navigate: Convert module to TypeScript.

tools/test-js-with-node

@@ -160,7 +160,7 @@ EXEMPT_FILES = make_set(
         "web/src/navbar_alerts.ts",
         "web/src/navbar_help_menu.ts",
         "web/src/navbar_menus.js",
-        "web/src/navigate.js",
+        "web/src/navigate.ts",
         "web/src/onboarding_steps.ts",
         "web/src/overlay_util.ts",
         "web/src/overlays.ts",

web/src/message_lists.ts

@@ -12,6 +12,9 @@ type MessageListView = {
     update_recipient_bar_background_color: () => void;
     rerender_messages: (messages: Message[], message_content_edited?: boolean) => void;
     is_fetched_end_rendered: () => boolean;
+    is_fetched_start_rendered: () => boolean;
+    first_rendered_message: () => Message | undefined;
+    last_rendered_message: () => Message | undefined;
     show_message_as_read: (message: Message, options: {from?: "pointer" | "server"}) => void;
     show_messages_as_unread: (message_ids: number[]) => void;
     _render_win_start: number;
@@ -46,6 +49,9 @@ export type MessageList = {
     can_mark_messages_read_without_setting: () => boolean;
     rerender_view: () => void;
     update_muting_and_rerender: () => void;
+    prev: () => number | undefined;
+    next: () => number | undefined;
+    is_at_end: () => boolean;
     prevent_reading: () => void;
     resume_reading: () => void;
     data: MessageListData;
@@ -55,6 +61,7 @@ export type MessageList = {
         messages: Message[],
         append_opts: {messages_are_new: boolean},
     ) => RenderInfo | undefined;
+    first: () => Message | undefined;
     last: () => Message | undefined;
     visibly_empty: () => boolean;
     selected_message: () => Message;

web/src/navigate.ts

@@ -4,12 +4,12 @@ import * as message_lists from "./message_lists";
 import * as message_viewport from "./message_viewport";
 import * as unread_ops from "./unread_ops";
 
-function go_to_row(msg_id) {
+function go_to_row(msg_id: number): void {
     assert(message_lists.current !== undefined);
     message_lists.current.select_id(msg_id, {then_scroll: true, from_scroll: true});
 }
 
-export function up() {
+export function up(): void {
     assert(message_lists.current !== undefined);
     message_viewport.set_last_movement_direction(-1);
     const msg_id = message_lists.current.prev();
@@ -19,7 +19,7 @@ export function up() {
     go_to_row(msg_id);
 }
 
-export function down(with_centering) {
+export function down(with_centering = false): void {
     assert(message_lists.current !== undefined);
     message_viewport.set_last_movement_direction(1);
 
@@ -45,22 +45,24 @@ export function down(with_centering) {
     go_to_row(msg_id);
 }
 
-export function to_home() {
+export function to_home(): void {
     assert(message_lists.current !== undefined);
     message_viewport.set_last_movement_direction(-1);
-    const first_id = message_lists.current.first().id;
-    message_lists.current.select_id(first_id, {then_scroll: true, from_scroll: true});
+    const first_message = message_lists.current.first();
+    assert(first_message !== undefined);
+    message_lists.current.select_id(first_message.id, {then_scroll: true, from_scroll: true});
 }
 
-export function to_end() {
+export function to_end(): void {
     assert(message_lists.current !== undefined);
-    const next_id = message_lists.current.last().id;
+    const last_message = message_lists.current.last();
+    assert(last_message !== undefined);
     message_viewport.set_last_movement_direction(1);
-    message_lists.current.select_id(next_id, {then_scroll: true, from_scroll: true});
+    message_lists.current.select_id(last_message.id, {then_scroll: true, from_scroll: true});
     unread_ops.process_visible();
 }
 
-function amount_to_paginate() {
+function amount_to_paginate(): number {
     // Some day we might have separate versions of this function
     // for Page Up vs. Page Down, but for now it's the same
     // strategy in either direction.
@@ -71,7 +73,7 @@ function amount_to_paginate() {
     // are especially worried about missing messages, so we want
     // a little bit of the old page to stay on the screen.  The
     // value chosen here is roughly 2 or 3 lines of text, but there
-    // is nothing sacred about it, and somebody more anal than me
+    // is nothing sacred about it, and somebody more anal than we
     // might wish to tie this to the size of some particular DOM
     // element.
     const overlap_amount = 55;
@@ -88,7 +90,7 @@ function amount_to_paginate() {
     return delta;
 }
 
-export function page_up_the_right_amount() {
+export function page_up_the_right_amount(): void {
     // This function's job is to scroll up the right amount,
     // after the user hits Page Up.  We do this ourselves
     // because we can't rely on the browser to account for certain
@@ -100,37 +102,42 @@ export function page_up_the_right_amount() {
     message_viewport.scrollTop(message_viewport.scrollTop() - delta);
 }
 
-export function page_down_the_right_amount() {
+export function page_down_the_right_amount(): void {
     // see also: page_up_the_right_amount
     const delta = amount_to_paginate();
     message_viewport.scrollTop(message_viewport.scrollTop() + delta);
 }
 
-export function page_up() {
+export function page_up(): void {
     assert(message_lists.current !== undefined);
     if (message_viewport.at_rendered_top() && !message_lists.current.visibly_empty()) {
         if (message_lists.current.view.is_fetched_start_rendered()) {
-            message_lists.current.select_id(message_lists.current.first().id, {then_scroll: false});
+            const first_message = message_lists.current.first();
+            assert(first_message !== undefined);
+            message_lists.current.select_id(first_message.id, {then_scroll: false});
         } else {
-            message_lists.current.select_id(
-                message_lists.current.view.first_rendered_message().id,
-                {
+            const first_rendered_message = message_lists.current.view.first_rendered_message();
+            assert(first_rendered_message !== undefined);
+            message_lists.current.select_id(first_rendered_message.id, {
                 then_scroll: false,
-                },
-            );
+            });
         }
     } else {
         page_up_the_right_amount();
     }
 }
 
-export function page_down() {
+export function page_down(): void {
     assert(message_lists.current !== undefined);
     if (message_viewport.at_rendered_bottom() && !message_lists.current.visibly_empty()) {
         if (message_lists.current.view.is_fetched_end_rendered()) {
-            message_lists.current.select_id(message_lists.current.last().id, {then_scroll: false});
+            const last_message = message_lists.current.last();
+            assert(last_message !== undefined);
+            message_lists.current.select_id(last_message.id, {then_scroll: false});
         } else {
-            message_lists.current.select_id(message_lists.current.view.last_rendered_message().id, {
+            const last_rendered_message = message_lists.current.view.last_rendered_message();
+            assert(last_rendered_message !== undefined);
+            message_lists.current.select_id(last_rendered_message.id, {
                 then_scroll: false,
             });
         }