emacs/lisp/erc/erc-common.el

;;; erc-common.el --- Macros and types for ERC  -*- lexical-binding:t -*-

;; Copyright (C) 2022-2024 Free Software Foundation, Inc.
;;
;; Maintainer: Amin Bandali <bandali@gnu.org>, F. Jason Park <jp@neverwas.me>
;; Keywords: comm, IRC, chat, client, internet
;;
;; 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:
;;; Code:

(eval-when-compile (require 'cl-lib) (require 'subr-x))
(require 'erc-compat)

(defvar erc--casemapping-rfc1459)
(defvar erc--casemapping-rfc1459-strict)
(defvar erc-channel-users)
(defvar erc-insert-this)
(defvar erc-modules)
(defvar erc-send-this)
(defvar erc-server-process)
(defvar erc-server-users)
(defvar erc-session-server)

(declare-function erc--get-isupport-entry "erc-backend" (key &optional single))
(declare-function erc--init-cusr-fallback-status "erc" (v h o a q))
(declare-function erc-get-buffer "erc" (target &optional proc))
(declare-function erc-server-buffer "erc" nil)
(declare-function widget-apply-action "wid-edit" (widget &optional event))
(declare-function widget-at "wid-edit" (&optional pos))
(declare-function widget-create-child-and-convert "wid-edit"
                  (parent type &rest args))
(declare-function widget-default-format-handler "wid-edit" (widget escape))
(declare-function widget-get-sibling "wid-edit" (widget))
(declare-function widget-move "wid-edit" (arg &optional suppress-echo))
(declare-function widget-type "wid-edit" (widget))

(cl-defstruct erc-input
  "Object shared among members of `erc-pre-send-functions'.
Any use outside of the hook is not supported."
  ( string "" :type string
    :documentation "String to send and, without `substxt', insert.
ERC treats separate lines as separate messages.")
  ( insertp nil :type boolean
    :documentation "Whether to insert outgoing message.
When nil, ERC still sends `string'.")
  ( sendp nil :type boolean
    :documentation "Whether to send and (for compat reasons) insert.
To insert without sending, define a (slash) command.")
  ( substxt nil :type (or function string null)
    :documentation "Alternate string to insert without splitting.
The function form is for internal use.")
  ( refoldp nil :type boolean
    :documentation "Whether to resplit a possibly overlong `string'.
ERC only refolds `string', never `substxt'."))

(cl-defstruct (erc--input-split (:include erc-input
                                          (string "" :read-only t)
                                          (insertp erc-insert-this)
                                          (sendp (with-suppressed-warnings
                                                     ((obsolete erc-send-this))
                                                   erc-send-this))))
  (lines nil :type (list-of string))
  (abortp nil :type (list-of symbol))
  (cmdp nil :type boolean))

(cl-defstruct (erc-server-user (:type vector) :named)
  ;; User data
  nickname host login full-name info
  ;; Buffers
  (buffers nil))

(cl-defstruct (erc-channel-user (:type vector)
                                (:constructor
                                 erc-channel-user--make
                                 (&key (status 0) (last-message-time nil)))
                                (:constructor
                                 make-erc-channel-user
                                 ( &key voice halfop op admin owner
                                   last-message-time
                                   &aux (status
                                         (if (or voice halfop op admin owner)
                                             (erc--init-cusr-fallback-status
                                              voice halfop op admin owner)
                                           0))))
                                :named)
  "Object containing channel-specific data for a single user."
  ;; voice halfop op admin owner
  (status 0 :type integer)
  ;; Last message time (in the form of the return value of
  ;; (current-time)
  ;;
  ;; This is useful for ordered name completion.
  (last-message-time nil))

(cl-defstruct erc--target
  (string "" :type string :documentation "Received name of target.")
  (symbol nil :type symbol :documentation "Case-mapped name as symbol."))

;; At some point, it may make sense to add a separate query type,
;; possibly with an account field to help reassociation across
;; reconnects and nick changes.

