Add change password feature

internal/dis/component/auth/home.go

@@ -3,6 +3,8 @@ package auth
 import (
 	"context"
 	_ "embed"
+	"errors"
+	"html/template"
 	"net/http"
 
 	"github.com/FAU-CDI/wisski-distillery/internal/dis/component/control/static"
@@ -22,3 +24,80 @@ func (auth *Auth) authHome(ctx context.Context) http.Handler {
 		Template: homeTemplate,
 	}, nil)
 }
+
+//go:embed "templates/password.html"
+var passwordHTMLString string
+var passwordTemplate = static.AssetsAuthLogin.MustParseShared("password.html", passwordHTMLString)
+
+type authpasswordContext struct {
+	Message string
+	Form    template.HTML
+}
+
+var (
+	errPasswordsNotIdentical = errors.New("passwords are not identical")
+	errPasswordIsEmpty       = errors.New("password is empty")
+	errPasswordIncorrect     = errors.New("old password is not correct")
+	errPasswordSetFailure    = errors.New("error saving new password")
+	errPasswordSet           = errors.New("password was updated")
+)
+
+func (auth *Auth) authPassword(ctx context.Context) http.Handler {
+	return &httpx.Form[struct{}]{
+		Fields: []httpx.Field{
+			{Name: "old", Type: httpx.PasswordField, EmptyOnError: true, Label: "Current Password"},
+			{Name: "new", Type: httpx.PasswordField, EmptyOnError: true, Label: "New Password"},
+			{Name: "new2", Type: httpx.PasswordField, EmptyOnError: true, Label: "New Password (again)"},
+		},
+		FieldTemplate: httpx.PureCSSFieldTemplate,
+
+		CSRF: auth.csrf.Get(nil),
+
+		RenderForm: func(template template.HTML, err error, w http.ResponseWriter, r *http.Request) {
+			ctx := authpasswordContext{
+				Message: "",
+				Form:    template,
+			}
+			if err != nil {
+				ctx.Message = err.Error()
+			}
+			httpx.WriteHTML(ctx, nil, passwordTemplate, "", w, r)
+		},
+
+		Validate: func(r *http.Request, values map[string]string) (struct{}, error) {
+			old, new, new2 := values["old"], values["new"], values["new2"]
+
+			if new != new2 {
+				return struct{}{}, errPasswordsNotIdentical
+			}
+
+			if new == "" {
+				return struct{}{}, errPasswordIsEmpty
+			}
+
+			user, err := auth.UserOf(r)
+			if err != nil {
+				return struct{}{}, err
+			}
+
+			{
+				err := user.CheckPassword(r.Context(), []byte(old))
+				if err != nil {
+					return struct{}{}, errPasswordIncorrect
+				}
+			}
+			{
+				err := user.SetPassword(r.Context(), []byte(new))
+				if err != nil {
+					return struct{}{}, errPasswordSetFailure
+				}
+			}
+
+			return struct{}{}, nil
+		},
+
+		RenderSuccess: func(_ struct{}, values map[string]string, w http.ResponseWriter, r *http.Request) error {
+			return errPasswordSet
+		},
+	}
+}