define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 12
    and ( Count("Qualifying Visit During Measurement Period") >= 2
        or exists "Preventive Visit During Measurement Period"
    )

define "Denominator 1":
  "Initial Population"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"

define "Numerator 1":
  "Most Recent Tobacco Use Screening Indicates Tobacco Non User" is not null
    or "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null

define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 12
    and ( Count("Qualifying Visit During Measurement Period") >= 2
        or exists "Preventive Visit During Measurement Period"
    )

define "Denominator 2":
  "Initial Population"
    and "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null

define "Denominator Exclusions":
  Hospice."Has Hospice Services"

define "Numerator 2":
  exists "Tobacco Cessation Counseling Given"
    or exists "Tobacco Cessation Pharmacotherapy Ordered"
    or exists "Active Pharmacotherapy for Tobacco Cessation"

define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 12
    and ( Count("Qualifying Visit During Measurement Period") >= 2
        or exists "Preventive Visit During Measurement Period"
    )

define "Denominator 3":
  "Initial Population"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"

define "Numerator 3":
  "Most Recent Tobacco Use Screening Indicates Tobacco Non User" is not null
    or ( "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null
        and ( exists "Tobacco Cessation Counseling Given"
            or exists "Tobacco Cessation Pharmacotherapy Ordered"
            or exists "Active Pharmacotherapy for Tobacco Cessation"
        )
    )

define "Has Hospice Services":
  exists ((([USQualityCore.Encounter: "Encounter Inpatient"]).isEncounterPerformed()) InpatientEncounter
      where (InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to home for hospice care (procedure)"
          or InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to healthcare facility for hospice care (procedure)"
      )
        and InpatientEncounter.period ends during day of "Measurement Period"
  )
    or exists ((([USQualityCore.Encounter: "Hospice Encounter"]).isEncounterPerformed()) HospiceEncounter
        where HospiceEncounter.period overlaps day of "Measurement Period"
    )
    // TODO: Shouldn't need to specify a code path here (see https://jira.hl7.org/browse/FHIR-53941)
    or exists ((([USQualityCore.ObservationScreeningAssessment: code ~ "Hospice care [Minimum Data Set]"]).isAssessmentPerformed()) HospiceAssessment
        where HospiceAssessment.value ~ "Yes (qualifier value)"
          and HospiceAssessment.effective.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([USQualityCore.ServiceRequest: "Hospice Care Ambulatory"]).isInterventionOrder()) HospiceOrder
        where HospiceOrder.authoredOn during day of "Measurement Period"
    )
    or exists ((([USQualityCore.Procedure: "Hospice Care Ambulatory"]).isInterventionPerformed()) HospicePerformed
        where HospicePerformed.performed.toInterval() overlaps day of "Measurement Period"
    )
    // TODO: Consider whether to keep this as the union of Problems and EncounterDiagnosis
    or exists ((([FHIR.Condition: "Hospice Diagnosis"]).verified()) HospiceCareDiagnosis
        where HospiceCareDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )

define "SDE Sex":
  case
    when Patient.sex() = '248153007' then "Male (finding)"
    when Patient.sex() = '248152002' then "Female (finding)"
    else null
  end

define "SDE Payer":
  [USQualityCore.Coverage: type in "Payer Type"] Payer
    return {
      code: Payer.type,
      period: Payer.period
    }

define "SDE Ethnicity":
  (Patient.ethnicity()) E
    return Tuple {
      codes: { E.ombCategory } union E.detailed,
      display: E.text
    }

define "SDE Race":
  (Patient.race()) R
    return Tuple {
      codes: R.ombCategory union R.detailed,
      display: R.text
    }

define "SDE Sex":
  SDE."SDE Sex"

