define "Initial Population":
  "Has Active HIV Diagnosis Before or in First 90 Days of Measurement Period"
    and "Has Qualifying Encounter During First 240 Days of Measurement Period"

define "Denominator":
  "Initial Population"

define "Numerator":
  "Most Recent Viral Load Test During Measurement Period".value < 200 '{copies}/mL'
    or "Most Recent Viral Load Test During Measurement Period".value ~ "Below threshold level (qualifier value)"
    or "Most Recent Viral Load Test During Measurement Period".value ~ "Not detected (qualifier value)"

define "Most Recent Viral Load Test During Measurement Period":
  Last(["Observation": "HIV Viral Load"] ViralLoad
      where QICoreCommon."Latest"(ViralLoad.effective) during day of "Measurement Period"
      sort by start of QICoreCommon."ToInterval"(effective)
  )

define "Numerator":
  "Most Recent Viral Load Test During Measurement Period".value < 200 '{copies}/mL'
    or "Most Recent Viral Load Test During Measurement Period".value ~ "Below threshold level (qualifier value)"
    or "Most Recent Viral Load Test During Measurement Period".value ~ "Not detected (qualifier value)"

define "Has Active HIV Diagnosis Before or in First 90 Days of Measurement Period":
  exists ["Condition": "HIV"] HIVDx
    where QICoreCommon."ToPrevalenceInterval" ( HIVDx ) starts before day of ( start of "Measurement Period" + 90 days )

define "Has Qualifying Encounter During First 240 Days of Measurement Period":
  exists ( ["Encounter": "Office Visit"]
    union ["Encounter": "Outpatient Consultation"]
    union ["Encounter": "Annual Wellness Visit"]
    union ["Encounter": "Face-to-Face Interaction"]
    union ["Encounter": "Home Healthcare Services"]
    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 Services, Initial Office Visit, 0 to 17"]
    union ["Encounter": "Preventive Care, Established Office Visit, 0 to 17"]
    union ["Encounter": "Telephone Visits"]
    union ["Encounter": "Preventive Care Services Other"] ) QualifyingEncounter
    where QualifyingEncounter.period during day of Interval[start of "Measurement Period", start of "Measurement Period" + 240 days]

define "Initial Population":
  "Has Active HIV Diagnosis Before or in First 90 Days of Measurement Period"
    and "Has Qualifying Encounter During First 240 Days of Measurement Period"

define "Denominator":
  "Initial Population"

/*
@description: Given an interval, returns the ending point if the interval has an ending boundary specified,
otherwise, returns the starting point
@deprecated: This function is deprecated. Use the fluent function `latest()` instead
*/
define function "Latest"(choice Choice<DateTime, Quantity, Interval<DateTime>, Interval<Quantity>> ):
  (choice.toInterval()) period
    return
      if (HasEnd(period)) then end of period
      else start of period

/*
@description: Normalizes a value that is a choice of timing-valued types to an equivalent interval
@comment: Normalizes a choice type of DateTime, Quanitty, Interval<DateTime>, or Interval<Quantity> 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 QICore, allowing this function to be used across any resource.
The input can be provided as a DateTime, Quantity, Interval<DateTime> or Interval<Quantity>.
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 Quantity, the quantity is expected to be a calendar-duration interpreted as an Age,
and the result is a DateTime Interval beginning on the Date the patient turned that age and ending immediately before one year later.
If the input is a DateTime Interval, the result is the input.
If the input is a Quantity Interval, the quantities are expected to be calendar-durations interpreted as an Age, and the result
is a DateTime Interval beginning on the date the patient turned the age given as the start of the quantity interval, and ending
immediately before one year later than the date the patient turned the age given as the end of the quantity interval.
Any other input will reslt in a null DateTime Interval
*/
define fluent function toInterval(choice Choice<DateTime, Quantity, Interval<DateTime>, Interval<Quantity>>):
  case
	  when choice is DateTime then
    	Interval[choice as DateTime, choice as DateTime]
		when choice is Interval<DateTime> then
  		choice as Interval<DateTime>
		when choice is Quantity then
		  Interval[Patient.birthDate + (choice as Quantity),
			  Patient.birthDate + (choice as Quantity) + 1 year)
		when choice is Interval<Quantity> then
		  Interval[Patient.birthDate + (choice.low as Quantity),
			  Patient.birthDate + (choice.high as Quantity) + 1 year)
		else
			null as Interval<DateTime>
	end

/*
@description: Normalizes a value that is a choice of timing-valued types to an equivalent interval
@comment: Normalizes a choice type of DateTime, Quanitty, Interval<DateTime>, or Interval<Quantity> 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 QICore, allowing this function to be used across any resource.
The input can be provided as a DateTime, Quantity, Interval<DateTime> or Interval<Quantity>.
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 Quantity, the quantity is expected to be a calendar-duration interpreted as an Age,
and the result is a DateTime Interval beginning on the Date the patient turned that age and ending immediately before one year later.
If the input is a DateTime Interval, the result is the input.
If the input is a Quantity Interval, the quantities are expected to be calendar-durations interpreted as an Age, and the result
is a DateTime Interval beginning on the date the patient turned the age given as the start of the quantity interval, and ending
immediately before one year later than the date the patient turned the age given as the end of the quantity interval.
Any other input will reslt in a null DateTime Interval
@deprecated: This function is deprecated. Use the fluent function `toInterval()` instead
*/
define function ToInterval(choice Choice<DateTime, Quantity, Interval<DateTime>, Interval<Quantity>>):
  case
	  when choice is DateTime then
    	Interval[choice as DateTime, choice as DateTime]
		when choice is Interval<DateTime> then
  		choice as Interval<DateTime>
		when choice is Quantity then
		  Interval[Patient.birthDate + (choice as Quantity),
			  Patient.birthDate + (choice as Quantity) + 1 year)
		when choice is Interval<Quantity> then
		  Interval[Patient.birthDate + (choice.low as Quantity),
			  Patient.birthDate + (choice.high as Quantity) + 1 year)
		when choice is QICore.Timing then
            null as Interval<DateTime>
		else
			null as Interval<DateTime>
	end

/*
@description: Returns an interval representing the normalized prevalence period of a given Condition.
@comment: Uses the ToInterval and ToAbatementInterval functions to determine the widest potential interval from
onset to abatement as specified in the given Condition. If the condition is active, the resulting interval will have
a closed ending boundary. If the condition is not active, the resulting interval will have an open ending boundary.
@deprecated: This function is deprecated. Use the `prevalenceInterval()` fluent function instead
*/
define function ToPrevalenceInterval(condition Condition):
if condition.clinicalStatus ~ "active"
  or condition.clinicalStatus ~ "recurrence"
  or condition.clinicalStatus ~ "relapse" then
  Interval[start of ToInterval(condition.onset), end of ToAbatementInterval(condition)]
else
  Interval[start of ToInterval(condition.onset), end of ToAbatementInterval(condition))