(cl-defstruct (erc--target-channel (:include erc--target))
  (joined-p nil :type boolean :documentation "Whether channel is joined."))

(cl-defstruct (erc--target-channel-local (:include erc--target-channel)))

;; Beginning in 5.5/29.1, the `tags' field may take on one of two
;; differing types.  See `erc-tags-format' for details.

(cl-defstruct (erc-response (:conc-name erc-response.))
  (unparsed "" :type string)
  (sender "" :type string)
  (command "" :type string)
  (command-args '() :type list)
  (contents "" :type string)
  (tags '() :type list))

(cl-defstruct (erc--ctcp-response
               (:include erc-response)
               (:constructor
                erc--ctcp-response-from-parsed
                (&key parsed buffer statusmsg prefix dispname
                      &aux (unparsed (erc-response.unparsed parsed))
                      (sender (erc-response.sender parsed))
                      (command (erc-response.command parsed))
                      (command-args (erc-response.command-args parsed))
                      (contents (erc-response.contents parsed))
                      (tags (erc-response.tags parsed)))))
  "Data for a processed CTCP query or reply."
  (buffer nil :type (or buffer null))
  (statusmsg nil :type (or null string))
  (prefix nil :type (or erc-channel-user null))
  (dispname nil :type (or string null)))

(cl-defstruct erc--isupport-data
  "Abstract \"class\" for parsed ISUPPORT data.
For use with the macro `erc--with-isupport-data'."
  (key nil :type (or null cons)))

(cl-defstruct (erc--parsed-prefix (:include erc--isupport-data))
  "Server-local data for recognized membership-status prefixes.
Derived from the advertised \"PREFIX\" ISUPPORT parameter."
  ( letters "vhoaq" :type string
    :documentation "Status letters ranked lowest to highest.")
  ( statuses "+%@&~" :type string
    :documentation "Status prefixes ranked lowest to highest.")
  ( alist nil :type (list-of cons)
    :documentation "Alist of letters-prefix pairs."))

(cl-defstruct (erc--channel-mode-types (:include erc--isupport-data))
  "Server-local \"CHANMODES\" data."
  (fallbackp nil :type boolean)
  (table (make-char-table 'erc--channel-mode-types) :type char-table)
  (shortargs (make-hash-table :test #'equal)))

;; After dropping 28, we can use prefixed "erc-autoload" cookies.
(defun erc--normalize-module-symbol (symbol)
  "Return preferred SYMBOL for `erc--module'."
  (while-let ((canonical (get symbol 'erc--module))
              ((not (eq canonical symbol))))
    (setq symbol canonical))
  symbol)

(defvar erc--inside-mode-toggle-p nil
  "Non-nil when a module's mode toggle is updating module membership.
This serves as a flag to inhibit the mutual recursion that would
otherwise occur between an ERC-defined minor-mode function, such
as `erc-services-mode', and the custom-set function for
`erc-modules'.  For historical reasons, the latter calls
`erc-update-modules', which, in turn, enables the minor-mode
functions for all member modules.  Also non-nil when a mode's
widget runs its set function.")

(defun erc--favor-changed-reverted-modules-state (name op)
  "Be more nuanced in displaying Custom state of `erc-modules'.
When `customized-value' differs from `saved-value', allow widget
to behave normally and show \"SET for current session\", as
though `customize-set-variable' or similar has been applied.
However, when `customized-value' and `standard-value' match but
differ from `saved-value', prefer showing \"CHANGED outside
Customize\" to prevent the widget from seeing a `standard'
instead of a `set' state, which precludes any actual saving."
  ;; Although the button "Apply and save" is fortunately grayed out,
  ;; `Custom-save' doesn't actually save (users must click the magic
  ;; state button instead).  The default behavior described in the doc
  ;; string is intentional and was introduced by bug#12864 "Make state
  ;; button interaction less confusing".  However, it is unfriendly to
  ;; rogue libraries (like ours) that insist on mutating user options
  ;; as a matter of course.
  (custom-load-symbol 'erc-modules)
  (funcall (get 'erc-modules 'custom-set) 'erc-modules
           (funcall op (erc--normalize-module-symbol name) erc-modules))
  (when (equal (pcase (get 'erc-modules 'saved-value)
                 (`((quote ,saved)) saved))
               erc-modules)
    (customize-mark-as-set 'erc-modules)))

