;; Common Lisp reader — converts token stream to CL AST forms.
;;
;; Depends on: lib/common-lisp/reader.sx  (cl-tokenize)
;;
;; AST representation:
;;   integer/float         → SX number (or {:cl-type "float"/:ratio ...})
;;   string                → SX string
;;   symbol FOO            → SX string "FOO"  (upcase)
;;   symbol NIL            → nil
;;   symbol T              → true
;;   :keyword              → {:cl-type "keyword" :name "FOO"}
;;   #\char                → {:cl-type "char"    :value "a"}
;;   #:uninterned          → {:cl-type "uninterned" :name "FOO"}
;;   ratio 1/3             → {:cl-type "ratio"   :value "1/3"}
;;   float 3.14            → {:cl-type "float"   :value "3.14"}
;;   proper list (a b c)   → SX list (a b c)
;;   dotted pair (a . b)   → {:cl-type "cons" :car a :cdr b}
;;   vector #(a b)         → {:cl-type "vector" :elements (list a b)}
;;   'x                    → ("QUOTE" x)
;;   `x                    → ("QUASIQUOTE" x)
;;   ,x                    → ("UNQUOTE" x)
;;   ,@x                   → ("UNQUOTE-SPLICING" x)
;;   #'x                   → ("FUNCTION" x)
;;
;; Public API:
;;   (cl-read src)         — parse first form from string, return form
;;   (cl-read-all src)     — parse all top-level forms, return list

;; ── number conversion ─────────────────────────────────────────────

(define
  cl-hex-val
  (fn
    (c)
    (let
      ((o (cl-ord c)))
      (cond
        ((and (>= o 48) (<= o 57)) (- o 48))
        ((and (>= o 65) (<= o 70)) (+ 10 (- o 65)))
        ((and (>= o 97) (<= o 102)) (+ 10 (- o 97)))
        (:else 0)))))

(define
  cl-parse-radix-str
  (fn
    (s radix start)
    (let
      ((n (string-length s)) (i start) (acc 0))
      (define
        loop
        (fn
          ()
          (when
            (< i n)
            (do
              (set! acc (+ (* acc radix) (cl-hex-val (substring s i (+ i 1)))))
              (set! i (+ i 1))
              (loop)))))
      (loop)
      acc)))

(define
  cl-convert-integer
  (fn
    (s)
    (let
      ((n (string-length s)) (neg false))
      (cond
        ((and (> n 2) (= (substring s 0 1) "#"))
          (let
            ((letter (downcase (substring s 1 2))))
            (cond
              ((= letter "x") (cl-parse-radix-str s 16 2))
              ((= letter "b") (cl-parse-radix-str s 2 2))
              ((= letter "o") (cl-parse-radix-str s 8 2))
              (:else (parse-int s 0)))))
        (:else (parse-int s 0))))))

;; ── reader ────────────────────────────────────────────────────────

;; Read one form from token list.
;; Returns {:form F :rest remaining-toks} or {:form nil :rest toks :eof true}
(define
  cl-read-form
  (fn
    (toks)
    (if
      (not toks)
      {:form nil :rest toks :eof true}
      (let
        ((tok (nth toks 0)) (nxt (rest toks)))
        (let
          ((type (get tok "type")) (val (get tok "value")))
          (cond
            ((= type "eof") {:form nil :rest toks :eof true})
            ((= type "integer") {:form (cl-convert-integer val) :rest nxt})
            ((= type "float") {:form {:cl-type "float" :value val} :rest nxt})
            ((= type "ratio") {:form {:cl-type "ratio" :value val} :rest nxt})
            ((= type "string") {:form val :rest nxt})
            ((= type "char") {:form {:cl-type "char" :value val} :rest nxt})
            ((= type "keyword") {:form {:cl-type "keyword" :name val} :rest nxt})
            ((= type "uninterned") {:form {:cl-type "uninterned" :name val} :rest nxt})
            ((= type "symbol")
              (cond
                ((= val "NIL") {:form nil :rest nxt})
                ((= val "T") {:form true :rest nxt})
                (:else {:form val :rest nxt})))
            ;; list forms
            ((= type "lparen") (cl-read-list nxt))
            ((= type "hash-paren") (cl-read-vector nxt))
            ;; reader macros that wrap the next form
            ((= type "quote") (cl-read-wrap "QUOTE" nxt))
            ((= type "backquote") (cl-read-wrap "QUASIQUOTE" nxt))
            ((= type "comma") (cl-read-wrap "UNQUOTE" nxt))
            ((= type "comma-at") (cl-read-wrap "UNQUOTE-SPLICING" nxt))
            ((= type "hash-quote") (cl-read-wrap "FUNCTION" nxt))
            ;; skip unrecognised tokens
            (:else (cl-read-form nxt))))))))

