;; ==========================================================================
;; deps.sx — Component dependency analysis specification
;;
;; Pure functions for analyzing component dependency graphs.
;; Used by the bundling system to compute per-page component bundles
;; instead of sending every definition to every page.
;;
;; All functions are pure — no IO, no platform-specific operations.
;; Each host bootstraps this to native code alongside eval.sx/render.sx.
;;
;; From eval.sx platform (already provided by every host):
;;   (type-of x)          → type string
;;   (symbol-name s)      → string name of symbol
;;   (component-body c)   → unevaluated AST of component body
;;   (component-name c)   → string name (without ~)
;;   (macro-body m)       → macro body AST
;;   (env-get env k)      → value or nil
;;
;; New platform functions for deps (each host implements):
;;   (component-deps c)       → cached deps list (may be empty)
;;   (component-set-deps! c d)→ cache deps on component
;;   (component-css-classes c)→ pre-scanned CSS class list
;;   (regex-find-all pat src) → list of capture group 1 matches
;;   (scan-css-classes src)   → list of CSS class strings from source
;; ==========================================================================


;; --------------------------------------------------------------------------
;; 1. AST scanning — collect ~component references from an AST node
;; --------------------------------------------------------------------------
;; Walks all branches of control flow (if/when/cond/case) to find
;; every component that *could* be rendered.

(define scan-refs :effects []
  (fn (node)
    (let ((refs (list)))
      (scan-refs-walk node refs)
      refs)))


(define scan-refs-walk :effects []
  (fn (node (refs :as list))
    (cond
      ;; Symbol starting with ~ → component reference
      (= (type-of node) "symbol")
        (let ((name (symbol-name node)))
          (when (starts-with? name "~")
            (when (not (contains? refs name))
              (append! refs name))))

      ;; List → recurse into all elements (covers all control flow branches)
      (= (type-of node) "list")
        (for-each (fn (item) (scan-refs-walk item refs)) node)

      ;; Dict → recurse into values
      (= (type-of node) "dict")
        (for-each (fn (key) (scan-refs-walk (dict-get node key) refs))
                  (keys node))

      ;; Literals (number, string, boolean, nil, keyword) → no refs
      :else nil)))


;; --------------------------------------------------------------------------
;; 2. Transitive dependency closure
;; --------------------------------------------------------------------------
;; Given a component name and an environment, compute all components
;; that it can transitively render.  Handles cycles via seen-set.

(define transitive-deps-walk :effects []
  (fn ((n :as string) (seen :as list) (env :as dict))
    (when (not (contains? seen n))
      (append! seen n)
      (let ((val (env-get env n)))
        (cond
          (or (= (type-of val) "component") (= (type-of val) "island"))
            (for-each (fn ((ref :as string)) (transitive-deps-walk ref seen env))
                      (scan-refs (component-body val)))
          (= (type-of val) "macro")
            (for-each (fn ((ref :as string)) (transitive-deps-walk ref seen env))
                      (scan-refs (macro-body val)))
          :else nil)))))


(define transitive-deps :effects []
  (fn ((name :as string) (env :as dict))
    (let ((seen (list))
          (key (if (starts-with? name "~") name (str "~" name))))
      (transitive-deps-walk key seen env)
      (filter (fn ((x :as string)) (not (= x key))) seen))))


;; --------------------------------------------------------------------------
;; 3. Compute deps for all components in an environment
;; --------------------------------------------------------------------------
;; Iterates env, calls transitive-deps for each component, and
;; stores the result via the platform's component-set-deps! function.
;;
;; Platform interface:
;;   (env-components env) → list of component names in env
;;   (component-set-deps! comp deps) → store deps on component

(define compute-all-deps :effects [mutation]
  (fn ((env :as dict))
    (for-each
      (fn ((name :as string))
        (let ((val (env-get env name)))
          (when (or (= (type-of val) "component") (= (type-of val) "island"))
            (component-set-deps! val (transitive-deps name env)))))
      (env-components env))))