(defun erc--assemble-toggle (localp name ablsym mode val body)
  (let ((arg (make-symbol "arg")))
    `(defun ,ablsym ,(if localp `(&optional ,arg) '())
       ,(erc--fill-module-docstring
         (if val "Enable" "Disable")
         " ERC " (symbol-name name) " mode" (and localp " locally") "."
         (when localp
           (concat "\nWhen called interactively,"
                   " do so in all buffers for the current connection.")))
       (interactive ,@(when localp '("p")))
       ,@(if localp
             `((when (derived-mode-p 'erc-mode)
                 (if ,arg
                     (erc-with-all-buffers-of-server erc-server-process nil
                       (,ablsym))
                   (setq ,mode ,val)
                   ,@body)))
           ;; No need for `default-value', etc. because a buffer-local
           ;; `erc-modules' only influences the next session and
           ;; doesn't survive the major-mode reset that soon follows.
           `((unless
                 (or erc--inside-mode-toggle-p
                     ,@(let ((v `(memq ',(erc--normalize-module-symbol name)
                                       erc-modules)))
                         `(,(if val v `(not ,v)))))
               (let ((erc--inside-mode-toggle-p t))
                 (erc--favor-changed-reverted-modules-state
                  ',name #',(if val 'cons 'delq))))
             (setq ,mode ,val)
             ,@body)))))

;; This is a migration helper that determines a module's `:group'
;; keyword argument from its name or alias.  A (global) module's minor
;; mode variable appears under the group's Custom menu.  Like
;; `erc--normalize-module-symbol', it must run when the module's
;; definition (rather than that of `define-erc-module') is expanded.
;; For corner cases in which this fails or the catch-all of `erc' is
;; more inappropriate, (global) modules can declare a top-level
;;
;;   (put 'foo 'erc-group 'erc-bar)
;;
;; where `erc-bar' is the group and `foo' is the normalized module.
;; Do this *before* the module's definition.  If `define-erc-module'
;; ever accepts arbitrary keywords, passing an explicit `:group' will
;; obviously be preferable.

(defun erc--find-group (&rest symbols)
  (catch 'found
    (dolist (s symbols)
      (let* ((downed (downcase (symbol-name s)))
             (known (intern-soft (concat "erc-" downed))))
        (when (and known
                   (or (get known 'group-documentation)
                       (rassq known custom-current-group-alist)))
          (throw 'found known))
        (when (setq known (intern-soft (concat "erc-" downed "-mode")))
          (when-let* ((found (custom-group-of-mode known)))
            (throw 'found found))))
      (when-let* ((found (get (erc--normalize-module-symbol s) 'erc-group)))
        (throw 'found found)))
    'erc))

;; This exists as a separate, top-level function to prevent the byte
;; compiler from warning about widget-related dependencies not being
;; loaded at runtime.

(defun erc--tick-module-checkbox (name &rest _) ; `name' must be normalized
  (customize-variable-other-window 'erc-modules)
  ;; Move to `erc-modules' section.
  (while (not (eq (widget-type (widget-at)) 'checkbox))
    (widget-move 1 t))
  ;; This search for a checkbox can fail when `name' refers to a
  ;; third-party module that modifies `erc-modules' (improperly) on
  ;; load.
  (let (w)
    (while (and (eq (widget-type (widget-at)) 'checkbox)
                (not (and (setq w (widget-get-sibling (widget-at)))
                          (eq (widget-value w) name))))
      (setq w nil)
      (widget-move 1 t)) ; the `suppress-echo' arg exists in 27.2
    (unless w
      (error "Failed to find %s in `erc-modules' checklist" name))
    (widget-apply-action (widget-at))
    (message "Hit %s to apply or %s to apply and save."
             (substitute-command-keys "\\[Custom-set]")
             (substitute-command-keys "\\[Custom-save]"))))

