// Minimal tokenizer for Ny v0 (ints, + - * /, ( ), return)

static box Tokenizer {
    tokenize(input) {
        local tokens = new ArrayBox()
        local i = 0
        local n = input.length()
        // helper: skip whitespace
        fn skip_ws() {
            loop(i < n) {
                local ch = input.substring(i, i+1)
                if ch == " " || ch == "\t" || ch == "\r" || ch == "\n" { i = i + 1 } else { return }
            }
        }
        // main loop
        loop(i < n) {
            skip_ws()
            if i >= n { break }
            local ch = input.substring(i, i+1)
            if ch == "+" || ch == "-" || ch == "*" || ch == "/" || ch == "(" || ch == ")" {
                local tok = new MapBox(); tok.set("type", ch)
                tokens.push(tok); i = i + 1; continue
            }
            // keyword: return
            if i + 6 <= n {
                local kw = input.substring(i, i+6)
                if kw == "return" {
                    local t = new MapBox(); t.set("type", "RETURN")
                    tokens.push(t); i = i + 6; continue
                }
            }
            // integer literal
            if ch >= "0" && ch <= "9" {
                local j = i
                loop(j < n) {
                    local cj = input.substring(j, j+1)
                    if cj >= "0" && cj <= "9" { j = j + 1 } else { break }
                }
                local num_str = input.substring(i, j)
                local tnum = new MapBox(); tnum.set("type", "INT"); tnum.set("value", num_str)
                tokens.push(tnum); i = j; continue
            }
            // unknown
            local err = new MapBox(); err.set("version", 0); err.set("kind", "Error")
            local e = new MapBox(); e.set("message", "Unknown token");
            local sp = new MapBox(); sp.set("start", i); sp.set("end", i+1)
            e.set("span", sp); err.set("error", e)
            return err
        }
        // EOF
        local eof = new MapBox(); eof.set("type", "EOF"); tokens.push(eof)
        return tokens
    }
}