define "Initial Population" :
  "Inpatient Encounter" Encounter
    with ["Encounter" : "Emergency Department Visit"] ED
     such that ED.status = 'finished'
       and ED.period ends 1 hour or less before start of Encounter.period

define "Measure Population" :
  "Initial Population"

define function "Measure Observation"(Encounter "Encounter") :
  duration in minutes of "Related ED Visit"(Encounter).period

define "Stratification 1" :
  "Inpatient Encounter" Encounter
    where not (Encounter.principalDiagnosis().diagnosis in "Psychiatric/Mental Health Patient")

define "Stratification 2" :
  "Inpatient Encounter" Encounter
    where Encounter.principalDiagnosis().diagnosis in "Psychiatric/Mental Health Patient"

define "Stratification 3" :
  "Inpatient Encounter" Encounter
    where Encounter.principalDiagnosis().diagnosis is null

define fluent function lengthInDays(Value Interval<DateTime> ):
  difference in days between start of Value and end of Value

define fluent function principalDiagnosis(encounter Encounter):
  singleton from (
    (encounter.claimDiagnosis()) CD
      where CD.type.includesCode("Principal Diagnosis")
  )

define fluent function claimDiagnosis(encounter Encounter):
  encounter E
    let 
      claim: ([Claim] C where C.status = 'active' and C.use = 'claim' and exists (C.item I where I.encounter.references(E))),
      claimItem: (claim.item I where I.encounter.references(E))
    return claim.diagnosis D where D.sequence in claimItem.diagnosisSequence

/*
@description: Returns true if any of the given references are to the given resource
@comment: Returns true if the `id` element of the given resource exactly equals the tail of any of the given references.
NOTE: This function assumes resources from the same source server.
*/
define fluent function references(references List<FHIR.Reference>, resource FHIR.Resource):
  exists (references R where R.references(resource))

/*
@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, '/'))

/*
@description: Returns true if the given code is in the given codeList
@comment: Returns true if the `code` is equivalent to any of the codes in the given `codeList`, false otherwise.
*/
define fluent function includesCode(codeList List<CodeableConcept>, code Concept):
  exists (codeList C where C ~ code)

/*
@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 ClaimStatus): value.value

define function ToString(value Use): value.value

define function ToString(value string): value.value

/*
@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
        }

/*
@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 ToString(value EncounterStatus): value.value

define "Inpatient Encounter" :
  ["Encounter"] Encounter
    where Encounter.period.lengthInDays() <= 120
      and Encounter.period ends during "Measurement Period"

define "Stratification 3" :
  "Inpatient Encounter" Encounter
    where Encounter.principalDiagnosis().diagnosis is null

define "Stratification 2" :
  "Inpatient Encounter" Encounter
    where Encounter.principalDiagnosis().diagnosis in "Psychiatric/Mental Health Patient"

define "Stratification 1" :
  "Inpatient Encounter" Encounter
    where not (Encounter.principalDiagnosis().diagnosis in "Psychiatric/Mental Health Patient")

define "Initial Population" :
  "Inpatient Encounter" Encounter
    with ["Encounter" : "Emergency Department Visit"] ED
     such that ED.status = 'finished'
       and ED.period ends 1 hour or less before start of Encounter.period

define "Measure Population" :
  "Initial Population"

define function "Measure Observation"(Encounter "Encounter") :
  duration in minutes of "Related ED Visit"(Encounter).period

//Measure Observation
define function "Related ED Visit"(Encounter "Encounter") :
  Last(["Encounter" : "Emergency Department Visit"] ED
    where ED.status = 'finished'
      and ED.period ends 1 hour or less before start of Encounter.period
    sort by start of period )