CREATE TABLE IF NOT EXISTS invoices (
    id CHAR(36) NOT NULL PRIMARY KEY,
    student_id CHAR(36) NOT NULL,
    invoice_number VARCHAR(50) NOT NULL UNIQUE,
    invoice_date DATE NOT NULL,
    due_date DATE NOT NULL,
    total_amount DECIMAL(10, 2) NOT NULL,
    status VARCHAR(20) NOT NULL DEFAULT 'Draft' CHECK (status IN ('Draft', 'Posted', 'Paid', 'Void')),
    journal_entry_id CHAR(36) DEFAULT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMP NOT NULL DEFAULT NOW(),
    FOREIGN KEY (student_id) REFERENCES students(id),
    FOREIGN KEY (journal_entry_id) REFERENCES journal_entries(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

CREATE TABLE IF NOT EXISTS invoice_lines (
    id CHAR(36) NOT NULL PRIMARY KEY,
    invoice_id CHAR(36) NOT NULL,
    description VARCHAR(255) NOT NULL,
    amount DECIMAL(10, 2) NOT NULL,
    revenue_account_id CHAR(36) NOT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMP NOT NULL DEFAULT NOW(),
    FOREIGN KEY (invoice_id) REFERENCES invoices(id) ON DELETE CASCADE,
    FOREIGN KEY (revenue_account_id) REFERENCES accounts(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;