function processors

[amitu]

-- future-result<integer> foo($a):
$processor$: http
integer $a:
$url$: https://www.example.com/get-integer
method: POST
header-foo: ??
content-type: ??

{
    "a": $a
}


-- integer $a: 20
-- integer x: foo($a=$a) ;; x will auto update

;; strictly type of x is wrong, it should be `future-result<integer>`, but future results can be 
;; deferred the UI till future is ready, 
;;
;; further on error we will panic the entire page if you do not want to handle result. further 
;; we can also have "component level error boundaries", and only the place that uses x in
;; UI will show the error. 

-- component f:
integer x: foo(a=30)

-- end: f

[siddhantk232]

Please explain this more, give more examples.

{
    "a": $a
}

The above is request body? Can I do something with the http response before returning it from foo? Like instantiate a record and return that record instance instead?

-- component f:
integer x: foo(a=30)

-- end: f

does this mean that calls to f won't render until the future (returned from foo) is resolved? How do you show a placeholder UI while the future resolution is happening?

[amitu]

Every function processor is also a function, and can be used as such.

-- integer x: fastn.http("https://some-api.com")

Function processors syntax allows you to wrap the function and create another function out of it.

-- future-result<integer> f(): ;; in 0.5 we won't have to repeat arguments here
integer v:
$processor$: fastn.http
url: https://some-api.com
arg1: yo ;; all args to fastn.http things are treated as query parameter
arg2: ${f.v} ;; we are using automatically switch to f-script syntax here

{
   "some": "post body",
   "something": "${f.v}"     ;; we can refer to variables in body as well
}

Similarly for fastn.sql:

-- future-result<integer> f(): ;; in 0.5 we won't have to repeat arguments here
integer v:
$processor$: fastn.sql

SELECT * from users where id = ${v};

Inside the body / args, we currently allow $x syntax to refer to arguments, should we move to ${v} syntax?

How to future-result?

You can use the match statement:

-- match x:

-- case: future-result.pending

-- ftd.text: pedning

-- case: future-result.error(e)

-- ftd.text: failed: ${e}

-- case: future-result.success(v)

-- ftd.integer: v

-- end: match

And while the page loads, that while x changes, the match statement will be re-evaluated, and appropriate UI will be shown/hidden.