There is nothing really “off the shelf” to do what you want, how complex it would be to implement something depends on what you have and what you want to achieve exactly.
The format of your data is still unclear
suggests a single file containing multiple metrics where as
suggests a separate file for each metric, assuming “harvested power” is a reference to the file and not just the entry in the file.
Do you have control over the format, creation and update of these files or is that dictated by a non-configurable device/software?
If the files are per metric you will possibly need to read and parse the data back into an array for each timestamp to post to emoncms in a way that allows more input processing, where as if you are just mirroring the data to emoncms with little or no input processing you can possibly do one file/metric at a time. eg if you want to combine the harvested power and instant mains power to calculate and create import/export or charge/discharge feeds, those 2 metrics must be posted simultaneously for each timestamp not as one batch and then the other as processing is generally done at input time.