;;;; SPDX-FileCopyrightText: Atlas Engineer LLC
;;;; SPDX-License-Identifier: BSD-3-Clause

(in-package :spinneret)

(defun %nstyle-body (forms)
  (reduce #'uiop:strcat
          (mapcar (lambda (f) (typecase f
                                (list (lass:compile-and-write f))
                                (string f)))
                  forms)))

(deftag :nstyle (body attrs &key &allow-other-keys)
  "Regular <style>, but with contents staying unescaped.
Forms in BODY can be:
- Literal strings --- get concatenated into a stylesheet as is.
- Lists --- get processed by LASS' `lass:compile-and-write' and then
  concatenated."
  `(:style ,@attrs (:raw (theme:with-theme (nyxt::theme nyxt:*browser*)
                           (%nstyle-body (list ,@body))))))

(defun %nscript-body (forms)
  (reduce #'uiop:strcat
          (mapcar (lambda (f) (typecase f
                                (list (ps:ps* f))
                                (string f)))
                  forms)))

(deftag :nscript (body attrs &key &allow-other-keys)
  "Regular <script>, but with contents staying unescaped.
Forms in BODY can be:
- Literal strings --- get concatenated into a stylesheet as is.
- Lists --- get processed by Parenscript's `ps:ps*' and then concatenated."
  `(:script ,@attrs (:raw (%nscript-body (list ,@body)))))

(serapeum:-> %nselect-onchange (string (nyxt:maybe nyxt:buffer) (nyxt:list-of list)) t)
(defun %nselect-onchange (id buffer clauses)
  "Compiles the CLAUSES body into Parenscript code.
Parenscript fetches values from <select> with ID and evaluates the respective
forms in BUFFER."
  (alexandria:when-let ((buffer (or buffer (nyxt:current-buffer))))
    (ps:ps*
     (with-ps-gensyms (var inner-var)
       `(nyxt/ps:lisp-eval
         (:title ,(format nil "nselect ~a choice" id)
                 ,@(when buffer
                     `(:buffer ,buffer)))
         (let ((,var (alexandria:ensure-list
                      (nyxt:ps-eval
                        (ps:chain *Array (from (ps:chain (nyxt/ps:qs document (+ "#" (ps:lisp ,id)))
                                                         selected-options))
                                  (map (lambda (e) (ps:@ e value))))))))
           (dolist (,inner-var ,var)
             (str:string-case ,inner-var
               ,@(loop for (clause . forms) in clauses
                       for value = (first (uiop:ensure-list clause))
                       collect (cons (nyxt:prini-to-string value)
                                     forms))))))))))

(serapeum:-> %nselect-options ((nyxt:list-of list)) t)
(defun %nselect-options (clauses)
  "Produces a set of options for :nselect based on CLAUSES list."
  (spinneret:with-html-string
    (loop for (value display title) in (mapcar (alexandria:compose #'uiop:ensure-list
                                                                   #'first)
                                               clauses)
          collect (:option
                   :value (nyxt:prini-to-string value)
                   (when title (list :title title))
                   (string-capitalize (or display (nyxt:prini-to-string value)))))))

(deftag :nselect (body attrs &key default (id (alexandria:required-argument 'id))
                       buffer &allow-other-keys)
  "Generate <select> tag from the BODY resembling cond clauses.

BODY is a list of forms, each given by ((VALUE DISPLAY TITLE) . FORMS).
It expands to <option value=\"value\" title=\"title\">display</option> and runs
FORMS when selected. DISPLAY and TITLE are optional literal strings.

In both cases, VALUEs should be literal (and printable) atoms. For instance,
symbol, number, string, or keyword.

BUFFER is a buffer to bind the actions of this tag to.

DEFAULT is a form evaluating to a string that is used as the default option.

In case some variable from the outer scope should be captured, injecting a
closure into the clause would work best.

