cider-inspector.el

;;; cider-inspector.el --- Object inspector -*- lexical-binding: t -*-

;; Copyright © 2013-2025 Vital Reactor, LLC
;; Copyright © 2014-2025  Bozhidar Batsov and CIDER contributors

;; Author: Ian Eslick <ian@vitalreactor.com>
;;         Bozhidar Batsov <bozhidar@batsov.dev>

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

;; This file is not part of GNU Emacs.

;;; Commentary:

;; Clojure object inspector inspired by SLIME.

;;; Code:

(require 'cl-lib)
(require 'easymenu)
(require 'seq)
(require 'cider-client)
(require 'cider-eval)

;; ===================================
;; Inspector Key Map and Derived Mode
;; ===================================

(defconst cider-inspector-buffer "*cider-inspect*")

;;; Customization
(defgroup cider-inspector nil
  "Presentation and behavior of the CIDER value inspector."
  :prefix "cider-inspector-"
  :group 'cider
  :package-version '(cider . "0.10.0"))

(defcustom cider-inspector-page-size 32
  "Default page size in paginated inspector view.
The page size can be also changed interactively within the inspector."
  :type '(integer :tag "Page size" 32)
  :package-version '(cider . "0.10.0"))

(defcustom cider-inspector-max-atom-length 150
  "Default max length of nested atoms before they are truncated.
'Atom' here means any collection member that satisfies (complement coll?).
The max length can be also changed interactively within the inspector."
  :type '(integer :tag "Max atom length" 150)
  :package-version '(cider . "1.1.0"))

(defcustom cider-inspector-max-coll-size 5
  "Default number of nested collection members to display before truncating.
The max size can be also changed interactively within the inspector."
  :type '(integer :tag "Max collection size" 5)
  :package-version '(cider . "1.1.0"))

(defcustom cider-inspector-max-nested-depth 5
  "Default level of nesting for collections to display before truncating.
The max depth can be also changed interactively within the inspector."
  :type '(integer :tag "Max nested collection depth" 5)
  :package-version '(cider . "1.14.0"))

(defvar cider-inspector-spacious-collections nil
  "Controls whether the inspector renders values in collections spaciously.")

(defcustom cider-inspector-fill-frame nil
  "Controls whether the CIDER inspector window fills its frame."
  :type 'boolean
  :package-version '(cider . "0.15.0"))

(defcustom cider-inspector-pretty-print nil
  "When true, pretty print values in the inspector."
  :type 'boolean
  :package-version '(cider . "1.18.0"))

(defcustom cider-inspector-skip-uninteresting t
  "Controls whether to skip over uninteresting values in the inspector.
Only applies to navigation with `cider-inspector-prev-inspectable-object'
and `cider-inspector-next-inspectable-object', values are still inspectable
by clicking or navigating to them by other means."
  :type 'boolean
  :package-version '(cider . "0.25.0"))

(defcustom cider-inspector-auto-select-buffer t
  "Determines if the inspector buffer should be auto selected."
  :type 'boolean
  :package-version '(cider . "0.27.0"))

(defcustom cider-inspector-display-analytics-hint t
  "When true, display hint about analytics feature for eligible objects.
Can be turned to nil once the user sees and acknowledges the feature."
  :type 'boolean
  :package-version '(cider . "1.18.0"))

(defvar cider-inspector-uninteresting-regexp
  (concat "nil"                      ; nils are not interesting
          "\\|:" clojure--sym-regexp ; nor keywords
          ;; FIXME: This range also matches ",", is it on purpose?
          "\\|[+-.0-9]+")            ; nor numbers. Note: BigInts, ratios etc. are interesting
  "Regexp of uninteresting and skippable values.")

