;;; erc-nicks.el -- Nick colors for ERC  -*- lexical-binding: t; -*-

;; Copyright (C) 2023 Free Software Foundation, Inc.

;; Author: David Leatherman <leathekd@gmail.com>
;;         Andy Stewart <lazycat.manatee@gmail.com>

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This file provides the `nicks' module for automatic nickname
;; highlighting.  Add `nicks' to `erc-modules' to get started.
;;
;; Use the command `erc-nicks-refresh' to review changes after
;; adjusting an option, like `erc-nicks-contrast-range'.  To change
;; the color of a nickname in a target buffer, click on it and choose
;; "Edit face" from the completion interface, and then perform your
;; adjustments in the resulting Customize menu.  Non-Customize users
;; on Emacs 28+ can persist changes permanently by clicking on the
;; face's "location" hyperlink and copying the generated code snippet
;; (`defface' or `use-package') to their init.el.  Customize users
;; need only click "Apply and Save", as usual.

;;; History:

;; This module has enjoyed a number of contributors across several
;; variants over the years, including:
;;
;;   Thibault Polge <thibault@thb.lt>
;;   Jay Kamat <jaygkamat@gmail.com>
;;   Alex Kost <alezost@gmail.com>
;;   Antoine Levitt <antoine dot levitt at gmail>
;;   Adam Porter <adam@alphapapa.net>
;;
;; To those not mentioned, your efforts are no less appreciated.

;; 2023/05 - erc-nicks
;;           Rewrite using internal API, and rebrand for ERC 5.6
;; 2020/03 - erc-hl-nicks 1.3.4
;;           Final release, see [1] for intervening history
;; 2014/05 - erc-highlight-nicknames.el
;;           Final release, see [2] for intervening history
;; 2011/08 - erc-hl-nicks 1.0
;;           Initial release forked from erc-highlight-nicknames.el
;; 2008/12 - erc-highlight-nicknames.el
;;           First release from Andy Stewart
;; 2007/09 - erc-highlight-nicknames.el
;;           Initial release by by André Riemann

;; [1] <https://www.github.com/leathekd/erc-hl-nicks>
;; [2] <https://www.emacswiki.org/emacs/ErcHighlightNicknames>

;;; Code:

(require 'erc-button)
(require 'color)

(defgroup erc-nicks nil
  "Colorize nicknames in ERC target buffers."
  :package-version '(ERC . "5.6") ; FIXME sync on release
  :group 'erc)

(defcustom erc-nicks-ignore-chars ",`'_-"
  "Trailing characters in a nick to ignore while highlighting.
Value should be a string containing characters typically appended
by IRC clients to secure a nickname after a rejection (see option
`erc-nick-uniquifier').  A value of nil means don't trim
anything."
  :type '(choice (string :tag "Chars to trim")
                 (const :tag "Don't trim" nil)))

(defcustom erc-nicks-skip-nicks nil
  "Nicks to avoid highlighting.
ERC only considers this option during module activation, so users
should adjust it before connecting."
  :type '(repeat string))

(defcustom erc-nicks-skip-faces '( erc-notice-face erc-current-nick-face
                                   erc-my-nick-face erc-pal-face erc-fool-face)
  "Faces to avoid highlighting atop."
  :type  (erc--with-dependent-type-match (repeat face) erc-match))

(defcustom erc-nicks-backing-face erc-button-nickname-face
  "Face to mix with generated one for emphasizing non-speakers."
  :type '(choice face (const nil)))

(defcustom erc-nicks-bg-color
  (frame-parameter (selected-frame) 'background-color)
  "Background color for calculating contrast.
Set this explicitly when the background color isn't discoverable,
which may be the case in terminal Emacs."
  :type 'string)

