package main

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

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

var (
	dbURL = flag.String("db", "julian:hi@/test", "Die URL zur Datenbank")
	table = flag.String("table", "Teilnehmer", "Die Tabelle")
	key   = flag.String("key", "Matrnr", "Der Tabellenschlüsselname")
	attr  = flag.String("attr", "Nachname", "Die Spalte zum Cleanen")
)

const (
	querySelect = "SELECT ?,? FROM ?"
	queryUpdate = "UPDATE ? SET ?=? WHERE ?=?"
)

func main() {
	flag.Parse()

	db, err := sql.Open("mysql", *dbURL)
	if err != nil {
		log.Fatal("error connecting to database:", err)
	}
	defer db.Close()

	statement, err := db.Prepare("SELECT " + *key + "," + *attr + " FROM " + *table)

	if err != nil {
		log.Fatal("error in precompiled statement:", querySelect+":", err)
	}
	defer statement.Close()

	rows, err := statement.Query()

	if err != nil {
		log.Fatal("error executing query:", err)
	}

	context, err := db.Begin()
	if err != nil {
		log.Fatal("error creating context:", err)
	}

	update, err := context.Prepare("UPDATE " + *table + " SET " + *attr + "=? WHERE " + *key + "=?")
	if err != nil {
		log.Fatal("error in precompiled statement:", queryUpdate+":", err)
	}

	var (
		keyBuffer    int
		dirty, clean string

		count int
	)

	for rows.Next() {
		if err = rows.Scan(&keyBuffer, &dirty); err != nil {
			log.Println("error while reading:", err)
		}

		clean = strip(dirty)
		if clean != dirty {
			if result, err := update.Exec(clean, keyBuffer); err != nil {
				log.Fatal("error on update, change canceled:", err)
			} else if i, err := result.RowsAffected(); err == nil && i != 1 {
				log.Fatal("changed to many rows... aborting")
			} else {
				count++
			}
		}
	}

	log.Println("committing change,", count, "rows affected")
	if err := context.Commit(); err != nil {
		log.Println("could not commit changed:", err)
	}
}