Jolt reference first element in array as target name - json

Question

I have been looking at this for a few weeks (in the background) and am stumped on how to convert JSON data approximating a CSV into a tagged set using the NiFi JoltTransformJson processor. What I mean by this is to use the data from the first row of an array in the input as the JSON object name in the output.
As an example I have this input data:
[
[
"Company",
"Retail Cost",
"Percentage"
],
[
"ABC",
"5,368.11",
"17.09%"
],
[
"DEF",
"101.47",
"0.32%"
],
[
"GHI",
"83.79",
"0.27%"
]
]
and what I am trying to get as output is:
[
{
"Company": "ABC",
"Retail Cost": "5,368.11",
"Percentage": "17.09%"
},
{
"Company": "DEF",
"Retail Cost": "101.47",
"Percentage": "0.32%"
},
{
"Company": "GHI",
"Retail Cost": "83.79",
"Percentage": "0.27%"
}
]
I see this as primarily 2 problems: getting access to the content of the first array and then making sure that the output data does not include that first array.
I would love to post a Jolt Specification showing myself getting somewhat close, but the closest gives me the correct shape of output without the correct content. It looks like this:
[
{
"operation": "shift",
"spec": {
"*": {
"*": "[&1].&0"
}
}
}
]
But it results in an output like this:
[ {
"0" : "Company",
"1" : "Retail Cost",
"2" : "Percentage"
}, {
"0" : "ABC",
"1" : "5,368.11",
"2" : "17.09%"
}, {
"0" : "DEF",
"1" : "101.47",
"2" : "0.32%"
}, {
"0" : "GHI",
"1" : "83.79",
"2" : "0.27%"
} ]
Which clearly has the wrong object name and it has 1 too many elements in the output.

Answer 1

Can do it, but wow it is hard to read / looks like terrible regex
Spec
[
{
// this does most of the work, but producs an output
// array with a null in the Zeroth space.
"operation": "shift",
"spec": {
// match the first item in the outer array and do
// nothing with it, because it is just "header" data
// e.g. "Company", "Retail Cost", "Percentage".
// we need to reference it, but not pass it thru
"0": null,
//
// loop over all the rest of the items in the outer array
"*": {
// this is rather confusing
// "*" means match the array indices of the innner array
// and we will write the value at that index "ABC" etc
// to "[&1].#(2,[0].[&])"
// "[&1]" means make the ouput be an array, and at index
// &1, which is the index of the outer array we are
// currently in.
// Then "lookup the key" (Company, Retail Cost) using
// #(2,[0].[&])
// Which is go back up the tree to the root, then
// come back down into the first item of the outer array
// and Index it by the by the array index of the current
// inner array that we are at.
"*": "[&1].#(2,[0].[&])"
}
}
},
{
// We know the first item in the array will be null / junk,
// because the first item in the input array was "header" info.
// So we match the first item, and then accumulate everything
// into a new array
"operation": "shift",
"spec": {
"0": null,
"*": "[]"
}
}
]