;; This stands apart to avoid needing forward declarations for
;; `wid-edit' functions in every file requiring `erc-common'.
(defun erc--make-show-me-widget (widget escape &rest plist)
  (if (eq escape ?i)
      (apply #'widget-create-child-and-convert widget 'push-button plist)
    (widget-default-format-handler widget escape)))

(defun erc--prepare-custom-module-type (name)
  `(let* ((name (erc--normalize-module-symbol ',name))
          (fmtd (format " `%s' " name)))
     `(boolean
       :format "%{%t%}: %i %[Deprecated Toggle%] %v \n%h\n"
       :format-handler
       ,(lambda (widget escape)
          (erc--make-show-me-widget
           widget escape
           :button-face '(custom-variable-obsolete custom-button)
           :tag "Show Me"
           :action (apply-partially #'erc--tick-module-checkbox name)
           :help-echo (lambda (_)
                        (let ((hasp (memq name erc-modules)))
                          (concat (if hasp "Remove" "Add") fmtd
                                  (if hasp "from" "to")
                                  " `erc-modules'.")))))
       :action widget-toggle-action
       :documentation-property
       ,(lambda (_)
          (let ((hasp (memq name erc-modules)))
            (concat
             "Setting a module's minor-mode variable is "
             (propertize "ineffective" 'face 'error)
             ".\nPlease " (if hasp "remove" "add") fmtd
             (if hasp "from" "to") " `erc-modules' directly instead.\n"
             "You can do so now by clicking "
             (propertize "Show Me" 'face 'custom-variable-obsolete)
             " above."))))))

(defun erc--fill-module-docstring (&rest strings)
  "Concatenate STRINGS and fill as a doc string."
  ;; Perhaps it's better to mimic `internal--format-docstring-line'
  ;; and use basic filling instead of applying a major mode?
  (with-temp-buffer
    (delay-mode-hooks
      (if (fboundp 'lisp-data-mode) (lisp-data-mode) (emacs-lisp-mode)))
    (insert (format "%S" (apply #'concat strings)))
    (goto-char (point-min))
    (forward-line)
    (let ((fill-column 65)
          (sentence-end-double-space t))
      (fill-paragraph))
    (goto-char (point-min))
    (read (current-buffer))))

(defmacro erc--find-feature (name alias)
  ;; Don't use this outside of the file that defines NAME.
  `(pcase (erc--find-group ',name ,(and alias (list 'quote alias)))
     ('erc (and-let* ((file (or (macroexp-file-name) buffer-file-name)))
             (intern (file-name-base file))))
     (v v)))

(defvar erc--module-toggle-prefix-arg nil
  "The interpreted prefix arg of the minor-mode toggle.
Non-nil inside an ERC module's activation (or deactivation)
command, such as `erc-spelling-enable', when it's been called
indirectly via the module's minor-mode toggle, i.e.,
`erc-spelling-mode'.  nil otherwise.  Its value is either the
symbol `toggle' or an integer produced by `prefix-numeric-value'.
See Info node `(elisp) Defining Minor Modes' for more.")

(defmacro define-erc-module (name alias doc enable-body disable-body
                                  &optional local-p)
  "Define a new minor mode using ERC conventions.
Expect NAME to be the module's name and ALIAS, when non-nil, to
be a retired name used only for compatibility purposes.  In new
code, assume NAME is the same symbol users should specify when
customizing `erc-modules' (see info node `(erc) Module Loading'
for more on naming).

DOC is the documentation string to use for the minor mode.
ENABLE-BODY is a list of expressions used to enable the mode.
DISABLE-BODY is a list of expressions used to disable the mode.
If LOCAL-P is non-nil, the mode will be created as a buffer-local
mode, rather than a global one.

