CREATE TABLE IF NOT EXISTS stock_transactions (
  id SERIAL PRIMARY KEY,
  component_id INTEGER NOT NULL REFERENCES components(id) ON DELETE CASCADE,
  transaction_type VARCHAR(20) NOT NULL DEFAULT 'purchase',
  quantity INTEGER NOT NULL,
  unit_cost NUMERIC(12,4) DEFAULT 0,
  total_cost NUMERIC(12,4) DEFAULT 0,
  supplier VARCHAR(255),
  supplier_part_number VARCHAR(100),
  order_reference VARCHAR(255),
  notes TEXT,
  created_at TIMESTAMPTZ DEFAULT NOW()
);

CREATE INDEX IF NOT EXISTS idx_stock_tx_component ON stock_transactions(component_id);
CREATE INDEX IF NOT EXISTS idx_stock_tx_created ON stock_transactions(created_at DESC);
CREATE INDEX IF NOT EXISTS idx_stock_tx_type ON stock_transactions(transaction_type);