commit 43c5ef6548fb08a89c4e4205d554231f311b4844
Author: Julian Daube <joposter@gmail.com>
Date:   Wed Mar 8 20:15:10 2017 +0100

    initial commit

diff --git a/cmd/importPunkte/main.go b/cmd/importPunkte/main.go
new file mode 100644
index 0000000..a6fbe41
--- /dev/null
+++ b/cmd/importPunkte/main.go
@@ -0,0 +1,141 @@
+package main
+
+import (
+	"bufio"
+	"database/sql"
+	"encoding/csv"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	_ "github.com/go-sql-driver/mysql"
+)
+
+var (
+	dbURL = flag.String("db", "julian:hi@/test", "The Database")
+)
+
+const (
+	queryInsert = "INSERT INTO Punkte (Matrnr, Aufgabe, Punkte) VALUES(?,?,?)"
+)
+
+// This function  assumes it input to be only one float
+func convertFloat(input string) string {
+	// replace all , with .
+	return strings.Replace(input, ",", ".", -1)
+}
+
+func YesNo() bool {
+	reader := bufio.NewReader(os.Stdin)
+	for {
+		line, _, err := reader.ReadLine()
+		if err != nil {
+			return false
+		}
+
+		// default case
+		if len(line) == 0 {
+			return true
+		}
+
+		switch line[0] {
+		case 'Y':
+			fallthrough
+		case 'y':
+			return true
+		case 'N':
+			fallthrough
+		case 'n':
+			return false
+		}
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	files := flag.Args()
+	if len(files) == 0 {
+		log.Fatal("no files given!")
+	}
+
+	db, err := sql.Open("mysql", *dbURL)
+	if err != nil {
+		log.Fatal("error connecting to Database:", err)
+	}
+	defer db.Close()
+
+	for _, f := range files {
+		log.Println("importing", f)
+		file, err := os.Open(f)
+		if err != nil {
+			log.Println("could not open file:", f+":", err)
+			continue
+		}
+
+		reader := csv.NewReader(file)
+		transaction, err := db.Begin()
+		if err != nil {
+			log.Fatal("cannot prepare statement:", err)
+		}
+
+		stmt, err := transaction.Prepare(queryInsert)
+		if err != nil {
+			log.Fatal("could not prepare insert statement:", err)
+		}
+		defer stmt.Close()
+
+		var (
+			line      []string
+			count     = 0
+			linecount = 0
+
+			ID      int
+			Aufgabe = 1
+			points  float64
+		)
+
+		for {
+			linecount++
+			line, err = reader.Read()
+			if err != nil || line == nil {
+				break
+			}
+
+			if len(line) < 2 {
+				log.Println(linecount, ": malformed line")
+				continue
+			}
+
+			if ID, err = strconv.Atoi(line[0]); err != nil {
+				log.Println(linecount, ": no ID given, could not convert:", err)
+				continue
+			}
+
+			fmt.Print(ID, " ")
+
+			Aufgabe = 1
+			for _, p := range line[1:] {
+				if points, err = strconv.ParseFloat(convertFloat(p), 32); err != nil {
+					log.Println(linecount, "A", Aufgabe, ": could not parse points:", err)
+				}
+				fmt.Print(points, " ")
+
+				if _, err = stmt.Exec(ID, Aufgabe, points); err != nil {
+					log.Println(linecount, ": error inserting:", err)
+				}
+				Aufgabe++
+			}
+			fmt.Println()
+			count++
+		}
+		fmt.Println("read", count, "Students")
+		fmt.Println("commit changes? (Y/n)")
+		if YesNo() {
+			transaction.Commit()
+		}
+	}
+}
diff --git a/cmd/importTeilnehmer/main.go b/cmd/importTeilnehmer/main.go
new file mode 100644
index 0000000..ec14115
--- /dev/null
+++ b/cmd/importTeilnehmer/main.go
@@ -0,0 +1,111 @@
+package main
+
+import (
+	"database/sql"
+	"encoding/csv"
+	"flag"
+	"log"
+	"os"
+	"strconv"
+
+	_ "github.com/go-sql-driver/mysql"
+)
+
+// Student from Database
+type Student struct {
+	Vorname, Nachname string
+	Matrikelnummer    int
+	StudiengangID     int
+}
+
+var (
+	databaseURL = flag.String("db", "julian:hi@/test", "The Database url")
+)
+
+const (
+	insertQuery = "INSERT INTO Teilnehmer (Nachname, Vorname, Matrnr, Studiengang) VALUES(?,?,?,?)"
+)
+
+// Main Function
+func main() {
+	flag.Parse()
+
+	if flag.NArg() == 0 {
+		log.Fatal("no file(s) given!")
