-- Add sales and sale_items tables for tracking transactions
CREATE TABLE sales (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    customer_id UUID REFERENCES customers(id) ON DELETE SET NULL,
    total_amount INTEGER NOT NULL DEFAULT 0,
    notes TEXT,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE sale_items (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    sale_id UUID NOT NULL REFERENCES sales(id) ON DELETE CASCADE,
    filament_id UUID NOT NULL REFERENCES filaments(id) ON DELETE RESTRICT,
    item_type VARCHAR(10) NOT NULL CHECK (item_type IN ('refill', 'spulna')),
    quantity INTEGER NOT NULL DEFAULT 1 CHECK (quantity > 0),
    unit_price INTEGER NOT NULL,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_sales_customer_id ON sales (customer_id);
CREATE INDEX idx_sales_created_at ON sales (created_at);
CREATE INDEX idx_sale_items_sale_id ON sale_items (sale_id);
CREATE INDEX idx_sale_items_filament_id ON sale_items (filament_id);