define "Qualifying Visit During Measurement Period":
  ( ( ( [Encounter] E
        where exists ( ( E.type ) T
            where T ~ "Health behavior intervention, individual, face-to-face; initial 30 minutes"
        )
    )
      union ( [Encounter] E
          where exists ( ( E.type ) T
              where T ~ "Health behavior assessment, or re-assessment (ie, health-focused clinical interview, behavioral observations, clinical decision making)"
          )
      )
      union [Encounter: "Home Healthcare Services"]
      union [Encounter: "Occupational Therapy Evaluation"]
      union [Encounter: "Office Visit"]
      union [Encounter: "Ophthalmological Services"]
      union [Encounter: "Physical Therapy Evaluation"]
      union [Encounter: "Psych Visit Diagnostic Evaluation"]
      union [Encounter: "Psych Visit Psychotherapy"]
      union [Encounter: "Psychoanalysis"]
      union [Encounter: "Speech and Hearing Evaluation"]
      union [Encounter: "Telephone Visits"]
      union [Encounter: "Virtual Encounter"]
  ).isEncounterPerformed ( ) ) OfficeBasedEncounter
    where OfficeBasedEncounter.period during day of "Measurement Period"

define "Preventive Visit During Measurement Period":
  ( ( [Encounter: "Annual Wellness Visit"]
      union [Encounter: "Preventive Care Services Established Office Visit, 18 and Up"]
      union [Encounter: "Preventive Care Services Initial Office Visit, 18 and Up"]
      union [Encounter: "Preventive Care, Established Office Visit, 0 to 17"]
      union [Encounter: "Preventive Care Services, Initial Office Visit, 0 to 17"]
      union [Encounter: "Preventive Care Services Group Counseling"]
      union [Encounter: "Preventive Care Services Individual Counseling"]
      union ( [Encounter] E
          where exists ( ( E.type ) T
              where T ~ "Unlisted preventive medicine service"
          )
      )
      union ( [Encounter] E
          where exists ( ( E.type ) T
              where T ~ "Postoperative follow-up visit, normally included in the surgical package, to indicate that an evaluation and management service was performed during a postoperative period for a reason(s) related to the original procedure"
          )
      )
      union [Encounter: "Nutrition Services"]
  ).isEncounterPerformed ( ) ) PreventiveEncounter
    where PreventiveEncounter.period during day of "Measurement Period"

define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 12
    and ( Count("Qualifying Visit During Measurement Period") >= 2
        or exists "Preventive Visit During Measurement Period"
    )

define "Denominator 3":
  "Initial Population"

define "Most Recent Tobacco Use Screening Indicates Tobacco Non User":
  ( Last((([USCore.SmokingStatusProfile]).isObservationSmokingStatus()) TobaccoUseScreening
      where TobaccoUseScreening.effective.toInterval() during day of "Measurement Period"
      sort by start of effective.toInterval()
  ) ) MostRecentTobaccoUseScreening
    where MostRecentTobaccoUseScreening.value as CodeableConcept in "Tobacco Non User"

define "Most Recent Tobacco Use Screening Indicates Tobacco User":
  ( Last((([USCore.SmokingStatusProfile]).isObservationSmokingStatus()) TobaccoUseScreening
      where TobaccoUseScreening.effective.toInterval() during day of "Measurement Period"
      sort by start of effective.toInterval()
  ) ) MostRecentTobaccoUseScreening
    where MostRecentTobaccoUseScreening.value as CodeableConcept in "Tobacco User"

define "Tobacco Cessation Counseling Given":
  ( ( ( [Procedure: "Tobacco Use Cessation Counseling"] ).isInterventionPerformed ( ) ) TobaccoCessationCounseling
      where TobaccoCessationCounseling.performed.toInterval ( ) during day of Interval[start of "Measurement Period" - 6 months, end of "Measurement Period"]
  )
    union ( ( ( [ConditionProblemsHealthConcerns: "Tobacco abuse counseling"]
          union [ConditionEncounterDiagnosis: "Tobacco abuse counseling"]
      ).verified ( ) ) TobaccoCounseling
        where TobaccoCounseling.onset.toInterval ( ) starts during day of Interval[start of "Measurement Period" - 6 months, end of "Measurement Period"]
    )

define "Tobacco Cessation Pharmacotherapy Ordered":
  ( ( [MedicationRequest: "Tobacco Use Cessation Pharmacotherapy"] ).isMedicationOrder ( ) ) CessationPharmacotherapyOrdered
    where CessationPharmacotherapyOrdered.authoredOn during day of Interval[start of "Measurement Period" - 6 months, end of "Measurement Period"]
      and not exists ( [TaskRejected] TaskReject
          where TaskReject.focus.references ( CessationPharmacotherapyOrdered )
            and TaskReject.code ~ "fulfill"
      )