(defun cider-inspector-open-thing-at-point ()
  "Opens the thing at point if found, without prompting."
  (interactive)
  (if-let ((url (thing-at-point 'url)))
      (browse-url url)
    (if-let ((filename (thing-at-point 'filename)))
        (find-file filename))))

(defvar cider-inspector-mode-map
  (let ((map (make-sparse-keymap)))
    (set-keymap-parent map cider-popup-buffer-mode-map)
    (define-key map (kbd "RET") #'cider-inspector-operate-on-point)
    (define-key map [mouse-1] #'cider-inspector-operate-on-click)
    (define-key map "l" #'cider-inspector-pop)
    (define-key map "g" #'cider-inspector-refresh)
    (define-key map "o" #'cider-inspector-open-thing-at-point)
    ;; Page-up/down
    (define-key map [next] #'cider-inspector-next-page)
    (define-key map [prior] #'cider-inspector-prev-page)
    (define-key map " " #'cider-inspector-next-page)
    (define-key map (kbd "M-SPC") #'cider-inspector-prev-page)
    (define-key map (kbd "S-SPC") #'cider-inspector-prev-page)
    (define-key map "s" #'cider-inspector-set-page-size)
    (define-key map "a" #'cider-inspector-set-max-atom-length)
    (define-key map "c" #'cider-inspector-set-max-coll-size)
    (define-key map "C" #'cider-inspector-set-max-nested-depth)
    (define-key map "v" #'cider-inspector-toggle-view-mode)
    (define-key map "y" #'cider-inspector-display-analytics)
    (define-key map "d" #'cider-inspector-def-current-val)
    (define-key map "t" #'cider-inspector-tap-current-val)
    (define-key map "1" #'cider-inspector-tap-at-point)
    (define-key map [tab] #'cider-inspector-next-inspectable-object)
    (define-key map "\C-i" #'cider-inspector-next-inspectable-object)
    (define-key map "n" #'cider-inspector-next-inspectable-object)
    (define-key map [(shift tab)] #'cider-inspector-previous-inspectable-object)
    (define-key map "p" #'cider-inspector-previous-inspectable-object)
    (define-key map "P" #'cider-inspector-toggle-pretty-print)
    (define-key map (kbd "C-c C-p") #'cider-inspector-print-current-value)
    (define-key map ":" #'cider-inspect-expr-from-inspector)
    (define-key map "f" #'forward-char)
    (define-key map "b" #'backward-char)
    (define-key map "9" #'cider-inspector-previous-sibling)
    (define-key map "0" #'cider-inspector-next-sibling)
    ;; Emacs translates S-TAB to BACKTAB on X.
    (define-key map [backtab] #'cider-inspector-previous-inspectable-object)
    (easy-menu-define cider-inspector-mode-menu map
      "Menu for CIDER's inspector."
      `("CIDER Inspector"
        ["Inspect" cider-inspector-operate-on-point]
        ["Pop" cider-inspector-pop]
        ["Refresh" cider-inspector-refresh]
        "--"
        ["Next Inspectable Object" cider-inspector-next-inspectable-object]
        ["Previous Inspectable Object" cider-inspector-previous-inspectable-object]
        "--"
        ["Next Page" cider-inspector-next-page]
        ["Previous Page" cider-inspector-prev-page]
        ["Set Page Size" cider-inspector-set-page-size]
        ["Set Max Atom Length" cider-inspector-set-max-atom-length]
        ["Set Max Collection Size" cider-inspector-set-max-coll-size]
        ["Define Var" cider-inspector-def-current-val]
        "--"
        ["Quit" cider-popup-buffer-quit-function]
        ))
    map))

(define-derived-mode cider-inspector-mode special-mode "Inspector"
  "Major mode for inspecting Clojure data structures.

