(module
  (import "env" "greet" (func $greet (param i32)))
  (memory 1)

  (type $func (func (param $callstack i32) (result i32)))

  (func $do_greet (param $callstack i32) (result i32)
    (local $greet_number i32)
    local.get $callstack
    i32.const 4
    i32.sub
    local.set $callstack
    local.get $callstack
    i32.load
    local.set $greet_number

    local.get $greet_number
    call $greet

    local.get $callstack
    i32.const -1 ;; return to caller
    i32.store
    local.get $callstack
    i32.const 4
    i32.add
    local.set $callstack
    local.get $callstack
    return
  )

  (func $on_module_loaded (param $callstack i32) (result i32)
    ;; Param 1: number to send to $greet
    local.get $callstack
    i32.const 29
    i32.store
    local.get $callstack
    i32.const 4
    i32.add
    local.set $callstack


    local.get $callstack
    i32.const 17 ;; goto do_greet
    i32.store
    local.get $callstack
    i32.const 4
    i32.add
    local.set $callstack
    local.get $callstack
    return
  )

  ;; You could have a $on_module_loaded.0 that processes
  ;; the result from greet

  (table 32 funcref)
  (elem (i32.const 16) $on_module_loaded)
  (elem (i32.const 17) $do_greet)

  (func $runtime (param $func i32) (param $callstack i32)
    loop $call_methods
    local.get $callstack
    local.get $func
    call_indirect (type $func)
    local.set $callstack

    ;; Pop the func number of the callback
    local.get $callstack
    i32.const 4
    i32.sub
    local.set $callstack
    local.get $callstack
    i32.load
    local.set $func

    ;; See if we still have a function to jump to
    local.get $func
    i32.const 0
    i32.ge_s
    br_if $call_methods
    end
  )

  (func $start
    i32.const 16
    i32.const 0
    call $runtime
  )
  (start $start)
)


;; A function that takes 3 params and returns 1
;; stack param0 param1 param2 func_id
;;  => $runtime pops func_id and calls its function
;; stack param0 param1 param2
;;  => function$func_id pops param2, param1 and param0
;; stack
;;  => function$func_id stores its return value
;; stack $result
;;  => function$func_id returns to $runtime
;; $runtime now has the $result on top of the stack, rather the func_id to call -.-