define "Active Pharmacotherapy for Tobacco Cessation":
  ( ( [MedicationRequest: "Tobacco Use Cessation Pharmacotherapy"] ).isMedicationActive ( ) ) TakingCessationPharmacotherapy
    where TakingCessationPharmacotherapy.medicationRequestPeriod ( ) during day of Interval[start of "Measurement Period" - 6 months, end of "Measurement Period"]

define "Numerator 3":
  "Most Recent Tobacco Use Screening Indicates Tobacco Non User" is not null
    or ( "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null
        and ( exists "Tobacco Cessation Counseling Given"
            or exists "Tobacco Cessation Pharmacotherapy Ordered"
            or exists "Active Pharmacotherapy for Tobacco Cessation"
        )
    )

define "Denominator 2":
  "Initial Population"
    and "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null

define "Numerator 1":
  "Most Recent Tobacco Use Screening Indicates Tobacco Non User" is not null
    or "Most Recent Tobacco Use Screening Indicates Tobacco User" is not null

define "SDE Payer":
  SDE."SDE Payer"

define "Numerator 2":
  exists "Tobacco Cessation Counseling Given"
    or exists "Tobacco Cessation Pharmacotherapy Ordered"
    or exists "Active Pharmacotherapy for Tobacco Cessation"

define "SDE Ethnicity":
  SDE."SDE Ethnicity"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"

define "SDE Race":
  SDE."SDE Race"

define "Denominator 1":
  "Initial Population"

/*
Calculates the Medication Period for a single MedicationRequest.
MedicationRequest instances provided to this function are expected
to conform to the [MMEMedicationRequest](http://build.fhir.org/ig/cqframework/opioid-mme-r4/StructureDefinition-mmemedicationrequest.html)
profile, which expects:
* 1 and only 1 dosageInstruction, multiple dosageInstruction elements will result in an error
* 1 and only 1 doseAndRate, multiple doseAndRate elements will result in an error
* 1 timing with 1 repeat, missing timing or repeat elements will result in a null
* frequency, frequencyMax, defaulting to 1
* period, periodUnit, defaulting to 1 'd'
* timeOfDay
* doseQuantity or doseRange, missing doseQuantity and doseRange will result in a null
Note that MedicationRequest status is not considered by this calculation, as the
list of MedicationRequest instances provided to this function should already have
considered appropriate statuses, depending on the use case, typically `completed`.

NOTE: Updated return to use "date from end of boundsPeriod" to ensure result is Interval<Date>
*/
define fluent function medicationRequestPeriod(Request MedicationRequest):
  Request R
    let
      dosage: singleton from R.dosageInstruction,
      doseAndRate: singleton from dosage.doseAndRate,
      timing: dosage.timing,
      frequency: Coalesce(timing.repeat.frequencyMax, timing.repeat.frequency),
      period: Quantity(timing.repeat.period, timing.repeat.periodUnit),
      doseRange: doseAndRate.dose as FHIR.Range,
      doseQuantity: doseAndRate.dose as FHIR.SimpleQuantity,

      dose: Coalesce(end of doseRange, doseQuantity),
      dosesPerDay: Coalesce(ToDaily(frequency, period), Count(timing.repeat.timeOfDay), 1.0),
      boundsPeriod: timing.repeat.bounds as Period,
      // TODO: this isn't working as expected, convert results in null
      //daysSupply: (convert(R.dispenseRequest.expectedSupplyDuration) to days).value,
      daysSupply: (R.dispenseRequest.expectedSupplyDuration).value,
      quantity: R.dispenseRequest.quantity,
      refills: Coalesce(R.dispenseRequest.numberOfRepeatsAllowed, 0),
      startDate:
        Coalesce(
          date from start of boundsPeriod,
          date from R.authoredOn,
          date from start of R.dispenseRequest.validityPeriod
        ),
      totalDaysSupplied: Coalesce(daysSupply, quantity.value / (dose.value * dosesPerDay)) * (1 + refills)
    return
      if startDate is not null and totalDaysSupplied is not null then
        Interval[startDate, startDate + Quantity(totalDaysSupplied - 1, 'day') ]
      else if startDate is not null and boundsPeriod."end" is not null then
        Interval[startDate, date from end of boundsPeriod]
      else
        null

