class PreComputedMonthlySales(ReportView):
    report_title = _("Crosstab Precomputed: Monthly Sales")
    report_description = _("Uses crosstab_precomputed=True on a model whose rows are already aggregated. "
                           "Columns are the distinct month values discovered at query time — no aggregation needed.")
    report_model = MonthlySalesSummary
    date_field = "month"
    group_by = "product"
    crosstab_field = "month"
    crosstab_precomputed = True # signals that data is already aggregated
    crosstab_columns = ["total_sales", "total_quantity"] # These fields are already computed/aggregated in database
    columns = ["name", "__crosstab__"]

    chart_settings = [
        Chart(
            _("Monthly Sales by Product"),
            Chart.BAR,
            data_source=["total_sales"],
            title_source=["name"],
        ),
        Chart(
            _("Monthly Quantity by Product"),
            Chart.LINE,
            data_source=["total_quantity"],
            title_source=["name"],
        ),
    ]