
				}
			}
			//handle Noon exception
			if ((str[0] == 'N' || str[0] == 'n') && (strstr(str, "Noon") != NULL || strstr(str, "noon") != NULL)) {
				conv_times->start_time = 1200;
				continue;
			}
			//Midnight exception
			if ((str[0] == 'M' || str[0] == 'm') && (strstr(str, "Midnight") != NULL || strstr(str, "midnight") != NULL)) {
				conv_times->end_time = 2359;
				continue;
			}
			if (str[1] == ':') { //has to be X:XX [AP]M format
				int hours, minutes;
				if (sscanf(str, "%d:%d", &hours, &minutes) != 2) {
					fprintf(stderr, "Failed sscanf, which should never occur here\n");
					exit(-1);
				}
				if (str[5] == 'A') {
					if (i == 1) {
						conv_times->end_time = hours * 100 + minutes;
					} else {
						conv_times->start_time = hours * 100 + minutes;
					}
				} else if (str[5] == 'P') {
					if (i == 1) {
						conv_times->end_time = (hours + 12) * 100 + minutes;
					} else {
						conv_times->start_time = (hours + 12) * 100 + minutes;
					}
				} else {
					fprintf(stderr, "In a perfect world, this should never occur\n");
					exit(-1);
				}
			} else if (str[0] > '1' && str[1] == ' ') { //has to be X [AP]M format
				if (str[2] == 'A') {
					if (i == 1) {
						conv_times->end_time = ((str[0] - ASCII_ZERO) * 100);
					} else {
						conv_times->start_time = ((str[0] - ASCII_ZERO) * 100);
					}
				} else if (str[2] == 'P') {
					if (i == 1) {
						conv_times->end_time = ((str[0] - ASCII_ZERO + 12) * 100);
					} else {
						conv_times->start_time = ((str[0] - ASCII_ZERO + 12) * 100);
					}
				} else {
					fprintf(stderr, "I do not think this should ever occur when parsing the time and AM/PM\n%s\n", str);
					exit(-1);
				}
			} else {
				if (str[2] == ':') { //XX:XX [AP]M format
					int hours, minutes;
					sscanf(str, "%d:%d", &hours, &minutes);
					if (str[6] == 'A') {
						if (hours == 12) {
							hours = 0;
						} else {
							hours *= 100;
						}
					} else if (str[6] == 'P') {
						if (hours == 12) {
							hours = 1200;
						} else {
							hours = (hours + 12) * 100;
						}
					} else {
						fprintf(stderr, "Should never occur when parsing the time and AM/PM\n");
						exit(-1);
					}
					if (i == 1) {
						conv_times->end_time = hours + minutes;
					} else {
						conv_times->start_time = hours + minutes;
					}
				} else { //XX [AP]M format
					int hours;
					sscanf(str, "%d", &hours);
					if (str[3] == 'A') {
						if (hours == 12) {
							hours = 0;
						} else {
							hours *= 100;
						}
					} else if (str[3] == 'P') {
						if (hours == 12) {
							hours = 1200;
						} else {
							hours = (hours + 12) * 100;
						}
					} else {
						fprintf(stderr, "Shouldn't occur when parsing AM/PM\n string was: %s", str);
						exit(-1);
					}
					if (i == 1) {
						conv_times->end_time = hours;
					} else {
						conv_times->start_time = hours;
					}
				}
			}
		}
	}

	return 0;
}


char* string_from_time(struct converted_time* conv_time, int day) {
	strncpy(time_string, "-------------------------------------------------", 50);
	switch (day) {
		case MONDAY:
			time_string[0] = 'M';
			break;
		case TUESDAY:
			time_string[0] = 'T';
			break;
		case WEDNESDAY:
			time_string[0] = 'W';
			break;
		case THURSDAY:
			time_string[0] = 'R';
			break;
		case FRIDAY:
			time_string[0] = 'F';
			break;
		case SATURDAY:
			time_string[0] = 's';
			break;
		case SUNDAY:
			time_string[0] = 'S';
			break;
		default:
			break;
	}

	//find starting point
	int start_index = (conv_time->start_time / 100) * 2;
	int y = (start_index / 2) * 100;
	y = conv_time->start_time - y;
	if (y > 0) {
		start_index++;
		if (y > 30) {
			start_index++;
		}
	}

	int end_index = -1;
	if (conv_time->start_time > conv_time-> end_time) {
		//store end_time in a special variable used to see if another day needs to add time to it
		//end of the array is 48 and will be set as our INCLUSIVE end in our for loop
		end_index = 48;
	} else {
		end_index = conv_time->end_time / 100 * 2;
		y = (end_index / 2) * 100;
		y = conv_time->end_time - y;
		if (y > 0) {
			end_index++;
			if (y > 30) {
				end_index++;
			}
		}
	}

	if (start_index == 0) {
		start_index = 1;
	}

	for (int i = start_index; i <= end_index; ++i) {
		time_string[i] = '@';
	}

	return time_string;
}


void parse_time(char* buf, struct building_info* building_struct)
{
	//basic setup
	enum {MON_OFFSET = 7, TUES_OFFSET = 8, WED_OFFSET = 10, THUR_OFFSET = 9, FRI_OFFSET = 7, SAT_OFFSET = 9, SUN_OFFSET = 7 };
	char* days_of_the_week[] = { "Monday",  "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" };
	int offset[] = {MON_OFFSET, TUES_OFFSET, WED_OFFSET, THUR_OFFSET, FRI_OFFSET, SAT_OFFSET, SUN_OFFSET};
	struct converted_time conv_times[NUM_DAYS];

	char* new_buf = strstr(buf, days_of_the_week[0]);

	for (int i = 0; i < NUM_DAYS; ++i) {
		new_buf = strstr(new_buf, days_of_the_week[i]);
		if (new_buf != NULL) { 
			new_buf += offset[i];
			convert_time(new_buf, &conv_times[i]);
	       		strncpy(building_struct->day_string[i], string_from_time(&conv_times[i], i), 50);
		} else {
			fprintf(stderr, "Substring: %s, not found in: %s!\n", days_of_the_week[i], new_buf);
			exit(-1);
		}
	}
}

void print_linked_list(struct building_info* building) 
{
	while (building->next != NULL) {
		printf("\n%s", building->name);
		for (int i = 0; i < NUM_DAYS; ++i) {
			printf("%s\n", building->day_string[i]);
		}
		printf("0 1 2 3 4 5 6 7 8 9       1 2 3 4 5 6 7 8 9      24\n\n");
		building = building->next;
	}
}