module javascript
imports libstrategolib signatures/-

signature
  constructors
    TopLevel: Ex -> Ex

rules
  js: TopLevel(x) -> $[const Stdio = {
    receives: v => { process.stdout.write(String(v)); return Stdio; }
  }
  [<js>x]]

  js: Stdio() -> $[Stdio]
  js: Int(x) -> x
  js: Sum(x) -> $[[<js>x].reduce((v,w) => v+w)]
  js: Receives(x, y) -> $[[<js>x].receives([<js>y])]
  js: [] -> $<[]>
  js: [x | xs] -> $<[<<js>x><<jstail>xs>]>

strategies
  // wrap expression in a toplevel and then apply code generation
  javascript = !TopLevel(<id>); js

  // translate each element of a list, prepending each with ',', and concatenate
  jstail = foldr(!"", \ (x,y) -> $<, <<js>x><y>> \)

  // Interface javascript code generation with editor services and file system
  to-javascript: (selected, _, _, path, project-path) -> (filename, result)
    with filename := <guarantee-extension(|"js")> path
       ; result   := <javascript> selected