;; --------------------------------------------------------------------------
;; 4. Scan serialized SX source for component references
;; --------------------------------------------------------------------------
;; Regex-based extraction of (~name patterns from SX wire format.
;; Returns list of names WITH ~ prefix.
;;
;; Platform interface:
;;   (regex-find-all pattern source) → list of matched group strings

(define scan-components-from-source :effects []
  (fn ((source :as string))
    (let ((matches (regex-find-all "\\(~([a-zA-Z_][a-zA-Z0-9_\\-:/]*)" source)))
      (map (fn ((m :as string)) (str "~" m)) matches))))


;; --------------------------------------------------------------------------
;; 5. Components needed for a page
;; --------------------------------------------------------------------------
;; Scans page source for direct component references, then computes
;; the transitive closure.  Returns list of ~names.

(define components-needed :effects []
  (fn ((page-source :as string) (env :as dict))
    (let ((direct (scan-components-from-source page-source))
          (all-needed (list)))

      ;; Add each direct ref + its transitive deps
      (for-each
        (fn ((name :as string))
          (when (not (contains? all-needed name))
            (append! all-needed name))
          (let ((val (env-get env name)))
            (let ((deps (if (and (= (type-of val) "component")
                                 (not (empty? (component-deps val))))
                          (component-deps val)
                          (transitive-deps name env))))
              (for-each
                (fn ((dep :as string))
                  (when (not (contains? all-needed dep))
                    (append! all-needed dep)))
                deps))))
        direct)

      all-needed)))


;; --------------------------------------------------------------------------
;; 6. Build per-page component bundle
;; --------------------------------------------------------------------------
;; Given page source and env, returns list of component names needed.
;; The host uses this list to serialize only the needed definitions
;; and compute a page-specific hash.
;;
;; This replaces the "send everything" approach with per-page bundles.

(define page-component-bundle :effects []
  (fn ((page-source :as string) (env :as dict))
    (components-needed page-source env)))


;; --------------------------------------------------------------------------
;; 7. CSS classes for a page
;; --------------------------------------------------------------------------
;; Returns the union of CSS classes from components this page uses,
;; plus classes from the page source itself.
;;
;; Platform interface:
;;   (component-css-classes c) → set/list of class strings
;;   (scan-css-classes source) → set/list of class strings from source

(define page-css-classes :effects []
  (fn ((page-source :as string) (env :as dict))
    (let ((needed (components-needed page-source env))
          (classes (list)))

      ;; Collect classes from needed components
      (for-each
        (fn ((name :as string))
          (let ((val (env-get env name)))
            (when (= (type-of val) "component")
              (for-each
                (fn ((cls :as string))
                  (when (not (contains? classes cls))
                    (append! classes cls)))
                (component-css-classes val)))))
        needed)

      ;; Add classes from page source
      (for-each
        (fn ((cls :as string))
          (when (not (contains? classes cls))
            (append! classes cls)))
        (scan-css-classes page-source))

      classes)))


;; --------------------------------------------------------------------------
;; 8. IO detection — scan component ASTs for IO primitive references
;; --------------------------------------------------------------------------
;; Extends the dependency walker to detect references to IO primitives.
;; IO names are provided by the host (from boundary.sx declarations).
;; A component is "pure" if it (transitively) references no IO primitives.
;;
;; Platform interface additions:
;;   (component-io-refs c)        → cached IO ref list (may be empty)
;;   (component-set-io-refs! c r) → cache IO refs on component

(define scan-io-refs-walk :effects []
  (fn (node (io-names :as list) (refs :as list))
    (cond
      ;; Symbol → check if name is in the IO set
      (= (type-of node) "symbol")
        (let ((name (symbol-name node)))
          (when (contains? io-names name)
            (when (not (contains? refs name))
              (append! refs name))))

      ;; List → recurse into all elements
      (= (type-of node) "list")
        (for-each (fn (item) (scan-io-refs-walk item io-names refs)) node)