Example:
\(:nselect :id \"number-guessing\"
  :default \"Guess the number\"
  '(1 (nyxt:echo \"Too low!\"))
  (list 2 (nyxt:echo \"Correct!\"))
  `(3 (funcall ,(lambda () (nyxt:echo \"Too high!\")))))"
  (once-only (id)
    (with-gensyms (body-var)
      `(let ((,body-var ,@body))
         (:select.button
          ,@attrs
          :id ,id
          :onchange (%nselect-onchange ,id ,buffer ,body-var)
          ,@(when default
              `((:option :selected t :disabled t ,default)))
          (:raw (%nselect-options ,body-var)))))))

(serapeum:-> %nradio-onchange (list (nyxt:maybe nyxt:buffer)) t)
(defun %nradio-onchange (onchange buffer)
  "Produce Parenscript to run ONCHANGE expression in BUFFER when :nradio is modified."
  (when (or buffer (nyxt:current-buffer))
    (ps:ps*
     `(nyxt/ps:lisp-eval
       (:title "nradio onchange"
               ,@(when buffer
                   (list :buffer buffer)))
       ,onchange))))

(serapeum:-> %nradio-inputs (string (nyxt:maybe nyxt:buffer) symbol boolean (nyxt:list-of list)) t)
(defun %nradio-inputs (name buffer checked vertical clauses)
  (spinneret:with-html-string
          (loop for (id label body) in (mapcar #'uiop:ensure-list clauses)
                collect (:label
                         :class "radio-label"
                         (:input
                          :class "radio-input"
                          :type "radio"
                          :id (nyxt:prini-to-string id)
                          :onchange (%nradio-onchange body buffer)
                          :name name
                          :checked (equal id checked))
                         label (when vertical (:br))))))

(deftag :nradio (body attrs &key (name (alexandria:required-argument 'name)) checked vertical buffer &allow-other-keys)
  "Generate radio buttons corresponding to clauses in BODY.
Clauses should be of the form (ID LABEL . FORM), where FORM is evaluated
when a radio button is selected."
  (let ((attrs attrs))
    ;; Hack to silence the fact that attrs is not used.
    (declare (ignore attrs))
    (with-gensyms (body-var)
      `(let ((,body-var ,(if (serapeum:single body)
                             (first body)
                             `(list ,@body))))
         (:div
          :class "radio-div"
          (:raw (%nradio-inputs ,name ,buffer ,checked ,vertical ,body-var)))))))

(serapeum:-> %ncheckbox-onchange (list list (nyxt:maybe nyxt:buffer)) t)
(defun %ncheckbox-onchange (checked-body unchecked-body buffer)
  "Produce Parenscript to run ONCHANGE expression in BUFFER when :ncheckbox is modified."
  (when (or buffer (nyxt:current-buffer))
    (ps:ps*
     `(if (ps:chain window event target checked)
         (nyxt/ps:lisp-eval
           (:title "ncheckbox checked"
                   ,@(when buffer
                       (list :buffer buffer)))
           ,checked-body)
         (nyxt/ps:lisp-eval
           (:title "ncheckbox unchecked"
                   ,@(when buffer
                       (list :buffer buffer)))
           ,unchecked-body)))))

(serapeum:-> %ncheckbox-inputs (string (nyxt:maybe nyxt:buffer) boolean list) t)
(defun %ncheckbox-inputs (name buffer checked body)
  (destructuring-bind ((id label) checked-body unchecked-body)
      (mapcar #'uiop:ensure-list body)
    (spinneret:with-html-string
      (:input
       :class "checkbox-input"
       :type "checkbox"
       :id (nyxt:prini-to-string id)
       :onchange (%ncheckbox-onchange checked-body unchecked-body buffer)
       :name name
       :checked checked)
      (:label
       :class "checkbox-label"
       :for name
       label))))

(deftag :ncheckbox (body attrs &key (name (alexandria:required-argument 'name)) checked buffer &allow-other-keys)
  "Generate a checkbox corresponding to BODY.
BODY should be of the form (ID LABEL FORM-CHECKED . FORM-UNCHECKED), where FORM-CHECKED is evaluated
when the checkbox is checked and FORM-UNCHECKED when it is unchecked."
  (let ((attrs attrs))
    ;; Hack to silence the fact that attrs is not used.
    (declare (ignore attrs))
    (with-gensyms (body-var)
      `(let* ((,body-var ,(if (serapeum:single body)
                              (first body)
                              `(list ,@body))))
         (:div
          :class "checkbox-div"
          (:raw (%ncheckbox-inputs ,name ,buffer ,checked ,body-var)))))))

