feature: Ability to add custom toolbar items to main page nav bar

* core.ts
 * Adds optional toolbarItems property to plugin interface

* HawtioHeader.tsx
 * Picks up the plugins from the context and find the plugin that is
   currently being displayed. If this plugin has a toolbar item property
   then pick up the components into a custom toolbar group

app/src/examples/example3/Example3.tsx

@@ -5,7 +5,12 @@ export const Example3: React.FunctionComponent = () => (
   <PageSection variant={PageSectionVariants.light}>
     <TextContent>
       <Text component='h1'>Example 3</Text>
-      <Text component='p'>This is yet another example plugin.</Text>
+      <Text component='p'>
+        This is another example plugin that also demonstrates the addition of custom components
+        to the main header toolbar.
+        Components should be added in the Plugin structure using the `headerItems` array.
+        Toolbar components should be created as single FunctionComponents and added to the array.
+      </Text>
     </TextContent>
   </PageSection>
 )

app/src/examples/example3/ToolbarItemComp.tsx

@@ -0,0 +1,91 @@
+import React from 'react'
+import { Button, Dropdown, DropdownItem, DropdownSeparator, DropdownToggle, Modal } from '@patternfly/react-core'
+
+export const ToolbarItemComp1: React.FunctionComponent = () => {
+  const [isModalOpen, setIsModalOpen] = React.useState(false)
+
+  const handleModalToggle = () => {
+    setIsModalOpen(!isModalOpen)
+  }
+
+  return (
+    <React.Fragment>
+      <Button variant='primary' onClick={handleModalToggle}>
+        Click Me!
+      </Button>
+
+      <Modal
+        title='Basic modal'
+        isOpen={isModalOpen}
+        onClose={handleModalToggle}
+        actions={[
+          <Button key='confirm' variant='primary' onClick={handleModalToggle}>
+            Confirm
+          </Button>,
+          <Button key='cancel' variant='link' onClick={handleModalToggle}>
+            Cancel
+          </Button>,
+        ]}
+      >
+        Hello World!
+      </Modal>
+    </React.Fragment>
+  )
+}
+
+export const ToolbarItemComp2: React.FunctionComponent = () => {
+  const [isOpen, setIsOpen] = React.useState(false)
+
+  const onToggle = (isOpen: boolean) => {
+    setIsOpen(isOpen)
+  }
+
+  const onFocus = () => {
+    const element = document.getElementById('toggle-basic')
+    element?.focus()
+  }
+
+  const onSelect = () => {
+    setIsOpen(false)
+    onFocus()
+  }
+
+  const dropdownItems = [
+    <DropdownItem key='link' tooltip='Tooltip for enabled link'>
+      Link
+    </DropdownItem>,
+    <DropdownItem key='action' component='button' tooltip='Tooltip for enabled button'>
+      Action
+    </DropdownItem>,
+    <DropdownItem key='disabled link' isDisabled href='www.google.com'>
+      Disabled link
+    </DropdownItem>,
+    <DropdownItem
+      key='disabled action'
+      isAriaDisabled
+      component='button'
+      tooltip='Tooltip for disabled item'
+      tooltipProps={{ position: 'top' }}
+    >
+      Disabled action
+    </DropdownItem>,
+    <DropdownSeparator key='separator' />,
+    <DropdownItem key='separated link'>Separated link</DropdownItem>,
+    <DropdownItem key='separated action' component='button'>
+      Separated action
+    </DropdownItem>,
+  ]
+
+  return (
+    <Dropdown
+      onSelect={onSelect}
+      toggle={
+        <DropdownToggle id='toggle-basic' onToggle={onToggle}>
+          Dropdown
+        </DropdownToggle>
+      }
+      isOpen={isOpen}
+      dropdownItems={dropdownItems}
+    />
+  )
+}

app/src/examples/example3/index.ts

@@ -1,12 +1,14 @@
 import { hawtio, HawtioPlugin } from '@hawtio/react'
 import { Example3 } from './Example3'
+import { ToolbarItemComp1, ToolbarItemComp2 } from './ToolbarItemComp'
 
 export const registerExample3: HawtioPlugin = () => {
   hawtio.addPlugin({
     id: 'example3',
     title: 'Example 3',
     path: '/example3',
     component: Example3,
+    headerItems: [ToolbarItemComp1, ToolbarItemComp2],
     isActive: async () => true,
   })
 }

packages/hawtio/src/core/core.ts

@@ -13,6 +13,9 @@ export interface Plugin {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   component: React.ComponentType<any>
 
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  headerItems?: React.ComponentType<any>[]
+
   /**
    * Returns if this plugin should be activated.
    * This method needs to return a promise as the process of resolving if a plugin

packages/hawtio/src/ui/page/HawtioHeader.tsx

@@ -1,5 +1,5 @@
 import { PUBLIC_USER, userService } from '@hawtiosrc/auth'
-import { DEFAULT_APP_NAME, useHawtconfig } from '@hawtiosrc/core'
+import { DEFAULT_APP_NAME, useHawtconfig, Plugin } from '@hawtiosrc/core'
 import { hawtioLogo, userAvatar } from '@hawtiosrc/img'
 import { preferencesService } from '@hawtiosrc/preferences/preferences-service'
 import { HawtioAbout } from '@hawtiosrc/ui/about'
@@ -22,7 +22,7 @@ import {
 } from '@patternfly/react-core'
 import { BarsIcon, HelpIcon } from '@patternfly/react-icons'
 import React, { useContext, useState } from 'react'
-import { Link } from 'react-router-dom'
+import { Link, useLocation } from 'react-router-dom'
 import './HawtioHeader.css'
 import { PageContext } from './context'
 
@@ -72,7 +72,8 @@ const HawtioBrand: React.FunctionComponent = () => {
 }
 
 const HawtioHeaderToolbar: React.FunctionComponent = () => {
-  const { username } = useContext(PageContext)
+  const { username, plugins } = useContext(PageContext)
+  const location = useLocation()
 
   const isPublic = username === PUBLIC_USER
 
@@ -104,9 +105,25 @@ const HawtioHeaderToolbar: React.FunctionComponent = () => {
     userItems.pop()
   }
 
+  /*
+   * Determine which plugin is currently displaying
+   * based on the path of the current location
+   */
+  const pluginFromLocation = (): Plugin | null => {
+    const path = location.pathname
+    return plugins.find(plugin => path.startsWith(plugin.path)) ?? null
+  }
+
+  const plugin = pluginFromLocation()
+
   return (
     <Toolbar id='hawtio-header-toolbar'>
       <ToolbarContent>
+        <ToolbarGroup>
+          {plugin?.headerItems?.map((comp, index) => (
+            <ToolbarItem key={`hawtio-header-toolbar-plugin-item-${index}`}>{React.createElement(comp)}</ToolbarItem>
+          ))}
+        </ToolbarGroup>
         <ToolbarGroup>
           <ToolbarItem>
             <Dropdown