This will define a minor mode called erc-NAME-mode, possibly
an alias erc-ALIAS-mode, as well as the helper functions
erc-NAME-enable, and erc-NAME-disable.

With LOCAL-P, these helpers take on an optional argument that,
when non-nil, causes them to act on all buffers of a connection.
This feature is mainly intended for interactive use and does not
carry over to their respective minor-mode toggles.  Beware that
for global modules, these helpers and toggles all mutate
`erc-modules'.

Example:

  ;;;###autoload(autoload \\='erc-replace-mode \"erc-replace\")
  (define-erc-module replace nil
    \"This mode replaces incoming text according to `erc-replace-alist'.\"
    ((add-hook \\='erc-insert-modify-hook
               #\\='erc-replace-insert))
    ((remove-hook \\='erc-insert-modify-hook
                  #\\='erc-replace-insert)))"
  (declare (doc-string 3) (indent defun))
  (let* ((sn (symbol-name name))
         (mode (intern (format "erc-%s-mode" (downcase sn))))
         (enable (intern (format "erc-%s-enable" (downcase sn))))
         (disable (intern (format "erc-%s-disable" (downcase sn))))
         (nmodule (erc--normalize-module-symbol name))
         (amod (and alias (intern (format "erc-%s-mode"
                                          (downcase (symbol-name alias)))))))
    `(progn
       (define-minor-mode
         ,mode
         ,(erc--fill-module-docstring (format "Toggle ERC %s mode%s.
If called interactively, enable `%s' if ARG is positive,
and disable it otherwise.  If called from Lisp, enable the mode
if ARG is omitted or nil.
\n%s" name (if local-p " locally" "") mode doc))
         :global ,(not local-p)
         :group (erc--find-group ',name ,(and alias (list 'quote alias)))
         ,@(unless local-p `(:require ',(erc--find-feature name alias)))
         ,@(unless local-p `(:type ,(erc--prepare-custom-module-type name)))
         (let ((erc--module-toggle-prefix-arg arg))
           (if ,mode (,enable) (,disable))))
       ,(erc--assemble-toggle local-p name enable mode t enable-body)
       ,(erc--assemble-toggle local-p name disable mode nil disable-body)
       ,@(and amod `((defalias ',amod #',mode)
                     (put ',amod 'erc-module ',nmodule)))
       (put ',mode 'erc-module ',nmodule)
       ;; For find-function and find-variable.
       (put ',mode    'definition-name ',name)
       (put ',enable  'definition-name ',name)
       (put ',disable 'definition-name ',name))))

(defmacro erc-with-buffer (spec &rest body)
  "Execute BODY in the buffer associated with SPEC.

SPEC should have the form

 (TARGET [PROCESS])

If TARGET is a buffer, use it.  Otherwise, use the buffer
matching TARGET in the process specified by PROCESS.

If PROCESS is nil, use the current `erc-server-process'.
See `erc-get-buffer' for details.

See also `with-current-buffer'.

\(fn (TARGET [PROCESS]) BODY...)"
  (declare (indent 1) (debug ((form &optional form) body)))
  (let ((buf (make-symbol "buf"))
        (proc (make-symbol "proc"))
        (target (make-symbol "target"))
        (process (make-symbol "process")))
    `(let* ((,target ,(car spec))
            (,process ,(cadr spec))
            (,buf (if (bufferp ,target)
                      ,target
                    (let ((,proc (or ,process
                                     (and (processp erc-server-process)
                                          erc-server-process))))
                      (if (and ,target ,proc)
                          (erc-get-buffer ,target ,proc))))))
       (when (buffer-live-p ,buf)
         (with-current-buffer ,buf
           ,@body)))))

