import GolangLean.Token
import GolangLean.Error

namespace GolangLean

/-! # Scanner — port of `go/scanner/scanner.go`.

Stub. The real implementation is a hand-written DFA over UTF-8 byte input,
faithful to the upstream Go scanner. We start with a `notImpl` sentinel so
the project compiles, then fill in token-by-token alongside the parser. -/

partial def scan (src : String) : Except GoError (Array Token) := do
  if src.isEmpty then
    return #[⟨.eof, ⟨1, 1, 0⟩⟩]
  else
    .error (.notImpl "Scanner.scan: see go-upstream/src/go/scanner/scanner.go")

end GolangLean