(defun %nxref-doc (type symbol &optional (class-name (when (eq type :slot)
                                                       (alexandria:required-argument 'class-name))))
  "NOTE: TYPE for classes is :CLASS, not :CLASS-NAME (as in `:nxref')."
  (format nil "[~a]~@[ ~a~]"
          (if class-name
              (format nil "SLOT of ~a" class-name)
              type)
          (when-let ((doc (case type
                            (:package (documentation (find-package symbol) t))
                            (:variable (documentation symbol 'variable))
                            ((:slot   ; KLUDGE: Any simple way to get slot docs?
                              :macro :function :command)
                             (documentation symbol 'function))
                            ((:mode :class)
                             (documentation symbol 'type)))))
            ;; Copied from describe.lisp to avoid `nyxt::first-line' use.
            (find-if (complement #'uiop:emptyp) (serapeum:lines doc)))))

(defun %nxref-link (type symbol &optional (class-name (when (eq type :slot)
                                                        (alexandria:required-argument 'class-name))))
  "Generate a nyxt: link to the describe-* page based on SYMBOL's TYPE.
CLASS-NAME is specific to :slot type."
  (case type
    (:package (nyxt:nyxt-url (read-from-string "nyxt:describe-package") :package symbol))
    (:variable (nyxt:nyxt-url (read-from-string "nyxt:describe-variable")
                              :variable symbol))
    ((:command :function :macro)
     (nyxt:nyxt-url (read-from-string "nyxt:describe-function")
                    :fn symbol))
    (:slot (nyxt:nyxt-url (read-from-string "nyxt:describe-slot")
                          :name symbol :class class-name))
    ((:mode :class)
     (nyxt:nyxt-url (read-from-string "nyxt:describe-class")
                    :class symbol))
    (t (nyxt:nyxt-url (read-from-string "nyxt:describe-any")
                      :input symbol))))

(deftag :nxref (body attrs &key slot mode class-name function macro command (command-key-p t) variable package (target "_self") &allow-other-keys)
  "Create a link to a respective describe-* page for BODY symbol.

Relies on the type keywords (SLOT, MODE, CLASS-NAME, FUNCTION, MACRO, COMMAND,
VARIABLE, PACKAGE, TARGET) to guess the right page, always provide those.

CLASS-NAME, if present, should be the symbol designating a class. It's not
called CLASS because Spinneret has special behavior for CLASS pre-defined and
non-overridable."
  (let* ((first (first body))
         (symbol (or package variable function macro command slot class-name mode
                     (when (symbolp first) first)))
         (printable (or (when (and (symbolp first) (eq first symbol))
                          (second body))
                        first package variable function macro command slot class-name mode))
         (type (cond
                 (package :package)
                 (variable :variable)
                 (macro :macro)
                 (command :command)
                 (function :function)
                 ((and slot class-name) :slot)
                 (mode :mode)
                 (class-name :class))))
    (when (and (getf attrs :class)
               (or (getf attrs :slot)
                   (every #'null (list slot class-name mode function macro command variable package))))
      (error ":class attribute used ambiguously in :nxref tag. Use :class-name instead."))
    `(:a.link
      :target ,target
      ,@attrs
      :href (%nxref-link ,type ,symbol
                         ,@(when (and slot class-name)
                             (list class-name)))
      :title (%nxref-doc ,type ,symbol
                         ,@(when (and slot class-name)
                             (list class-name)))
      (:code
       (let ((*print-escape* nil))
         (nyxt:prini-to-string ,printable))
       ,@(when (and command command-key-p)
           `(" ("
             (funcall (read-from-string "nyxt::binding-keys")
                      ,command ,@(when mode
                                   `(:modes (cl:list (make-instance ,mode)))))
             ")"))))))

