mono/shared/sx/ref/render.sx

;; ==========================================================================
;; render.sx — Reference rendering specification
;;
;; Defines how evaluated SX expressions become output (DOM nodes, HTML
;; strings, or SX wire format). Each target provides a renderer adapter
;; that implements the platform-specific output operations.
;;
;; Three rendering modes (matching the Python/JS implementations):
;;
;;   1. render-to-dom   — produces DOM nodes (browser only)
;;   2. render-to-html  — produces HTML string (server)
;;   3. render-to-sx    — produces SX wire format (server → client)
;;
;; This file specifies the LOGIC of rendering. Platform-specific
;; operations are declared as interfaces at the bottom.
;; ==========================================================================


;; --------------------------------------------------------------------------
;; HTML tag registry
;; --------------------------------------------------------------------------
;; Tags known to the renderer. Unknown names are treated as function calls.
;; Void elements self-close (no children). Boolean attrs emit name only.

(define HTML_TAGS
  (list
    ;; Document
    "html" "head" "body" "title" "meta" "link" "script" "style" "noscript"
    ;; Sections
    "header" "nav" "main" "section" "article" "aside" "footer"
    "h1" "h2" "h3" "h4" "h5" "h6" "hgroup"
    ;; Block
    "div" "p" "blockquote" "pre" "figure" "figcaption" "address" "details" "summary"
    ;; Inline
    "a" "span" "em" "strong" "small" "b" "i" "u" "s" "mark" "sub" "sup"
    "abbr" "cite" "code" "time" "br" "wbr" "hr"
    ;; Lists
    "ul" "ol" "li" "dl" "dt" "dd"
    ;; Tables
    "table" "thead" "tbody" "tfoot" "tr" "th" "td" "caption" "colgroup" "col"
    ;; Forms
    "form" "input" "textarea" "select" "option" "optgroup" "button" "label"
    "fieldset" "legend" "output" "datalist"
    ;; Media
    "img" "video" "audio" "source" "picture" "canvas" "iframe"
    ;; SVG
    "svg" "path" "circle" "rect" "line" "polyline" "polygon" "text"
    "g" "defs" "use" "clipPath" "mask" "pattern" "linearGradient"
    "radialGradient" "stop" "filter" "feGaussianBlur" "feOffset"
    "feBlend" "feColorMatrix" "feComposite" "feMerge" "feMergeNode"
    "animate" "animateTransform" "foreignObject"
    ;; Other
    "template" "slot" "dialog" "menu"))

(define VOID_ELEMENTS
  (list "area" "base" "br" "col" "embed" "hr" "img" "input"
        "link" "meta" "param" "source" "track" "wbr"))

(define BOOLEAN_ATTRS
  (list "disabled" "checked" "selected" "readonly" "required" "hidden"
        "autofocus" "autoplay" "controls" "loop" "muted" "defer" "async"
        "novalidate" "formnovalidate" "multiple" "open" "allowfullscreen"))


;; --------------------------------------------------------------------------
;; render-to-html — server-side HTML rendering
;; --------------------------------------------------------------------------

(define render-to-html
  (fn (expr env)
    (let ((result (trampoline (eval-expr expr env))))
      (render-value-to-html result env))))

(define render-value-to-html
  (fn (val env)
    (case (type-of val)
      "nil"     ""
      "string"  (escape-html val)
      "number"  (str val)
      "boolean" (if val "true" "false")
      "list"    (render-list-to-html val env)
      "raw-html" (raw-html-content val)
      :else     (escape-html (str val)))))

(define render-list-to-html
  (fn (expr env)
    (if (empty? expr)
      ""
      (let ((head (first expr)))
        (if (not (= (type-of head) "symbol"))
          ;; Data list — render each item
          (join "" (map (fn (x) (render-value-to-html x env)) expr))
          (let ((name (symbol-name head))
                (args (rest expr)))
            (cond
              ;; Fragment
              (= name "<>")
                (join "" (map (fn (x) (render-to-html x env)) args))

              ;; Raw HTML passthrough
              (= name "raw!")
                (join "" (map (fn (x) (str (trampoline (eval-expr x env)))) args))

              ;; HTML tag
              (contains? HTML_TAGS name)
                (render-html-element name args env)

              ;; Component call (~name)
              (starts-with? name "~")
                (let ((comp (env-get env name)))
                  (if (component? comp)
                    (render-to-html
                      (trampoline (call-component comp args env))
                      env)
                    (error (str "Unknown component: " name))))

              ;; Macro expansion
              (and (env-has? env name) (macro? (env-get env name)))
                (render-to-html
                  (trampoline
                    (eval-expr
                      (expand-macro (env-get env name) args env)
                      env))
                  env)

              ;; Special form / function call — evaluate then render result
              :else
                (render-value-to-html
                  (trampoline (eval-expr expr env))
                  env))))))))


(define render-html-element
  (fn (tag args env)
    (let ((parsed (parse-element-args args env))
          (attrs  (first parsed))
          (children (nth parsed 1))
          (is-void (contains? VOID_ELEMENTS tag)))
      (str "<" tag
        (render-attrs attrs)
        (if is-void
          " />"
          (str ">"
            (join "" (map (fn (c) (render-to-html c env)) children))
            "</" tag ">"))))))


