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rose-ash/sx/sx/home-stepper.sx
giles cd25f85837
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Imperative code view: spans built once, classes updated on each step
Code view uses a lake with imperative DOM spans. Each token has its
base syntax colour class stored. On each step, update-code-highlight
iterates all spans and sets class based on step-idx: evaluated tokens
go bold, current step gets violet bg, future stays normal.

No reactive re-rendering of the code view — direct DOM class updates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-14 20:47:10 +00:00

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(defisland ~home/stepper ()
(let ((source "(div (~cssx/tw :tokens \"p-6 rounded-lg border border-stone-200 bg-white text-center\")\n (h1 (~cssx/tw :tokens \"text-3xl font-bold mb-2\")\n (span (~cssx/tw :tokens \"text-rose-500\") \"the \")\n (span (~cssx/tw :tokens \"text-amber-500\") \"joy \")\n (span (~cssx/tw :tokens \"text-emerald-500\") \"of \")\n (span (~cssx/tw :tokens \"text-violet-600 text-4xl\") \"sx\")))")
(steps (signal (list)))
(step-idx (signal 0))
(dom-stack-sig (signal (list)))
(code-tokens (signal (list)))
(code-spans (list)))
(letrec
((split-tag (fn (expr result)
(cond
(not (list? expr))
(append! result {"type" "leaf" "expr" expr})
(empty? expr) nil
(not (= (type-of (first expr)) "symbol"))
(append! result {"type" "leaf" "expr" expr})
(is-html-tag? (symbol-name (first expr)))
(let ((ctag (symbol-name (first expr)))
(cargs (rest expr))
(cch (list))
(cat (list))
(spreads (list))
(ckw false))
(for-each (fn (a)
(cond
(= (type-of a) "keyword") (do (set! ckw true) (append! cat a))
ckw (do (set! ckw false) (append! cat a))
(and (list? a) (not (empty? a))
(= (type-of (first a)) "symbol")
(starts-with? (symbol-name (first a)) "~"))
(do (set! ckw false) (append! spreads a))
:else (do (set! ckw false) (append! cch a))))
cargs)
(append! result {"type" "open" "tag" ctag "attrs" cat "spreads" spreads})
(for-each (fn (c) (split-tag c result)) cch)
(append! result {"type" "close" "tag" ctag}))
:else
(append! result {"type" "expr" "expr" expr}))))
(build-code-tokens (fn (expr tokens step-ref indent)
(cond
(string? expr)
(do (append! tokens {"text" (str "\"" expr "\"") "cls" "text-emerald-700" "step" (get step-ref "v")})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(number? expr)
(do (append! tokens {"text" (str expr) "cls" "text-amber-700" "step" (get step-ref "v")})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(= (type-of expr) "keyword")
(append! tokens {"text" (str ":" (keyword-name expr)) "cls" "text-violet-600" "step" (get step-ref "v")})
(= (type-of expr) "symbol")
(let ((name (symbol-name expr)))
(append! tokens {"text" name "cls"
(cond
(is-html-tag? name) "text-sky-700 font-semibold"
(starts-with? name "~") "text-rose-600 font-semibold"
:else "text-stone-700")
"step" (get step-ref "v")}))
(list? expr)
(when (not (empty? expr))
(let ((head (first expr))
(is-tag (and (= (type-of head) "symbol") (is-html-tag? (symbol-name head))))
(is-comp (and (= (type-of head) "symbol") (starts-with? (symbol-name head) "~")))
(open-step (get step-ref "v")))
(append! tokens {"text" "(" "cls" "text-stone-400" "step" open-step})
(when (or is-tag is-comp)
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(build-code-tokens head tokens step-ref indent)
(for-each (fn (a)
(let ((is-child (and (list? a) (not (empty? a))
(= (type-of (first a)) "symbol")
(or (is-html-tag? (symbol-name (first a)))
(starts-with? (symbol-name (first a)) "~")))))
(if (and is-tag is-child)
(do (append! tokens {"text" (str "\n" (join "" (map (fn (_) " ") (range 0 (+ indent 1))))) "cls" "" "step" -1})
(build-code-tokens a tokens step-ref (+ indent 1)))
(do (append! tokens {"text" " " "cls" "" "step" -1})
(build-code-tokens a tokens step-ref indent)))))
(rest expr))
(append! tokens {"text" ")" "cls" "text-stone-400" "step" (if is-tag (get step-ref "v") open-step)})
(when is-tag
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))))