(defun %ncode-resolve-linkable-symbols (form)
  "Helper function for :NCODE tag.
Returns all the linkable symbols from FORM as multiple values:
- Function symbols.
- Variable symbols.
- Macro symbols.
- All the special forms (including some macros and functions needing extra care).
- All the strings that may potentially be resolvable with
  `nyxt:resolve-backtick-quote-links'."
  (let ((functions (list))
        (classes (list))
        (variables (list))
        (macros (list))
        (specials (list))
        (all-specials '(quote
                        flet labels symbol-macrolet macrolet
                        block catch eval-when progv lambda
                        progn prog1 unwind-protect tagbody setf setq multiple-value-prog1
                        let let* prog prog*
                        return-from throw the
                        multiple-value-call funcall apply
                        function
                        go locally))
        (linkable-strings (list)))
    (labels ((resolve-symbols-internal (form)
               (typecase form
                 (boolean nil)
                 (keyword nil)
                 (cons
                  (let ((first (first form)))
                    (alexandria:destructuring-case form
                      ;; More forms: def*, make-instance, slots, special forms?
                      ((make-instance class &rest args)
                       (push first functions)
                       (if (and (listp class)
                                (eq 'quote (first class)))
                           (push (second class) classes)
                           (resolve-symbols-internal class))
                       (resolve-symbols-internal args))
                      (((flet labels symbol-macrolet macrolet)
                        (&rest bindings) &body body)
                       (push first specials)
                       (mapcar (lambda (b)
                                 (resolve-symbols-internal (cddr b)))
                               bindings)
                       (mapc #'resolve-symbols-internal body))
                      (((block catch eval-when progv lambda) arg &body body)
                       (declare (ignore arg))
                       (push first specials)
                       (mapc #'resolve-symbols-internal body))
                      (((progn prog1 unwind-protect tagbody setf setq multiple-value-prog1)
                        &body body)
                       (push first specials)
                       (mapc #'resolve-symbols-internal body))
                      (((let let* prog prog*) (&rest bindings) &body body)
                       (push first specials)
                       (mapcar (alexandria:compose
                                #'resolve-symbols-internal #'second #'uiop:ensure-list)
                               bindings)
                       (mapc #'resolve-symbols-internal body))
                      (((return-from throw the) arg &optional value)
                       (declare (ignore arg))
                       (push first specials)
                       (resolve-symbols-internal value))
                      (((multiple-value-call funcall apply) function &rest args)
                       (push first specials)
                       (match function
                         ((list 'quote name)
                          (pushnew name functions))
                         ((list 'function name)
                          (when (symbolp name)
                            (pushnew name functions))))
                       (mapc #'resolve-symbols-internal args))
                      ((function value)
                       (push first specials)
                       (when (symbolp value)
                         (pushnew value functions)))
                      (((go locally) &rest values)
                       (declare (ignore values))
                       (push first specials))
                      ((t &rest rest)
                       (cond
                         ((listp first)
                          (resolve-symbols-internal first)
                          (mapc #'resolve-symbols-internal rest))
                         ((member first all-specials)
                          (pushnew first specials))
                         ((and (symbolp first)
                               (nsymbols:macro-symbol-p first))
                          (pushnew first macros)
                          (let* ((arglist (trivial-arguments:arglist first))
                                 (rest-position (or (position '&rest arglist)
                                                    (position '&body arglist))))
                            (if rest-position
                                (mapc #'resolve-symbols-internal (nthcdr rest-position rest))
                                (mapc #'resolve-symbols-internal rest))))
                         ((and (symbolp first)
                               (nsymbols:function-symbol-p first))
                          (pushnew first functions)
                          (mapc #'resolve-symbols-internal rest)))))))
                 (symbol
                  (when (nsymbols:variable-symbol-p form)
                    (pushnew form variables)))
                 (string
                  (pushnew form linkable-strings)))))
      (resolve-symbols-internal form)
      (values (set-difference functions all-specials) classes variables macros specials linkable-strings))))

(defun %ncode-prini (object package)
  "Custom `:ncode'-specific `nyxt:prini-to-string' with narrower margins."
  (nyxt:prini-to-string object :readably t :right-margin 70 :package package))

