;; sample-module.wat: the source of sample-module.wasm, in WebAssembly text format.
;; Free sample from 99helpers.com/file-types/wasm
;; Build it with:  wat2wasm --enable-annotations sample-module.wat -o sample-module.wasm
(module
  ;; 1. An import: the module asks its host for a function called env.log.
  ;;    In a browser, JavaScript supplies it; the module cannot print by itself.
  (import "env" "log" (func $log (param i32 i32)))

  ;; 2. Linear memory: 1 page of 64 KiB, exported so JavaScript can read it.
  (memory (export "memory") 1)

  ;; 3. A data segment: these bytes are copied into memory at offset 0
  ;;    when the module is instantiated.
  (data (i32.const 0) "Hello from 99helpers.com/file-types/wasm")

  ;; 4. A global: a constant other code can read, here the message length.
  (global $msgLen i32 (i32.const 40))

  ;; 5. A function with two 32-bit integer parameters and one result.
  ;;    Wasm is a stack machine: push a, push b, add them.
  (func $add (export "add") (param $a i32) (param $b i32) (result i32)
    local.get $a
    local.get $b
    i32.add)

  ;; 6. A loop with 64-bit integers: n! for n up to 20.
  (func $factorial (export "factorial") (param $n i64) (result i64)
    (local $acc i64)
    i64.const 1
    local.set $acc
    (block $done
      (loop $next
        ;; stop when n <= 1
        local.get $n
        i64.const 1
        i64.le_s
        br_if $done
        ;; acc = acc * n
        local.get $acc
        local.get $n
        i64.mul
        local.set $acc
        ;; n = n - 1, then go round again
        local.get $n
        i64.const 1
        i64.sub
        local.set $n
        br $next))
    local.get $acc)

  ;; 7. Calling the import: pass the message's address and length to env.log,
  ;;    and JavaScript decodes the bytes from memory into a string.
  (func $greet (export "greet")
    i32.const 0
    global.get $msgLen
    call $log)

  ;; 8. A custom section: extra bytes engines ignore, written with the
  ;;    custom annotation syntax that Wasm 3.0 added to the text format.
  (@custom "about" (after data) "Free sample from 99helpers.com/file-types/wasm")
)