>From b58ad0d7c08d0002276f261d508cfca4056cc9ac Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Fri, 22 Apr 2022 03:56:25 -0700
Subject: [PATCH 4/4] [SQUASH-ME] Add hook for splitting multiline input in ERC

* lisp/erc/erc.el (erc-pre-send-split-functions): Add new hook
allowing members to revise individual lines before sending.
(erc-discard-trailing-multiline-nulls): Conditionally truncate
list of lines to be sent, skipping trailing blanks.
(erc-input-split): Add new struct containing split input line.
(erc-send-input): Call hook `erc-pre-send-split-functions'.
---
 lisp/erc/erc.el | 74 ++++++++++++++++++++++++++++++++++---------------
 1 file changed, 51 insertions(+), 23 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index f3685dd2a7..e2fe5c6476 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1040,7 +1040,7 @@ erc-send-pre-hook
   :type 'hook)
 (make-obsolete-variable 'erc-send-pre-hook 'erc-pre-send-functions "27.1")
 
-(defcustom erc-pre-send-functions '(erc-discard-trailing-multiline-nulls)
+(defcustom erc-pre-send-functions nil
   "Special hook run to possibly alter the string that is sent.
 The functions are called with one argument, an `erc-input' struct,
 and should alter that struct.
@@ -1052,7 +1052,26 @@ erc-pre-send-functions
   `sendp': Whether the string should be sent to the irc server."
   :group 'erc
   :type 'hook
-  :package-version '(ERC . "5.4.1")) ; FIXME increment upon publishing to ELPA
+  :version "27.1")
+
+(defcustom erc-pre-send-split-functions '(erc-discard-trailing-multiline-nulls)
+  "Special hook for modifying individual lines in multiline prompt input.
+The functions are called with one argument, an `erc-input-split' struct,
+which they can optionally modify.
+
+The struct has five slots:
+
+  `string': The input string delivered by `erc-pre-send-functions'.
+  `insertp': Whether the lines should be inserted into the ERC buffer.
+  `sendp': Whether the lines should be sent to the IRC server.
+  `lines': A list of lines to be sent, each one a `string'.
+  `cmdp': Whether to interpret the input as a command, like /ignore.
+
+The `string' field is effectively read-only.  When `cmdp' is non-nil,
+all but the first line will be discarded."
+  :group 'erc
+  :type 'hook
+  :package-version '(ERC . "5.4.1"))
 
 (defvar erc-insert-this t
   "Insert the text into the target buffer or not.
@@ -5572,8 +5591,13 @@ erc-discard-trailing-multiline-nulls
   "Ensure last line of `erc-input' STATE's string is non-null.
 But only when `erc-send-whitespace-lines' is non-nil."
   (when erc-send-whitespace-lines
-    (cl-callf (lambda (s) (string-trim-right s "[\r\n]+"))
-        (erc-input-string state))))
+    (when (string-match "[\r\n]+\\'" (erc-input-string state))
+      (setf (erc-input-split-lines state)
+            (split-string (substring (erc-input-string state)
+                                     0
+                                     (match-beginning 0))
+                          erc--input-line-delim-regexp)
+            (erc-input-split-cmdp state) nil))))
 
 (defun erc-check-prompt-input-for-multiline-blanks (string)
   "Return non-nil when multiline prompt input has blank lines."
@@ -5664,6 +5688,9 @@ erc-command-regexp
 (cl-defstruct erc-input
   string insertp sendp)
 
+(cl-defstruct (erc-input-split (:include erc-input))
+  lines cmdp)
+
 (defun erc-send-input (input &optional skip-ws-chk)
   "Treat INPUT as typed in by the user.
 It is assumed that the input and the prompt is already deleted.
@@ -5693,26 +5720,27 @@ erc-send-input
 				  :insertp erc-insert-this
 				  :sendp erc-send-this))
       (run-hook-with-args 'erc-pre-send-functions state)
+      (setq state (make-erc-input-split
+                   :string (erc-input-string state)
+                   :insertp (erc-input-insertp state)
+                   :sendp (erc-input-sendp state)
+                   :lines (split-string (erc-input-string state)
+                                        erc--input-line-delim-regexp)
+                   :cmdp (string-match erc-command-regexp
+                                       (erc-input-string state))))
+      (run-hook-with-args 'erc-pre-send-split-functions state)
       (when (and (erc-input-sendp state)
-		 erc-send-this)
-	(let ((string (erc-input-string state)))
-          (if (or (if (>= emacs-major-version 28)
-                      (string-search "\n" string)
-                    (string-match "\n" string))
-                  (not (string-match erc-command-regexp string)))
-              (mapc
-               (lambda (line)
-		 (mapc
-                  (lambda (line)
-                    ;; Insert what has to be inserted for this.
-		    (when (erc-input-insertp state)
-                      (erc-display-msg line))
-                    (erc-process-input-line (concat line "\n")
-                                            (null erc-flood-protect) t))
-                  (or (and erc-flood-protect (erc-split-line line))
-                      (list line))))
-               (split-string string erc--input-line-delim-regexp))
-            (erc-process-input-line (concat string "\n") t nil))
+                 erc-send-this)
+        (let ((lines (erc-input-split-lines state)))
+          (if (and (erc-input-split-cmdp state) (not (cdr lines)))
+              (erc-process-input-line (concat (car lines) "\n") t nil)
+            (dolist (line lines)
+              (dolist (line (or (and erc-flood-protect (erc-split-line line))
+                                (list line)))
+                (when (erc-input-insertp state)
+                  (erc-display-msg line))
+                (erc-process-input-line (concat line "\n")
+                                        (null erc-flood-protect) t))))
           t)))))
 
 ;; (defun erc-display-command (line)
-- 
2.35.1