(defcustom erc-nicks-color-adjustments
  '(erc-nicks-add-contrast erc-nicks-cap-contrast erc-nicks-ensaturate)
  "Treatments applied to improve aesthetics or visibility.
For example, the function `erc-nicks-invert' inverts a nick when
it's too close to the background, and `erc-nicks-add-contrast'
attempts to find a decent contrast ratio by brightening or
darkening.  When `erc-nicks-colors' is set to the symbol
`defined' or a user-provided list of colors, ERC uses this option
as a guide for culling any colors that don't fall within
`erc-nicks-contrast-range' or `erc-nicks-saturation-range', as
appropriate.  For example, if `erc-nicks-cap-contrast' is present
in this option's value, and a color's contrast exceeds the CDR of
`erc-nicks-contrast-range', ERC will purge that color from its
rolls when initializing this module.  Specify a value of nil to
inhibit this process."
  :type '(repeat
          (choice (function-item :tag "Invert" erc-nicks-invert)
                  (function-item :tag "Add contrast" erc-nicks-add-contrast)
                  (function-item :tag "Cap contrast" erc-nicks-cap-contrast)
                  (function-item :tag "Bound saturation" erc-nicks-ensaturate)
                  function)))

(defcustom erc-nicks-contrast-range '(4.3 . 12.5)
  "Desired range of contrast as a cons of (MIN . MAX).
When `erc-nicks-add-contrast' and/or `erc-nicks-invert' appear in
`erc-nicks-color-adjustments', MIN specifies the minimum amount
of contrast allowed between a buffer's background and its
foreground colors.  Depending on the background, nicks may appear
tinted in pastels or shaded with muted grays.  MAX works
similarly for reducing contrast, but only when
`erc-nicks-cap-contrast' is active.  Users with lighter
backgrounds may want to lower MAX significantly.  Either value
can range from 1.0 to 21.0(:1) but may produce unsatisfactory
results toward either extreme."
  :type '(cons float float))

(defcustom erc-nicks-saturation-range '(0.2 . 0.8)
  "Desired range for constraining saturation.
Expressed as a cons of decimal proportions.  Only matters when
`erc-nicks-ensaturate' appears in `erc-nicks-color-adjustments'."
  :type '(cons float float))

(defcustom erc-nicks-colors 'all
  "Pool of colors.
List of colors as strings (hex or named) or, alternatively, a
single symbol representing a set of colors, like that produced by
the function `defined-colors', which ERC associates with the
symbol `defined'.  Similarly, `all' tells ERC to use any 24-bit
color.  When specifying a list, users may want to set the option
`erc-nicks-color-adjustments' to nil to prevent unwanted culling."
  :type '(choice (const all) (const defined) (repeat string)))

(defcustom erc-nicks-key-suffix-format "@%n"
  "Template for latter portion of keys to generate colors from.
ERC passes this to `format-spec' with the following specifiers:
%n for the current network and %m for your nickname (not the one
being colorized).  If you don't like the generated palette, try
adding extra characters or padding, for example, with something
like \"@%-012n\"."
  :type 'string)

(defvar erc-nicks--max-skip-search 3 ; make this an option?
  "Max number of faces to visit when testing `erc-nicks-skip-faces'.")

(defvar erc-nicks--colors-rejects nil)
(defvar erc-nicks--custom-keywords '(:group erc-nicks :group erc-faces))
(defvar erc-nicks--grad-steps 9)

(defvar-local erc-nicks--face-table nil
  "Hash table mapping nicks to unique, named faces.
Keys are nonempty strings but need not be valid nicks.")

(defvar-local erc-nicks--downcased-skip-nicks nil
  "Case-mapped copy of `erc-nicks-skip-nicks'.")

(defvar-local erc-nicks--bg-luminance nil)
(defvar-local erc-nicks--bg-mode-value nil)
(defvar-local erc-nicks--colors-len nil)
(defvar-local erc-nicks--colors-pool nil)
(defvar-local erc-nicks--fg-rgb nil)

(defvar help-xref-stack)
(defvar help-xref-stack-item)

;; https://stackoverflow.com/questions/596216#answer-56678483
(defun erc-nicks--get-luminance (color)
  "Return relative luminance of COLOR.
COLOR can be a list of normalized values or a name.  This is the
same as the Y component returned by `color-srgb-to-xyz'."
  (let ((out 0)
        (coefficients '(0.2126 0.7152 0.0722))
        (chnls (if (stringp color) (color-name-to-rgb color) color)))
    (dolist (ch chnls out)
      (cl-incf out (* (pop coefficients)
                      (if (<= ch 0.04045)
                          (/ ch 12.92)
                        (expt (/ (+ ch 0.055) 1.055) 2.4)))))))

