feat: add test mode to quizzes and withhold its solutions

- mode, navigation and max_attempts columns with Go-side defaults
- classes.Withheld gates every solution field of the answer feedback
  and the attempt result while a test attempt is open
- a test's quiz detail lists no questions before the attempt starts
- admin fields and lang keys for the three settings

models/quiz.go

@@ -10,8 +10,28 @@ import (
 	"gorm.io/gorm"
 )
 
+// Quiz modes.
+const (
+	ModeLearning = "learning"
+	ModeTest     = "test"
+)
+
+// QuizModes lists the valid values of Quiz.Mode.
+var QuizModes = []string{ModeLearning, ModeTest}
+
+// Test navigation.
+const (
+	NavigationFree   = "free"
+	NavigationOneWay = "one_way"
+)
+
+// QuizNavigations lists the valid values of Quiz.Navigation.
+var QuizNavigations = []string{NavigationFree, NavigationOneWay}
+
 // Quiz is a set of questions a signed-in user can attempt. Context is a
 // free-form link to a record of another plugin, such as "acme.shop:course:12".
+// Mode test withholds solutions until the attempt is finished; Navigation
+// (free or one_way) and MaxAttempts (nil is unlimited) only apply to tests.
 type Quiz struct {
 	ID               uint       `gorm:"column:id;primaryKey"`
 	Title            string     `gorm:"column:title"`
@@ -23,6 +43,9 @@ type Quiz struct {
 	PassingScore     int        `gorm:"column:passing_score"`
 	ShuffleQuestions bool       `gorm:"column:shuffle_questions"`
 	RoundSize        *int       `gorm:"column:round_size"`
+	Mode             string     `gorm:"column:mode"`
+	Navigation       string     `gorm:"column:navigation"`
+	MaxAttempts      *int       `gorm:"column:max_attempts"`
 	CreatedAt        time.Time  `gorm:"column:created_at"`
 	UpdatedAt        time.Time  `gorm:"column:updated_at"`
 	Questions        []Question `gorm:"foreignKey:QuizID"`
@@ -36,6 +59,7 @@ func (Quiz) Fillable() []string {
 	return []string{
 		"title", "slug", "description", "context", "is_published",
 		"time_limit_seconds", "passing_score", "shuffle_questions", "round_size",
+		"mode", "navigation", "max_attempts",
 	}
 }
 
@@ -49,22 +73,42 @@ func (Quiz) Rules() map[string]string {
 		"passing_score":      "required|integer|between:0,100",
 		"time_limit_seconds": "nullable|integer|min:1",
 		"round_size":         "nullable|integer|min:1",
+		"mode":               "nullable|in:learning,test",
+		"navigation":         "nullable|in:free,one_way",
+		"max_attempts":       "nullable|integer|min:1",
 	}
 }
 
-// BeforeValidate fills the slug from the title before the admin form
-// validates, so the unique rule sees the final slug.
+// BeforeValidate fills the slug from the title and the mode defaults before
+// the admin form validates, so the rules see the final values.
 func (q *Quiz) BeforeValidate(*gorm.DB) error {
 	q.fillSlug()
+	q.fillDefaults()
 	return nil
 }
 
-// BeforeSave fills the slug from the title on every other write path.
+// BeforeSave fills the slug and the mode defaults on every other write path.
 func (q *Quiz) BeforeSave(*gorm.DB) error {
 	q.fillSlug()
+	q.fillDefaults()
 	return nil
 }
 
+// fillDefaults stores an empty mode or navigation as learning / free and a
+// non-positive attempt limit as unlimited. GORM writes Go zero values, so
+// without it a models.Quiz{} would hit the columns' CHECK constraints.
+func (q *Quiz) fillDefaults() {
+	if q.Mode == "" {
+		q.Mode = ModeLearning
+	}
+	if q.Navigation == "" {
+		q.Navigation = NavigationFree
+	}
+	if q.MaxAttempts != nil && *q.MaxAttempts <= 0 {
+		q.MaxAttempts = nil
+	}
+}
+
 func (q *Quiz) fillSlug() {
 	if strings.TrimSpace(q.Slug) == "" {
 		q.Slug = Slugify(q.Title)

models/quiz_test.go

@@ -0,0 +1,29 @@
+package models
+
+import "testing"
+
+func TestQuizDefaults(t *testing.T) {
+	zero, negative := 0, -1
+	for name, hook := range map[string]func(*Quiz) error{
+		"BeforeSave":     func(q *Quiz) error { return q.BeforeSave(nil) },
+		"BeforeValidate": func(q *Quiz) error { return q.BeforeValidate(nil) },
+	} {
+		for _, limit := range []*int{&zero, &negative} {
+			q := &Quiz{Title: "Q", MaxAttempts: limit}
+			if err := hook(q); err != nil {
+				t.Fatalf("%s: %v", name, err)
+			}
+			if q.Mode != ModeLearning || q.Navigation != NavigationFree || q.MaxAttempts != nil {
+				t.Errorf("%s with max_attempts %d = %q %q %v, want learning free nil", name, *limit, q.Mode, q.Navigation, q.MaxAttempts)
+			}
+		}
+		two := 2
+		q := &Quiz{Title: "Q", Mode: ModeTest, Navigation: NavigationOneWay, MaxAttempts: &two}
+		if err := hook(q); err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		if q.Mode != ModeTest || q.Navigation != NavigationOneWay || q.MaxAttempts == nil || *q.MaxAttempts != 2 {
+			t.Errorf("%s changed a test quiz: %q %q %v", name, q.Mode, q.Navigation, q.MaxAttempts)
+		}
+	}
+}

models/quizzes/columns.yaml

@@ -8,6 +8,8 @@ columns:
     context:
         label: golem15.quizzes::lang.quizzes.context
         searchable: true
+    mode:
+        label: golem15.quizzes::lang.quizzes.mode
     is_published:
         label: golem15.quizzes::lang.quizzes.is_published
         type: switch

models/quizzes/fields.yaml

@@ -42,3 +42,26 @@ fields:
         label: golem15.quizzes::lang.quizzes.shuffle_questions
         type: switch
         span: right
+    mode:
+        label: golem15.quizzes::lang.quizzes.mode
+        type: dropdown
+        span: left
+        default: learning
+        options:
+            learning: golem15.quizzes::lang.quizzes.mode_learning
+            test: golem15.quizzes::lang.quizzes.mode_test
+        comment: golem15.quizzes::lang.quizzes.mode_comment
+    navigation:
+        label: golem15.quizzes::lang.quizzes.navigation
+        type: dropdown
+        span: right
+        default: free
+        options:
+            free: golem15.quizzes::lang.quizzes.navigation_free
+            one_way: golem15.quizzes::lang.quizzes.navigation_one_way
+        comment: golem15.quizzes::lang.quizzes.navigation_comment
+    max_attempts:
+        label: golem15.quizzes::lang.quizzes.max_attempts
+        type: number
+        span: left
+        comment: golem15.quizzes::lang.quizzes.max_attempts_comment