define "Antenatal care contact":
  ["Encounter": type in BCx."Antenatal care contact"]

define "First antenatal care contact":
  BaseData."Antenatal care contact" C
    where C.reasonCode in Cx."First Antenatal Care Contact Choices"

/*
  @dataElement: ANC.B6.DE17 Gestational age
  @activity: ANC.B6 Profile
  @description: Gestational age in weeks and/or days depending on the source of gestational age
*/
define "Gestational age":
  WC.MostRecent(
  [Observation: Cx."Gestational age"] O
    where O.status in { 'final', 'amended', 'corrected' }
      and Coalesce(WC.ModifierExtension(O, 'who-notDone').value, false) is false
      and Last(Split(O.encounter.reference, '/')) = Last(Split(encounter, '/'))
  ).value as FHIR.Quantity

/*
Numerator: Number of pregnant women who had their first ANC contact before 12 weeks (facility level)
Numerator Computation: Count of women whose gestational age <= 12 weeks at the time of first contact
*/
define Numerator:
  exists (
    "First antenatal care contact" C
      where C.period starts during "Measurement Period"
        and ContactData."Gestational age" <= 12 weeks
  )

/*
By Patient Age as of the start of the Measurement Period
Age (10-14, 15-19, 20+)
*/
define "By Age":
  case
    when AgeInYearsAt(start of "Measurement Period") in Interval[10, 14] then "P10Y--P14Y"
    when AgeInYearsAt(start of "Measurement Period") in Interval[15, 19] then "P15Y--P19Y"
    when AgeInYearsAt(start of "Measurement Period") >= 20 then "P20Y--P9999Y"
    else null
  end

/*
Disaggregation: Age (10-14, 15-19, 20+)
*/
define "Age Stratifier":
  Stratifiers."By Age"

/*
Denominator: Total number of antenatal clients with a first contact
Denominator Computation: Count of all women who had first contact within the last reporting period
*/
define Denominator:
  exists (
    "First antenatal care contact" C
      where C.period starts during "Measurement Period"
  )

/*
By Patient Education Level (none, don't know, primary, secondary, higher)
*/
define "By Education Level":
  Patient.extension E
    where E.url = 'http://smart.who.int/anc/StructureDefinition/educationlevel'
    return E.value as CodeableConcept

/*
Disaggregation: Education Level (none, don't know, primary, secondary, higher)
*/
define "Education Level Stratifier":
  Stratifiers."By Education Level"

/*
define "Pregnant":
  "Pregnancy" is not null
    or "Pregnancy status" in BCx."Pregnancy status - pregnant"

define "Pregnancy status":
  FHIRHelpers.ToConcept(
    Last(
      [Observation: BCx."Pregnancy status"] O
        where O.status = 'final'
        sort by FHIRHelpers.ToDateTime(effective as FHIR.dateTime)
    ).value
  )
*/

define "Antenatal care case":
  ["EpisodeOfCare": type in BCx."Antenatal care case"]

/*
Initial population: Antenatal clients
*/
define "Initial Population":
  exists (BaseData."Antenatal care case")

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 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 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 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

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 MostRecent(observations List<Observation>):
  Last(
    observations O
      sort by issued
  )

define function ToString(value ObservationStatus): value.value

define function ToBoolean(value boolean): value.value

/*
@description: Returns the single WHO core modifier extension (if present) on the given resource with the specified id.
@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 function ModifierExtension(domainResource DomainResource, id String):
  singleton from ModifierExtensions(domainResource, id)

/*
@description: Returns any WHO core modifier extensions defined on the given resource with the specified id.
@comment: NOTE: Extensions are not the preferred approach, but are used as a way to access
content that is defined by extensions but not yet surfaced in the
CQL model info.
*/
define function ModifierExtensions(domainResource DomainResource, id String):
  domainResource.modifierExtension E
	  where E.url = ('http://fhir.org/guides/who/core/StructureDefinition/' + id)
		return E

define function ToString(value uri): value.value

define function ToString(value string): value.value