[#1223] lens/tui: Add app help

Signed-off-by: Aleksey Savchuk <a.savchuk@yadro.com>

cmd/frostfs-lens/internal/tui/help-pages/hotkeys.txt

@@ -0,0 +1,38 @@
+[green::b]HOTKEYS[-::-]
+
+    [green::b]Navigation[-::-]
+
+        [yellow::b]Down Arrow[-::-] / [yellow::b]j[-::-]
+            Scroll down.
+
+        [yellow::b]Up Arrow[-::-] / [yellow::b]k[-::-]
+            Scroll up.
+
+        [yellow::b]Page Down[-::-] / [yellow::b]Ctrl-f[-::-]
+            Scroll down by a full page.
+
+        [yellow::b]Page Up[-::-] / [yellow::b]Ctrl-b[-::-]
+            Scroll up by a full page.
+
+    [green::b]Actions[-::-]
+
+        [yellow::b]Enter[-::-]
+            Perform actions based on the current context:
+            - In Buckets View:
+                - Expand/collapse the selected bucket to show/hide its nested buckets.
+                - If no nested buckets exist, navigate to the selected bucket's records.
+            - In Records View: Open the detailed view of the selected record.
+
+        [yellow::b]Escape[-::-]
+            Return to the previous page, opposite of [yellow::b]Enter[-::-].
+
+        Refer to the [green::b]SEARCHING[-::-] section for more specific actions.
+
+
+    [green::b]Alternative Action Hotkeys[-::-]
+
+        [yellow::b]Ctrl-r[-::-]
+            Directly navigate to the selected bucket's records.
+
+        [yellow::b]Ctrl-d[-::-]
+            Access the detailed view of the selected bucket.

cmd/frostfs-lens/internal/tui/help-pages/searching.txt

@@ -0,0 +1,26 @@
+[green::b]SEARCHING[-::-]
+
+	[green::b]Hotkeys[-::-]
+
+		[yellow::b]/[-::-]
+			Initiate the search prompt.
+			- The prompt follows this syntax: [yellow::b]tag:value [+ tag:value]...[-::-]
+			- Multiple filter can be combined with [yellow::b]+[-::-], the result is an intersection of those filters' result sets.
+			- Any leading and trailing whitespace will be ignored.
+			- An empty prompt will return all results with no filters applied.
+			- Refer to the [green::b]Available Search Filters[-::-] section below for a list of valid filter tags.
+
+		[yellow::b]Enter[-::-]
+			Execute the search based on the entered prompt.
+			- If the prompt is invalid, an error message will be displayed.
+
+		[yellow::b]Escape[-::-]
+			Exit the search prompt without performing a search.
+
+		[yellow::b]Down Arrow[-::-], [yellow::b]Up Arrow[-::-]
+			Scroll through the search history.
+
+
+	[green::b]Available Search Filters[-::-]
+
+%s

cmd/frostfs-lens/internal/tui/help.go

@@ -0,0 +1,101 @@
+package tui
+
+import (
+	_ "embed"
+	"fmt"
+	"strings"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/tview"
+)
+
+var (
+	//go:embed help-pages/hotkeys.txt
+	hotkeysHelpText string
+
+	//go:embed help-pages/searching.txt
+	searchingHelpText string
+)
+
+type HelpPage struct {
+	*tview.Box
+	pages       []*tview.TextView
+	currentPage int
+
+	filters     []string
+	filterHints map[string]string
+}
+
+func NewHelpPage(filters []string, hints map[string]string) *HelpPage {
+	hp := &HelpPage{
+		Box:         tview.NewBox(),
+		filters:     filters,
+		filterHints: hints,
+	}
+
+	page := tview.NewTextView().
+		SetDynamicColors(true).
+		SetText(hotkeysHelpText)
+	hp.addPage(page)
+
+	page = tview.NewTextView().
+		SetDynamicColors(true).
+		SetText(fmt.Sprintf(searchingHelpText, hp.getFiltersText()))
+	hp.addPage(page)
+
+	return hp
+}
+
+func (hp *HelpPage) addPage(page *tview.TextView) {
+	hp.pages = append(hp.pages, page)
+}
+
+func (hp *HelpPage) getFiltersText() string {
+	if len(hp.filters) == 0 {
+		return "\t\tNo filters defined.\n"
+	}
+
+	filtersText := strings.Builder{}
+	gapSize := 4
+
+	tagMaxWidth := 3
+	for _, filter := range hp.filters {
+		tagMaxWidth = max(tagMaxWidth, len(filter))
+	}
+	filtersText.WriteString("\t\t[yellow::b]Tag")
+	filtersText.WriteString(strings.Repeat(" ", gapSize))
+	filtersText.WriteString("\tValue[-::-]\n\n")
+
+	for _, filter := range hp.filters {
+		filtersText.WriteString("\t\t")
+		filtersText.WriteString(filter)
+		filtersText.WriteString(strings.Repeat(" ", tagMaxWidth-len(filter)+gapSize))
+		filtersText.WriteString(hp.filterHints[filter])
+		filtersText.WriteRune('\n')
+	}
+
+	return filtersText.String()
+}
+
+func (hp *HelpPage) Draw(screen tcell.Screen) {
+	x, y, width, height := hp.GetInnerRect()
+	hp.pages[hp.currentPage].SetRect(x+1, y+1, width-2, height-2)
+	hp.pages[hp.currentPage].Draw(screen)
+}
+
+func (hp *HelpPage) InputHandler() func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {
+	return hp.WrapInputHandler(func(event *tcell.EventKey, _ func(tview.Primitive)) {
+		if event.Key() == tcell.KeyEnter {
+			hp.currentPage++
+			hp.currentPage %= len(hp.pages)
+			return
+		}
+		hp.pages[hp.currentPage].InputHandler()(event, func(tview.Primitive) {})
+	})
+}
+
+func (hp *HelpPage) MouseHandler() func(action tview.MouseAction, event *tcell.EventMouse, setFocus func(p tview.Primitive)) (consumed bool, capture tview.Primitive) {
+	return hp.WrapMouseHandler(func(action tview.MouseAction, event *tcell.EventMouse, _ func(tview.Primitive)) (consumed bool, capture tview.Primitive) {
+		return hp.pages[hp.currentPage].MouseHandler()(action, event, func(tview.Primitive) {})
+	})
+}

cmd/frostfs-lens/internal/tui/ui.go

@@ -60,6 +60,8 @@ type UI struct {
 	loadingBar *LoadingBar
 	helpBar    *tview.TextView
 
+	helpPage *HelpPage
+
 	searchErrorBar *tview.TextView
 
 	isSearching    bool
@@ -275,7 +277,17 @@ func (ui *UI) draw(screen tcell.Screen) {
 
 	switch {
 	case ui.isShowingHelp:
-		pageToDraw = ui.pageStub
+		if ui.helpPage == nil {
+			var filters []string
+			for f := range ui.filters {
+				filters = append(filters, f)
+			}
+			for f := range ui.compositeFilters {
+				filters = append(filters, f)
+			}
+			ui.helpPage = NewHelpPage(filters, ui.filterHints)
+		}
+		pageToDraw = ui.helpPage
 	case ui.mountedPage != nil:
 		pageToDraw = ui.mountedPage
 	default:
@@ -429,6 +441,7 @@ func (ui *UI) handleInputOnShowingHelp(event *tcell.EventKey) {
 	case k == tcell.KeyRune && r == 'q':
 		ui.stop()
 	default:
+		ui.helpPage.InputHandler()(event, func(tview.Primitive) {})
 	}
 }