app/cody: small window UI for cody chat page (#53384)

Closes https://github.com/sourcegraph/sourcegraph/issues/53112

Significantly improves the small window/mobile UI in the Cody chat page,
perfect for docking the App on the side of the screen.

## Test plan


https://github.com/sourcegraph/sourcegraph/assets/206864/406589c6-a73b-41a8-8f97-86e6f7c34021

Author: limitedmage

client/web/src/cody/chat/CodyChatPage.module.scss

@@ -1,13 +1,55 @@
+@import 'wildcard/src/global-styles/breakpoints';
+
+.page-header {
+    display: flex;
+    margin-bottom: 1rem;
+
+    @media (--sm-breakpoint-down) {
+        display: none;
+    }
+}
+
 .chat-main-wrapper {
+    display: flex;
+    flex-direction: column;
     filter: none;
     border: 1px solid var(--border-color-2);
     border-radius: var(--border-radius);
     padding: 0;
+
+    @media (--sm-breakpoint-down) {
+        &-with-mobile-history {
+            display: none;
+        }
+    }
+}
+
+.page {
+    @media (--sm-breakpoint-down) {
+        // These need to be !important to override the `py-4` default padding on the page
+        padding-top: 0 !important;
+        padding-bottom: 0 !important;
+    }
 }
 
 .page-wrapper {
     padding-top: 0.625rem;
     height: 93%;
+
+    @media (--sm-breakpoint-down) {
+        padding-top: 0;
+        height: 100%;
+    }
+}
+
+.sidebar-wrapper {
+    display: flex;
+    flex-direction: column;
+    height: 100%;
+
+    @media (--sm-breakpoint-down) {
+        display: none;
+    }
 }
 
 .sidebar {
@@ -53,3 +95,44 @@
         cursor: pointer;
     }
 }
+
+.mobile-top-bar {
+    display: none;
+
+    @media (--sm-breakpoint-down) {
+        display: flex;
+        justify-content: space-around;
+        align-items: center;
+        padding: 0.25rem 0.5rem;
+        border-bottom: 1px solid var(--border-color-2);
+    }
+}
+
+.mobile-top-bar-button {
+    color: var(--text-muted);
+    padding: 0.5rem 2rem;
+    justify-content: center;
+
+    &:active {
+        background-color: var(--color-bg-1);
+    }
+}
+
+.mobile-top-bar-divider {
+    height: 1.25rem;
+}
+
+.mobile-history-wrapper {
+    display: none;
+
+    @media (--sm-breakpoint-down) {
+        display: flex;
+        flex-direction: column;
+        height: 100%;
+        width: 100%;
+    }
+}
+
+.mobile-history {
+    overflow-y: auto;
+}

client/web/src/cody/chat/CodyChatPage.tsx

@@ -1,6 +1,15 @@
 import React, { useEffect, useState } from 'react'
 
-import { mdiClose, mdiCogOutline, mdiDelete, mdiDotsVertical, mdiOpenInNew, mdiPlus, mdiChevronRight } from '@mdi/js'
+import {
+    mdiClose,
+    mdiCogOutline,
+    mdiDelete,
+    mdiDotsVertical,
+    mdiOpenInNew,
+    mdiPlus,
+    mdiChevronRight,
+    mdiViewList,
+} from '@mdi/js'
 import classNames from 'classnames'
 import { useLocation, useNavigate } from 'react-router-dom'
 
@@ -41,6 +50,7 @@ import styles from './CodyChatPage.module.scss'
 
 interface CodyChatPageProps {
     authenticatedUser: AuthenticatedUser | null
+    isSourcegraphApp: boolean
     context: Pick<SourcegraphContext, 'authProviders'>
 }
 
@@ -78,7 +88,11 @@ const onTranscriptHistoryLoad = (
     }
 }
 
-export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({ authenticatedUser, context }) => {
+export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({
+    authenticatedUser,
+    context,
+    isSourcegraphApp,
+}) => {
     const { pathname } = useLocation()
     const navigate = useNavigate()
 
