Convert a value string in metatable to table for lookup - lua

Question

I have an enormous table of functions named engine_api with inline documentation. Because it's becoming so large I'd like to make it more modular.
The api is set up like this:
-- Engine API module
local engine_api = {
engine = {
-- engine functions...
version = ...
},
image = {
-- image functions...
jpeg = {
-- jpeg specific bits
},
},
project = {
-- project functions
}
}
return engine_api
As you can see, it's more than 2 levels deep.
The whole thing is returned as a single table so other parts of the system can call into this api like this:
local api = require "engine_api"
print("Engine version:", engine_api.engine.version());
I still need it to work this way. But what I'd like to do is separate various parts of the API into different files. I thought I might be able to do this using metamethods. But when the metamethod is looked up, the value is actually a string so this naive approach will not work.
local engine = {
-- engine functions...
version = function()
print("engine.version")
end
}
local image = {
-- image functions
get = function()
print("image.get")
end
}
local project = {
-- project functions
load = function()
print("project.load()")
end
}
-- Engine API module
local engine_api = {
}
local engine_api_mt = {
__index = function(tbl, k)
print("k=", k)
return k
end
}
setmetatable(engine_api, engine_api_mt)
Instead I seem to have to do bunch of if then else statements to compare the table name with the string and then return the table and not the string. Is there a way of performing the conversion automatically?

Answer 1

You can make engine_api a single file and require files inside that table, like so:
engine_api.lua:
local engine_api = {
engine = require("engine"),
image = require("image"),
project = require("project"),
}
return engine_api
engine.lua:
local engine = {
version = function()
print("my version")
end
}
return engine
And so on, that way you can call engine_api.engine.version() with no problems at all. I think the metatable is just over the top, unless you are doing something more specific?