CDAWeb virtual variables need to be implemented

[jbfaden]

Meeting with the CDAWeb team earlier this week we resolved that alternate_view was pointless and should be dropped, and then serveral of the virtual functions should be implemented. These include:

• time shifting for MMS datasets
• quality filtering with THEMIS and other datasets.

I need to identify examples of these virtual functions and implement these. (And I need to identify the virtual functions too.)

[jbfaden]

Here's an example virtual variable which will be a good example to implement:
MMS1_FGM_SRVY_L2 mms1_fgm_b_gsm_srvy_l2_clean

I'm still looking for the time shift ones.

[jbfaden]

alternate_view is now implemented with the new code, and mms1_fgm_b_gsm_srvy_l2_clean now works:
vap+hapi:http://localhost:8280/HapiServer/hapi?id=AC_OR_SSC&parameters=Time,XYZ_GSEO&timerange=2025-07-30

Closing redundant ticket #70

[jbfaden]

Virtual DEPEND_0
https://cottagesystems.com/~jbf/hapi/p/cdaweb/data/hapi/info/THA_L2_GMOM@2.json

[jbfaden]

This fails with a 500:

vap+hapi:https://cottagesystems.com/server/cdaweb/hapi?id=THA_L2_GMOM@2&parameters=Time,tha_ptirf_sc_potQ&timerange=2025-09-05
vap+hapi:http://localhost:8280/HapiServer/hapi?id=THA_L2_GMOM@2&parameters=Time,tha_ptirf_sc_potQ&timerange=2025-09-05

This one has both a virtual timetag and quality filter.

[jbfaden]

Here are the IDL implementations:

https://cdaweb.gsfc.nasa.gov/pub/software/cdawlib/source/read_myCDF.pro

and

https://cdaweb.gsfc.nasa.gov/pub/software/cdawlib/source/virtual_funcs.pro

[jbfaden]

I've learned that there's more to virtual variables than I imagined. At least two functions use additional metadata.

function name	component_0	additional variables
arr_slice	name of the source	ARR_INDEX,ARR_DIM
apply_filter_flag	name of the source	HANDLE, COMPARE_OPERATOR, COMPARE_VAL