;;;; String: owned, growable, always valid UTF-8. Multi-byte append, insert
;;;; and remove by character position, iteration by runes, the byte length
;;;; beside the character count, a copy, printing inside a structure, and a
;;;; String crossing into dyn as a copy of its text.

(defstruct Named [label String  n i32])

(defn as-dyn [d] dyn d)

(defn main [] i32
  (let [s (string-new "héllo")]
    (append s " wörld")
    (append s 0x65e5)          ; 日, three bytes
    (append s \!)
    (println s)
    (println (length s) (rune-count s))
    ;; Positions are characters: 1 is after the h, whatever é takes.
    (insert s 1 "→")
    (insert s 0 0x1f600)       ; four bytes at the front
    (println s)
    (println (remove s 2))     ; the → that was inserted, as a code point
    (println (remove s 0))     ; the emoji
    (println s)
    ;; Appending a String to itself reads the bytes it had before growing.
    (let [t (string-new "ab")]
      (append t t)
      (append t t)
      (println t (length t))
      (free t))
    ;; Iteration by runes.
    (let [it (runes s)
          going true
          n 0]
      (while going
        (match (runes-next (addr it))
          (Some c) (do (when (> c 127) (print c "")) (set n (+ n 1)))
          None (set going false)))
      (println n))
    ;; A copy is independent of the original.
    (let [c (clone s)]
      (append c "?")
      (println (length s) (length c))
      (free c))
    ;; The str view and the byte view cost nothing.
    (println (= (str s) "héllo wörld日!"))
    (println (length (bytes-view s)))
    ;; Inside a structure it prints quoted, as a str field does.
    (let [m (Named {.label (string-new "x") .n 3})]
      (println m)
      (free (.label m)))
    ;; Crossing into dyn copies the text, which the dyn side then owns.
    (let [d (as-dyn s)]
      (append s "tail")
      (println d)
      (println (type-of d)))
    ;; The builders answer Strings.
    (let [j (join (slice [(bytes-view "a") (bytes-view "b")]) (bytes-view "-"))]
      (println j)
      (free j))
    (let [e (string-new)]
      (println (length e) (rune-count e))
      (free e))
    (free s))
  0)