\\{cider-inspector-mode-map}"
  (set-syntax-table clojure-mode-syntax-table)
  (setq-local electric-indent-chars nil)
  (setq-local sesman-system 'CIDER)
  (visual-line-mode 1))

;;;###autoload
(defun cider-inspect-last-sexp ()
  "Inspect the result of the the expression preceding point."
  (interactive)
  (cider-inspect-expr (cider-last-sexp) (cider-current-ns)))

;;;###autoload
(defun cider-inspect-defun-at-point ()
  "Inspect the result of the \"top-level\" expression at point."
  (interactive)
  (cider-inspect-expr (cider-defun-at-point) (cider-current-ns)))

;;;###autoload
(defun cider-inspect-last-result ()
  "Inspect the most recent eval result."
  (interactive)
  (cider-inspect-expr "*1" (cider-current-ns)))

;;;###autoload
(defun cider-inspect (&optional arg)
  "Inspect the result of the preceding sexp.

With a prefix argument ARG it inspects the result of the \"top-level\" form.
With a second prefix argument it prompts for an expression to eval and inspect."
  (interactive "p")
  (pcase arg
    (1 (cider-inspect-last-sexp))
    (4 (cider-inspect-defun-at-point))
    (16 (call-interactively #'cider-inspect-expr))))

(defvar cider-inspector-location-stack nil
  "A stack used to save point locations in inspector buffers.
These locations are used to emulate `save-excursion' between
`cider-inspector-push' and `cider-inspector-pop' operations.")

;; Operations
;;;###autoload
(defun cider-inspect-expr (expr ns)
  "Evaluate EXPR in NS and inspect its value.
Interactively, EXPR is read from the minibuffer, and NS the
current buffer's namespace."
  (interactive (list (cider-read-from-minibuffer "Inspect expression: " (cider-sexp-at-point))
                     (cider-current-ns)))
  (let ((result (cider-sync-request:inspect-expr expr ns)))
    (when (nrepl-dict-get result "value")
      (setq cider-inspector-location-stack nil)
      (cider-inspector--render-value result :next-inspectable))))

(defun cider-inspect-expr-from-inspector ()
  "Performs `cider-inspect-expr' in a way that is suitable from the Inspector itself.
In particular, it does not read `cider-sexp-at-point'."
  (interactive)
  (let* ((ns (cider-current-ns))
         (prompt (format "Inspect expression in %s"
                         (substring-no-properties (funcall cider-repl-prompt-function ns)))))
    (cider-inspect-expr (cider-read-from-minibuffer prompt nil 'skip-colon)
                        ns)))

(defun cider-inspector-pop ()
  "Pop the last value off the inspector stack and render it."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-pop"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result :pop))))

(defun cider-inspector-push (idx)
  "Inspect the value at IDX in the inspector stack and render it."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-push"
                                                 "idx" ,idx))))
    (when (nrepl-dict-get result "value")
      (push (point) cider-inspector-location-stack)
      (cider-inspector--render-value result :next-inspectable))))

(defun cider-inspector-inspect-last-exception (index &optional ex-data)
  "Inspects the exception in the cause stack identified by INDEX.
If EX-DATA is true, inspect ex-data of the exception instead."
  (interactive)
  (cl-assert (numberp index))
  (let ((result (cider-nrepl-send-sync-request
                 `("op" "inspect-last-exception"
                   "index" ,index
                   ,@(when ex-data
                       `("ex-data" "true"))))))
    (when (nrepl-dict-get result "value")
      (setq cider-inspector-location-stack nil)
      (cider-inspector--render-value result :next-inspectable))))

(defun cider-inspector-previous-sibling ()
  "Inspect the previous sibling value within a sequential parent."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-previous-sibling"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector-next-sibling ()
  "Inspect the next sibling value within a sequential parent."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-next-sibling"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector--refresh-with-opts (&rest opts)
  "Invokes `inspect-refresh' op with supplied extra OPTS.
Re-renders the currently inspected value."
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-refresh" ,@opts))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector-refresh ()
  "Re-render the currently inspected value."
  (interactive)
  (cider-inspector--refresh-with-opts))

(defun cider-inspector-next-page ()
  "Jump to the next page when inspecting a paginated sequence/map.

