feat: add open questions with a pending grading state

- migration: open question type, rubric, max_length, quiz grader and
  the grading and review columns of attempt answers
- open answers are checked, stored as pending and never scored on
  answer; a changed text resets the grading state
- student JSON gains text, grading_status, grader_feedback,
  review_comment, max_length, needs_review and open_answers; the
  rubric is never serialized

updates/20261109180000_add_open_questions_and_grading.go

@@ -0,0 +1,108 @@
+// Code generated by summer make. DO NOT EDIT.
+
+package updates
+
+import (
+	"fmt"
+
+	"github.com/go-gormigrate/gormigrate/v2"
+	"gorm.io/gorm"
+)
+
+// AddOpenQuestionsAndGrading returns the 20261109180000_add_open_questions_and_grading gormigrate entry.
+// It adds the open question type (answered in free text, graded against the
+// model answer and an owner-only rubric), the quiz grader and the grading
+// and review state of each attempt answer. Every existing question, quiz and
+// answer keeps today's behaviour: the grader is manual, no question is open
+// and every existing answer row has no grading state.
+func AddOpenQuestionsAndGrading() *gormigrate.Migration {
+	return &gormigrate.Migration{
+		ID: "20261109180000_add_open_questions_and_grading",
+		Migrate: func(tx *gorm.DB) error {
+			// The original type CHECK is an unnamed inline constraint, so
+			// it is found by the column it checks rather than by an assumed
+			// name. Its definition cannot be matched on "IN": Postgres
+			// stores it as type = ANY (ARRAY[...]).
+			for _, stmt := range []string{
+				`DO $$
+DECLARE c RECORD;
+BEGIN
+    FOR c IN
+        SELECT con.conname FROM pg_constraint con
+        JOIN pg_attribute att ON att.attrelid = con.conrelid AND att.attname = 'type'
+        WHERE con.conrelid = 'golem15_quizzes_questions'::regclass
+          AND con.contype = 'c'
+          AND con.conkey = ARRAY[att.attnum]
+    LOOP
+        EXECUTE format('ALTER TABLE golem15_quizzes_questions DROP CONSTRAINT %I', c.conname);
+    END LOOP;
+END $$`,
+				`ALTER TABLE golem15_quizzes_questions
+    ADD CONSTRAINT golem15_quizzes_questions_type_check CHECK (type IN ('single', 'multiple', 'self_check', 'open')),
+    ADD COLUMN rubric TEXT NULL,
+    ADD COLUMN max_length INTEGER NULL CHECK (max_length IS NULL OR max_length BETWEEN 1 AND 20000)`,
+				`ALTER TABLE golem15_quizzes_quizzes
+    ADD COLUMN grader VARCHAR(64) NOT NULL DEFAULT 'manual'`,
+				`ALTER TABLE golem15_quizzes_attempt_answers
+    ADD COLUMN text_answer TEXT NULL,
+    ADD COLUMN grading_status VARCHAR(20) NULL CHECK (grading_status IS NULL OR grading_status IN ('pending', 'graded', 'failed', 'reviewed')),
+    ADD COLUMN grading_seq INTEGER NOT NULL DEFAULT 0,
+    ADD COLUMN grading_attempts INTEGER NOT NULL DEFAULT 0,
+    ADD COLUMN grader VARCHAR(64) NULL,
+    ADD COLUMN grader_points DOUBLE PRECISION NULL,
+    ADD COLUMN grader_feedback TEXT NULL,
+    ADD COLUMN grading_error TEXT NULL,
+    ADD COLUMN graded_at TIMESTAMPTZ NULL,
+    ADD COLUMN review_comment TEXT NULL,
+    ADD COLUMN reviewed_at TIMESTAMPTZ NULL,
+    ADD COLUMN reviewed_by_user_id INTEGER NULL,
+    ADD COLUMN reviewed_by_admin_id INTEGER NULL`,
+				`CREATE INDEX golem15_quizzes_attempt_answers_grading_index ON golem15_quizzes_attempt_answers (grading_status)
+    WHERE grading_status IN ('pending', 'graded', 'failed')`,
+			} {
+				if err := tx.Exec(stmt).Error; err != nil {
+					return err
+				}
+			}
+			return nil
+		},
+		Rollback: func(tx *gorm.DB) error {
+			var n int64
+			if err := tx.Raw(`SELECT COUNT(*) FROM golem15_quizzes_questions WHERE type = 'open'`).Scan(&n).Error; err != nil {
+				return err
+			}
+			if n > 0 {
+				return fmt.Errorf("quizzes: rollback refused: %d open questions exist; delete them first", n)
+			}
+			for _, stmt := range []string{
+				`DROP INDEX IF EXISTS golem15_quizzes_attempt_answers_grading_index`,
+				`ALTER TABLE golem15_quizzes_attempt_answers
+    DROP COLUMN IF EXISTS reviewed_by_admin_id,
+    DROP COLUMN IF EXISTS reviewed_by_user_id,
+    DROP COLUMN IF EXISTS reviewed_at,
+    DROP COLUMN IF EXISTS review_comment,
+    DROP COLUMN IF EXISTS graded_at,
+    DROP COLUMN IF EXISTS grading_error,
+    DROP COLUMN IF EXISTS grader_feedback,
+    DROP COLUMN IF EXISTS grader_points,
+    DROP COLUMN IF EXISTS grader,
+    DROP COLUMN IF EXISTS grading_attempts,
+    DROP COLUMN IF EXISTS grading_seq,
+    DROP COLUMN IF EXISTS grading_status,
+    DROP COLUMN IF EXISTS text_answer`,
+				`ALTER TABLE golem15_quizzes_quizzes DROP COLUMN IF EXISTS grader`,
+				`ALTER TABLE golem15_quizzes_questions
+    DROP COLUMN IF EXISTS max_length,
+    DROP COLUMN IF EXISTS rubric,
+    DROP CONSTRAINT IF EXISTS golem15_quizzes_questions_type_check`,
+				`ALTER TABLE golem15_quizzes_questions
+    ADD CONSTRAINT golem15_quizzes_questions_type_check CHECK (type IN ('single', 'multiple', 'self_check'))`,
+			} {
+				if err := tx.Exec(stmt).Error; err != nil {
+					return err
+				}
+			}
+			return nil
+		},
+	}
+}