(defun erc-nicks--get-contrast (fg &optional bg)
  "Return a float between 1 and 21 for colors FG and BG.
If FG or BG are floats, interpret them as luminance values."
  (let* ((lum-fg (if (numberp fg) fg (erc-nicks--get-luminance fg)))
         (lum-bg (if bg
                     (if (numberp bg) bg (erc-nicks--get-luminance bg))
                   (or erc-nicks--bg-luminance
                       (setq erc-nicks--bg-luminance
                             (erc-nicks--get-luminance erc-nicks-bg-color))))))
    (when (< lum-fg lum-bg) (cl-rotatef lum-fg lum-bg))
    (/ (+ 0.05 lum-fg) (+ 0.05 lum-bg))))

(defmacro erc-nicks--bg-mode ()
  `(or erc-nicks--bg-mode-value
       (setq erc-nicks--bg-mode-value
             ,(cond ((fboundp 'frame--current-background-mode)
                     '(frame--current-background-mode (selected-frame)))
                    ((fboundp 'frame--current-backround-mode)
                     '(frame--current-backround-mode (selected-frame)))
                    (t
                     '(frame-parameter (selected-frame) 'background-mode))))))

;; https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html
(defun erc-nicks--adjust-contrast (color target &optional decrease)
  (let* ((lum-bg (or erc-nicks--bg-luminance
                     (setq erc-nicks--bg-luminance
                           (erc-nicks--get-luminance erc-nicks-bg-color))))
         (stop (if decrease
                   (color-name-to-rgb erc-nicks-bg-color)
                 erc-nicks--fg-rgb))
         ;; From `color-gradient' in color.el
         (r (nth 0 color))
         (g (nth 1 color))
         (b (nth 2 color))
         (interval (float (1+ (expt 2 erc-nicks--grad-steps))))
         (r-step (/ (- (nth 0 stop) r) interval))
         (g-step (/ (- (nth 1 stop) g) interval))
         (b-step (/ (- (nth 2 stop) b) interval))
         (maxtries erc-nicks--grad-steps)
         started)
    ;; FIXME stop when sufficiently close instead of exhausting.
    (while (let* ((lum-fg (erc-nicks--get-luminance (list r g b)))
                  (darker (if (< lum-bg lum-fg) lum-bg lum-fg))
                  (lighter (if (= darker lum-bg) lum-fg lum-bg))
                  (cur (/ (+ 0.05 lighter) (+ 0.05 darker)))
                  (scale (expt 2 maxtries)))
             (cond ((if decrease (> cur target) (< cur target))
                    (setq r (+ r (* r-step scale))
                          g (+ g (* g-step scale))
                          b (+ b (* b-step scale))))
                   (started
                    (setq r (- r (* r-step scale))
                          g (- g (* g-step scale))
                          b (- b (* b-step scale))))
                   (t (setq maxtries 1)))
             (unless started
               (setq started t))
             (setq r (min 1.0 (max 0 r))
                   g (min 1.0 (max 0 g))
                   b (min 1.0 (max 0 b)))
             (not (zerop (cl-decf maxtries)))))
    (list r g b)))

(defun erc-nicks-add-contrast (color)
  "Increase COLOR's contrast by blending it with the foreground.
Unless sufficient contrast exists between COLOR and the
background, raise it to meet the lower bound of
`erc-nicks-contrast-range'."
  (erc-nicks--adjust-contrast color (car erc-nicks-contrast-range)))

(defun erc-nicks-cap-contrast (color)
  "Reduce COLOR's contrast by blending it with the background.
If excessive contrast exists between COLOR and the background,
lower it to the upper bound of `erc-nicks-contrast-range'."
  (erc-nicks--adjust-contrast color (cdr erc-nicks-contrast-range) 'remove))

(defun erc-nicks-invert (color)
  "Invert COLOR based on the CAR of `erc-nicks-contrast-range'.
Don't bother if the inverted color has less contrast than the
input."
  (if-let ((con-input (erc-nicks--get-contrast color))
           ((< con-input (car erc-nicks-contrast-range)))
           (flipped (mapcar (lambda (c) (- 1.0 c)) color))
           ((> (erc-nicks--get-contrast flipped) con-input)))
      flipped
    color))