Does nothing if already on the last page."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request '("op" "inspect-next-page"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector-prev-page ()
  "Jump to the previous page when expecting a paginated sequence/map.

Does nothing if already on the first page."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request '("op" "inspect-prev-page"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector-set-page-size (page-size)
  "Set the page size in pagination mode to the specified PAGE-SIZE.

Current page will be reset to zero."
  (interactive (list (read-number "Page size: " cider-inspector-page-size)))
  (cider-inspector--refresh-with-opts "page-size" page-size))

(defun cider-inspector-set-max-atom-length (max-length)
  "Set the max length of nested atoms to MAX-LENGTH."
  (interactive (list (read-number "Max atom length: " cider-inspector-max-atom-length)))
  (cider-inspector--refresh-with-opts "max-atom-length" max-length))

(defun cider-inspector-set-max-coll-size (max-size)
  "Set the number of nested collection members to display before truncating.
MAX-SIZE is the new value."
  (interactive (list (read-number "Max collection size: " cider-inspector-max-coll-size)))
  (cider-inspector--refresh-with-opts "max-coll-size" max-size))

(defun cider-inspector-set-max-nested-depth (max-nested-depth)
  "Set the level of nesting for collections to display beflore truncating.
MAX-NESTED-DEPTH is the new value."
  (interactive (list (read-number "Max nested depth: " cider-inspector-max-nested-depth)))
  (cider-inspector--refresh-with-opts "max-nested-depth" max-nested-depth))

(defun cider-inspector-display-analytics ()
  "Toggle the display of analytics for the inspected object."
  (interactive)
  ;; Disable hint about analytics feature so that it is never displayed again.
  (when cider-inspector-display-analytics-hint
    (customize-set-variable 'cider-inspector-display-analytics-hint nil))
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-display-analytics"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result :next-inspectable))))

(defun cider-inspector-toggle-pretty-print ()
  "Toggle the pretty printing of values in the inspector."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-toggle-pretty-print"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result))))

(defun cider-inspector-toggle-view-mode ()
  "Toggle the view mode of the inspector between normal and object view mode."
  (interactive)
  (let ((result (cider-nrepl-send-sync-request `("op" "inspect-toggle-view-mode"))))
    (when (nrepl-dict-get result "value")
      (cider-inspector--render-value result :next-inspectable))))

(defcustom cider-inspector-preferred-var-names nil
  "The preferred var names to be suggested by `cider-inspector-def-current-val'.

If you choose a different one while completing interactively,
it will be included (in the first position) the next time
you use `cider-inspector-def-current-val'."
  :type '(repeat string)
  :group 'cider
  :package-version '(cider . "1.8.0"))

(defun cider-inspector--read-var-name-from-user (ns)
  "Reads a var name from the user, to be defined within NS.
Grows `cider-inspector-preferred-var-names' if the user chose a new name,
making that new name take precedence for subsequent usages."
  (let ((v (completing-read (format "Name of the var to be defined in ns %s: " ns)
                            cider-inspector-preferred-var-names)))
    (unless (member v cider-inspector-preferred-var-names)
      (setq cider-inspector-preferred-var-names (cons v cider-inspector-preferred-var-names)))
    v))

(defun cider-inspector-def-current-val (var-name ns)
  "Defines a var with VAR-NAME in current namespace.

Doesn't modify current page.  When called interactively NS defaults to
current-namespace."
  (interactive (let ((ns (cider-current-ns)))
                 (list (cider-inspector--read-var-name-from-user ns)
                       ns)))
  (when-let* ((result (cider-nrepl-send-sync-request `("op" "inspect-def-current-value"
                                                       "ns" ,ns
                                                       "var-name" ,var-name))))
    (cider-inspector--render-value result)
    (message "Defined current inspector value as #'%s/%s" ns var-name)))

