exports.up = (pgm) => {
  pgm.sql(`
    CREATE TABLE IF NOT EXISTS favorites (
      customer_id INTEGER NOT NULL REFERENCES customers(id) ON DELETE CASCADE,
      item_id INTEGER NOT NULL REFERENCES items(id) ON DELETE CASCADE,
      created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
      PRIMARY KEY (customer_id, item_id)
    );

    -- The primary key covers lookups by customer. Notifying everyone who
    -- favorited an item that just sold goes the other way.
    CREATE INDEX IF NOT EXISTS favorites_item_id_idx ON favorites (item_id);

    -- A consent of its own rather than reusing marketing_consent. Being told
    -- that a specific item you asked about has gone is a narrower thing than
    -- agreeing to marketing, and folding one into the other would make the
    -- existing consent record no longer describe what was agreed to.
    --
    -- Mirrors the marketing consent columns: the flag, when it was given, and
    -- the exact wording shown at the time.
    ALTER TABLE customers ADD COLUMN IF NOT EXISTS favorite_alerts BOOLEAN NOT NULL DEFAULT false;
    ALTER TABLE customers ADD COLUMN IF NOT EXISTS favorite_alerts_at TIMESTAMPTZ;
    ALTER TABLE customers ADD COLUMN IF NOT EXISTS favorite_alerts_text TEXT;
  `);
};

exports.down = (pgm) => {
  pgm.sql(`
    ALTER TABLE customers DROP COLUMN IF EXISTS favorite_alerts_text;
    ALTER TABLE customers DROP COLUMN IF EXISTS favorite_alerts_at;
    ALTER TABLE customers DROP COLUMN IF EXISTS favorite_alerts;
    DROP TABLE IF EXISTS favorites;
  `);
};