(defun erc-nicks-ensaturate (color)
  "Ensure COLOR falls within `erc-nicks-saturation-range'."
  (pcase-let ((`(,min . ,max) erc-nicks-saturation-range)
              (`(,h ,s ,l) (apply #'color-rgb-to-hsl color)))
    (cond ((> s max) (setq color (color-hsl-to-rgb h max l)))
          ((< s min) (setq color (color-hsl-to-rgb h min l)))))
  color)

;; From https://elpa.gnu.org/packages/ement.  The bit depth has been
;; scaled up to try and avoid components being exactly 0.0, which our
;; contrast function doesn't seem to like.
(defun erc-nicks--gen-color (string)
  "Generate normalized RGB color from STRING."
  (let* ((ratio (/ (float (abs (random string))) (float most-positive-fixnum)))
         (color-num (round (* #xffffffffffff ratio))))
    (list (/ (float (logand color-num #xffff)) #xffff)
          (/ (float (ash (logand color-num #xffff0000) -16)) #xffff)
          (/ (float (ash (logand color-num #xffff00000000) -32)) #xffff))))

;; This doesn't add an entry to the face table because "@" faces are
;; interned in the global `obarray' and thus easily accessible.
(defun erc-nicks--revive (new-face old-face nick net)
  (put new-face 'erc-nicks--custom-face t)
  (put new-face 'erc-nicks--nick nick)
  (put new-face 'erc-nicks--netid erc-networks--id)
  (put old-face 'erc-nicks--key nil)
  (apply #'custom-declare-face new-face (face-user-default-spec old-face)
         (format "Persistent `erc-nicks' color for %s on %s." nick net)
         erc-nicks--custom-keywords))

(defun erc-nicks--create-defface-template (face)
  (pop-to-buffer (get-buffer-create (format "*New face %s*" face)))
  (erase-buffer)
  (lisp-interaction-mode)
  (insert ";; If you *don't* use Customize, put something like this in your\n"
          (substitute-command-keys
           ";; init.el and use \\[eval-last-sexp] to apply any edits.\n\n")
          (format "(defface %s\n  '%S\n  %S"
                  face (face-user-default-spec face) (face-documentation face))
          (cl-loop for (k v) on erc-nicks--custom-keywords by #'cddr
                   concat (format "\n  %s %S" k (list 'quote v)))
          ")\n\n;; Or, if you use use-package\n(use-package erc-nicks\n"
          "  :custom-face\n"
          (format "  (%s %S)" face (face-user-default-spec face))
          ")\n"))

(defun erc-nicks--redirect-face-widget-link (args)
  (pcase args
    (`(,widget face-link . ,plist)
     (when-let ((face (widget-value widget))
                ((get face 'erc-nicks--custom-face)))
       (unless (symbol-file face)
         (setf (plist-get plist :action)
               (lambda (&rest _) (erc-nicks--create-defface-template face))))
       (setf (plist-get plist :help-echo) "Create or edit `defface'."
             (cddr args) plist))))
  args)

(defun erc-nicks--reduce (color)
  "Fold adjustment strategies over COLOR, a string or normalized triple.
Return a hex string."
  (apply #'color-rgb-to-hex
         (seq-reduce (lambda (color strategy) (funcall strategy color))
                     erc-nicks-color-adjustments
                     (if (stringp color) (color-name-to-rgb color) color))))

(defun erc-nicks--create-pool (adjustments colors)
  "Return COLORS that fall within parameters indicated by ADJUSTMENTS."
  (let (addp capp satp pool)
    (dolist (adjustment adjustments)
      (pcase adjustment
        ((or 'erc-nicks-invert 'erc-nicks-add-contrast) (setq addp t))
        ('erc-nicks-cap-contrast (setq capp t))
        ('erc-nicks-ensaturate (setq satp t))))
    (dolist (color colors)
      (let* ((rgb (color-name-to-rgb color))
             (contrast (and (or addp capp) (erc-nicks--get-contrast rgb))))
        (if (or (and addp (< contrast (car erc-nicks-contrast-range)))
                (and capp (> contrast (cdr erc-nicks-contrast-range)))
                (and-let* ((satp)
                           (s (cadr (apply #'color-rgb-to-hsl rgb))))
                  (or (< s (car erc-nicks-saturation-range))
                      (> s (cdr erc-nicks-saturation-range)))))
            (when erc-nicks--colors-rejects
              (push color erc-nicks--colors-rejects))
          (push color pool))))
    (nreverse pool)))

