Expression solution for transformation

I have to transform documents that look like the following:
[{
“Id”: 999,
“field1”: “value1”,
“field2”: “value2”,
“field3”: “value3”
}
]
Into output like this.
[{
“Id”: 999,
“entity”: {
“path”: “field1”,
“op”: “replace”,
“value”: “value1”
}
},
{
“Id”: 999,
“entity”: {
“path”: “field2”,
“op”: “replace”,
“value”: “value2”
}
},
{
“Id”: 999,
“entity”: {
“path”: “field3”,
“op”: “replace”,
“value”: “value3”
}
}
]
There can be multiple documents being processed and the number of “fields” is more (30+) than the example shows. I have created a Mapper snap to do this work for a few fields but would like not to have to do it for 30+. I feel there is an expression/javascript solution to this but I am not well versed at this time.
Any ideas would be appreciated.
Regards,