(defun cider-inspector-print-current-value ()
  "Print the current value of the inspector."
  (interactive)
  (cider-ensure-connected)
  (cider-ensure-op-supported "inspect-print-current-value")
  (let ((buffer (cider-popup-buffer cider-result-buffer nil 'clojure-mode 'ancillary)))
    (cider-nrepl-send-request
     `("op" "inspect-print-current-value"
       ,@(cider--nrepl-print-request-plist fill-column))
     (cider-popup-eval-handler buffer))))

(defun cider-inspector-tap-current-val ()
  "Sends the current Inspector current value to `tap>'."
  (interactive)
  (let ((response (cider-nrepl-send-sync-request '("op" "inspect-tap-current-value"))))
    (nrepl-dbind-response response (value err)
      (if value
          (message "Successfully tapped the current Inspector value")
        (error "Could not tap the current Inspector value: %s" err)))))

(defun cider-inspector-tap-at-point ()
  "Sends the current Inspector current sub-value (per POINT) to `tap>'."
  (interactive)
  (seq-let (property value) (cider-inspector-property-at-point)
    (pcase property
      (`cider-value-idx
       (cl-assert value)
       (nrepl-dbind-response (cider-nrepl-send-sync-request `("op" "inspect-tap-indexed"
                                                              "idx" ,value))
           (value err)
         (if value
             (message "Successfully tapped the Inspector item at point")
           (error "Could not tap the Inspector item at point: %s" err))))
      (_ (error "No object at point")))))

;; nREPL interactions

(defun cider-sync-request:inspect-expr (expr ns)
  "Evaluate EXPR in context of NS and inspect its result.
Set the page size in paginated view to PAGE-SIZE, maximum length of atomic
collection members to MAX-ATOM-LENGTH, and maximum size of nested collections to
MAX-COLL-SIZE if non nil."
  (thread-first
    (append (nrepl--eval-request expr ns)
            `("inspect" "true"
              ,@(when cider-inspector-page-size
                  `("page-size" ,cider-inspector-page-size))
              ,@(when cider-inspector-max-atom-length
                  `("max-atom-length" ,cider-inspector-max-atom-length))
              ,@(when cider-inspector-max-coll-size
                  `("max-coll-size" ,cider-inspector-max-coll-size))
              ,@(when cider-inspector-max-nested-depth
                  `("max-nested-depth" ,cider-inspector-max-nested-depth))
              ,@(when cider-inspector-display-analytics-hint
                  `("display-analytics-hint" "true"))
              ,@(when cider-inspector-pretty-print
                  `("pretty-print" "true"))))
    (cider-nrepl-send-sync-request)))

(declare-function cider-set-buffer-ns "cider-mode")

;; Render Inspector from Structured Values
(defun cider-inspector--render-value (dict-or-value &optional point-action)
  "Render DICT-OR-VALUE.
It can either be a value directly or a inspector response that contains
`value' field.
POINT-ACTION can either be nil (leave point where it is now), `:pop' (pop point
from stack), `:next-inspectable' (move point to next inspectable object)."
  (let* ((value (if (nrepl-dict-p dict-or-value)
                    (nrepl-dict-get dict-or-value "value")
                  dict-or-value))
         (ns (cider-current-ns))
         (font-size (when-let* ((b (get-buffer cider-inspector-buffer))
                                (variable 'text-scale-mode-amount)
                                (continue (local-variable-p variable b)))
                      ;; The font size is lost between inspector 'screens',
                      ;; because on each re-rendering, we wipe everything, including the mode.
                      ;; Enabling cider-inspector-mode is the specific step that loses the font size.
                      (buffer-local-value variable b)))
         (truncate-lines-defined (when-let* ((b (get-buffer cider-inspector-buffer)))
                                   (local-variable-p 'truncate-lines b)))
         (truncate-lines-p (when-let* ((b (get-buffer cider-inspector-buffer))
                                       (continue truncate-lines-defined))
                             (buffer-local-value 'truncate-lines b)))
         (repl (cider-current-repl))
         (current-point (point)))
    (cider-make-popup-buffer cider-inspector-buffer 'cider-inspector-mode 'ancillary)
    (cider-inspector-render cider-inspector-buffer value
                            :font-size font-size
                            :truncate-lines-defined truncate-lines-defined
                            :truncate-lines-p truncate-lines-p)
    (cider-popup-buffer-display cider-inspector-buffer cider-inspector-auto-select-buffer)
    (when cider-inspector-fill-frame (delete-other-windows))
    (with-current-buffer cider-inspector-buffer
      (setq cider--ancillary-buffer-repl repl)
      (cider-set-buffer-ns ns)
      (cond ((eq point-action nil) (goto-char current-point))
            ((eq point-action :next-inspectable) (ignore-errors (cider-inspector-next-inspectable-object 1)))
            ((eq point-action :pop)
             (goto-char (or (when cider-inspector-location-stack
                              (pop cider-inspector-location-stack))
                            current-point)))))))

