-- ═══════════════════════════════════════════════════════════════
-- 022: Exam Preparation Module
--
-- Generic exam preparation infrastructure parameterized by exam_key.
-- Supports multiple exams (math9, phys9, chem9, math11ce, etc.) sharing
-- the same task bank, attempts tracking, mock sessions, and study plans.
--
-- See docs/exam-prep-plan.md for full architecture.
-- ═══════════════════════════════════════════════════════════════

-- ── Exam tracks registry ────────────────────────────────────────
CREATE TABLE exam_tracks (
  exam_key          TEXT PRIMARY KEY,
  title             TEXT NOT NULL,
  subject_slug      TEXT NOT NULL,
  grade             INTEGER NOT NULL,
  duration_min      INTEGER NOT NULL,
  tasks_per_variant INTEGER NOT NULL,
  variants_count    INTEGER NOT NULL,
  scoring_json      TEXT,
  intro_html        TEXT,
  enabled           INTEGER NOT NULL DEFAULT 1,
  sort_order        INTEGER NOT NULL DEFAULT 0
);

-- ── Task bank (one row per task across all variants) ────────────
CREATE TABLE exam_tasks (
  id            INTEGER PRIMARY KEY,
  exam_key      TEXT NOT NULL REFERENCES exam_tracks(exam_key) ON DELETE CASCADE,
  variant       INTEGER NOT NULL,
  task_idx      INTEGER NOT NULL,
  task_type     TEXT NOT NULL CHECK (task_type IN ('mc','open','long')),
  text_html     TEXT NOT NULL,
  figure_html   TEXT,
  opts_json     TEXT,
  answer        TEXT,
  solution_html TEXT NOT NULL,
  topic         TEXT,
  subtopic      TEXT,
  difficulty    INTEGER,
  UNIQUE(exam_key, variant, task_idx)
);
CREATE INDEX idx_exam_tasks_topic   ON exam_tasks(exam_key, topic);
CREATE INDEX idx_exam_tasks_variant ON exam_tasks(exam_key, variant);
CREATE INDEX idx_exam_tasks_type    ON exam_tasks(exam_key, task_type);

-- ── User attempts ───────────────────────────────────────────────
CREATE TABLE exam_attempts (
  id              INTEGER PRIMARY KEY,
  user_id         INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  exam_task_id    INTEGER NOT NULL REFERENCES exam_tasks(id) ON DELETE CASCADE,
  user_answer     TEXT,
  is_correct      INTEGER,
  time_ms         INTEGER,
  mode            TEXT NOT NULL CHECK (mode IN ('practice','variant','topic','mock')),
  session_id      INTEGER,
  hint_used       INTEGER NOT NULL DEFAULT 0,
  solution_viewed INTEGER NOT NULL DEFAULT 0,
  created_at      INTEGER NOT NULL
);
CREATE INDEX idx_exam_attempts_user_time ON exam_attempts(user_id, created_at DESC);
CREATE INDEX idx_exam_attempts_task      ON exam_attempts(exam_task_id);
CREATE INDEX idx_exam_attempts_session   ON exam_attempts(session_id);
CREATE INDEX idx_exam_attempts_user_task ON exam_attempts(user_id, exam_task_id, created_at DESC);

-- ── Mock exam sessions ──────────────────────────────────────────
CREATE TABLE exam_mock_sessions (
  id                   INTEGER PRIMARY KEY,
  user_id              INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  exam_key             TEXT NOT NULL,
  variant              INTEGER,
  source               TEXT NOT NULL CHECK (source IN ('variant','random','weak-topics')),
  task_ids_json        TEXT NOT NULL,
  started_at           INTEGER NOT NULL,
  finished_at          INTEGER,
  duration_planned_min INTEGER NOT NULL,
  score                INTEGER,
  total_correct        INTEGER,
  total_tasks          INTEGER,
  status               TEXT NOT NULL DEFAULT 'active' CHECK (status IN ('active','finished','abandoned'))
);
CREATE INDEX idx_mock_user ON exam_mock_sessions(user_id, started_at DESC);

-- ── User preparation plan ───────────────────────────────────────
CREATE TABLE exam_user_plan (
  user_id      INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  exam_key     TEXT NOT NULL,
  exam_date    TEXT NOT NULL,
  daily_target INTEGER NOT NULL DEFAULT 10,
  weak_focus   INTEGER NOT NULL DEFAULT 1,
  created_at   INTEGER NOT NULL,
  updated_at   INTEGER NOT NULL,
  PRIMARY KEY (user_id, exam_key)
);

-- ── Topic dictionary (populated in F6) ──────────────────────────
CREATE TABLE exam_topics (
  slug         TEXT PRIMARY KEY,
  exam_key     TEXT NOT NULL,
  parent_slug  TEXT,
  title        TEXT NOT NULL,
  description  TEXT,
  sort_order   INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX idx_topics_exam ON exam_topics(exam_key, parent_slug);

-- ── Seed: math9 track ───────────────────────────────────────────
-- Placeholder scoring grid (simple proportional). Replace with the actual
-- Belarus 9th-grade math exam grid once published per academic year.
INSERT INTO exam_tracks (
  exam_key, title, subject_slug, grade, duration_min,
  tasks_per_variant, variants_count, scoring_json, intro_html, enabled, sort_order
) VALUES (
  'math9',
  'Экзамен 9 класс — Математика',
  'math',
  9,
  180,
  10,
  80,
  '[{"correct":30,"score":10},{"correct":27,"score":9},{"correct":24,"score":8},{"correct":21,"score":7},{"correct":18,"score":6},{"correct":15,"score":5},{"correct":12,"score":4},{"correct":9,"score":3},{"correct":6,"score":2},{"correct":3,"score":1},{"correct":0,"score":0}]',
  '<p>Полная подготовка к выпускному экзамену по математике за 9 класс. 80 реальных вариантов, разбор каждого задания, тренажёр по темам, пробные экзамены с таймером.</p>',
  1,
  10
);