      ;; Dict → recurse into values
      (= (type-of node) "dict")
        (for-each (fn (key) (scan-io-refs-walk (dict-get node key) io-names refs))
                  (keys node))

      ;; Literals → no IO refs
      :else nil)))


(define scan-io-refs :effects []
  (fn (node (io-names :as list))
    (let ((refs (list)))
      (scan-io-refs-walk node io-names refs)
      refs)))


;; --------------------------------------------------------------------------
;; 9. Transitive IO refs — follow component deps and union IO refs
;; --------------------------------------------------------------------------

(define transitive-io-refs-walk :effects []
  (fn ((n :as string) (seen :as list) (all-refs :as list) (env :as dict) (io-names :as list))
    (when (not (contains? seen n))
      (append! seen n)
      (let ((val (env-get env n)))
        (cond
          (= (type-of val) "component")
            (do
              ;; Scan this component's body for IO refs
              (for-each
                (fn ((ref :as string))
                  (when (not (contains? all-refs ref))
                    (append! all-refs ref)))
                (scan-io-refs (component-body val) io-names))
              ;; Recurse into component deps
              (for-each
                (fn ((dep :as string)) (transitive-io-refs-walk dep seen all-refs env io-names))
                (scan-refs (component-body val))))

          (= (type-of val) "macro")
            (do
              (for-each
                (fn ((ref :as string))
                  (when (not (contains? all-refs ref))
                    (append! all-refs ref)))
                (scan-io-refs (macro-body val) io-names))
              (for-each
                (fn ((dep :as string)) (transitive-io-refs-walk dep seen all-refs env io-names))
                (scan-refs (macro-body val))))

          :else nil)))))


(define transitive-io-refs :effects []
  (fn ((name :as string) (env :as dict) (io-names :as list))
    (let ((all-refs (list))
          (seen (list))
          (key (if (starts-with? name "~") name (str "~" name))))
      (transitive-io-refs-walk key seen all-refs env io-names)
      all-refs)))


;; --------------------------------------------------------------------------
;; 10. Compute IO refs for all components in an environment
;; --------------------------------------------------------------------------

(define compute-all-io-refs :effects [mutation]
  (fn ((env :as dict) (io-names :as list))
    (for-each
      (fn ((name :as string))
        (let ((val (env-get env name)))
          (when (= (type-of val) "component")
            (component-set-io-refs! val (transitive-io-refs name env io-names)))))
      (env-components env))))


(define component-io-refs-cached :effects []
  (fn ((name :as string) (env :as dict) (io-names :as list))
    (let ((key (if (starts-with? name "~") name (str "~" name))))
      (let ((val (env-get env key)))
        (if (and (= (type-of val) "component")
                 (not (nil? (component-io-refs val)))
                 (not (empty? (component-io-refs val))))
          (component-io-refs val)
          ;; Fallback: not yet cached (shouldn't happen after compute-all-io-refs)
          (transitive-io-refs name env io-names))))))

(define component-pure? :effects []
  (fn ((name :as string) (env :as dict) (io-names :as list))
    (let ((key (if (starts-with? name "~") name (str "~" name))))
      (let ((val (env-get env key)))
        (if (and (= (type-of val) "component")
                 (not (nil? (component-io-refs val))))
          ;; Use cached io-refs (empty list = pure)
          (empty? (component-io-refs val))
          ;; Fallback
          (empty? (transitive-io-refs name env io-names)))))))


;; --------------------------------------------------------------------------
;; 5. Render target — boundary decision per component
;; --------------------------------------------------------------------------
;; Combines IO analysis with affinity annotations to decide where a
;; component should render:
;;
;;   :affinity :server  → always "server" (auth-sensitive, secrets)
;;   :affinity :client  → "client" even if IO-dependent (IO proxy)
;;   :affinity :auto    → "server" if IO-dependent, "client" if pure
;;
;; Returns: "server" | "client"

