resolve half of the integer_arithmetic lints, couple misc changes

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/admin/appservice/appservice_command.rs

@@ -4,7 +4,7 @@ use crate::{service::admin::escape_html, services, Result};
 
 pub(crate) async fn register(body: Vec<&str>) -> Result<RoomMessageEventContent> {
 	if body.len() > 2 && body[0].trim().starts_with("```") && body.last().unwrap().trim() == "```" {
-		let appservice_config = body[1..body.len() - 1].join("\n");
+		let appservice_config = body[1..body.len().checked_sub(1).unwrap()].join("\n");
 		let parsed_config = serde_yaml::from_str::<Registration>(&appservice_config);
 		match parsed_config {
 			Ok(yaml) => match services().appservice.register_appservice(yaml).await {

src/service/admin/debug/debug_commands.rs

@@ -121,7 +121,7 @@ pub(crate) async fn get_remote_pdu_list(
 	if body.len() > 2 && body[0].trim().starts_with("```") && body.last().unwrap().trim() == "```" {
 		let list = body
 			.clone()
-			.drain(1..body.len() - 1)
+			.drain(1..body.len().checked_sub(1).unwrap())
 			.filter_map(|pdu| EventId::parse(pdu).ok())
 			.collect::<Vec<_>>();
 
@@ -381,7 +381,7 @@ pub(crate) async fn change_log_level(
 
 pub(crate) async fn sign_json(body: Vec<&str>) -> Result<RoomMessageEventContent> {
 	if body.len() > 2 && body[0].trim().starts_with("```") && body.last().unwrap().trim() == "```" {
-		let string = body[1..body.len() - 1].join("\n");
+		let string = body[1..body.len().checked_sub(1).unwrap()].join("\n");
 		match serde_json::from_str(&string) {
 			Ok(mut value) => {
 				ruma::signatures::sign_json(
@@ -404,7 +404,7 @@ pub(crate) async fn sign_json(body: Vec<&str>) -> Result<RoomMessageEventContent
 
 pub(crate) async fn verify_json(body: Vec<&str>) -> Result<RoomMessageEventContent> {
 	if body.len() > 2 && body[0].trim().starts_with("```") && body.last().unwrap().trim() == "```" {
-		let string = body[1..body.len() - 1].join("\n");
+		let string = body[1..body.len().checked_sub(1).unwrap()].join("\n");
 		match serde_json::from_str(&string) {
 			Ok(value) => {
 				let pub_key_map = RwLock::new(BTreeMap::new());

src/service/admin/media/media_commands.rs

@@ -139,14 +139,19 @@ pub(crate) async fn delete(
 
 pub(crate) async fn delete_list(body: Vec<&str>) -> Result<RoomMessageEventContent> {
 	if body.len() > 2 && body[0].trim().starts_with("```") && body.last().unwrap().trim() == "```" {
-		let mxc_list = body.clone().drain(1..body.len() - 1).collect::<Vec<_>>();
+		let mxc_list = body
+			.clone()
+			.drain(1..body.len().checked_sub(1).unwrap())
+			.collect::<Vec<_>>();
 
-		let mut mxc_deletion_count = 0;
+		let mut mxc_deletion_count: u32 = 0;
 
 		for mxc in mxc_list {
 			debug!("Deleting MXC {mxc} in bulk");
 			services().media.delete(mxc.to_owned()).await?;
-			mxc_deletion_count += 1;
+			mxc_deletion_count = mxc_deletion_count
+				.checked_add(1)
+				.expect("mxc_deletion_count should not get this high");
 		}
 
 		return Ok(RoomMessageEventContent::text_plain(format!(

src/service/admin/room/room_directory_commands.rs

@@ -39,7 +39,7 @@ pub(crate) async fn process(command: RoomDirectoryCommand, _body: Vec<&str>) ->
 
 			let rooms = rooms
 				.into_iter()
-				.skip(page.saturating_sub(1) * PAGE_SIZE)
+				.skip(page.checked_sub(1).unwrap().checked_mul(PAGE_SIZE).unwrap())
 				.take(PAGE_SIZE)
 				.collect::<Vec<_>>();
 

src/service/admin/server/server_commands.rs

@@ -33,9 +33,9 @@ pub(crate) async fn memory_usage(_body: Vec<&str>) -> Result<RoomMessageEventCon
 	Ok(RoomMessageEventContent::text_plain(format!(
 		"Services:\n{response0}\n\nDatabase:\n{response1}\n{}",
 		if !response2.is_empty() {
-			"Allocator:\n{response2}"
+			format!("Allocator:\n {response2}")
 		} else {
-			""
+			String::new()
 		}
 	)))
 }

src/service/admin/user/user_commands.rs

@@ -61,8 +61,13 @@ pub(crate) async fn create(
 
 	// If `new_user_displayname_suffix` is set, registration will push whatever
 	// content is set to the user's display name with a space before it
-	if !services().globals.new_user_displayname_suffix().is_empty() {
-		displayname.push_str(&(" ".to_owned() + services().globals.new_user_displayname_suffix()));
+	if !services()
+		.globals
+		.config
+		.new_user_displayname_suffix
+		.is_empty()
+	{
+		_ = write!(displayname, " {}", services().globals.config.new_user_displayname_suffix);
 	}
 
 	services()