data-dwh-dbt-project/models/intermediate/xero/int_xero__sales_monthly_trends.sql

with
    int_xero__sales_denom_mart as (
        select * from {{ ref("int_xero__sales_denom_mart") }}
    ),
    -- This ensures that we will have future records for comparison over time, 
    -- even if a deal or another category stops being invoiced
    first_invoiced_month_per_category as (
        select
            coalesce(document_status, 'UNSET') as document_status,
            coalesce(document_type, 'UNSET') as document_type,
            coalesce(id_deal, 'UNSET') as id_deal,
            coalesce(
                accounting_financial_l1_aggregation, 'UNSET'
            ) as accounting_financial_l1_aggregation,
            coalesce(
                accounting_financial_l2_aggregation, 'UNSET'
            ) as accounting_financial_l2_aggregation,
            coalesce(
                accounting_financial_l3_aggregation, 'UNSET'
            ) as accounting_financial_l3_aggregation,
            min(
                date_trunc('month', document_is_effective_at_end_of_month_utc)::date
            ) as first_invoiced_month_utc
        from int_xero__sales_denom_mart
        where document_is_effective_at_end_of_month_utc is not null
        group by 1, 2, 3, 4, 5, 6
    ),
    unique_months as (
        select distinct
            date_trunc('month', document_is_effective_at_end_of_month_utc)::date
            as document_issued_month_utc
        from int_xero__sales_denom_mart
        where document_is_effective_at_end_of_month_utc is not null
    ),
    category_skeleton as (
        select distinct
            fimpc.document_status,
            fimpc.document_type,
            fimpc.id_deal,
            fimpc.accounting_financial_l1_aggregation,
            fimpc.accounting_financial_l2_aggregation,
            fimpc.accounting_financial_l3_aggregation,
            um.document_issued_month_utc,
            case
                when extract(month from um.document_issued_month_utc) >= 4
                then extract(year from um.document_issued_month_utc) + 1  -- Fiscal Year labeled by the next year
                else extract(year from um.document_issued_month_utc)  -- Fiscal Year labeled by the current year
            end as fiscal_year,
            -- Previous Fiscal Year (for YTD comparison)
            case
                when extract(month from um.document_issued_month_utc) >= 4
                then extract(year from um.document_issued_month_utc)  -- Previous Fiscal Year labeled by the current year
                else extract(year from um.document_issued_month_utc) - 1  -- Previous Fiscal Year labeled by last year
            end as previous_fiscal_year
        from unique_months um
        left join
            first_invoiced_month_per_category fimpc
            on fimpc.first_invoiced_month_utc <= um.document_issued_month_utc
    ),
    aggregated_amount_wo_taxes_in_gbp as (
        select
            date_trunc('month', document_is_effective_at_end_of_month_utc)::date
            as document_issued_month_utc,
            coalesce(document_status, 'UNSET') as document_status,
            coalesce(document_type, 'UNSET') as document_type,
            coalesce(id_deal, 'UNSET') as id_deal,
            coalesce(
                accounting_financial_l1_aggregation, 'UNSET'
            ) as accounting_financial_l1_aggregation,
            coalesce(
                accounting_financial_l2_aggregation, 'UNSET'
            ) as accounting_financial_l2_aggregation,
            coalesce(
                accounting_financial_l3_aggregation, 'UNSET'
            ) as accounting_financial_l3_aggregation,
            sum(line_amount_wo_taxes_in_gbp) as amount_wo_taxes_in_gbp
        from int_xero__sales_denom_mart
        where document_is_effective_at_end_of_month_utc is not null
        group by 1, 2, 3, 4, 5, 6, 7
    ),
    monthly_data_with_lag as (
        select
            -- Time-based dimensions --
            cs.document_issued_month_utc,
            cs.fiscal_year,
            cs.previous_fiscal_year,
            -- Document-based dimensions --
            cs.document_status,
            cs.document_type,
            -- Deal-based dimensions --
            cs.id_deal,
            -- Accounting-based dimensions --
            cs.accounting_financial_l1_aggregation,
            cs.accounting_financial_l2_aggregation,
            cs.accounting_financial_l3_aggregation,
            -- Metrics --
            aawtig.amount_wo_taxes_in_gbp,
            -- Previous month amount 
            lag(aawtig.amount_wo_taxes_in_gbp) over (
                partition by
                    cs.document_status,
                    cs.document_type,
                    cs.id_deal,
                    cs.accounting_financial_l1_aggregation,
                    cs.accounting_financial_l2_aggregation,
                    cs.accounting_financial_l3_aggregation
                order by cs.document_issued_month_utc
            ) as previous_month_amount_wo_taxes_in_gbp,
            -- Previous year amount (same month last year)
            lag(aawtig.amount_wo_taxes_in_gbp, 12) over (
                partition by
                    cs.document_status,
                    cs.document_type,
                    cs.id_deal,
                    cs.accounting_financial_l1_aggregation,
                    cs.accounting_financial_l2_aggregation,
                    cs.accounting_financial_l3_aggregation
                order by cs.document_issued_month_utc
            ) as previous_year_amount_wo_taxes_in_gbp
        from category_skeleton cs
        left join
            aggregated_amount_wo_taxes_in_gbp aawtig
            on cs.document_issued_month_utc = aawtig.document_issued_month_utc
            and cs.document_status = aawtig.document_status
            and cs.document_type = aawtig.document_type
            and cs.id_deal = aawtig.id_deal
            and cs.accounting_financial_l1_aggregation
            = aawtig.accounting_financial_l1_aggregation
            and cs.accounting_financial_l2_aggregation
            = aawtig.accounting_financial_l2_aggregation
            and cs.accounting_financial_l3_aggregation
            = aawtig.accounting_financial_l3_aggregation

    )
select
    *,
    -- Year-to-Date (YTD) within the current fiscal year
    sum(amount_wo_taxes_in_gbp) over (
        partition by
            document_status,
            document_type,
            id_deal,
            accounting_financial_l1_aggregation,
            accounting_financial_l2_aggregation,
            accounting_financial_l3_aggregation,
            fiscal_year
        order by document_issued_month_utc
        rows between unbounded preceding and current row
    ) as ytd_amount_wo_taxes_in_gbp,

    -- Previous Year YTD (Same running total but for the previous fiscal year)
    sum(previous_year_amount_wo_taxes_in_gbp) over (
        partition by
            document_status,
            document_type,
            id_deal,
            accounting_financial_l1_aggregation,
            accounting_financial_l2_aggregation,
            accounting_financial_l3_aggregation,
            fiscal_year
        order by document_issued_month_utc
        rows between unbounded preceding and current row
    ) as previous_year_ytd_amount_wo_taxes_in_gbp
from monthly_data_with_lag