(defun %ncode-htmlize-body (form package &optional (listing (%ncode-prini form package)))
  "Turn the FORM into an HTMLized rich text, augmented with `:nxref's to the used entities.
LISTING is the string to enrich, autogenerated from FORM on demand."
  (let ((*suppress-inserted-spaces* t)
        (*html-style* :tree)
        (*print-pretty* nil))
    (when (listp form)
      (multiple-value-bind (functions classes variables macros specials linkable-strings)
          (%ncode-resolve-linkable-symbols form)
        ;; We use \\s, because lots of Lisp symbols include non-word
        ;; symbols and would break if \\b was used.
        (macrolet ((replace-symbol-occurences (symbols type &key (prefix "(\\()") (suffix "(\\)|\\s)") (style :plain))
                     (alexandria:with-gensyms (sym sym-listing)
                       `(dolist (,sym ,symbols)
                          (when (search (%ncode-prini ,sym package) listing)
                            (let ((,sym-listing (%ncode-prini ,sym package)))
                              (setf listing
                                    (ppcre:regex-replace-all
                                     (uiop:strcat
                                      ,prefix (ppcre:quote-meta-chars ,sym-listing) ,suffix)
                                     listing
                                     (list
                                      0 ,(case style
                                           (:link `(with-html-string
                                                     (:nxref ,type ,sym ,sym-listing)))
                                           (:plain `(with-html-string
                                                      (:nxref :style "color: inherit; background-color: inherit;" ,type ,sym ,sym-listing)))
                                           (:span `(with-html-string
                                                     (:span.action ,sym-listing))))
                                      1)))))))))
          (replace-symbol-occurences macros :macro :style :link)
          (replace-symbol-occurences functions :function :prefix "(\\(|#'|')")
          (replace-symbol-occurences classes :class-name :prefix "(')")
          (replace-symbol-occurences
           variables :variable :prefix "(\\s)" :suffix "(\\)|\\s)")
          (replace-symbol-occurences specials nil :style :span))
        (dolist (string linkable-strings)
          (setf listing (str:replace-all (%ncode-prini string package)
                                         (nyxt:prini-to-string
                                          (nyxt:resolve-backtick-quote-links string package)
                                          :escape t :readably t :package package)
                                         listing)))))
    listing))

(defun %ncode-htmlize-unless-string (form package)
  (typecase form
    (string form)
    (list (%ncode-htmlize-body form package))))

(defun %ncode-inline-p (body package)
  "BODY is only inline if it actually is a one-liner, literal or printed out."
  (and (serapeum:single body)
       (zerop (count #\newline
                     (if (stringp (first body))
                         (first body)
                         (%ncode-prini (first body) package))))))

(deftag :ncode (body attrs &key
                     (package :nyxt)
                     (inline-p nil inline-provided-p)
                     (copy-p t) file (external-editor-p file)
                     &allow-other-keys)
  "Generate the <pre>/<code> listing from the provided Lisp BODY.

Forms in BODY should be quoted.

INLINE-P is about omitting newlines and <pre> tags---basically a <code> tag with
syntax highlighting and actions. If not provided, is determined automatically
based on BODY length.

Most *-P arguments mandate whether to add the buttons for:
- Copying the source to clipboard (COPY-P).
- Editing the FILE it comes from (if present), in `nyxt:external-editor-program'
  (EXTERNAL-EDITOR-P)."
  (once-only (package)
    (with-gensyms (body-var inline-var file-var first plaintext htmlized)
      (let* ((*print-escape* nil)
             (id (nyxt:prini-to-string (gensym)))
             (select-code
               `(:nselect
                 :id ,id
                 :class "code-select"
                 :default "☰"
                 :style (if ,inline-var "font-weight: bold" "font-weight: normal")
                 (list
                  ,@(when copy-p
                      `(`((copy "Copy" "Copy the code to clipboard.")
                          (funcall (read-from-string "nyxt:ffi-buffer-copy")
                                   (nyxt:current-buffer) ,,plaintext))))
                  ,@(when (and file external-editor-p)
                      `(`((external-editor
                           "Open in external editor"
                           "Open the file this code comes from in external editor.")
                          (funcall (read-from-string "nyxt/mode/file-manager:edit-file-with-external-editor")
                                   (uiop:ensure-list ,,file-var)))))))))
        `(let* ((,body-var (list ,@body))
                (,first (first ,body-var))
                (,inline-var ,(if inline-provided-p
                                  inline-p
                                  `(%ncode-inline-p ,body-var ,package)))
                (,file-var ,file)
                (,plaintext (cond
                              ((and (serapeum:single ,body-var)
                                    (stringp ,first))
                               ,first)
                              ((serapeum:single ,body-var)
                               (%ncode-prini ,first ,package))
                              (t (str:join
                                  (make-string 2 :initial-element #\newline)
                                  (mapcar (lambda (f) (if (stringp f)
                                                          f
                                                          (%ncode-prini f ,package)))
                                          ,body-var)))))
                (,htmlized (if (serapeum:single ,body-var)
                               (%ncode-htmlize-unless-string ,first ,package)
                               (str:join
                                (make-string 2 :initial-element #\newline)
                                (mapcar (lambda (f) (%ncode-htmlize-unless-string f ,package)) ,body-var)))))
           (declare (ignorable ,plaintext ,file-var))
           ,(if inline-p
                `(:span (:code ,@attrs (:raw ,htmlized)) ,select-code)
                `(:div :style "position: relative"
                       (:pre ,@attrs ,select-code
                             (:code (:raw ,htmlized))))))))))

