BEGIN:VCALENDAR
PRODID:-//COVIDPass//www.covidpass.cz//EN
VERSION:2.0
METHOD:PUBLISH
BEGIN:VTIMEZONE
TZID:Central Europe Standard Time
BEGIN:STANDARD
DTSTART:16011028T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010325T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:4a55be4a-c27b-4482-a304-98522a71f34d
CLASS:PUBLIC
DESCRIPTION:\n
DTSTART;TZID="Central Europe Standard Time":20211211T080000
DTEND;TZID="Central Europe Standard Time":20211211T081500
LOCATION:COVIDPASS - Budějovická 303\, Jesenice\, 252 42
PRIORITY:5
SEQUENCE:0
SUMMARY;LANGUAGE=cs:COVIDPass - Test na COVID
TRANSP:OPAQUE
BEGIN:VALARM
TRIGGER:-PT60M
ACTION:DISPLAY
DESCRIPTION:Reminder
END:VALARM
END:VEVENT
END:VCALENDAR

#include <stdio.h>
#include <stdlib.h>
#include <magic.h>

#define READ_SIZE 4096 // We'll read the first 4KB of the file

int main(int argc, char *argv[]) {
    // 1. Check for command-line argument
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
        return 1;
    }
    const char *filename = argv[1];

    // 2. Open the file and read into a buffer
    FILE *fp = fopen(filename, "rb");
    if (fp == NULL) {
        perror("Error opening file");
        return 1;
    }

    char buffer[READ_SIZE];
    size_t bytes_read = fread(buffer, 1, READ_SIZE, fp);
    fclose(fp);

    if (bytes_read == 0) {
        fprintf(stderr, "File is empty or could not be read.\n");
        return 1;
    }

    // 3. Initialize libmagic
    // MAGIC_MIME_TYPE tells libmagic to return the MIME type string
    magic_t magic_cookie = magic_open(MAGIC_MIME_TYPE);
    if (magic_cookie == NULL) {
        fprintf(stderr, "Error initializing libmagic\n");
        return 1;
    }

    // Load the default magic database files
    if (magic_load(magic_cookie, NULL) != 0) {
        fprintf(stderr, "Error loading magic database: %s\n", magic_error(magic_cookie));
        magic_close(magic_cookie);
        return 1;
    }

    // 4. Determine MIME type from the buffer
    const char *mime_type = magic_buffer(magic_cookie, buffer, bytes_read);

    // 5. Print the result
    if (mime_type == NULL) {
        fprintf(stderr, "Error identifying file type: %s\n", magic_error(magic_cookie));
    } else {
        printf("MIME Type of '%s': %s\n", filename, mime_type);
    }

    // 6. Clean up
    magic_close(magic_cookie);

    return 0;
}