(defun treesit-docgen--get-function-node (node)
  "Get the function node the given NODE belongs to. Or nil"
  (treesit-parent-until node
                        (lambda (n)
                          (or (equal (treesit-node-type n) "function_definition")
                              (and (equal (treesit-node-type n) "declaration"))
                              (equal (treesit-node-type (treesit-node-child-by-field-name n "declarator"))
                                     "function_declarator")))
                        t)
  )

(defun treesit-docgen--fn-template-node (fn-node)
  "Get the template node of a function or nil"
  (let* ((par (treesit-node-parent fn-node))
         (par-t (treesit-node-type par)))
    (when (string= par-t "template_declaration") par)
    ))

(defun treesit-docgen--fn-tpars (fn-node)
  "Get the template parameters of the function node or nil"
  (let* ((template (treesit-docgen--fn-template-node fn-node))
         (tpars (treesit-node-child-by-field-name template "parameters")))
    (when tpars
      (mapcar (lambda (tpar) (treesit-node-text tpar)) (treesit-node-children tpars)))
    ))

(defun treesit-docgen--fn-type (fn-node)
  "Get the return type of the function node"
  (let ((fn-type-node (treesit-node-child-by-field-name fn-node "type")))
    (treesit-node-text fn-type-node)))

(defun treesit-docgen--fn-pars (fn-node)
  "Get the parameter names of the function node"
  (let* ((fn-node-decl (treesit-node-child-by-field-name fn-node "declarator"))
         (fn-node-pars (treesit-node-child-by-field-name fn-node-decl "parameters"))
         )
    (mapcar (lambda (par) (treesit-node-text par)) (treesit-node-children fn-node-pars))))

(defun treesit-docgen-insert-doc ()
  "Insert a documentation template for the function at point"
  (interactive)
  (let* ((node (treesit-node-at (point)))
         (fn-node (treesit-docgen--get-function-node node))
         )
    (when fn-node
      (message "FN-Type: %s, FN-Pars: %s, FN-TPars: %s"
               (or (treesit-docgen--fn-type fn-node) "none")
               (or (treesit-docgen--fn-pars fn-node) "none")
               (or (treesit-docgen--fn-tpars fn-node) "none")
               ))))