(defun %nsection-id (title)
  (if (stringp title)
      (reduce (lambda (string char)
                (if (and (plusp (length string))
                         (eql (elt string (1- (length string))) #\-)
                         (eql char #\-))
                    string
                    (uiop:strcat string char)))
              (substitute-if-not
               #\- #'alphanumericp
               (string-trim serapeum:whitespace (string-downcase title)))
              :initial-value "")
      (alexandria:required-argument 'id)))

(deftag :nsection (body attrs &key (title (alexandria:required-argument 'title))
                        level
                        (anchor-p t)
                        (open-p t)
                        (id (if (stringp title)
                                (str:remove-punctuation (str:downcase title) :replacement "-")
                                (alexandria:required-argument 'id)))
                        &allow-other-keys)
  "Collapsible and reference-able <section> with a neader.
TITLE should be a human-readable title for a section, or the form producing one.
LEVEL (if provided), is the level of heading for the section. If it's 2, the
heading is <h2>, if it's 3, then <h3> etc. If not provided, uses <h*> Spinneret
tag to intelligently guess the current heading level.
ID is the string identifier with which to reference the section elsewhere. Is
auto-generated from title by replacing all the punctuation and spaces with
hyphens, if not provided AND if the TITLE is a string.
OPEN-P mandates whether the section is collapsed or not. True (= not collapsed)
by default."
  (check-type level (or null (integer 2 6)))
  (with-gensyms (id-var)
    `(let ((spinneret::*html-path*
             ;; Push as many :section tags into the path, as necessary to imply
             ;; LEVEL for the sections inside this one. A trick on Spinneret to
             ;; make it think it's deeply nested already.
             (append
              spinneret::*html-path*
              (make-list ,(if level
                              `(1- (- ,level (spinneret::heading-depth)))
                              0)
                         :initial-element :section)))
           (,id-var ,id))
       (:section.section
        :id ,id-var
        (:details
         :open ,open-p
         (:summary
          :class "nsection-summary"
          (:header
           :style "display: inline"
           (:h* :style "display: inline"
             ,@attrs ,title)
           " " (when ,anchor-p
                 (:a :class "link nsection-anchor" :href (uiop:strcat "#" ,id-var) "#"))))
         ,@body)))))

(serapeum:-> %nbutton-onclick (string (nyxt:maybe nyxt:buffer) (nyxt:list-of list)) t)
(defun %nbutton-onclick (title buffer clauses)
  "Produce Parenscript to run Lisp CLAUSES in BUFFER.
TITLE is the debuggable name for the callback."
  (when (or buffer (nyxt:current-buffer))
    (ps:ps*
     `(nyxt/ps:lisp-eval
       (:title ,(format nil "nbutton ~a" title)
               ,@(when buffer
                   (list :buffer buffer)))
       ,@clauses))))

(deftag :nbutton (body attrs &key (text (alexandria:required-argument 'text)) title buffer
                       &allow-other-keys)
  "A Lisp-invoking button with TEXT text and BODY action.
Evaluates (via `nyxt/ps:lisp-eval') the BODY in BUFFER when clicked.

BODY can consist of quoted lists or forms producing those. These will be
compiled, so, if you want to close over some value, inject a closure right
inside the forms.