(defun erc-nicks--init-pool ()
  "Initialize colors and optionally display faces or color palette."
  (unless (eq erc-nicks-colors 'all)
    (let* ((colors (or (and (listp erc-nicks-colors) erc-nicks-colors)
                       (defined-colors)))
           (pool (erc-nicks--create-pool erc-nicks-color-adjustments colors)))
      (setq erc-nicks--colors-pool pool
            erc-nicks--colors-len (length pool)))))

(defun erc-nicks--determine-color (key)
  (if (eq erc-nicks-colors 'all)
      (erc-nicks--reduce (erc-nicks--gen-color key))
    (let ((pool (erc-with-server-buffer erc-nicks--colors-pool))
          (len (erc-with-server-buffer erc-nicks--colors-len)))
      (nth (% (abs (random key)) len) pool))))

(defun erc-nicks--get-face (nick key)
  "Retrieve a face for trimmed and downcased NICK.
If NICK is new, use KEY to derive color, and store under NICK.
Favor a custom erc-nicks-NICK@NETWORK-face when defined."
  (let ((table (erc-with-server-buffer erc-nicks--face-table)))
    (or (gethash nick table)
        (and-let* ((face (intern-soft (concat "erc-nicks-" nick "@"
                                              (erc-network-name) "-face")))
                   ((or (and (facep face) face)
                        (erc-nicks--revive face face nick (erc-network))))))
        (let ((color (erc-nicks--determine-color key))
              (new-face (make-symbol (concat "erc-nicks-" nick "-face"))))
          (put new-face 'erc-nicks--nick nick)
          (put new-face 'erc-nicks--netid erc-networks--id)
          (put new-face 'erc-nicks--key key)
          (face-spec-set new-face `((t :foreground ,color)) 'face-defface-spec)
          (set-face-documentation
           new-face (format "Internal face for %s on %s." nick (erc-network)))
          (puthash nick new-face table)))))

(define-inline erc-nicks--anon-face-p (face)
  (inline-quote (and (consp ,face) (pcase (car ,face)
                                     ((pred keywordp) t)
                                     ('foreground-color t)
                                     ('background-color t)))))

(defun erc-nicks--skip-p (prop option limit)
  "Return non-nil if a face in PROP appears in OPTION.
Abandon search after examining LIMIT faces."
  (setq prop (if (erc-nicks--anon-face-p prop) (list prop) (ensure-list prop)))
  (catch 'found
    (while-let (((> limit 0))
                (elem (pop prop)))
      (while (and (consp elem) (not (erc-nicks--anon-face-p elem)))
        (when (cdr elem)
          (push (cdr elem) prop))
        (setq elem (car elem)))
      (when elem
        (cl-decf limit)
        (when (if (symbolp elem) (memq elem option) (member elem option))
          (throw 'found elem))))))

(defun erc-nicks--trim (nickname)
  "Return downcased NICKNAME sans trailing `erc-nicks-ignore-chars'."
  (erc-downcase
   (if erc-nicks-ignore-chars
       (string-trim-right nickname
                          (rx-to-string
                           `(: (+ (any ,erc-nicks-ignore-chars)) eot)))
     nickname)))

(defun erc-nicks--gen-key-from-format-spec (nickname)
  "Generate key for NICKNAME according to `erc-nicks-key-suffix-format'."
  (concat nickname (format-spec erc-nicks-key-suffix-format
                                `((?n . ,(erc-network))
                                  (?m . ,(erc-current-nick))))))

(defun erc-nicks--highlight (nickname &optional base-face)
  "Return face for NICKNAME unless it or BASE-FACE is blacklisted."
  (when-let ((trimmed (erc-nicks--trim nickname))
             ((not (member trimmed erc-nicks--downcased-skip-nicks)))
             ((not (and base-face
                        (erc-nicks--skip-p base-face erc-nicks-skip-faces
                                           erc-nicks--max-skip-search))))
             (key (erc-nicks--gen-key-from-format-spec trimmed))
             (out (erc-nicks--get-face trimmed key)))
    (if (or (null erc-nicks-backing-face)
            (eq base-face erc-nicks-backing-face))
        out
      (cons out (erc-list erc-nicks-backing-face)))))