(cl-defun cider-inspector-render (buffer str &key font-size truncate-lines-defined truncate-lines-p)
  "Render STR in BUFFER."
  (with-current-buffer buffer
    (cider-inspector-mode)
    (when font-size
      (text-scale-set font-size))
    (when truncate-lines-defined
      (setq-local truncate-lines truncate-lines-p))
    (let ((inhibit-read-only t))
      (condition-case nil
          (cider-inspector-render* (car (read-from-string str)))
        (error (insert "\nInspector error for: " str))))
    (goto-char (point-min))))

(defvar cider-inspector-looking-at-java-p nil)

(defun cider-inspector-render* (elements)
  "Render ELEMENTS."
  (setq cider-inspector-looking-at-java-p nil)
  (dolist (el elements)
    (cider-inspector-render-el* el)))

(defconst cider--inspector-java-headers
  ;; NOTE "--- Static fields:" "--- Instance fields:" are for objects,
  ;; and don't deserve Java syntax highlighting (they can contain a Clojure value like `:foo/bar`, for instance)
  '("--- Interfaces:"
    "--- Fields:" ;; rendered only for Class objects (and not other objects) - see previous comment
    "--- Constructors:"
    "--- Methods:"
    "--- Imports:"))

(defun cider-inspector-render-el* (el)
  "Render EL."
  (let ((header-p (or (member el cider--inspector-java-headers)
                      (and (stringp el)
                           (string-prefix-p "--- " el)))))
    ;; Headers reset the Java syntax coloring:
    (when header-p
      (setq cider-inspector-looking-at-java-p nil))

    (cond ((symbolp el) (insert (symbol-name el)))
          ((stringp el) (insert (if cider-inspector-looking-at-java-p
                                    (cider-font-lock-as 'java-mode el)
                                  (let ((trimmed-el (replace-regexp-in-string (regexp-quote "<non-inspectable value>")
                                                                              ""
                                                                              el)))
                                    (propertize trimmed-el 'font-lock-face (if header-p
                                                                               'font-lock-comment-face
                                                                             'font-lock-keyword-face))))))
          ((and (consp el) (eq (car el) :newline))
           (insert "\n"))
          ((and (consp el) (eq (car el) :value))
           (cider-inspector-render-value (cadr el) (cl-caddr el)))
          (t (message "Unrecognized inspector object: %s" el))))

  ;; Java-related headers indicate that the next elements to be rendered
  ;; should be syntax-colored as Java:
  (when (member el cider--inspector-java-headers)
    (setq cider-inspector-looking-at-java-p t)))

(defun cider-inspector-render-value (value idx)
  "Render VALUE at IDX."
  (cider-propertize-region
      (list 'cider-value-idx idx
            'mouse-face 'highlight)
    (cider-inspector-render-el* (cider-font-lock-as-clojure value))))


;; ===================================================
;; Inspector Navigation (lifted from SLIME inspector)
;; ===================================================

(defun cider-find-inspectable-object (direction limit)
  "Find the next/previous inspectable object.
DIRECTION can be either 'next or 'prev.
LIMIT is the maximum or minimum position in the current buffer.

