Dynamic two-way references with different levels of depth.

[cueckoo]

Originally opened by @rlopez-plenty in cuelang/cue#953

Hello Community.

We have a special case, having objects with different levels of depth (we have about 6 levels) and we have mappings at different levels, for example this case, I added a mapping from Beta1 to Alpha and in that order we also want to generate that reverse mapping in Alpha to Beta1, do you have any thoughts?

There was a related ticket that is resolved in the community discussion with mappings between specific level of depth.This is bit more complex case.
cuelang/cue#907

// This final output matches what we are hoping to achieve
// but is hardcoded to work, need a dynamic solution
_TEMP: {
    // If we define a mapping here, the inverse should show up at that mapping
    // ie, Alpha.Alpha1.id should now map to Beta.Beta1.id
    // (are there potential recursive infinite loop problems?)
    #Object: {...}
	Beta: #Object & { 
		Beta1: #Object & {
		    id: "B1234"
		    // would like to keep string1, string2, and mappedId hidden
		    // or ideally, just use the "to" definition to access the right values
			mappings: [{to: Alpha.Alpha1.id},{to: Alpha.id}]
		}
	}
    // Object we want to map back to Beta.Beta1.id
	Alpha: #Object & {
		id: "A1"
		//mappings: [{to: Beta.Beta1.id}] //we also want to generate this dynamically
		Alpha1: #Object & {
			id:    "A1234"
			//mappings: [{to: Beta.Beta1.id}] //we want to generate this dynamically
		}
	}
}
let lookup = {
	for string1, x in _TEMP
	for string2, y in x {
		"\(y.id)": [string1, string2]
	}
}
TEMP2: _TEMP
TEMP2: {
  for x in _TEMP {
    for y in x {
      if y.mappings != _|_ {
        for m in y.mappings {
          let path = lookup[m.to]
             "\(path[0])": "\(path[1])": mappings: [{to: y.id}]}
          }
        }
    }
}

We want something like this output (The mappings from Alpha and Alpha1 were generated automatically):

{
    "TEMP": {
        "Beta": {
            "Beta1": {
                "id": "B1234",
                "mappings": [
                    {
                        "to": "A123",
                        "to": "A1234",
                    }
                ]
            }
        },
        "Alpha": {
            "id":"A123"
            "mappings": [
                    {
                        "to": "B1234"
                    }
                ]
            "Alpha1": {
                "id": "A1234"
                "mappings": [
                    {
                        "to": "B1234"
                    }
                ]
            }
        }
    }
}

I really appreciate any help in this case.

Have a nice day!