(defun erc-nicks--highlight-button (nick-object)
  "Possibly add face to `erc-button--nick-user' NICK-OBJECT."
  (when-let
      ((nick-object)
       (face (get-text-property (car (erc-button--nick-bounds nick-object))
                                'font-lock-face))
       (nick (erc-server-user-nickname (erc-button--nick-user nick-object)))
       (out (erc-nicks--highlight nick face)))
    (setf (erc-button--nick-nickname-face nick-object) out))
  nick-object)

(define-erc-module nicks nil
  "Uniquely colorize nicknames in target buffers."
  ((if erc--target
       (progn
         (erc-with-server-buffer
           (unless erc-nicks-mode
             (erc--warn-once-before-connect 'erc-nicks-mode
               "Module `nicks' must be enabled or disabled session-wide."
               " Toggling it in individual target buffers is unsupported.")
             (erc-nicks-mode +1))) ; but do it anyway
         (setq erc-nicks--downcased-skip-nicks
               (mapcar #'erc-downcase erc-nicks-skip-nicks))
         (add-function :filter-return (local 'erc-button--modify-nick-function)
                       #'erc-nicks--highlight-button '((depth . 80)))
         (erc-button--phantom-users-mode +1))
     (unless erc-button-mode
       (unless (memq 'button erc-modules)
         (erc--warn-once-before-connect 'erc-nicks-mode
           "Enabling default global module `button' needed by local"
           " module `nicks'. This will impact \C-]all\C-] ERC"
           " sessions. Add `button' to `erc-modules' to avoid this"
           " warning. See Info:\"(erc) Modules\" for more."))
       (erc-button-mode +1))
     (when (equal erc-nicks-bg-color "unspecified-bg")
       (let ((temp (if (eq (erc-nicks--bg-mode) 'light) "white" "black")))
         (erc-button--display-error-notice-with-keys
          "Module `nicks' unable to determine background color.  Setting to \""
          temp "\" globally.  Please see `erc-nicks-bg-color'.")
         (custom-set-variables (list 'erc-nicks-bg-color temp))))
     (erc-nicks--init-pool)
     (erc--restore-initialize-priors erc-nicks-mode
       erc-nicks--face-table (make-hash-table :test #'equal)))
   (setq erc-nicks--fg-rgb
         (or (color-name-to-rgb
              (face-foreground 'erc-default-face nil 'default))
             (color-name-to-rgb
              (readable-foreground-color erc-nicks-bg-color))))
   (setf (alist-get "Edit face" erc-button--nick-popup-alist nil nil #'equal)
         #'erc-nicks-customize-face)
   (advice-add 'widget-create-child-and-convert :filter-args
               #'erc-nicks--redirect-face-widget-link))
  ((kill-local-variable 'erc-nicks--face-table)
   (kill-local-variable 'erc-nicks--bg-mode-value)
   (kill-local-variable 'erc-nicks--bg-luminance)
   (kill-local-variable 'erc-nicks--fg-rgb)
   (kill-local-variable 'erc-nicks--colors-len)
   (kill-local-variable 'erc-nicks--colors-pool)
   (kill-local-variable 'erc-nicks--downcased-skip-nicks)
   (when (fboundp 'erc-button--phantom-users-mode)
     (erc-button--phantom-users-mode -1))
   (remove-function (local 'erc-button--modify-nick-function)
                    #'erc-nicks--highlight-button)
   (setf (alist-get "Edit face"
                    erc-button--nick-popup-alist nil 'remove #'equal)
         nil)
   (unless erc-button--nick-popup-alist
     (kill-local-variable 'erc-button--nick-popup-alist)))
  'local)

(defun erc-nicks-customize-face (nick)
  "Customize or create persistent face for NICK."
  (interactive (list (or (car (get-text-property (point) 'erc-data))
                         (completing-read "nick: " (or erc-channel-users
                                                       erc-server-users)))))
  (setq nick (erc-nicks--trim (substring-no-properties nick)))
  (let* ((net (erc-network))
         (key (erc-nicks--gen-key-from-format-spec nick))
         (old-face (erc-nicks--get-face nick key))
         (new-face (intern (format "erc-nicks-%s@%s-face" nick net))))
    (unless (eq new-face old-face)
      (erc-nicks--revive new-face old-face nick net)
      (set-face-attribute old-face nil :foreground 'unspecified)
      (set-face-attribute old-face nil :inherit new-face))
    (customize-face new-face)))

