feat: implement window kill command

it works for both the active window (no id specified) and to kill a
specific window

src/commands.c

@@ -42,6 +42,8 @@ void window_switch_command(char *tokens[], int ntokens, char *response,
 						 struct turtile_context *context);
 void window_cycle_command(char *tokens[], int ntokens, char *response,
 						 struct turtile_context *context);
+void window_kill_command(char *tokens[], int ntokens, char *response,
+						 struct turtile_context *context);
 void workspace_command(char *tokens[], int ntokens, char *response,
 					   struct turtile_context *context);
 void workspace_list_command(char *tokens[], int ntokens, char *response,
@@ -61,6 +63,7 @@ static command_t commands[] = {
     {"window", "list", window_list_command},
     {"window", "switch", window_switch_command},
     {"window", "cycle", window_cycle_command},
+    {"window", "kill", window_kill_command},
     {"window", NULL, window_command},
     {"workspace", "list", workspace_list_command},
     {"workspace", "switch", workspace_switch_command},
@@ -227,6 +230,35 @@ void window_cycle_command(char *tokens[], int ntokens, char *response,
 			 next_toplevel->xdg_toplevel->title);
 }
 
+void window_kill_command(char *tokens[], int ntokens, char *response,
+					struct turtile_context *context){
+	// kill designated toplevel
+	struct turtile_server *server = context->server;
+	struct turtile_toplevel *toplevel;
+
+	if(ntokens >= 1){
+		char *new_toplevel_id = tokens[0];
+
+		wl_list_for_each(toplevel, &server->focus_toplevels, flink) {
+			if(strcmp(toplevel->id, new_toplevel_id) == 0){
+				kill_toplevel(toplevel);
+				snprintf(response, MAX_MSG_SIZE,
+						 "{\"success\": \"kill: %s\"}",
+						 toplevel->xdg_toplevel->title);
+				return;
+			}
+		}
+		snprintf(response, MAX_MSG_SIZE,
+				 "{\"error\": \"window %s not found\"}", new_toplevel_id);
+
+	} else{
+		toplevel = get_first_toplevel(server);
+		kill_toplevel(toplevel);
+		snprintf(response, MAX_MSG_SIZE,
+				 "{\"success\": \"kill: %s\"}", toplevel->xdg_toplevel->title);
+	}
+}
+
 void workspace_command(char *tokens[], int ntokens, char *response,
 					   struct turtile_context *context){
 	// TODO: use this function as a help for the other workspace subcommands

src/toplevel.c

@@ -76,6 +76,27 @@ void focus_toplevel(struct turtile_toplevel *toplevel, struct wlr_surface *surfa
 	server_redraw_windows(server);
 }
 
+void kill_toplevel(struct turtile_toplevel *toplevel) {
+	struct turtile_server *server = toplevel->server;
+
+	struct wl_list workspace_toplevels; 
+	get_workspace_toplevels(server->active_workspace, &workspace_toplevels);
+
+	if (wl_list_empty(&workspace_toplevels)){
+		wlr_xdg_toplevel_send_close(toplevel->xdg_toplevel);
+		return;
+	} else if (wl_list_length(&workspace_toplevels) < 2) {
+		wlr_xdg_toplevel_send_close(toplevel->xdg_toplevel);
+		return;
+	} 		
+
+	struct turtile_toplevel *next_toplevel =
+		wl_container_of(workspace_toplevels.next, next_toplevel, auxlink);
+	focus_toplevel(next_toplevel, next_toplevel->xdg_toplevel->base->surface);
+
+	wlr_xdg_toplevel_send_close(toplevel->xdg_toplevel);
+}
+
 struct turtile_toplevel *get_first_toplevel(struct turtile_server *server) {
 	struct turtile_toplevel *toplevel;
 	wl_list_for_each(toplevel, &server->focus_toplevels, flink)

src/toplevel.h

@@ -60,6 +60,9 @@ struct turtile_toplevel {
  */
 void focus_toplevel(struct turtile_toplevel *toplevel,
                            struct wlr_surface *surface);
+
+void kill_toplevel(struct turtile_toplevel *toplevel);
+
 /**
  * Retrieves the first toplevel on the active workspace of the given server.
  * If no such toplevel is found, NULL is returned.