(defmacro erc-with-server-buffer (&rest body)
  "Execute BODY in the current ERC server buffer.
If no server buffer exists, return nil."
  (declare (indent 0) (debug (body)))
  (let ((varp (and (symbolp (car body))
                   (not (cdr body))
                   (special-variable-p (car body))))
        (buffer (make-symbol "buffer")))
    `(when-let* (((processp erc-server-process))
                 (,buffer (process-buffer erc-server-process))
                 ((buffer-live-p ,buffer)))
       ,(if varp
            `(buffer-local-value ',(car body) ,buffer)
          `(with-current-buffer ,buffer
             ,@body)))))

(defmacro erc-with-all-buffers-of-server (process pred &rest forms)
  "Evaluate FORMS in all buffers of PROCESS in which PRED returns non-nil.
When PROCESS is nil, do so in all ERC buffers.  When PRED is nil,
run FORMS unconditionally."
  (declare (indent 2) (debug (form form body)))
  (macroexp-let2 nil pred pred
    `(erc-buffer-filter (lambda ()
                          (when (or (not ,pred) (funcall ,pred))
                            ,@forms))
                        ,process)))

(defvar-local erc--target nil
  "A permanent `erc--target' struct instance in channel and query buffers.")

(define-inline erc-target ()
  "Return target of current buffer, if any, as a string."
  (inline-quote (and erc--target (erc--target-string erc--target))))

(defun erc-log-aux (string)
  "Do the debug logging of STRING."
  (let ((cb (current-buffer))
        (point 1)
        (was-eob nil)
        (session-buffer (erc-server-buffer)))
    (if session-buffer
        (progn
          (set-buffer session-buffer)
          (defvar erc-dbuf)
          (if (not (and erc-dbuf (bufferp erc-dbuf) (buffer-live-p erc-dbuf)))
              (progn
                (setq erc-dbuf (get-buffer-create
                                (concat "*ERC-DEBUG: "
                                        erc-session-server "*")))))
          (set-buffer erc-dbuf)
          (setq point (point))
          (setq was-eob (eobp))
          (goto-char (point-max))
          (insert (concat "** " string "\n"))
          (if was-eob (goto-char (point-max))
            (goto-char point))
          (set-buffer cb))
      (message "ERC: ** %s" string))))

(defvar erc-log-p nil
  "When non-nil, generate debug messages in an \"*ERC-DEBUG*\" buffer.")

(define-inline erc-log (string)
  "Logs STRING if logging is on (see `erc-log-p')."
  (inline-quote
   (when erc-log-p
     (erc-log-aux ,string))))

(defun erc-downcase (string)
  "Return a downcased copy of STRING with properties.
Use the CASEMAPPING ISUPPORT parameter to determine the style."
  (with-case-table (pcase (erc--get-isupport-entry 'CASEMAPPING 'single)
                     ("ascii" ascii-case-table)
                     ("rfc1459-strict" erc--casemapping-rfc1459-strict)
                     (_ erc--casemapping-rfc1459))
    (downcase string)))

(define-inline erc-get-channel-member (nick)
  "Find NICK in the current buffer's `erc-channel-members' hash table."
  (inline-quote (gethash (erc-downcase ,nick) erc-channel-users)))
(defalias 'erc-get-channel-user #'erc-get-channel-member)

(define-inline erc-get-server-user (nick)
  "Find NICK in the current server's `erc-server-users' hash table."
  (inline-letevals (nick)
    (inline-quote
     (gethash (erc-downcase ,nick)
              (erc-with-server-buffer erc-server-users)))))

(defun erc--get-server-user (nick)
  (erc-get-server-user nick))

(define-inline erc--remove-user-from-targets (downcased-nick buffers)
  "Remove DOWNCASED-NICK from `erc-channel-members' in BUFFERS."
  (inline-quote
   (progn
     (defvar erc-channel-members-changed-hook)
     (dolist (buffer ,buffers)
       (when (buffer-live-p buffer)
         (with-current-buffer buffer
           (remhash ,downcased-nick erc-channel-users)
           (when erc-channel-members-changed-hook
             (run-hooks 'erc-channel-members-changed-hook))))))))