Example:
\(:nbutton
  :buffer buffer
  :text \"Do something\"
  '(nyxt:echo \"Hello!\")
  (list 'foo)
  `(funcall ,(lambda () (do-something-with closed-over-value))))"
  `(:button.button
    :onclick (%nbutton-onclick ,(or title text) ,buffer (list ,@body))
    ,@(when title
        (list :title title))
    ,@attrs
    ,text))

(serapeum:-> %ninput-onfocus (list (nyxt:maybe nyxt:buffer)) t)
(defun %ninput-onfocus (onfocus buffer)
  "Produce Parenscript to run ONFOCUS expression in BUFFER when :ninput is focused."
  (when (or buffer (nyxt:current-buffer))
    (ps:ps*
     `(nyxt/ps:lisp-eval
       (:title "ninput onfocus"
               ,@(when buffer
                   (list :buffer buffer)))
       ,onfocus))))

(serapeum:-> %ninput-onchange (list (nyxt:maybe nyxt:buffer)) t)
(defun %ninput-onchange (onchange buffer)
  "Produce Parenscript to run ONCHANGE expression in BUFFER when :ninput is modified."
  (when (or buffer (nyxt:current-buffer))
    (ps:ps*
     `(nyxt/ps:lisp-eval
       (:title "ninput onchange"
               ,@(when buffer
                   (list :buffer buffer)))
       ,onchange))))

(deftag :ninput (body attrs &key rows cols onfocus onchange buffer &allow-other-keys)
  "Nicely styled <textarea> with a reasonable number of ROWS/COLS to accommodate the BODY.
Calls Lisp forms in ONFOCUS and ONCHANGE when one focuses and edits the input (respectively).

BODY should be a string or an implicit progn producing a string.

ONFOCUS, and ONCHANGE can consist of quoted lists or forms producing
those. These lists will be compiled, so, if you want to close over some value,
inject a closure right inside the forms."
  (once-only (buffer)
    (with-gensyms (input)
      ;; NOTE: It's unlikely that BODY will have multiple forms, but better
      ;; prepare for it, just in case someone goes stateful.
      `(let ((,input (progn ,@body)))
         (:textarea.input
          :rows (or ,rows (1+ (count #\Newline ,input)) 1)
          :cols (or ,cols (ignore-errors (reduce #'max (mapcar #'length (str:lines ,input)))) 80)
          ,@(when onfocus
              `(:onfocus (%ninput-onfocus ,onfocus ,buffer)))
          ,@(when onchange
              ;; More events here.
              `(:onkeydown (%ninput-onchange ,onchange ,buffer)))
          ,@attrs
          (:raw (the string ,input)))))))

(serapeum:-> %ntoc-create-toc ((integer 2 6) string) *)
(defun %ntoc-create-toc (depth body)
  "Generate the code for the table of contents based on string BODY."
  (labels ((parent-section (elem)
             (find-if #'nyxt/dom:section-element-p (nyxt/dom:parents elem)))
           (format-section (heading level)
             (with-html-string
               (let ((parent-section (parent-section heading)))
                 (:li (:a :href (format nil "#~a" (plump:attribute parent-section "id"))
                          (plump:text heading)))
                 (serapeum:and-let* (((< level depth))
                                     (inner-level (1+ level))
                                     (inner-headers
                                      (clss:ordered-select (format nil "h~a" inner-level) parent-section)))
                   (:ul (loop for inner-header across inner-headers
                              collect (:raw (format-section inner-header inner-level)))))))))
    (let* ((dom (nyxt/dom:named-html-parse body))
           (h2s (clss:ordered-select "h2" dom)))
      (with-html-string
        (loop for h2 across h2s
              collect (:ul (:raw (format-section h2 2))))))))

(deftag :ntoc (body attrs &key (title "Table of contents") (depth 3) &allow-other-keys)
  "Generate table of contents for BODY up to DEPTH.
Looks for section tags with ID-s to link to.
:nsection sections are perfectly suitable for that."
  (with-gensyms (body-var)
    `(let* ((*html-style* :tree)
            (,body-var (with-html-string ,@body)))
       (:nav#toc
        ,@attrs
        (:nsection
         :title ,title
         (:raw (%ntoc-create-toc ,depth ,body-var))))
       (:raw ,body-var))))
