xC: quote text coming from a bracketed paste

Not having this has caused me much annoyance over the years.

xC.c

@@ -238,8 +238,8 @@ struct input_vtable
 	/// Bind Alt+key to the given named function
 	void (*bind_meta) (void *input, char key, const char *fn);
 
-	/// Get the current line input
-	char *(*get_line) (void *input);
+	/// Get the current line input and position within
+	char *(*get_line) (void *input, int *position);
 	/// Clear the current line input
 	void (*clear_line) (void *input);
 	/// Insert text at current position
@@ -361,9 +361,10 @@ input_rl_insert (void *input, const char *s)
 }
 
 static char *
-input_rl_get_line (void *input)
+input_rl_get_line (void *input, int *position)
 {
 	(void) input;
+	if (position) *position = rl_point;
 	return rl_copy_text (0, rl_end);
 }
 
@@ -860,10 +861,12 @@ input_el_insert (void *input, const char *s)
 }
 
 static char *
-input_el_get_line (void *input)
+input_el_get_line (void *input, int *position)
 {
 	struct input_el *self = input;
 	const LineInfo *info = el_line (self->editline);
+	int point = info->cursor - info->buffer;
+	if (position) *position = point;
 	return xstrndup (info->buffer, info->lastchar - info->buffer);
 }
 
@@ -2439,6 +2442,13 @@ static struct config_schema g_config_behaviour[] =
 	  .type      = CONFIG_ITEM_BOOLEAN,
 	  .default_  = "on",
 	  .on_change = on_config_word_wrapping_change },
+	{ .name      = "editor_command",
+	  .comment   = "VIM: \"vim +%Bgo %F\", Emacs: \"emacs -nw +%L:%C %F\"",
+	  .type      = CONFIG_ITEM_STRING },
+	{ .name      = "process_pasted_text",
+	  .comment   = "Normalize newlines and quote the command prefix in pastes",
+	  .type      = CONFIG_ITEM_BOOLEAN,
+	  .default_  = "on" },
 	{ .name      = "date_change_line",
 	  .comment   = "Input to strftime(3) for the date change line",
 	  .type      = CONFIG_ITEM_STRING,
@@ -6894,7 +6904,7 @@ irc_handle_join (struct server *s, const struct irc_message *msg)
 
 		buffer_add (s->ctx, buffer);
 
-		char *input = CALL (s->ctx->input, get_line);
+		char *input = CALL_ (s->ctx->input, get_line, NULL);
 		if (!*input)
 			buffer_activate (s->ctx, buffer);
 		else
@@ -12618,8 +12628,6 @@ process_input (struct app_context *ctx, char *user_input)
 	else
 	{
 		struct strv lines = strv_make ();
-
-		// XXX: this interprets commands in pasted text
 		cstr_split (input, "\r\n", false, &lines);
 		for (size_t i = 0; i < lines.len; i++)
 			(void) process_input_utf8 (ctx,
@@ -13152,7 +13160,7 @@ dump_input_to_file (struct app_context *ctx, char *template, struct error **e)
 	if (fd < 0)
 		return error_set (e, "%s", strerror (errno));
 
-	char *input = CALL (ctx->input, get_line);
+	char *input = CALL_ (ctx->input, get_line, NULL);
 	bool success = xwrite (fd, input, strlen (input), e);
 	free (input);
 
@@ -13180,6 +13188,103 @@ try_dump_input_to_file (struct app_context *ctx)
 	return NULL;
 }
 
+static struct strv
+build_editor_command (struct app_context *ctx, const char *filename)
+{
+	struct strv argv = strv_make ();
+	const char *editor = get_config_string
+		(ctx->config.root, "behaviour.editor_command");
+	if (!editor)
+	{
+		const char *command;
+		if (!(command = getenv ("VISUAL"))
+		 && !(command = getenv ("EDITOR")))
+			command = "vi";
+
+		strv_append (&argv, command);
+		strv_append (&argv, filename);
+		return argv;
+	}
+
+	int cursor = 0;
+	char *input = CALL_ (ctx->input, get_line, &cursor);
+	hard_assert (cursor >= 0);
+
+	mbstate_t ps;
+	memset (&ps, 0, sizeof ps);
+
+	wchar_t wch;
+	size_t len, processed = 0, line_one_based = 1, column = 0;
+	while (processed < (size_t) cursor
+		&& (len = mbrtowc (&wch, input + processed, cursor - processed, &ps))
+		&& len != (size_t) -2 && len != (size_t) -1)
+	{
+		// Both VIM and Emacs use the caret notation with columns.
+		// Consciously leaving tabs broken, they're too difficult to handle.
+		int width = wcwidth (wch);
+		if (width < 0)
+			width = 2;
+
+		processed += len;
+		if (wch == '\n')
+		{
+			line_one_based++;
+			column = 0;
+		}
+		else
+			column += width;
+	}
+	free (input);
+
+	// Trivially split the command on spaces and substitute our values
+	struct str argument = str_make ();
+	for (; *editor; editor++)
+	{
+		if (*editor == ' ')
+		{
+			if (argument.len)
+			{
+				strv_append_owned (&argv, str_steal (&argument));
+				argument = str_make ();
+			}
+			continue;
+		}
+		if (*editor != '%' || !editor[1])
+		{
+			str_append_c (&argument, *editor);
+			continue;
+		}
+
+		// None of them are zero-length, thus words don't get lost
+		switch (*++editor)
+		{
+		case 'F':
+			str_append (&argument, filename);
+			break;
+		case 'L':
+			str_append_printf (&argument, "%zu", line_one_based);
+			break;
+		case 'C':
+			str_append_printf (&argument, "%zu", column + 1);
+			break;
+		case 'B':
+			str_append_printf (&argument, "%d",  cursor + 1);
+			break;
+		case '%':
+		case ' ':
+			str_append_c (&argument, *editor);
+			break;
+		default:
+			print_warning ("unknown substitution variable");
+		}
+	}
+	if (argument.len)
+		strv_append_owned (&argv, str_steal (&argument));
+	else
+		str_free (&argument);
+	return argv;
+}
+
 static bool
 on_edit_input (int count, int key, void *user_data)
 {
@@ -13191,16 +13296,15 @@ on_edit_input (int count, int key, void *user_data)
 	if (!(filename = try_dump_input_to_file (ctx)))
 		return false;
 
