/**
Library: HIV.B2.DT Logic

@DecisionID: HIV.B2.DT
@BusinessRule: Check for signs of serious illness
@Trigger: HIV.B2 Check for signs of serious illness
@Trigger: HIV.D3 Check for signs of serious illness
@HitPolicy: Rule Order
@Description: Check for serious illness

Data Concepts:
 * HIV.A.DE17: Age | Calculated age (number of years) of the client based on date of birth
 * HIV.D.DE17: Signs of serious illness | Signs that may indicate the client has a serious illness and needs triage or an emergency referral
 * HIV.D.DE9: Body temperature | Temperature of the client in Celsius

Consolidated guidelines on HIV prevention, testing, treatment, service delivery and monitoring: recommendations for a public health approach (2021) Chapter 5: Advanced HIV Disease. Figure 5.1: Algorithm for providing a package of care for people with advanced HIV disease.
*/

library HIVB2DTLogic

using FHIR version '4.0.1'

include HIVCommon version '0.0.1' called HIC
include HIVConcepts called Concepts
include HIVEncounterElements called Elements
include FHIRHelpers version '4.0.1'

include WHOCommon called WCom

context Patient

 /*
  @input: "Age 10 or older"
  @pseudocode: 'Age' >= 10 years
  */
define "Age 10 or older":
  AgeInYearsAt(Today()) >= 10

 /*
  @input: "Age under 10"
  @pseudocode: 'Age' < 10 years
  */
define "Age under 10":
  AgeInYearsAt(Today()) < 10

/*
 @output: "Immediately take action or refer for care if a client is having this issue"
 */
define "Immediately take action or refer for care if a client is having this issue":
  "Age 10 or older" and exists(
    Elements."Signs of serious illness Observation" O
      where O.value ~ Concepts."Tachycardia"
  )

/*
 @output "Immediately take action or refer for care if client is showing this sign of a serious illness."
 */
define "Immediately take action or refer for care if client is showing this sign of a serious illness":
  "Signs of serious illness age 10 or older" or "Signs of serious illness age under 10"

/*
 @output "Use clinical judgement and consider local epidemiology to determine if symptoms suggest client is seriously ill"
 */
define "Use clinical judgement and consider local epidemiology to determine if symptoms suggest client is seriously ill":
  "Signs of serious illness requiring clinical judgement age 10 or older" or "Signs of serious illness requiring clinical judgement age under 10"

/*
 @dynamicValue: Guidance
 */
define "Guidance":
  case 
  when "Immediately take action or refer for care if a client is having this issue" 
    then 'Immediately take action or refer for care if a client is having this issue.'
  when "Immediately take action or refer for care if client is showing this sign of a serious illness" and "Age 10 or older"
    then 'Immediately take action or refer for care if client is showing this sign of a serious illness.'
  when "Immediately take action or refer for care if client is showing this sign of a serious illness" and "Age under 10"
    then '''This is a sign and/or symptom of a serious health condition.
  
Immediately take action or refer for care if client is showing this sign of a serious illness.'''
  else null
  end

/*
 Supporting Logic
*/
define "Signs of serious illness age 10 or older":
  "Age 10 or older" and exists(
    Elements."Signs of serious illness Observation" O
      where
        O.value ~ Concepts."Tachypnea" or
        O.value ~ Concepts."Unable to walk unaided"
  )

define "Signs of serious illness age under 10":
  "Age under 10" and exists(
    Elements."Signs of serious illness Observation" O
      where
        O.value ~ Concepts."Lethargy - HIV.D.DE22" or
        O.value ~ Concepts."Unconsciousness" or
        O.value ~ Concepts."Convulsions" or
        O.value ~ Concepts."Unable to breastfeed" or
        O.value ~ Concepts."Unable to drink" or
        O.value ~ Concepts."Repeated vomiting"
    )

define "Signs of serious illness requiring clinical judgement age 10 or older":
  "Age 10 or older" and exists(
    Elements."Signs of serious illness Observation" O
      where
        O.value ~ Concepts."Fever of 39 C or greater" or
        O.value ~ Concepts."Other sign of serious illness"
  )

define "Signs of serious illness requiring clinical judgement age under 10":
  "Age under 10" and exists(
    Elements."Signs of serious illness Observation" O
      where
        O.value ~ Concepts."Fever of 39 C or greater" or
        O.value ~ Concepts."Other sign of serious illness"
  )