package main

import (
	"database/sql"
	"flag"
	"fmt"
	"log"

	"encoding/json"

	_ "github.com/go-sql-driver/mysql"
)

var (
	dbURL = flag.String("db", "julian:hi@/test", "The Database")
)

func main() {
	flag.Parse()

	db, err := sql.Open("mysql", *dbURL)
	if err != nil {
		log.Fatal(err)
	}
	if err = readStudiengaenge(db); err != nil {
		log.Fatal("readStudiengaenge:", err)
	}

	result, err := db.Query("SELECT Vorname, Nachname, Matrnr, Studiengang FROM Teilnehmer")
	if err != nil {
		log.Fatal("error fetching students:", err)
	}

	var (
		stud Student
		ID   int
	)

	for result.Next() {
		if err = result.Scan(&stud.Vorname, &stud.Nachname, &stud.Matrnr, &ID); err != nil {
			log.Println("could not retrieve Student:", err)
			continue
		}

		name, ok := studiengaenge[ID]
		if !ok {
			log.Println("illegal Studiengang:", ID)
			continue
		}

		stud.Studiengang = name

		out, err := json.Marshal(stud)
		if err != nil {
			log.Fatal("could not marshal to json:", err)
		}
		fmt.Println(string(out))
	}
}