Add Noten parsing and rework some existing code

session.go

@@ -5,17 +5,30 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 
 	"github.com/pkg/errors"
 )
 
+// Error variables
+var (
+	ErrInvalSID error = errors.New("invalid session id")
+)
+
+// Session contains the session id and whatever this obscure asi token is.
 type Session struct {
 	SID string
+	// ASI is a string you somehow have to pass to some endpoints.
+	ASI string
 }
 
+// Valid checks if the session id of the session is valid
 func (s *Session) Valid() (bool, error) {
 	client := &http.Client{}
+	// GET the logged in mail page.
+	// If correctly logged in there is a logout button.
+	// Otherwise there is a login button.
 	req, err := http.NewRequest("GET", "https://lsf.hs-worms.de/qisserver/rds?state=user&type=8&topitem=functions&breadCrumbSource=portal", nil)
 	if err != nil {
 		return false, errors.Wrap(err, "could not prepare the request")
@@ -39,6 +52,9 @@ func (s *Session) Valid() (bool, error) {
 	return false, errors.New("unexpected response body")
 }
 
+// Login tries to login with the given username and password.
+// If successful a new Session with the session id and asi
+// will be created and returned.
 func Login(username, password string) (*Session, error) {
 	client := &http.Client{
 		CheckRedirect: func(req *http.Request, via []*http.Request) error { // don't follow redirects
@@ -61,8 +77,13 @@ func Login(username, password string) (*Session, error) {
 	if resp.StatusCode == 302 {
 		for _, c := range resp.Cookies() {
 			if c.Name == "JSESSIONID" {
+				asi, err := asi(c.Value)
+				if err != nil {
+					return nil, errors.Wrap(err, "could not get asi")
+				}
 				return &Session{
 					SID: c.Value,
+					ASI: asi,
 				}, nil
 			}
 		}
@@ -73,3 +94,52 @@ func Login(username, password string) (*Session, error) {
 	}
 	return nil, errors.New("unexpected response status code")
 }
+
+// NewSessionBySID checks whether the given session id is valid and if so
+// a new Session with the session id and asi will be created and returned.
+func NewSessionBySID(sid string) (*Session, error) {
+	s := &Session{
+		SID: sid,
+	}
+	valid, err := s.Valid()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not check session")
+	}
+	if !valid {
+		return nil, ErrInvalSID
+	}
+	asi, err := asi(sid)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get asi")
+	}
+	return &Session{
+		SID: sid,
+		ASI: asi,
+	}, nil
+}
+
+func asi(sid string) (string, error) {
+	client := &http.Client{}
+	// GET Request with JESSIONID cookie to sitemap endpoint
+	req, err := http.NewRequest("GET", "https://lsf.hs-worms.de/qisserver/rds?state=sitemap&topitem=leer&breadCrumbSource=portal", nil)
+	if err != nil {
+		return "", errors.Wrap(err, "could not prepare the request")
+	}
+	req.Header.Add("Cookie", fmt.Sprintf("JSESSIONID=%s", sid))
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", errors.Wrap(err, "could not do the request")
+	}
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", errors.Wrap(err, "could not read the response body")
+	}
+	// The asi is in some links as GET parameter.
+	// Filter it with regexp
+	re := regexp.MustCompile(`asi=([^"]+)`)
+	match := re.FindSubmatch(b)
+	if len(match) != 2 {
+		return "", errors.New("no asi found")
+	}
+	return string(match[1]), nil
+}