CREATE TABLE IF NOT EXISTS users (
    id            SERIAL PRIMARY KEY,
    username      TEXT NOT NULL,
    password_hash TEXT NOT NULL,
    created_at    TIMESTAMPTZ NOT NULL DEFAULT now()
);
CREATE UNIQUE INDEX IF NOT EXISTS users_username_lower_key ON users (lower(username));

CREATE TABLE IF NOT EXISTS sessions (
    token_hash BYTEA PRIMARY KEY,
    user_id    INT NOT NULL REFERENCES users ON DELETE CASCADE,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    expires_at TIMESTAMPTZ NOT NULL
);
CREATE INDEX IF NOT EXISTS sessions_user_id_idx ON sessions (user_id);

CREATE TABLE IF NOT EXISTS genres (
    id   SMALLSERIAL PRIMARY KEY,
    name TEXT NOT NULL UNIQUE
);

-- WHERE NOT EXISTS instead of ON CONFLICT: ON CONFLICT consumes a sequence value per row
-- on every startup, which would eventually overflow SMALLSERIAL.
INSERT INTO genres (name)
SELECT seed.name
  FROM (VALUES ('Fiction'), ('Non-Fiction'), ('Mystery'), ('Thriller'), ('Science Fiction'),
               ('Fantasy'), ('Romance'), ('Horror'), ('Historical Fiction'), ('Biography'),
               ('Memoir'), ('Self-Help'), ('Science'), ('History'), ('Poetry'), ('Other')) AS seed(name)
 WHERE NOT EXISTS (SELECT 1 FROM genres WHERE genres.name = seed.name);

CREATE TABLE IF NOT EXISTS books (
    id           SERIAL PRIMARY KEY,
    user_id      INT NOT NULL REFERENCES users ON DELETE CASCADE,
    title        TEXT NOT NULL CHECK (btrim(title) <> ''),
    author       TEXT NOT NULL CHECK (btrim(author) <> ''),
    genre_id     SMALLINT NOT NULL REFERENCES genres,
    total_pages  INT NOT NULL CHECK (total_pages > 0),
    current_page INT NOT NULL DEFAULT 0,
    created_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT books_current_page_range CHECK (current_page BETWEEN 0 AND total_pages)
);
CREATE INDEX IF NOT EXISTS books_user_id_idx ON books (user_id);

CREATE TABLE IF NOT EXISTS notes (
    id         SERIAL PRIMARY KEY,
    book_id    INT NOT NULL REFERENCES books ON DELETE CASCADE,
    body       TEXT NOT NULL CHECK (btrim(body) <> ''),
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);
CREATE INDEX IF NOT EXISTS notes_book_id_idx ON notes (book_id);