/**********************************************************************/
/* Functions in this region are copied from opioid-mme-r4             */
/**********************************************************************/

define function Quantity(value Decimal, unit String):
  if value is not null then
    System.Quantity { value: value, unit: unit }
  else
    null

/*
 Goal is to get to number of days
 Two broad approaches to the calculation:
  1) Based on supply and frequency, calculate the number of expected days the medication will cover/has covered
  2) Based on relevant period, determine a covered interval and calculate the length of that interval in days

This topic covers several use cases and illustrates how to calculate Cumulative
Medication Duration for each type of medication resource using the supply and
frequency approach.
*/

/*
  For the first approach, we need to get from frequency to a frequency/day
  So we define ToDaily
*/

/*
  Calculates daily frequency given frequency within a period
*/
define function ToDaily(frequency System.Integer, period System.Quantity):
  case period.unit
    when 'h' then frequency * (24.0 / period.value)
    when 'min' then frequency * (24.0 / period.value) * 60
    when 's' then frequency * (24.0 / period.value) * 60 * 60
    when 'd' then frequency * (24.0 / period.value) / 24
    when 'wk' then frequency * (24.0 / period.value) / (24 * 7)
    when 'mo' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'a' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hour' then frequency * (24.0 / period.value)
    when 'minute' then frequency * (24.0 / period.value) * 60
    when 'second' then frequency * (24.0 / period.value) * 60 * 60
    when 'day' then frequency * (24.0 / period.value) / 24
    when 'week' then frequency * (24.0 / period.value) / (24 * 7)
    when 'month' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'year' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hours' then frequency * (24.0 / period.value)
    when 'minutes' then frequency * (24.0 / period.value) * 60
    when 'seconds' then frequency * (24.0 / period.value) * 60 * 60
    when 'days' then frequency * (24.0 / period.value) / 24
    when 'weeks' then frequency * (24.0 / period.value) / (24 * 7)
    when 'months' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'years' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    else Message(null, true, 'CMDLogic.ToDaily.UnknownUnit', ErrorLevel, 'Unknown unit ' & period.unit)
  end

//Encounter, Performed
//General usage unless required otherwise by measure intent (e.g., follow-up encounters)
define fluent function isEncounterPerformed(Enc List<FHIR.Encounter>):
  Enc E
    where E.status = 'finished'

//Observation Smoking Status
define fluent function isObservationSmokingStatus(Obs List<SmokingStatusProfile>):
  Obs O
    where O.status = 'final'

//Intervention, Performed
define fluent function isInterventionPerformed(Proc List<FHIR.Procedure>):
  Proc P
    where P.status ~ 'completed'

// TODO: Deprecate because this is now in FHIRCommon
//Condition
/*
@description: Returns conditions in the given list that either have no verification status or have a verification status of confirmed, unconfirmed, provisional, or differential
@deprecated: Use the USCoreCommon verified function insteada
*/
define fluent function verified(conditions List<Choice<ConditionProblemsHealthConcerns, ConditionEncounterDiagnosis>>):
  conditions C
    where C.verificationStatus is not null implies
      (C.verificationStatus ~ "confirmed"
        or C.verificationStatus ~ "unconfirmed"
        or C.verificationStatus ~ "provisional"
        or C.verificationStatus ~ "differential"
      )

//Medication, Order
define fluent function isMedicationOrder(MedicationRequest List<FHIR.MedicationRequest>):
  MedicationRequest M
    where M.status in { 'active', 'completed' }
    and M.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

//Medication, Active
define fluent function isMedicationActive(MedicationRequest List<FHIR.MedicationRequest>):
  MedicationRequest M
    where M.status = 'active'
      and M.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

//Assessment, Performed
define fluent function isAssessmentPerformed(Obs List<ObservationScreeningAssessment>):
  Obs O
    where O.status in { 'final', 'amended', 'corrected' }

//Intervention, Order
define fluent function isInterventionOrder(ServiceRequest List<FHIR.ServiceRequest>):
  ServiceRequest S
    where S.status in { 'active', 'completed' }
      and S.intent in {'order', 'original-order', 'reflex-order', 'filler-order', 'instance-order'}

define function ToString(value string): value.value

define function ToString(value uri): value.value

define function ToDate(value date): value.value

define function ToString(value EncounterStatus): value.value

/*
@description: Converts the given FHIR [CodeableConcept](https://hl7.org/fhir/datatypes.html#CodeableConcept) value to a CQL Concept.
*/
define function ToConcept(concept FHIR.CodeableConcept):
    if concept is null then
        null
    else
        System.Concept {
            codes: concept.coding C return ToCode(C),
            display: concept.text.value
        }

