-- Apply after database_schema.sql. Rollback: disable the new endpoints, preserve
-- attempt rows for audit, then remove the column/table only after export.
ALTER TABLE student_error_notebook
  ADD COLUMN retention_due_at TIMESTAMP NULL DEFAULT NULL AFTER mastered_at;

-- Existing question rows remain draft. A reviewer must approve each question
-- against the named lesson and record its source before it may prove remediation.
ALTER TABLE questions
  ADD COLUMN remediation_review_status ENUM('draft','approved','rejected') NOT NULL DEFAULT 'draft',
  ADD COLUMN remediation_reviewed_by BIGINT UNSIGNED NULL,
  ADD COLUMN remediation_reviewed_at TIMESTAMP NULL DEFAULT NULL,
  ADD COLUMN remediation_source_reference VARCHAR(700) NULL;

CREATE TABLE IF NOT EXISTS error_notebook_quiz_attempts (
  id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
  uuid CHAR(36) NOT NULL,
  error_id BIGINT UNSIGNED NOT NULL,
  student_id BIGINT UNSIGNED NOT NULL,
  phase ENUM('initial','retention') NOT NULL,
  question_ids_json JSON NOT NULL,
  answer_key_json JSON NOT NULL,
  status ENUM('open','passed','failed') NOT NULL DEFAULT 'open',
  answers_sha256 CHAR(64) NULL,
  correct_count TINYINT UNSIGNED NULL,
  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  expires_at TIMESTAMP NOT NULL,
  submitted_at TIMESTAMP NULL DEFAULT NULL,
  PRIMARY KEY (id),
  UNIQUE KEY uq_error_quiz_uuid (uuid),
  KEY idx_error_quiz_student (student_id,error_id,status),
  CONSTRAINT fk_error_quiz_error FOREIGN KEY (error_id) REFERENCES student_error_notebook(id) ON DELETE RESTRICT,
  CONSTRAINT fk_error_quiz_student FOREIGN KEY (student_id) REFERENCES students(id) ON DELETE RESTRICT
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;