Postgres, jsonb & jsonb_set - json

Question

Depending on the HTTP_USER_AGENT I have to return a very specialized formatted version of a json structure to the client.
The json object is generated as usual with standard postgres functions.
Lets assume the generated json looks similar to this:
{
"return_code" : 0,
"payload" : {
"name" : "smith",
"age": 17,
"address" :{
"street" : "<whatever>",
"city" : "<anycity>"
}
}
}
Now under some circumstances I have to return this json in the following format:
{
"return_code" : 0,
"payload" : "{"name" : "smith", "age": 17, "address" :"{"street" : "<whatever>", "city" : "<anycity>"}"}"
}
As you can see the nested payload object should be returned as a string - masking ignored here for better readability.
Further else the address property should also be returned as a string, not as a json object.
My postgres code that should do this is simply:
response := jsonb_set(response, '{payload}', to_jsonb((response->'payload')::text));
But the result from the code above looks like:
{
"return_code" : 0,
"payload" : "{"name" : "smith", "age": 17, "address" :{"street" : "<whatever>", "city" : "<anycity>"}}"
}
Consider the quotes are missing (just two) for the address-object.
How can I fix this?
Thank You!

Answer 1

It seems to me that you need a further level of escaping / quoting on the address property, because you have:
Your substitution: { "payload" : { ... } } -> { "payload" : "{ ... }" }
Extra substitution: { "address": { ... } } -> { "address": "{ ... }" }
You'll need to do this before the existing line, so I think what you want is this (requires an extra jsonb variable, payload):
payload := jsonb_set(response->'payload', '{address}', to_jsonb((response->'payload'->address)::text));
response := jsonb_set(response, '{payload}', to_jsonb(payload::text));