-- ============ 用户与会话 ============
CREATE TABLE users (
  id            UUID PRIMARY KEY,
  email         TEXT NOT NULL UNIQUE,
  password_hash TEXT NOT NULL,
  display_name  TEXT NOT NULL,
  is_admin      BOOLEAN NOT NULL DEFAULT FALSE,
  created_at    TIMESTAMPTZ NOT NULL DEFAULT now(),
  updated_at    TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE TABLE user_sessions (
  id           UUID PRIMARY KEY,
  user_id      UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  token_hash   BYTEA NOT NULL UNIQUE,
  expires_at   TIMESTAMPTZ NOT NULL,
  last_seen_at TIMESTAMPTZ,
  created_at   TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX idx_user_sessions_user_id ON user_sessions(user_id);
CREATE INDEX idx_user_sessions_expires_at ON user_sessions(expires_at);

-- ============ 站内信 ============
CREATE TABLE notifications (
  id         UUID PRIMARY KEY,
  user_id    UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  topic      TEXT NOT NULL,
  severity   TEXT NOT NULL,
  title      TEXT NOT NULL,
  body       TEXT NOT NULL,
  link       TEXT,
  metadata   JSONB,
  read_at    TIMESTAMPTZ,
  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX idx_notifications_user_created ON notifications(user_id, created_at DESC);
CREATE INDEX idx_notifications_user_unread ON notifications(user_id) WHERE read_at IS NULL;

-- ============ 审计日志 ============
CREATE TABLE audit_logs (
  id          BIGSERIAL PRIMARY KEY,
  user_id     UUID REFERENCES users(id) ON DELETE SET NULL,
  action      TEXT NOT NULL,
  target_type TEXT,
  target_id   TEXT,
  ip          INET,
  metadata    JSONB,
  created_at  TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX idx_audit_user_created ON audit_logs(user_id, created_at DESC);
CREATE INDEX idx_audit_action_created ON audit_logs(action, created_at DESC);