dont append to the end but seek END:VCALENDAR

src/Makefile

@@ -21,11 +21,6 @@ main.o: main.c
 all:
 	gcc -Wall *.c
 
-.PHONY:debug
-debug:
-	gcc -Wall -g *.c
-	gdb a.out
-
 .PHONY:run
 run:
 	gcc -Wall *.c

src/insert_event.c

@@ -6,7 +6,7 @@
 #include <unistd.h>
 
 void insert_event(char *file_name) {
-	int myfd = open(file_name, O_APPEND | O_WRONLY);
+	int myfd = open(file_name, O_RDWR);
 
 	char summary_buf[256] = "SUMMARY:";
 
@@ -24,10 +24,34 @@ void insert_event(char *file_name) {
 	summary_buf[strlen(summary_buf)-1] = '\r';
 	summary_buf[strlen(summary_buf)] = '\n';
 
+	seek_cal_end(myfd);
 	write(myfd, "BEGIN:VEVENT\r\n", strlen("BEGIN:VEVENT\r\n"));
 	write(myfd, summary_buf, strlen(summary_buf));
+	write(myfd, "END:VCALENDAR\r\n", strlen("END:VCALENDAR\r\n"));
 
 	close(myfd);
 
 	exit(0);
 }
+
+void seek_cal_end(int fd) {
+	char search_string[] = "END:VCALENDAR";
+	int j = 0;
+	char char_reader = '\0';
+
+	lseek(fd, -1, SEEK_END);
+
+	while(read(fd, &char_reader, 1)) {
+		// no need to compare to the null terminator of the search_string
+		if (char_reader == search_string[strlen(search_string)-j-1]) {
+			j++;
+		} else {
+			j = 0;
+		}
+		if (j == (strlen(search_string))) {
+			lseek(fd, -1, SEEK_CUR);
+			break;
+		}
+		lseek(fd, -2, SEEK_CUR);
+	}
+}

src/insert_event.h

@@ -1,3 +1,4 @@
 #pragma once
 
 void insert_event(char *file_name);
+void seek_cal_end(int fd);