;; Wrap next form in a list: (name form)
(define
  cl-read-wrap
  (fn
    (name toks)
    (let
      ((inner (cl-read-form toks)))
      {:form (list name (get inner "form")) :rest (get inner "rest")})))

;; Read list forms until ')'; handles dotted pair (a . b)
;; Called after consuming '('
(define
  cl-read-list
  (fn
    (toks)
    (let
      ((result (cl-read-list-items toks (list))))
      {:form (get result "items") :rest (get result "rest")})))

(define
  cl-read-list-items
  (fn
    (toks acc)
    (if
      (not toks)
      {:items acc :rest toks}
      (let
        ((tok (nth toks 0)))
        (let
          ((type (get tok "type")))
          (cond
            ((= type "eof") {:items acc :rest toks})
            ((= type "rparen") {:items acc :rest (rest toks)})
            ;; dotted pair: read one more form then expect ')'
            ((= type "dot")
              (let
                ((cdr-result (cl-read-form (rest toks))))
                (let
                  ((cdr-form (get cdr-result "form"))
                    (after-cdr (get cdr-result "rest")))
                  ;; skip the closing ')'
                  (let
                    ((close (if after-cdr (nth after-cdr 0) nil)))
                    (let
                      ((remaining
                          (if
                            (and close (= (get close "type") "rparen"))
                            (rest after-cdr)
                            after-cdr)))
                      ;; build dotted structure
                      (let
                        ((dotted (cl-build-dotted acc cdr-form)))
                        {:items dotted :rest remaining}))))))
            (:else
              (let
                ((item (cl-read-form toks)))
                (cl-read-list-items
                  (get item "rest")
                  (concat acc (list (get item "form"))))))))))))

;; Build dotted form: (a b . c) → ((DOTTED a b) . c) style
;; In CL (a b c . d) means a proper dotted structure.
;; We represent it as {:cl-type "cons" :car a :cdr (list->dotted b c d)}
(define
  cl-build-dotted
  (fn
    (head-items tail)
    (if
      (= (len head-items) 0)
      tail
      (if
        (= (len head-items) 1)
        {:cl-type "cons" :car (nth head-items 0) :cdr tail}
        (let
          ((last-item (nth head-items (- (len head-items) 1)))
            (but-last (slice head-items 0 (- (len head-items) 1))))
          {:cl-type "cons"
            :car (cl-build-dotted but-last (list last-item))
            :cdr tail})))))

;; Read vector #(…) elements until ')'
(define
  cl-read-vector
  (fn
    (toks)
    (let
      ((result (cl-read-vector-items toks (list))))
      {:form {:cl-type "vector" :elements (get result "items")} :rest (get result "rest")})))

(define
  cl-read-vector-items
  (fn
    (toks acc)
    (if
      (not toks)
      {:items acc :rest toks}
      (let
        ((tok (nth toks 0)))
        (let
          ((type (get tok "type")))
          (cond
            ((= type "eof") {:items acc :rest toks})
            ((= type "rparen") {:items acc :rest (rest toks)})
            (:else
              (let
                ((item (cl-read-form toks)))
                (cl-read-vector-items
                  (get item "rest")
                  (concat acc (list (get item "form"))))))))))))

;; ── public API ────────────────────────────────────────────────────

(define
  cl-read
  (fn
    (src)
    (let
      ((toks (cl-tokenize src)))
      (get (cl-read-form toks) "form"))))

(define
  cl-read-all
  (fn
    (src)
    (let
      ((toks (cl-tokenize src)))
      (define
        loop
        (fn
          (toks acc)
          (if
            (or (not toks) (= (get (nth toks 0) "type") "eof"))
            acc
            (let
              ((result (cl-read-form toks)))
              (if
                (get result "eof")
                acc
                (loop (get result "rest") (concat acc (list (get result "form")))))))))
      (loop toks (list)))))