/*
    Prescribing spend by patient template
    =====================================

    Purpose:
    Rank patients by estimated prescribing cost over a selected period and
    medicine definition.

    Use this when looking for high-cost patients or checking the shape of cost
    concentration before doing deeper clinical review.

    Default source is the maintained unified prescribing table, which already
    includes parsed quantity and estimated price. If that table is unavailable
    or needs rebuilding, see 06_advanced_methods/product_price_and_quantity_parsing_template.sql.

    Keep at least one medicine filter set. Leaving BNF, VTM, and VMP filters all
    NULL can scan all prescribing and is usually not a useful starting point.
*/

SET START_DATE = '2025-04-01';
SET END_DATE = '2026-03-31';
SET BNF_PREFIX = '0403';
SET VTM_SNOMED_CODE = NULL;
SET VMP_SNOMED_CODE = NULL;
SET TOP_N = 100;

WITH products AS (
    -- Keep at least one of the filters below populated so the product set is intentional.
    SELECT DISTINCT
        "ProductSnomedCode",
        "ProductDescription",
        "TherapeuticMoietyName",
        "BNFCode",
        "BNFParagraphCode"
    FROM DATA_HUB.DWH."DimMedicineAndDevice"
    WHERE ($BNF_PREFIX IS NOT NULL AND "BNFCode" LIKE $BNF_PREFIX || '%')
       OR ($VTM_SNOMED_CODE IS NOT NULL AND "TherapeuticMoietySnomedCode" = $VTM_SNOMED_CODE)
       OR ($VMP_SNOMED_CODE IS NOT NULL AND "MedicinalLatestSnomedCode" = $VMP_SNOMED_CODE)
),
patient_costs AS (
    -- Aggregate first at patient/practice level so ranking is not inflated by joins.
    SELECT
        rx."PersonKey",
        rx."CurrentGeneralPractice" AS "PracticeCode",
        COUNT(*) AS "PrescriptionRows",
        COUNT(DISTINCT prod."ProductSnomedCode") AS "DistinctProducts",
        SUM(COALESCE(rx."EstPrice", 0)) AS "EstimatedCost"
    FROM REPORTING_DATASETS_ICB.SCRATCHPAD."MEDS__UnifiedPrescribingTable" rx
    INNER JOIN products prod
        ON rx."SNOMEDCode" = prod."ProductSnomedCode"
    WHERE rx."DateMedicationStart" BETWEEN $START_DATE AND $END_DATE
      AND rx."PersonKey" IS NOT NULL
    GROUP BY rx."PersonKey", rx."CurrentGeneralPractice"
),
practice_lookup AS (
    -- De-duplicated practice labels prevent site-level duplicates in the ranking output.
    SELECT
        "OrganisationCode" AS "PracticeCode",
        MIN("OrganisationName") AS "PracticeName",
        MIN("PCNName") AS "PCNName",
        MIN("PlaceName") AS "PlaceName",
        MIN("AllianceName") AS "AllianceName"
    FROM DATA_HUB.DWH."DimOrganisationAndSite"
    WHERE "OrganisationSubType" = 'GP Practice'
      AND "IsSiteActive" = 'Yes'
      AND "IsSiteNorfolkAndSuffolk" = 'Yes'
      AND "SiteCode" = "OrganisationCode"
    GROUP BY "OrganisationCode"
),
ranked AS (
    SELECT
        ROW_NUMBER() OVER (ORDER BY pc."EstimatedCost" DESC NULLS LAST) AS "Rank",
        gp."PracticeName",
        gp."PCNName",
        gp."PlaceName",
        gp."AllianceName",
        pc."PersonKey",
        pc."PracticeCode",
        pc."PrescriptionRows",
        pc."DistinctProducts",
        pc."EstimatedCost"
    FROM patient_costs pc
    INNER JOIN practice_lookup gp
        ON pc."PracticeCode" = gp."PracticeCode"
)
SELECT
    "Rank",
    "PracticeName",
    "PCNName",
    "PlaceName",
    "AllianceName",
    "PersonKey",
    "PracticeCode",
    "PrescriptionRows",
    "DistinctProducts",
    "EstimatedCost"
FROM ranked
WHERE "Rank" <= $TOP_N
ORDER BY "Rank";