package main

import (
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"

	"github.com/charmbracelet/log"
)

const calendar_url = "https://frontdoor.spa.gla.ac.uk/spacett/download/uogtimetable.ics"

var authorization string

func fetch_calendar() ([]byte, error) {
	// create request
	req, err := http.NewRequest("GET", calendar_url, nil)
	if err != nil {
		return []byte{}, err
	}
	req.Header.Set("Authorization", authorization)

	// send request
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return []byte{}, err
	}

	// read response
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return []byte{}, err
	}

	// check if authentication failed
	if resp.StatusCode == 401 {
		return []byte{}, errors.New("authentication failed")
	} else {
		return body, nil
	}
}

func main() {
	// collect guid and password
	var (
		guid     string
		password string
	)
	fmt.Print("Enter your GUID: ")
	fmt.Scan(&guid)
	fmt.Print("Enter your password: ")
	fmt.Scan(&password)
	b64 := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", guid, password)))
	authorization = fmt.Sprintf("Basic %s", b64)

	// fetch calendar
	calendar, err := fetch_calendar()
	if err != nil {
		log.Fatal(err)
	}
	os.WriteFile("calendar.ics", calendar, 0644)
}