(defun erc-nicks--list-faces-help-button-action (face)
  (when-let (((or (get face 'erc-nicks--custom-face)
                  (y-or-n-p (format "Create new persistent face for %s?"
                                    (get face 'erc-nicks--key)))))
             (nid (get face 'erc-nicks--netid))
             (foundp (lambda ()
                       (erc-networks--id-equal-p nid erc-networks--id)))
             (server-buffer (car (erc-buffer-filter foundp))))
    (with-current-buffer server-buffer
      (erc-nicks-customize-face (get face 'erc-nicks--nick)))))

(defun erc-nicks-list-faces ()
  "Show faces owned by ERC-nicks in a help buffer."
  (interactive)
  (save-excursion
    (list-faces-display (rx bot "erc-nicks-"))
    (with-current-buffer "*Faces*"
      (setq help-xref-stack nil
            help-xref-stack-item '(erc-nicks-list-faces))
      (with-silent-modifications
        (goto-char (point-min))
        (while (zerop (forward-line))
          (when (and (get-text-property (point) 'button)
                     (facep (car (button-get (point) 'help-args))))
            (button-put (point) 'help-function
                        #'erc-nicks--list-faces-help-button-action)
            (if-let ((face (car (button-get (point) 'help-args)))
                     ((not (get face 'erc-nicks--custom-face)))
                     ((not (get face 'erc-nicks--key))))
                (progn (delete-region (pos-bol) (1+ (pos-eol)))
                       (forward-line -1))
              (when-let ((nid (get face 'erc-nicks--netid))
                         (net (symbol-name (erc-networks--id-symbol nid))))
                (goto-char (button-end (point)))
                (skip-syntax-forward "-")
                (put-text-property (point) (1+ (point)) 'rear-nonsticky nil)
                (forward-char)
                (when (stringp (face-foreground face))
                  (setq net (format "%-13.13s %s" (substring-no-properties
                                                   (face-foreground face))
                                    net)))
                (insert-and-inherit net)
                (delete-region (button-start (point))
                               (1+ (button-start (point))))
                (delete-region (point) (pos-eol))))))))))

(defun erc-nicks-refresh (debug)
  "Recompute faces for all nicks on current network.
With DEBUG, review affected faces or colors.  Which one depends
on the value of `erc-nicks-colors'."
  (interactive "P")
  (unless (derived-mode-p 'erc-mode)
    (user-error "Not an ERC buffer"))
  (erc-with-server-buffer
    (unless erc-nicks-mode (user-error "Module `nicks' disabled"))
    (let ((erc-nicks--colors-rejects (and debug (list t))))
      (erc-nicks--init-pool)
      (dolist (nick (hash-table-keys erc-nicks--face-table))
        ;; User-tuned faces do not have an `erc-nicks--key' property.
        (when-let ((face (gethash nick erc-nicks--face-table))
                   (key (get face 'erc-nicks--key)))
          (setq key (erc-nicks--gen-key-from-format-spec nick))
          (put face 'erc-nicks--key key)
          (set-face-foreground face (erc-nicks--determine-color key))))
      (when debug
        (if (eq erc-nicks-colors 'all)
            (erc-nicks-list-faces)
          (pcase-dolist (`(,name ,pool)
                         `(("*erc-nicks-pool*" ,erc-nicks--colors-pool)
                           ("*erc-nicks-rejects*"
                            ,(cdr (nreverse erc-nicks--colors-rejects)))))
            (when (buffer-live-p (get-buffer name))
              (kill-buffer name))
            (when pool
              (save-excursion
                (list-colors-display
                 pool name
                 (lambda (c)
                   (message "contrast: %.3f :saturation: %.3f"
                            (erc-nicks--get-contrast c)
                            (cadr (apply #'color-rgb-to-hsl
                                         (color-name-to-rgb c))))))))))))))

(provide 'erc-nicks)

;;; erc-nicks.el ends here