@@ -119,6 +133,12 @@ export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({ authe
         }
     }, [transcriptId, loaded, pathname, navigate])
 
+    const [showMobileHistory, setShowMobileHistory] = useState<boolean>(false)
+    // Close mobile history list when transcript changes
+    useEffect(() => {
+        setShowMobileHistory(false)
+    }, [transcript])
+
     if (!loaded) {
         return null
     }
@@ -137,7 +157,7 @@ export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({ authe
     }
 
     return (
-        <Page className="overflow-hidden">
+        <Page className={classNames('d-flex flex-column', styles.page)}>
             <PageTitle title="Cody AI Chat" />
             <PageHeader
                 actions={
@@ -154,23 +174,25 @@ export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({ authe
                         graph.
                     </>
                 }
-                className="mb-3"
+                className={styles.pageHeader}
             >
                 <PageHeader.Heading as="h2" styleAs="h1">
                     <PageHeader.Breadcrumb icon={CodyColorIcon}>
                         <div className="d-inline-flex align-items-center">
                             Cody Chat
-                            <Badge variant="info" className="ml-2">
-                                Beta
-                            </Badge>
+                            {!isSourcegraphApp && (
+                                <Badge variant="info" className="ml-2">
+                                    Beta
+                                </Badge>
+                            )}
                         </div>
                     </PageHeader.Breadcrumb>
                 </PageHeader.Heading>
             </PageHeader>
 
             {/* Page content */}
-            <div className={classNames('row mb-5', styles.pageWrapper)}>
-                <div className="d-flex flex-column col-sm-3 h-100">
+            <div className={classNames('row flex-1 overflow-hidden', styles.pageWrapper)}>
+                <div className={classNames('col-md-3', styles.sidebarWrapper)}>
                     <div className={styles.sidebarHeader}>
                         <H4>
                             <b>Chats</b>
@@ -285,9 +307,54 @@ export const CodyChatPage: React.FunctionComponent<CodyChatPageProps> = ({ authe
                         ))}
                 </div>
 
-                <div className={classNames('d-flex flex-column col-sm-9 h-100', styles.chatMainWrapper)}>
+                <div
+                    className={classNames(
+                        'col-md-9 h-100',
+                        styles.chatMainWrapper,
+                        showMobileHistory && styles.chatMainWrapperWithMobileHistory
+                    )}
+                >
+                    <div className={styles.mobileTopBar}>
+                        <Button
+                            variant="icon"
+                            className={styles.mobileTopBarButton}
+                            onClick={() => setShowMobileHistory(true)}
+                        >
+                            <Icon aria-hidden={true} svgPath={mdiViewList} className="mr-2" />
+                            All chats
+                        </Button>
+                        <div className={classNames('border-right', styles.mobileTopBarDivider)} />
+                        <Button variant="icon" className={styles.mobileTopBarButton} onClick={initializeNewChat}>
+                            <Icon aria-hidden={true} svgPath={mdiPlus} className="mr-2" />
+                            New chat
+                        </Button>
+                    </div>
                     <ChatUI codyChatStore={codyChatStore} />
                 </div>
+
+                {showMobileHistory && (
+                    <div className={styles.mobileHistoryWrapper}>
+                        <div className={styles.mobileTopBar}>
+                            <Button
+                                variant="icon"
+                                className={classNames('w-100', styles.mobileTopBarButton)}
+                                onClick={() => setShowMobileHistory(false)}
+                            >
+                                <Icon aria-hidden={true} svgPath={mdiClose} className="mr-2" />
+                                Close
+                            </Button>
+                        </div>
+                        <div className={styles.mobileHistory}>
+                            <HistoryList
+                                currentTranscript={transcript}
+                                transcriptHistory={transcriptHistory}
+                                truncateMessageLength={60}
+                                loadTranscriptFromHistory={loadTranscriptFromHistory}
+                                deleteHistoryItem={deleteHistoryItem}
+                            />
+                        </div>
+                    </div>
+                )}
             </div>
         </Page>
     )