How to Serialize/Deserialize table using schema in lua - serialization

Question

I have the following table:
local obj = {
firstname = "John",
lastname = "Bush",
age = 22,
height = 186,
friends = {
{ firstname = "Paul", lastname = "Graham", age = 20, height = 178 },
{ firstname = "Gianou", lastname = "Kwnstantina", age = 25, height = 172 }
},
bodies = { 4, 3, 10 }
}
and I want to transform it to this: (when inserting to database)
local tuple = {
'John', 'Bush', 22, 186, { { 'Paul', 'Graham', 20, 178 }, { 'Gianou', 'Kwnstantina', 25, 172 } }, { 4, 3, 10 }
}
which I managed to generate using:
function encode(schema, data)
local array = {}
function rec(arr, schema, d)
for i, field in ipairs(schema) do
arr[i] = {}
if field.type == "array" and type(field.items) == "table" then
for it, piece in ipairs(d[field.name]) do
arr[i][it] = {}
rec(arr[i][it], field.items, piece)
end
else
arr[i] = d[field.name]
end
end
end
rec(array, schema, data)
return array
end
My problem is that I want to reconstruct that data to the initial form when I retrieve it. I found some tools that can do this in other languages but the problem is that they transform the data to binary, I just want that array.
To be able to reconstruct I need something like a schema:
local schema = {
{ name = "firstname", type = "string" },
{ name = "lastname", type = "string" },
{ name = "age", type = "int" },
{ name = "height", type = "int" },
{ name = "friends", type = "array", items = {
{ name = "firstname", type = "string" },
{ name = "lastname", type = "string" },
{ name = "age", type = "int" },
{ name = "height", type = "int" }
}},
{ name = "bodies", type = "array", items = "int"}
}
I found that it's pretty easy to encode it just by retrieving the values but being able to validate and decode it seems pretty hard, is there a concept (name) for this operation in computer science, or a library that I can study (it needs to use a schema)?
I need a keyword to google...
Thank you!
EDIT: Just reversing the encode I found a simple way to decode.
function decode(schema, data)
local obj = {}
function rec(object, sch, d)
for i, field in ipairs(sch) do
if field.type == "array" and type(field.items) == "table" then
object[field.name] = {}
for it, piece in ipairs(d[i]) do
object[field.name][it] = {}
rec(object[field.name][it], field.items, piece)
end
else
object[field.name] = d[i]
end
end
end
rec(obj, schema, data)
return obj
end
I would still love suggestions on the code and where can I found more info on this type of info.
present version: https://pastebin.com/Ub4vZ0GU