CREATE TABLE words (
  id TEXT PRIMARY KEY,
  headword TEXT NOT NULL,
  language_code TEXT NOT NULL,
  pos TEXT NOT NULL,
  created_at TEXT DEFAULT (datetime('now')),
  UNIQUE(headword, language_code, pos)
);

CREATE TABLE senses (
  id TEXT PRIMARY KEY,
  word_id TEXT NOT NULL REFERENCES words(id),
  sense_index INTEGER NOT NULL DEFAULT 0,
  difficulty TEXT NOT NULL,
  definitions TEXT NOT NULL DEFAULT '[]',
  examples TEXT NOT NULL DEFAULT '[]',
  created_at TEXT DEFAULT (datetime('now')),
  UNIQUE(word_id, sense_index)
);

CREATE TABLE translations (
  id TEXT PRIMARY KEY,
  sense_id TEXT NOT NULL REFERENCES senses(id),
  target_language_code TEXT NOT NULL,
  translation TEXT NOT NULL,
  gender TEXT,
  difficulty TEXT NOT NULL,
  created_at TEXT DEFAULT (datetime('now')),
  UNIQUE(sense_id, target_language_code, translation)
);