define "Is Infant Patient":
  Patient.birthDate is not null
  and difference in years between Patient.birthDate and start of "Measurement Period" < 1

/* End of Age of infant */

/*
@dataElement: HIV.E.DE112 - HIV-exposed infant or child
@activity: HIV.F6 Check whether infant/child had HIV exposure
@description: Whether the infant or child was determined to have had HIV exposure
*/
define "HIV-exposed infant or child E.DE112":

  [Observation: Concepts."HIV-exposed infant or child - HIV.E.DE112"] O
    where O.status in { 'final', 'amended', 'corrected' }

/* End of Age of infant */

/*
@dataElement: HIV.E.DE112 - HIV-exposed infant or child
@activity: HIV.F6 Check whether infant/child had HIV exposure
@description: Whether the infant or child was determined to have had HIV exposure
*/
define "is HIV-exposed infant or child E.DE112":
  "Is Infant Patient" and 
  exists(Elements."HIV-exposed infant or child E.DE112" O
    where O.effective.toInterval() during "Measurement Period")

/* End of Currently pregnant B.DE29 */

/*
@dataElement: HIV.B.DE32 - Breastfeeding
@activity: HIV.B6 Capture or update client history
@description: Infant is being breastfed by mother
*/

define "Breastfeeding B.DE32":
  [Observation: Concepts."Breastfeeding - HIV.B.DE32"] O
    where O.status in { 'final', 'amended', 'corrected' }
      and O.value is true

/* End of Currently pregnant B.DE29 */

/*
@dataElement: HIV.B.DE32 - Breastfeeding
@activity: HIV.B6 Capture or update client history
@description: Infant is being breastfed by mother
*/

define "Breastfeeding B.DE32":
  Elements."Breastfeeding B.DE32" O
    where O.effective.toInterval() during "Measurement Period"

/* End of Newly on ART during labour and delivery */

/*
@dataElement: HIV.E.DE46 - Delivery date
@activity: HIV.E1 Capture or update mother's history
@description: Date on which the woman delivered
*/
define "Live Birth Delivery":
  [Observation: Concepts."Live birth"] O
    where O.status in { 'final', 'amended', 'corrected' }

/* End of Newly on ART during labour and delivery */

/*
@dataElement: HIV.E.DE46 - Delivery date
@activity: HIV.E1 Capture or update mother's history
@description: Date on which the woman delivered
*/
define "Live Birth Delivery":
  Elements."Live Birth Delivery" O
    where O.effective.toInterval() during "Measurement Period"

/* End of Serodiscordant partner D.DE37 */

/*
@dataElement: HIV.D.DE38 - On ART
@activity: HIV.D8 Capture or update client history
@description: Client is currently taking ART
*/

define "On ART D.DE38":
    [MedicationStatement] MS
    where exists(MS.reasonCode C where C ~ Concepts."On ART - HIV.D.DE38")
    sort by start of effective.toInterval()

/**
 * Numerator
 * 
 * Definition: Number of HIV-exposed breastfeeding infants whose mothers are receiving ART at 12 months (and 24 months*) postpartum
 * Calculation: COUNT of infants who are an "HIV-exposed infant or child" AND whose mothers are "Breastfeeding" 12 months after "Delivery date" AND mothers with "On ART"=True 12 months after "Delivery date" |  | Also reported for 24 months after "Delivery date"
 */

define "Numerator":
  HIE."is HIV-exposed infant or child E.DE112"
  and exists(HIE."Breastfeeding B.DE32" B 
  where months between end of B.effective.toInterval() and end of Last(HIE."Live Birth Delivery" B where B.effective.toInterval() before "Measurement Period").effective.toInterval() > 12 months
  )
  and 
  exists ( 
    HE."On ART D.DE38" A 
    where months between end of A.effective.toInterval() and end of Last(HIE."Live Birth Delivery" B where B.effective.toInterval() before "Measurement Period").effective.toInterval() > 12 months
  )

/* End of Dual HIV/syphilis rapid diagnostic test E.DE172 */

/*
@dataElement: HIV.E.DE173 - Maternal and child health service visit
@activity: HIV.E1 Capture or update mother's history
@description: Maternal and child health service visit attended by an HIV-exposed infant
*/

define "Maternal and child health service visit":
    [Encounter] E
    where E.type.coding.code contains Concepts."Maternal and child health service visit".code

/* End of Maternal and child health service visit */

/*
@dataElement: HIV.E.DE174 - 12-month visit
@activity: HIV.E1 Capture or update mother's history
@description: HIV-exposed infant attending MCH services for a 12-month visit
*/

define "12-month visit":
  "Maternal and child health service visit" E
    where E.type.coding.code contains Concepts."12-month visit".code

/* End of Maternal and child health service visit */

/*
@dataElement: HIV.E.DE174 - 12-month visit
@activity: HIV.E1 Capture or update mother's history
@description: HIV-exposed infant attending MCH services for a 12-month visit
*/

define "12-month visit":
  exists Elements."12-month visit" E
  where E.period.toInterval() during "Measurement Period"

define "Not Breastfeeding B.DE32":
  [Observation: Concepts."Breastfeeding - HIV.B.DE32"] O
    where O.status in { 'final', 'amended', 'corrected' }
      and O.value is false

/**
 * Denominator
 *
 * Definition: Number of HIV-exposed infants attending MNCH services for a 12-month visit (and 24-month visit or first visit after the end of breastfeeding)
 * Calculation: COUNT of infants who are an "HIV-exposed infant or child" AND [(whose mothers attend a 12-month "Maternal and child health service visit") OR (first "Maternal and child health service visit" after "Delivery date" where mother is NOT "Breastfeeding")] |  | Also reported for mothers attending 24-month "Maternal and child health service visit"
 */

define "Denominator":
  HIE."is HIV-exposed infant or child E.DE112"
  and (HIE."12-month visit"
  or 
  exists(HE."Not Breastfeeding B.DE32" B 
  with HE."Maternal and child health service visit" E
  such that B.encounter.references(E) and E.period.toInterval() after end of Last(HIE."Live Birth Delivery" B where B.effective.toInterval() before "Measurement Period").effective.toInterval())
  )

/* Populations */

/*
 *Initial Population
 */

define "Initial Population":
  true

define function ToDate(value date): value.value

define function ToString(value ObservationStatus): value.value

define function ToBoolean(value boolean): value.value

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 ToString(value string): value.value

/*
From FHIRCommon 4.1.0:
*/

/*
@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

define function ToDateTime(value dateTime): value.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 ToDateTime(value instant): value.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

/*
@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, '/'))