-- 001_init.sql
PRAGMA foreign_keys = ON;

CREATE TABLE IF NOT EXISTS users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL UNIQUE,
  password_salt TEXT NOT NULL,
  password_hash TEXT NOT NULL,
  rating INTEGER NOT NULL DEFAULT 0,
  created_at INTEGER NOT NULL
);

CREATE TABLE IF NOT EXISTS sessions (
  token TEXT PRIMARY KEY,
  user_id INTEGER NOT NULL,
  expires_at INTEGER NOT NULL,
  created_at INTEGER NOT NULL,
  FOREIGN KEY(user_id) REFERENCES users(id) ON DELETE CASCADE
);

CREATE TABLE IF NOT EXISTS problems (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  slug TEXT NOT NULL UNIQUE,
  title TEXT NOT NULL,
  statement_md TEXT NOT NULL,
  difficulty INTEGER NOT NULL DEFAULT 1,
  source TEXT NOT NULL DEFAULT "",
  created_at INTEGER NOT NULL
);

CREATE TABLE IF NOT EXISTS problem_tags (
  problem_id INTEGER NOT NULL,
  tag TEXT NOT NULL,
  PRIMARY KEY(problem_id, tag),
  FOREIGN KEY(problem_id) REFERENCES problems(id) ON DELETE CASCADE
);

CREATE TABLE IF NOT EXISTS submissions (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  user_id INTEGER NOT NULL,
  problem_id INTEGER NOT NULL,
  language TEXT NOT NULL,
  code TEXT NOT NULL,
  status TEXT NOT NULL,
  score INTEGER NOT NULL DEFAULT 0,
  time_ms INTEGER NOT NULL DEFAULT 0,
  memory_kb INTEGER NOT NULL DEFAULT 0,
  created_at INTEGER NOT NULL,
  FOREIGN KEY(user_id) REFERENCES users(id) ON DELETE CASCADE,
  FOREIGN KEY(problem_id) REFERENCES problems(id) ON DELETE CASCADE
);

CREATE TABLE IF NOT EXISTS wrong_book (
  user_id INTEGER NOT NULL,
  problem_id INTEGER NOT NULL,
  last_submission_id INTEGER,
  note TEXT NOT NULL DEFAULT "",
  updated_at INTEGER NOT NULL,
  PRIMARY KEY(user_id, problem_id),
  FOREIGN KEY(user_id) REFERENCES users(id) ON DELETE CASCADE,
  FOREIGN KEY(problem_id) REFERENCES problems(id) ON DELETE CASCADE,
  FOREIGN KEY(last_submission_id) REFERENCES submissions(id) ON DELETE SET NULL
);

CREATE INDEX IF NOT EXISTS idx_submissions_user_created_at ON submissions(user_id, created_at DESC);
CREATE INDEX IF NOT EXISTS idx_submissions_problem_created_at ON submissions(problem_id, created_at DESC);