Add a Wrapper For fhirPath expressions, cqf-calculatedValue, cqf-library and cqf-expression.

[RaaziaTarique]

Is your feature request related to a problem? Please describe. FhirPathEngine, DataRenderer and related classes to evaluate fhirPath expressions, cqf-calculatedValue, cqf-library and cqf-expression will be used multiple time in the project so it's better to have central wrapper for these classes.

Following issues which may use this wrapper in the future:

https://github.com/google/android-fhir/issues/1040 (This wrapper is a Pre-Requisite) https://github.com/google/android-fhir/issues/1033 https://github.com/google/android-fhir/issues/1059

Describe the solution you'd like Add a wrapper in the common module.

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context @jingtang10 proposed this solution in the SDK ticket discussion call held on 18th March, 2022 CC: @f-odhiambo

Would you like to work on the issue? Please state if this issue should be assigned to you or who you think could help to solve this issue.

[jingtang10]

as a first step to speed up development, i think it's ok to create this new api as an internal api in the datacapture module. as a next step we can move it to the common module (which will require a separate release).

[ekigamba]

I recommend(draft) the following:

class FhirPathWrapper

functions:

• evaluate - Can be used by cqf-calculatedValue, cqf-express, calculatedExpression extensions
• evaluateToBoolean - Can be used by enableWhen extension

It can also be used in the FHIR Path variable issue at a later point

Most of these output either a boolean or a list of resources.

The wrapper can be extended to support constant extensions that need local support such as %questionnaire, qitem(), sum() etc defined here

FhirPathWrapper can also be modified to add support for other expressions as well such as answerExpression and others if needed.

@RaaziaTarique I don't know if this is what @jingtang10 wanted but I believe it's a start based on my understanding

Edited with @RaaziaTarique

[fredhersch]

@RaaziaTarique @jingtang10 has the approach here been resolved? Thanks

[f-odhiambo]

Updates on this

1. Min/Max validation Works for Date but not other data types - PR https://github.com/google/android-fhir/pull/1442 ready
2. calculated-expression - PR https://github.com/google/android-fhir/pull/1380 ready
3. calculated-value - PR https://github.com/google/android-fhir/pull/1442 ready
4. Implement calculated-expression extension 1059 | variables -> PR https://github.com/google/android-fhir/pull/1328 ready
5. CQF Expression not implemented yet - Needs a discussion CC @maimoonak

[f-odhiambo]

CC @fredhersch @jingtang10

[jingtang10]

1. https://github.com/google/android-fhir/pull/1442 has comments to be addressed.
2. just left a review. also requested @joiskash to review.
3. that's the same PR as 1
4. just left a review
5. can you set up something please @maimoonak

[maimoonak]

The expressions support has a long list https://build.fhir.org/ig/HL7/sdc/expressions.html and https://build.fhir.org/ig/HL7/sdc/behavior.html. Some of the expressions discussed in current thread are below

• Date picker restrict -> https://github.com/google/android-fhir/issues/1040 -> PR UNDER REVIEW https://github.com/google/android-fhir/pull/1442
• Initial expression -> https://github.com/google/android-fhir/issues/1033 -> PR MERGED -> https://github.com/google/android-fhir/pull/1228
• Variable support -> https://github.com/google/android-fhir/issues/1059 -> PR APPROVED -> https://github.com/google/android-fhir/pull/1328
• Calculated expression -> https://github.com/google/android-fhir/issues/971 -> PR AWAITING PR 1328 (variables work) -> https://github.com/google/android-fhir/pull/1380
• Calculated value -> PR READY -> https://github.com/google/android-fhir/pull/1442
• Answer expression -> https://github.com/google/android-fhir/issues/1039 -> PR UNDER REVIEW -> https://github.com/google/android-fhir/pull/1480
• EnableWhen expression -> https://github.com/google/android-fhir/issues/819 -> PR MERGED (long ago) -> https://github.com/google/android-fhir/pull/1294
• Candidate expression -> https://github.com/google/android-fhir/issues/1038 -> AWAITING PR 1480 (overlaps functionality)
• CQF Expression -> very vast range http://hl7.org/fhir/R4/extension-cqf-expression.html -> not implemented yet and no specific issue or use case exists/linked - Needs a discussion

@f-odhiambo @jingtang10 @Tarun-Bhardwaj

[f-odhiambo]

@fredhersch See the summery above on the related FHIRPath expression tickets

[jingtang10]

I think as a tracking issue this issue can be closed as the only item left is 1038.