Return a list of two values: If an object could be found, the
starting position of the found object and T is returned;
otherwise LIMIT and NIL is returned."
  (let ((finder (cl-ecase direction
                  (next 'next-single-property-change)
                  (prev 'previous-single-property-change))))
    (let ((prop nil) (curpos (point)))
      (while (and (not prop) (not (= curpos limit)))
        (let ((newpos (funcall finder curpos 'cider-value-idx nil limit)))
          (setq prop (get-text-property newpos 'cider-value-idx))
          (setq curpos newpos)))
      (list curpos (and prop t)))))

(defun cider-inspector-next-inspectable-object (arg)
  "Move point to the next inspectable object.
With optional ARG, move across that many objects.
If ARG is negative, move backwards."
  (interactive "p")
  (let ((maxpos (point-max)) (minpos (point-min))
        (previously-wrapped-p nil))
    ;; Forward.
    (while (> arg 0)
      (seq-let (pos foundp) (cider-find-inspectable-object 'next maxpos)
        (if foundp
            (progn (goto-char pos)
                   (unless (and cider-inspector-skip-uninteresting
                                (looking-at-p cider-inspector-uninteresting-regexp))
                     (setq arg (1- arg))
                     (setq previously-wrapped-p nil)))
          (if (not previously-wrapped-p) ; cycle detection
              (progn (goto-char minpos) (setq previously-wrapped-p t))
            (error "No inspectable objects")))))
    ;; Backward.
    (while (< arg 0)
      (seq-let (pos foundp) (cider-find-inspectable-object 'prev minpos)
        ;; CIDER-OPEN-INSPECTOR inserts the title of an inspector page
        ;; as a presentation at the beginning of the buffer; skip
        ;; that.  (Notice how this problem can not arise in ``Forward.'')
        (if (and foundp (/= pos minpos))
            (progn (goto-char pos)
                   (unless (and cider-inspector-skip-uninteresting
                                (looking-at-p cider-inspector-uninteresting-regexp))
                     (setq arg (1+ arg))
                     (setq previously-wrapped-p nil)))
          (if (not previously-wrapped-p) ; cycle detection
              (progn (goto-char maxpos) (setq previously-wrapped-p t))
            (error "No inspectable objects")))))))

(defun cider-inspector-previous-inspectable-object (arg)
  "Move point to the previous inspectable object.
With optional ARG, move across that many objects.
If ARG is negative, move forwards."
  (interactive "p")
  (cider-inspector-next-inspectable-object (- arg)))

(defun cider-inspector-property-at-point ()
  "Return property at point."
  (let* ((properties '(cider-value-idx cider-range-button
                                       cider-action-number))
         (find-property
          (lambda (point)
            (cl-loop for property in properties
                     for value = (get-text-property point property)
                     when value
                     return (list property value)))))
    (or (funcall find-property (point))
        (funcall find-property (max (point-min) (1- (point)))))))

(defun cider-inspector-operate-on-point ()
  "Invoke the command for the text at point.
1. If point is on a value then recursively call the inspector on
that value.
2. If point is on an action then call that action.
3. If point is on a range-button fetch and insert the range."
  (interactive)
  (seq-let (property value) (cider-inspector-property-at-point)
    (pcase property
      (`cider-value-idx
       (cider-inspector-push value))
      ;; TODO: range and action handlers
      (_ (error "No object at point")))))

(defun cider-inspector-operate-on-click (event)
  "Move to EVENT's position and operate the part."
  (interactive "@e")
  (let ((point (posn-point (event-end event))))
    (cond ((and point
                (or (get-text-property point 'cider-value-idx)))
           (goto-char point)
           (cider-inspector-operate-on-point))
          (t
           (error "No clickable part here")))))

(provide 'cider-inspector)

;;; cider-inspector.el ends here