(define render-target :effects []
  (fn ((name :as string) (env :as dict) (io-names :as list))
    (let ((key (if (starts-with? name "~") name (str "~" name))))
      (let ((val (env-get env key)))
        (if (not (= (type-of val) "component"))
          "server"
          (let ((affinity (component-affinity val)))
            (cond
              (= affinity "server") "server"
              (= affinity "client") "client"
              ;; auto: decide from IO analysis
              (not (component-pure? name env io-names)) "server"
              :else "client")))))))


;; --------------------------------------------------------------------------
;; 6. Page render plan — pre-computed boundary decisions for a page
;; --------------------------------------------------------------------------
;; Given page source + env + IO names, returns a render plan dict:
;;
;;   {:components {~name "server"|"client" ...}
;;    :server     (list of ~names that render server-side)
;;    :client     (list of ~names that render client-side)
;;    :io-deps    (list of IO primitives needed by server components)}
;;
;; This is computed once at page registration and cached on the page def.
;; The async evaluator and client router both use it to make decisions
;; without recomputing at every request.

(define page-render-plan :effects []
  (fn ((page-source :as string) (env :as dict) (io-names :as list))
    (let ((needed (components-needed page-source env))
          (comp-targets (dict))
          (server-list (list))
          (client-list (list))
          (io-deps (list)))

      (for-each
        (fn ((name :as string))
          (let ((target (render-target name env io-names)))
            (dict-set! comp-targets name target)
            (if (= target "server")
              (do
                (append! server-list name)
                ;; Collect IO deps from server components (use cache)
                (for-each
                  (fn ((io-ref :as string))
                    (when (not (contains? io-deps io-ref))
                      (append! io-deps io-ref)))
                  (component-io-refs-cached name env io-names)))
              (append! client-list name))))
        needed)

      {:components comp-targets
       :server server-list
       :client client-list
       :io-deps io-deps})))


;; --------------------------------------------------------------------------
;; Host obligation: selective expansion in async partial evaluation
;; --------------------------------------------------------------------------
;; The spec classifies components as pure or IO-dependent and provides
;; per-component render-target decisions. Each host's async partial
;; evaluator (the server-side rendering path that bridges sync evaluation
;; with async IO) must use this classification:
;;
;;   render-target "server" → expand server-side (IO must resolve)
;;   render-target "client" → serialize for client (can render anywhere)
;;   Layout slot context    → expand all (server needs full HTML)
;;
;; The spec provides: component-io-refs, component-pure?, render-target,
;; component-affinity. The host provides the async runtime that acts on it.
;; This is not SX semantics — it is host infrastructure. Every host
;; with a server-side async evaluator implements the same rule.
;; --------------------------------------------------------------------------


;; --------------------------------------------------------------------------
;; Platform interface summary
;; --------------------------------------------------------------------------
;;
;; From eval.sx (already provided):
;;   (type-of x)          → type string
;;   (symbol-name s)      → string name of symbol
;;   (env-get env k)      → value or nil
;;
;; New for deps.sx (each host implements):
;;   (component-body c)       → AST body of component
;;   (component-name c)       → name string
;;   (component-deps c)       → cached deps list (may be empty)
;;   (component-set-deps! c d)→ cache deps on component
;;   (component-css-classes c)→ pre-scanned CSS class list
;;   (component-io-refs c)       → cached IO ref list (may be empty)
;;   (component-set-io-refs! c r)→ cache IO refs on component
;;   (component-affinity c)      → "auto" | "client" | "server"
;;   (macro-body m)           → AST body of macro
;;   (regex-find-all pat src) → list of capture group matches
;;   (scan-css-classes src)   → list of CSS class strings from source
;; --------------------------------------------------------------------------


;; --------------------------------------------------------------------------
;; env-components — list component/macro names in an environment
;; --------------------------------------------------------------------------
;; Moved from platform to spec: pure logic using type predicates.

(define env-components :effects []
  (fn ((env :as dict))
    (filter
      (fn ((k :as string))
        (let ((v (env-get env k)))
          (or (component? v) (macro? v))))
      (keys env))))