(defmacro erc--with-dependent-type-match (type &rest features)
  "Massage Custom :type TYPE with :match function that pre-loads FEATURES."
  `(backquote-list* ',(car type)
                    :match (lambda (w v)
                             ,@(mapcar (lambda (ft) `(require ',ft)) features)
                             (,(widget-get (widget-convert type) :match) w v))
                    ',(cdr type)))

;; This internal variant exists as a transition aid to avoid
;; immediately having to reflow lengthy definition lists, like the one
;; in erc.el.  These sites should switch to using the public macro
;; when undergoing their next major edit.
(defmacro erc--define-catalog (name entries)
  "Define `erc-display-message' formatting templates for NAME, a symbol.

See `erc-define-message-format-catalog' for the meaning of
ENTRIES, an alist, and `erc-tests-common-pp-propertized-parts' in
tests/lisp/erc/erc-tests.el for a convenience command to convert
a literal string into a sequence of `propertize' forms, which are
much easier to review and edit.  When ENTRIES begins with a
sequence of keyword-value pairs remove them and consider their
evaluated values before processing the alist proper.

Currently, the only recognized keyword is `:parent', which tells
ERC to search recursively for a given template key using the
keyword's associated value, another catalog symbol, if not found
in catalog NAME."
  (declare (indent 1))
  (let (out)
    (while (keywordp (car entries))
      (push (pcase-exhaustive (pop entries)
              (:parent `(put ',name 'erc--base-format-catalog
                             ,(pop entries))))
            out))
    (dolist (e entries (cons 'progn (nreverse out)))
      (push `(defvar ,(intern (format "erc-message-%s-%s" name (car e)))
               ,(cdr e)
               ,(let* ((first (format "Message template for key `%s'" (car e)))
                       (last (format "catalog `%s'." name))
                       (combined (concat first " in " last)))
                  (if (< (length combined) 80)
                      combined
                    (concat first ".\nFor use with " last))))
            out))))

(defmacro erc-define-message-format-catalog (language &rest entries)
  "Define message-formatting templates for LANGUAGE, a symbol.
Expect ENTRIES to be pairs of (KEY . FORMAT), where KEY is a
symbol, and FORMAT evaluates to a format string compatible with
`format-spec'.  Expect modules that only define a handful of
entries to do so manually, instead of using this macro, so that
the resulting variables will end up with more useful doc strings."
  (declare (indent 1)
           (debug (symbolp [&rest [keywordp form]] &rest (symbolp . form))))
  `(erc--define-catalog ,language ,entries))

(define-inline erc--strpos (char string)
  "Return position of CHAR in STRING or nil if not found."
  (inline-quote (string-search (string ,char) ,string)))

(define-inline erc--solo (list-or-atom)
  "If LIST-OR-ATOM is a list of one element, return that element.
Otherwise, return LIST-OR-ATOM."
  (inline-letevals (list-or-atom)
    (inline-quote
     (if (and (consp ,list-or-atom) (null (cdr ,list-or-atom)))
         (car ,list-or-atom)
       ,list-or-atom))))

(defmacro erc--doarray (spec &rest body)
  "Map over ARRAY, running BODY with VAR bound to iteration element.
Behave more or less like `seq-doseq', but tailor operations for
arrays.

\(fn (VAR ARRAY [RESULT]) BODY...)"
  (declare (indent 1) (debug ((symbolp form &optional form) body)))
  (let ((array (make-symbol "array"))
        (len (make-symbol "len"))
        (i (make-symbol "i")))
    `(let* ((,array ,(nth 1 spec))
            (,len (length ,array))
            (,i 0))
       (while-let (((< ,i ,len))
                   (,(car spec) (aref ,array ,i)))
         ,@body
         (cl-incf ,i))
       ,(nth 2 spec))))

(provide 'erc-common)

;;; erc-common.el ends here