define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 18
    and exists "Primary Open Angle Glaucoma Encounter"

define "Denominator":
  "Initial Population"

define "Denominator Exceptions":
  exists "Medical Reason for Not Performing Cup to Disc Ratio"
    or exists "Medical Reason for Not Performing Optic Disc Exam"

define "Numerator":
  exists "Cup to Disc Ratio Performed with Result"
    and exists "Optic Disc Exam Performed with Result"

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 Encounter During Measurement Period":
  ( ["Encounter": "Office Visit"]
    union ["Encounter": "Ophthalmological Services"]
    union ["Encounter": "Outpatient Consultation"]
    union ["Encounter": "Nursing Facility Visit"]
    union ["Encounter": "Care Services in Long-Term Residential Facility"] ) QualifyingEncounter
    where QualifyingEncounter.period during day of "Measurement Period"
      and QualifyingEncounter.status = 'finished'
      and QualifyingEncounter.class !~ "virtual"

define "Primary Open Angle Glaucoma Encounter":
  "Qualifying Encounter During Measurement Period" ValidQualifyingEncounter
    with ( ["ConditionProblemsHealthConcerns": "Primary Open-Angle Glaucoma"]
      union ["ConditionEncounterDiagnosis": "Primary Open-Angle Glaucoma"] ) PrimaryOpenAngleGlaucoma
      such that PrimaryOpenAngleGlaucoma.onset.toInterval ( ) overlaps day of ValidQualifyingEncounter.period
        and PrimaryOpenAngleGlaucoma.isVerified ( )

define "Cup to Disc Ratio Performed with Result":
  ["ObservationClinicalResult": "Cup to Disc Ratio"] CupToDiscExamPerformed
    with "Primary Open Angle Glaucoma Encounter" EncounterWithPOAG
      such that CupToDiscExamPerformed.effective.toInterval ( ) during day of EncounterWithPOAG.period
    where CupToDiscExamPerformed.value is not null
      and CupToDiscExamPerformed.status in { 'final', 'amended', 'corrected' }

define "Optic Disc Exam Performed with Result":
  ["ObservationClinicalResult": "Optic Disc Exam for Structural Abnormalities"] OpticDiscExamPerformed
    with "Primary Open Angle Glaucoma Encounter" EncounterWithPOAG
      such that OpticDiscExamPerformed.effective.toInterval ( ) during day of EncounterWithPOAG.period
    where OpticDiscExamPerformed.value is not null
      and OpticDiscExamPerformed.status in { 'final', 'amended', 'corrected' }

define "Numerator":
  exists "Cup to Disc Ratio Performed with Result"
    and exists "Optic Disc Exam Performed with Result"

define "Initial Population":
  AgeInYearsAt(date from start of "Measurement Period") >= 18
    and exists "Primary Open Angle Glaucoma Encounter"

define "Denominator":
  "Initial Population"

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

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

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

define "Medical Reason for Not Performing Cup to Disc Ratio":
  ["ObservationCancelled": "Cup to Disc Ratio"] CupToDiscExamNotPerformed
    with "Primary Open Angle Glaucoma Encounter" EncounterWithPOAG
      such that CupToDiscExamNotPerformed.issued during day of EncounterWithPOAG.period
    where CupToDiscExamNotPerformed.notDoneReason ( ) in "Medical Reason"

define "Medical Reason for Not Performing Optic Disc Exam":
  ["ObservationCancelled": "Optic Disc Exam for Structural Abnormalities"] OpticDiscExamNotPerformed
    with "Primary Open Angle Glaucoma Encounter" EncounterWithPOAG
      such that OpticDiscExamNotPerformed.issued during day of EncounterWithPOAG.period
    where OpticDiscExamNotPerformed.notDoneReason ( ) in "Medical Reason"

define "Denominator Exceptions":
  exists "Medical Reason for Not Performing Cup to Disc Ratio"
    or exists "Medical Reason for Not Performing Optic Disc Exam"

define fluent function isVerified(condition Choice<ConditionEncounterDiagnosis, ConditionProblemsHealthConcerns>):
  condition.verificationStatus is not null implies ( condition.verificationStatus ~ Status."confirmed"
      or condition.verificationStatus ~ Status."unconfirmed"
      or condition.verificationStatus ~ Status."provisional"
      or condition.verificationStatus ~ Status."differential"
  )

define function ToString(value string): value.value

define function ToString(value uri): value.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 EncounterStatus): value.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
        }

define function ToDateTime(value dateTime): value.value

define function ToDateTime(value instant): value.value

define function ToDate(value date): 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

/*
@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
        }

define function ToString(value ObservationStatus): 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 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 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
    }

/*
@description: Returns the notDoneReason for an ObservationCancelled
*/
define fluent function notDoneReason(observationCancelled ObservationCancelled):
  observationCancelled.ext('http://fhir.org/guides/astp/us-quality-core/StructureDefinition/us-quality-core-notDoneReason').value as FHIR.CodeableConcept