/*
@description: Converts the given FHIR [Coding](https://hl7.org/fhir/datatypes.html#Coding) value to a CQL Code.
*/
define function ToCode(coding FHIR.Coding):
    if coding is null then
        null
    else
        System.Code {
          code: coding.code.value,
          system: coding.system.value,
          version: coding.version.value,
          display: coding.display.value
        }

/*
@description: Converts the given [Period](https://hl7.org/fhir/datatypes.html#Period)
value to a CQL DateTime Interval
@comment: If the start value of the given period is unspecified, the starting
boundary of the resulting interval will be open (meaning the start of the interval
is unknown, as opposed to interpreted as the beginning of time).
*/
define function ToInterval(period FHIR.Period):
    if period is null then
        null
    else
        if period."start" is null then
            Interval(period."start".value, period."end".value]
        else
            Interval[period."start".value, period."end".value]

define function ToString(value ObservationStatus): value.value

define function ToDateTime(value dateTime): value.value

define function ToDateTime(value instant): value.value

/*
@description: Converts the given FHIR [Quantity](https://hl7.org/fhir/datatypes.html#Quantity) 
value to a CQL Quantity
@comment: If the given quantity has a comparator specified, a runtime error is raised. If the given quantity
has a system other than UCUM (i.e. `http://unitsofmeasure.org`) or CQL calendar units (i.e. `http://hl7.org/fhirpath/CodeSystem/calendar-units`)
an error is raised. For UCUM to calendar units, the `ToCalendarUnit` function is used.
@seealso: ToCalendarUnit
*/
define function ToQuantity(quantity FHIR.Quantity):
    case
        when quantity is null then null
        when quantity.value is null then null
        when quantity.comparator is not null then
            Message(null, true, 'FHIRHelpers.ToQuantity.ComparatorQuantityNotSupported', 'Error', 'FHIR Quantity value has a comparator and cannot be converted to a System.Quantity value.')
        when quantity.system is null or quantity.system.value = 'http://unitsofmeasure.org'
              or quantity.system.value = 'http://hl7.org/fhirpath/CodeSystem/calendar-units' then
            System.Quantity { value: quantity.value.value, unit: ToCalendarUnit(Coalesce(quantity.code.value, quantity.unit.value, '1')) }
        else
            Message(null, true, 'FHIRHelpers.ToQuantity.InvalidFHIRQuantity', 'Error', 'Invalid FHIR Quantity code: ' & quantity.unit.value & ' (' & quantity.system.value & '|' & quantity.code.value & ')')
    end

/*
@description: Converts a UCUM definite duration unit to a CQL calendar duration
unit using conversions specified in the [quantities](https://cql.hl7.org/02-authorsguide.html#quantities) 
topic of the CQL specification.
@comment: Note that for durations above days (or weeks), the conversion is understood to be approximate
*/
define function ToCalendarUnit(unit System.String):
    case unit
        when 'ms' then 'millisecond'
        when 's' then 'second'
        when 'min' then 'minute'
        when 'h' then 'hour'
        when 'd' then 'day'
        when 'wk' then 'week'
        when 'mo' then 'month'
        when 'a' then 'year'
        else unit
    end

define function ToString(value ProcedureStatus): value.value

define function ToString(value MedicationRequestStatus): value.value

define function ToString(value MedicationRequestIntent): value.value

define function ToDecimal(value decimal): value.value

define function ToString(value UnitsOfTime): value.value

/*
@description: Converts the given FHIR [Range](https://hl7.org/fhir/datatypes.html#Range) value to a CQL Interval of Quantity
*/
define function ToInterval(range FHIR.Range):
    if range is null then
        null
    else
        Interval[ToQuantity(range.low), ToQuantity(range.high)]

define function ToInteger(value integer): value.value

define function ToString(value ServiceRequestStatus): value.value

define function ToString(value ServiceRequestIntent): value.value

/*
@description: Returns the single extension (if present) on the given resource with the specified url.
@comment: This function uses singleton from to ensure that a run-time exception is thrown if there
is more than one extension on the given resource with the specified url.
*/
define fluent function ext(domainResource DomainResource, url String):
  singleton from domainResource.exts(url)