(define parse-element-args
  (fn (args env)
    ;; Parse (:key val :key2 val2 child1 child2) into (attrs-dict children-list)
    (let ((attrs (dict))
          (children (list)))
      (reduce
        (fn (state arg)
          (let ((skip (get state "skip")))
            (if skip
              (assoc state "skip" false)
              (if (and (= (type-of arg) "keyword")
                       (< (inc (get state "i")) (len args)))
                (let ((val (trampoline (eval-expr (nth args (inc (get state "i"))) env))))
                  (dict-set! attrs (keyword-name arg) val)
                  (assoc state "skip" true "i" (inc (get state "i"))))
                (do
                  (append! children arg)
                  (assoc state "i" (inc (get state "i"))))))))
        (dict "i" 0 "skip" false)
        args)
      (list attrs children))))


(define render-attrs
  (fn (attrs)
    (join ""
      (map
        (fn (key)
          (let ((val (dict-get attrs key)))
            (cond
              ;; Boolean attrs
              (and (contains? BOOLEAN_ATTRS key) val)
                (str " " key)
              (and (contains? BOOLEAN_ATTRS key) (not val))
                ""
              ;; Nil values — skip
              (nil? val) ""
              ;; Normal attr
              :else (str " " key "=\"" (escape-attr (str val)) "\""))))
        (keys attrs)))))


;; --------------------------------------------------------------------------
;; render-to-sx — server-side SX wire format (for client rendering)
;; --------------------------------------------------------------------------
;; This mode serializes the expression as SX source text.
;; Component calls are NOT expanded — they're sent to the client.
;; HTML tags are serialized as-is. Special forms are evaluated.

(define render-to-sx
  (fn (expr env)
    (let ((result (aser expr env)))
      (serialize result))))

(define aser
  (fn (expr env)
    ;; Evaluate for SX wire format — serialize rendering forms,
    ;; evaluate control flow and function calls.
    (case (type-of expr)
      "number"  expr
      "string"  expr
      "boolean" expr
      "nil"     nil

      "symbol"
        (let ((name (symbol-name expr)))
          (cond
            (env-has? env name)     (env-get env name)
            (primitive? name)       (get-primitive name)
            (= name "true")        true
            (= name "false")       false
            (= name "nil")         nil
            :else (error (str "Undefined symbol: " name))))

      "keyword" (keyword-name expr)

      "list"
        (if (empty? expr)
          (list)
          (aser-list expr env))

      :else expr)))


(define aser-list
  (fn (expr env)
    (let ((head (first expr))
          (args (rest expr)))
      (if (not (= (type-of head) "symbol"))
        (map (fn (x) (aser x env)) expr)
        (let ((name (symbol-name head)))
          (cond
            ;; Fragment — serialize children
            (= name "<>")
              (aser-fragment args env)

            ;; Component call — serialize WITHOUT expanding
            (starts-with? name "~")
              (aser-call name args env)

            ;; HTML tag — serialize
            (contains? HTML_TAGS name)
              (aser-call name args env)

            ;; Special/HO forms — evaluate (produces data)
            (or (special-form? name) (ho-form? name))
              (aser-special name expr env)

            ;; Macro — expand then aser
            (and (env-has? env name) (macro? (env-get env name)))
              (aser (expand-macro (env-get env name) args env) env)

            ;; Function call — evaluate fully
            :else
              (let ((f (trampoline (eval-expr head env)))
                    (evaled-args (map (fn (a) (trampoline (eval-expr a env))) args)))
                (cond
                  (and (callable? f) (not (lambda? f)) (not (component? f)))
                    (apply f evaled-args)
                  (lambda? f)
                    (trampoline (call-lambda f evaled-args env))
                  (component? f)
                    (aser-call (str "~" (component-name f)) args env)
                  :else (error (str "Not callable: " (inspect f)))))))))))


(define aser-fragment
  (fn (children env)
    ;; Serialize (<> child1 child2 ...) to sx source string
    (let ((parts (filter
                   (fn (x) (not (nil? x)))
                   (map (fn (c) (aser c env)) children))))
      (if (empty? parts)
        ""
        (str "(<> " (join " " (map serialize parts)) ")")))))


(define aser-call
  (fn (name args env)
    ;; Serialize (name :key val child ...) — evaluate args but keep as sx
    (let ((parts (list name)))
      (reduce
        (fn (state arg)
          (let ((skip (get state "skip")))
            (if skip
              (assoc state "skip" false)
              (if (and (= (type-of arg) "keyword")
                       (< (inc (get state "i")) (len args)))
                (let ((val (aser (nth args (inc (get state "i"))) env)))
                  (when (not (nil? val))
                    (append! parts (str ":" (keyword-name arg)))
                    (append! parts (serialize val)))
                  (assoc state "skip" true "i" (inc (get state "i"))))
                (let ((val (aser arg env)))
                  (when (not (nil? val))
                    (append! parts (serialize val)))
                  (assoc state "i" (inc (get state "i"))))))))
        (dict "i" 0 "skip" false)
        args)
      (str "(" (join " " parts) ")"))))


;; --------------------------------------------------------------------------
;; Platform rendering interface
;; --------------------------------------------------------------------------
;;
;; HTML rendering (server targets):
;;   (escape-html s)           → HTML-escaped string
;;   (escape-attr s)           → attribute-value-escaped string
;;   (raw-html-content r)      → unwrap RawHTML marker to string
;;
;; DOM rendering (browser target):
;;   (create-element tag)      → DOM Element
;;   (create-text-node s)      → DOM Text
;;   (create-fragment)         → DOM DocumentFragment
;;   (set-attribute el k v)    → void
;;   (append-child parent c)   → void
;;
;; Serialization:
;;   (serialize val)           → SX source string representation of val
;;
;; Form classification:
;;   (special-form? name)      → boolean
;;   (ho-form? name)           → boolean
;;   (aser-special name expr env) → evaluate special/HO form through aser
;; --------------------------------------------------------------------------