+	}
+
+	// try to open file
+	file, err := os.Open(flag.Arg(0))
+	if err != nil {
+		log.Fatal("could not open file:", err)
+	}
+	defer file.Close()
+
+	reader := csv.NewReader(file)
+
+	defer log.Println("shutdown completed")
+	// list all Database providers
+	log.Println("Database providers:", sql.Drivers())
+
+	// connect to database
+	db, err := sql.Open("mysql", *databaseURL)
+
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+	log.Println("mysql connection established")
+	// prepare Queries
+	newStudent, err := db.Prepare(insertQuery)
+	if err != nil {
+		log.Fatal("Error preparing statement:", insertQuery+":", err)
+	}
+
+	defer newStudent.Close()
+
+	// init completed
+	defer log.Println("shutting down")
+
+	var (
+		line       []string
+		linenumber = 0
+		count      = 0
+	)
+
+	for ; err == nil; line, err = reader.Read() {
+		linenumber++
+		if len(line) < 4 {
+			log.Println("line", linenumber, "malformed")
+			continue
+		}
+
+		number, err := strconv.Atoi(line[2])
+		if err != nil {
+			log.Println("line", linenumber, ":could not convert ID:"+line[2]+":", err)
+			continue
+		}
+		if number < 0 {
+			log.Println("line", linenumber, ":ID invalid:", number)
+			continue
+		}
+
+		studiengang, err := strconv.Atoi(line[3])
+		if err != nil {
+			log.Println("line", linenumber, ":studiengang could not be converted:", err)
+			continue
+		}
+		if studiengang < 0 || studiengang > 2 {
+			log.Println("line", linenumber, ":Studiengang does not exist:", studiengang)
+			continue
+		}
+
+		if _, err := newStudent.Exec(line[0], line[1], number, studiengang); err != nil {
+			log.Println("line", linenumber, ":could not execute INSERT:", err)
+			continue
+		}
+
+		count++
+	}
+
+	log.Println("done, inserted", count, "records")
+}
diff --git a/cmd/list/main.go b/cmd/list/main.go
new file mode 100644
index 0000000..052b62c
--- /dev/null
+++ b/cmd/list/main.go
@@ -0,0 +1,59 @@
+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))
+	}
+}
diff --git a/cmd/list/studenten.go b/cmd/list/studenten.go
new file mode 100644
index 0000000..9cbfc22
--- /dev/null
+++ b/cmd/list/studenten.go
@@ -0,0 +1,17 @@
+package main
+
+import (
+	"strconv"
+)
+
+// Ein Student
+type Student struct {
+	Vorname, Nachname string
+	Matrnr            int
+	Studiengang       Studiengang
+}
+
+// Gibt den Studenten als String zurück
+func (s Student) String() string {
+	return "{" + strconv.Itoa(s.Matrnr) + " " + s.Nachname + ", " + s.Vorname + " \"" + *s.Studiengang + "\"}"
+}
diff --git a/cmd/list/studiengang.go b/cmd/list/studiengang.go
new file mode 100644
index 0000000..d81635c
--- /dev/null
+++ b/cmd/list/studiengang.go
@@ -0,0 +1,32 @@
+package main
+
+import "database/sql"
+
+// Ein Studiengang
+type Studiengang *string
+
+// globale Tabelle aller Studiengänge
+var studiengaenge map[int]Studiengang
+
+// lese alle Studiengänge aus der mysql Tabelle
+func readStudiengaenge(db *sql.DB) error {
+	studiengaenge = make(map[int]Studiengang)
+	result, err := db.Query("SELECT ID, Studiengaenge.Name FROM Studiengaenge")
+	if err != nil {
+		return err
+	}
+
+	var (
+		ID   int
+		stud string
+	)
+
+	for result.Next() {
+		if err = result.Scan(&ID, &stud); err != nil {
+			return err
+		}
+		studiengaenge[ID] = Studiengang(&stud)
+	}
+
+	return nil
+}
diff --git a/cmd/stripColumns/main.go b/cmd/stripColumns/main.go
new file mode 100644
index 0000000..a950d1a
--- /dev/null
+++ b/cmd/stripColumns/main.go
@@ -0,0 +1,83 @@
+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)
+	}
+}
diff --git a/cmd/stripColumns/strip.go b/cmd/stripColumns/strip.go
new file mode 100644
index 0000000..6e778ca
--- /dev/null
+++ b/cmd/stripColumns/strip.go
@@ -0,0 +1,15 @@
+package main
+
+func strip(str string) (output string) {
+	var (
+		start = 0
+		end   = len(str)
+	)
+	for ; start < len(str) && str[start] == ' '; start++ {
+	}
+
+	for ; end > 0 && str[end-1] == ' '; end-- {
+	}
+
+	return str[start:end]
+}