:else nil)))
(get-preview (fn () (dom-query "[data-sx-lake=\"home-preview\"]")))
(get-code-view (fn () (dom-query "[data-sx-lake=\"code-view\"]")))
(get-stack (fn () (deref dom-stack-sig)))
(set-stack (fn (v) (reset! dom-stack-sig v)))
(push-stack (fn (el) (reset! dom-stack-sig (append (deref dom-stack-sig) (list el)))))
(pop-stack (fn ()
(let ((s (deref dom-stack-sig)))
(when (> (len s) 1)
(reset! dom-stack-sig (slice s 0 (- (len s) 1)))))))
(update-code-highlight (fn ()
(let ((cur (deref step-idx)))
(for-each (fn (s)
(let ((step-num (get s "step"))
(el (get s "el"))
(base (get s "cls")))
(when (not (= step-num -1))
(dom-set-attr el "class"
(str base
(cond
(= step-num cur) " bg-violet-100 rounded px-0.5 font-bold"
(< step-num cur) " opacity-50"
:else ""))))))
code-spans))))
(do-step (fn ()
(when (< (deref step-idx) (len (deref steps)))
(when (empty? (get-stack))
(let ((p (get-preview)))
(when p (set-stack (list p)))))
(let ((step (nth (deref steps) (deref step-idx)))
(step-type (get step "type"))
(parent (if (empty? (get-stack)) (get-preview) (last (get-stack)))))
(cond
(= step-type "open")
(let ((el (dom-create-element (get step "tag") nil))
(attrs (get step "attrs"))
(spreads (or (get step "spreads") (list))))
(let loop ((i 0))
(when (< i (len attrs))
(dom-set-attr el (keyword-name (nth attrs i)) (nth attrs (+ i 1)))
(loop (+ i 2))))
(for-each (fn (sp)
(let ((result (eval-expr sp (make-env))))
(when (and result (spread? result))
(let ((sattrs (spread-attrs result)))
(for-each (fn (k)
(if (= k "class")
(dom-set-attr el "class"
(str (or (dom-get-attr el "class") "") " " (get sattrs k)))
(dom-set-attr el k (get sattrs k))))
(keys sattrs))))))
spreads)
(when parent (dom-append parent el))
(push-stack el))
(= step-type "close")
(pop-stack)
(= step-type "leaf")
(when parent
(let ((val (get step "expr")))
(dom-append parent (create-text-node (if (string? val) val (str val))))))
(= step-type "expr")
(let ((rendered (render-to-dom (get step "expr") (make-env) nil)))
(when (and parent rendered)
(dom-append parent rendered)))))
(swap! step-idx inc)
(update-code-highlight))))
(do-back (fn ()
(when (> (deref step-idx) 0)
(let ((target (- (deref step-idx) 1))
(container (get-preview)))
(when container (dom-set-prop container "innerHTML" ""))
(set-stack (list (get-preview)))
(reset! step-idx 0)
(for-each (fn (_) (do-step)) (slice (deref steps) 0 target)))))))
;; Auto-parse via effect
(effect (fn ()
(let ((parsed (sx-parse source)))
(when (not (empty? parsed))
(let ((result (list))
(step-ref (dict "v" 0)))
(split-tag (first parsed) result 0)
(reset! steps result)
;; Build code tokens
(let ((tokens (list)))
(dict-set! step-ref "v" 0)
(build-code-tokens (first parsed) tokens step-ref 0)
(reset! code-tokens tokens)
;; Build code DOM spans
(let ((code-el (get-code-view)))
(when code-el
(dom-set-prop code-el "innerHTML" "")
(set! code-spans (list))
(for-each (fn (tok)
(let ((sp (dom-create-element "span" nil)))
(dom-set-attr sp "class" (get tok "cls"))
(dom-set-prop sp "textContent" (get tok "text"))
(dom-append code-el sp)
(append! code-spans (dict "el" sp "step" (get tok "step") "cls" (get tok "cls")))))
tokens)))))))))
(div :class "space-y-4"
;; Code view lake — spans built imperatively, classes updated on step
(lake :id "code-view" :tag "pre"
:class "text-sm font-mono bg-stone-50 rounded p-4 overflow-x-auto leading-relaxed")
;; Controls
(div :class "flex items-center justify-center gap-2"
(button :on-click (fn (e) (do-back))
:class (str "px-3 py-1.5 rounded text-sm "
(if (> (deref step-idx) 0)
"bg-stone-200 text-stone-700 hover:bg-stone-300"
"bg-stone-100 text-stone-300 cursor-not-allowed"))
"\u25c0")
(button :on-click (fn (e) (do-step))
:class (str "px-3 py-1.5 rounded text-sm "
(if (< (deref step-idx) (len (deref steps)))
"bg-violet-500 text-white hover:bg-violet-600"
"bg-violet-200 text-violet-400 cursor-not-allowed"))
"Step \u25b6")
(span :class "text-xs text-stone-400" (deref step-idx))
(span :class "text-xs text-stone-400" " / 16"))
;; Live preview lake
(lake :id "home-preview")))))