/*
@description: Returns any extensions defined on the given resource with the specified url
*/
define fluent function exts(domainResource DomainResource, url String):
  domainResource.extension E
    where E.url = url
    return E

/*
@description: Normalizes a value that is a choice of timing-valued types to an equivalent interval
@comment: Normalizes a choice type of FHIR.dateTime, FHIR.Period, FHIR.Timing, FHIR.instance, FHIR.string, FHIR.Age, or FHIR.Range types
to an equivalent interval. This selection of choice types is a superset of the majority of choice types that are used as possible
representations for timing-valued elements in FHIR, allowing this function to be used across any resource.

The input can be provided as a dateTime, Period, Timing, instant, string, Age, or Range.
The intent of this function is to provide a clear and concise mechanism to treat single
elements that have multiple possible representations as intervals so that logic doesn't have to account
for the variability. More complex calculations (such as medication request period or dispense period
calculation) need specific guidance and consideration. That guidance may make use of this function, but
the focus of this function is on single element calculations where the semantics are unambiguous.
If the input is a dateTime, the result a DateTime Interval beginning and ending on that dateTime.
If the input is a Period, the result is a DateTime Interval.
If the input is a Timing, an error is raised indicating a single interval cannot be computed from a Timing.
If the input is an instant, the result is a DateTime Interval beginning and ending on that instant.
If the input is a string, an error is raised indicating a single interval cannot be computed from a string.
If the input is an Age, the result is a DateTime Interval beginning when the patient was the given Age,
and ending immediately prior to when the patient was the given Age plus one year.
If the input is a Range, the result is a DateTime Interval beginning when the patient was the Age given
by the low end of the Range, and ending immediately prior to when the patient was the Age given by the
high end of the Range plus one year.

NOTE: Due to the
complexity of determining a single interval from a Timing or String type, this function will throw a run-time exception if it is used
with a Timing or String.
*/
define fluent function toInterval(choice Choice<FHIR.dateTime, FHIR.Period, FHIR.Timing, FHIR.instant, FHIR.string, FHIR.Age, FHIR.Range>):
  case
    when choice is FHIR.dateTime then
      Interval[FHIRHelpers.ToDateTime(choice as FHIR.dateTime), FHIRHelpers.ToDateTime(choice as FHIR.dateTime)]
    when choice is FHIR.Period then
      FHIRHelpers.ToInterval(choice as FHIR.Period)
    when choice is FHIR.instant then
      Interval[FHIRHelpers.ToDateTime(choice as FHIR.instant), FHIRHelpers.ToDateTime(choice as FHIR.instant)]
    when choice is FHIR.Age then
      Interval[FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity(choice as FHIR.Age),
        FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity(choice as FHIR.Age) + 1 year)
    when choice is FHIR.Range then
      Interval[FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity((choice as FHIR.Range).low),
        FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity((choice as FHIR.Range).high) + 1 year)
    when choice is FHIR.Timing then
      Message(null as Interval<DateTime>, true, 'NOT_IMPLEMENTED', 'Error', 'Calculation of an interval from a Timing value is not supported')
    when choice is FHIR.string then
      Message(null as Interval<DateTime>, true, 'NOT_IMPLEMENTED', 'Error', 'Calculation of an interval from a String value is not supported')
    else
      null as Interval<DateTime>
  end

/*
@description: Returns true if the given reference is to the given resource
@comment: Returns true if the `id` element of the given resource exactly equals the tail of the given reference.
NOTE: This function assumes resources from the same source server.
*/
define fluent function references(reference FHIR.Reference, resource FHIR.Resource):
  resource.id = Last(Split(reference.reference, '/'))

/*
@description: Returns the single extension (if present) on the given element with the specified url.
@comment: This function uses singleton from to ensure that a run-time exception is thrown if there
is more than one extension on the given element with the specified url.
*/
define fluent function ext(element Element, url String):
  singleton from element.exts(url)

/*
@description: Returns any extensions defined on the given element with the specified url.
*/
define fluent function exts(element Element, url String):
  element.extension E
    where E.url = url
    return E

/*
@description: Returns conditions in the given list that either have no verification status or have a verification status of confirmed, unconfirmed, provisional, or differential
*/
define fluent function verified(conditions List<FHIR.Condition>):
  conditions C
    where C.verificationStatus is not null implies
      (C.verificationStatus ~ "confirmed"
        or C.verificationStatus ~ "unconfirmed"
        or C.verificationStatus ~ "provisional"
        or C.verificationStatus ~ "differential"
      )

/*
@description: Returns an interval representing the normalized prevalence period of a given Condition resource.
@comment: Uses the toInterval and toAbatementInterval functions to determine the widest potential interval from
onset to abatement as specified in the given Condition.
*/
define fluent function prevalenceInterval(condition Condition):
if condition.clinicalStatus ~ "active"
  or condition.clinicalStatus ~ "recurrence"
  or condition.clinicalStatus ~ "relapse" then
  Interval[start of condition.onset.toInterval(), end of condition.abatementInterval()]
else
  (end of condition.abatementInterval()) abatementDate
    return 
	  if abatementDate is null then
        Interval[start of condition.onset.toInterval(), abatementDate)
      else
        Interval[start of condition.onset.toInterval(), abatementDate]

/*
@description: Returns an interval representing the normalized Abatement of a given Condition resource.
@comment: @comment: If the abatement element of the Condition is represented as a DateTime, the result
is an interval beginning and ending on that DateTime.
If the abatement is represented as a Quantity, the quantity is expected to be a calendar-duration and is interpreted as the age of the patient. The
result is an interval from the date the patient turned that age to immediately before one year later.
If the abatement is represented as a Quantity Interval, the quantities are expected to be calendar-durations and are interpreted as an age range during
which the abatement occurred. The result is an interval from the date the patient turned the starting age of the quantity interval, and ending immediately
before one year later than the date the patient turned the ending age of the quantity interval.

NOTE: Due to the complexity of determining an interval from a String, this function will throw
a run-time exception if used with a Condition instance that has a String as the abatement value.
*/
define fluent function abatementInterval(condition Condition):
  if condition.abatement is FHIR.dateTime then
    Interval[FHIRHelpers.ToDateTime(condition.abatement as FHIR.dateTime), FHIRHelpers.ToDateTime(condition.abatement as FHIR.dateTime)]
  else if condition.abatement is FHIR.Period then
    FHIRHelpers.ToInterval(condition.abatement as FHIR.Period)
  else if condition.abatement is FHIR.string then
    Message(null as Interval<DateTime>, true, 'NOT_IMPLEMENTED', 'Error', 'Calculation of an interval from a String value is not supported')
  else if condition.abatement is FHIR.Age then
    Interval[FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity(condition.abatement as FHIR.Age),
      FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity(condition.abatement as FHIR.Age) + 1 year)
  else if condition.abatement is FHIR.Range then
    Interval[FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity((condition.abatement as FHIR.Range).low),
      FHIRHelpers.ToDate(Patient.birthDate) + FHIRHelpers.ToQuantity((condition.abatement as FHIR.Range).high) + 1 year)
  else if condition.abatement is FHIR.boolean then
    Interval[end of condition.onset.toInterval(), condition.recordedDate)
  else 
    null

/*
@description: Returns the sex element as defined for the USCore patient profile
*/
define fluent function sex(patient Patient):
  patient.ext('http://hl7.org/fhir/us/core/StructureDefinition/us-core-sex').value as FHIR.code

define fluent function ethnicity(patient Patient):
  (patient.ext('http://hl7.org/fhir/us/core/StructureDefinition/us-core-ethnicity')) E
    return {
      ombCategory: E.ext('ombCategory').value as FHIR.Coding,
      detailed: (E.exts('detailed')) d return d.value as FHIR.Coding,
      text: E.ext('text').value as FHIR.string
    }

define fluent function race(patient Patient):
  (patient.ext('http://hl7.org/fhir/us/core/StructureDefinition/us-core-race')) E
    return {
      ombCategory: (E.exts('ombCategory')) o return o.value as FHIR.Coding,
      detailed: (E.exts('detailed')) d return d.value as FHIR.Coding,
      text: E.ext('text').value as FHIR.string
    }