-	const char *command;
-	if (!(command = getenv ("VISUAL"))
-	 && !(command = getenv ("EDITOR")))
-		command = "vi";
+	struct strv argv = build_editor_command (ctx, filename);
+	if (!argv.len)
+		strv_append (&argv, "true");
 
 	hard_assert (!ctx->running_editor);
 	switch (spawn_helper_child (ctx))
 	{
 	case 0:
-		execlp (command, command, filename, NULL);
+		execvp (argv.vector[0], argv.vector);
 		print_error ("%s: %s",
 			"Failed to launch editor", strerror (errno));
 		_exit (EXIT_FAILURE);
@@ -13213,6 +13317,7 @@ on_edit_input (int count, int key, void *user_data)
 		ctx->running_editor = true;
 		ctx->editor_filename = filename;
 	}
+	strv_free (&argv);
 	return true;
 }
 
@@ -13698,19 +13803,33 @@ on_editline_complete (EditLine *editline, int key)
 
 	// Insert the best match instead
 	el_insertstr (editline, completions[0]);
+
+	// I'm not sure if Readline's menu-complete can at all be implemented
+	// with Editline--we have no way of detecting what the last executed handler
+	// was.  Employ the formatter's wrapping feature to spew all options.
 	bool only_match = !completions[1];
+	if (!only_match)
+	{
+		CALL (ctx->input, hide);
+		redraw_screen (ctx);
+
+		struct formatter f = formatter_make (ctx, NULL);
+		for (char **p = completions; *++p; )
+			formatter_add (&f, " #l", *p);
+		formatter_add (&f, "\n");
+		formatter_flush (&f, stdout, 0);
+		formatter_free (&f);
+
+		CALL (ctx->input, show);
+	}
+
 	for (char **p = completions; *p; p++)
 		free (*p);
 	free (completions);
-
-	// I'm not sure if Readline's menu-complete can at all be implemented
-	// with Editline.  Spamming the terminal with possible completions
-	// probably isn't what the user wants and we have no way of detecting
-	// what the last executed handler was.
 	if (!only_match)
 		return CC_REFRESH_BEEP;
 
-	// But if there actually is just one match, finish the word
+	// If there actually is just one match, finish the word
 	el_insertstr (editline, " ");
 	return CC_REFRESH;
 }
@@ -14117,6 +14236,40 @@ done:
 
 #define BRACKETED_PASTE_LIMIT 102400    ///< How much text can be pasted
 
+static bool
+insert_paste (struct app_context *ctx, char *paste, size_t len)
+{
+	if (!get_config_boolean (ctx->config.root, "behaviour.process_pasted_text"))
+		return CALL_ (ctx->input, insert, paste);
+
+	// Without ICRNL, which Editline keeps but Readline doesn't,
+	// the terminal sends newlines as carriage returns (seen on urxvt)
+	for (size_t i = 0; i < len; i++)
+		if (paste[i] == '\r')
+			paste[i] = '\n';
+
+	int position = 0;
+	char *input = CALL_ (ctx->input, get_line, &position);
+	bool quote_first_slash = !position || strchr ("\r\n", input[position - 1]);
+	free (input);
+
+	// Executing commands by accident is much more common than pasting them
+	// intentionally, although the latter may also have security consequences
+	struct str processed = str_make ();
+	str_reserve (&processed, len);
+	for (size_t i = 0; i < len; i++)
+	{
+		if (paste[i] == '/'
+			&& ((!i && quote_first_slash) || (i && paste[i - 1] == '\n')))
+			str_append_c (&processed, paste[i]);
+		str_append_c (&processed, paste[i]);
+	}
+
+	bool success = CALL_ (ctx->input, insert, processed.str);
+	str_free (&processed);
+	return success;
+}
+
 static void
 process_bracketed_paste (const struct pollfd *fd, struct app_context *ctx)
 {
@@ -14141,7 +14294,7 @@ process_bracketed_paste (const struct pollfd *fd, struct app_context *ctx)
 			(int) (text_len = BRACKETED_PASTE_LIMIT));
 
 	buf->str[text_len] = '\0';
-	if (CALL_ (ctx->input, insert, buf->str))
+	if (insert_paste (ctx, buf->str, text_len))
 		goto done;
 
 error: