[#1223] lens/tui: Enchance help page

- Make help multipage: one page for each chapter.
- Improve help information.
- Add markup.

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

cmd/frostfs-lens/internal/tuiutil/help-pages/development.txt

@@ -0,0 +1 @@
+[green::b]Development[white::-] (Work in Progress)

cmd/frostfs-lens/internal/tuiutil/help-pages/navigation.txt

@@ -0,0 +1,27 @@
+[green::b]General Navigation[white::-]
+
+    [yellow::b]Down Arrow[white::-] / [yellow::b]j[white::-]
+        Scroll down.
+
+    [yellow::b]Up Arrow[white::-] / [yellow::b]k[white::-]
+        Scroll up.
+
+    [yellow::b]Page Down[white::-] / [yellow::b]Ctrl-f[white::-]
+        Scroll down by a full page.
+
+    [yellow::b]Page Up[white::-] / [yellow::b]Ctrl-b[white::-]
+        Scroll up by a full page.
+
+    [yellow::b]Enter[white::-]
+        Navigate to a nested view:
+        - In Buckets View: Navigate to the selected bucket's records.
+        - In Records View: Navigate to the selected record's detailed view.
+
+    [yellow::b]Escape[white::-]
+        Return to the previous page, opposite of [yellow::b]Enter[white::-].
+
+
+[green::b]Buckets View Interactions[white::-]
+
+    [yellow::b]Space[white::-]
+        Expand or collapse the selected bucket to show or hide its nested buckets.

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

@@ -0,0 +1,16 @@
+[green::b]Searching[white::-]
+
+	[yellow::b]/[white::-]
+		Initiate a search prompt. Prompt syntax: [yellow::b]<tag>:<args>[white::-]. Leading and trailing white spaces are ignored. See [green::b]Available Search Filters[white::-] section for available filter tags.
+
+	[yellow::b]Enter[white::-]
+		Execute the search based on the entered prompt. An error message will display if the prompt is invalid.
+
+	[yellow::b]Escape[white::-]
+		Exit the search prompt.
+
+
+[green::b]Available Search Filters[white::-]
+
+%s
+	If you want to define a new filter, see [green::b]Development[white::-] section.

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

@@ -1,6 +1,7 @@
 package tuiutil
 
 import (
+	_ "embed"
 	"fmt"
 	"strings"
 
@@ -8,76 +9,101 @@ import (
 	"github.com/rivo/tview"
 )
 
-const text = `[green]Navigation[white]
+var (
+	//go:embed help-pages/navigation.txt
+	navigationHelpText string
 
-- [yellow]Up arrow[white]                Move up.
+	//go:embed help-pages/searching.txt
+	searchingHelpText string
 
-- [yellow]Down arrow[white]              Move down.
-
-- [yellow]Space[white]                   Show a bucket's subbuckets if on the buckets view.
-
-- [yellow]Enter[white]                   Show a bucket's records if on the buckets view,
-						  or show a record's detailed view if on the
-						  records view. It always navigates to a new page.
-
-- [yellow]Escape[white]                  Go to the previous page.
-
-
-[green]Searching[white]
-
-- [yellow]/[white]                       Start search prompt.
-						  Prompt syntax is <filter tag>:<filter args...>.
-						  It tolerates leading and trailing white space.
-
-- [yellow]Enter[white]                   Start searching based on prompt. It shows an
-						  error message if the prompt is invalid.
-
-- [yellow]Escape[white]                  Stop search prompt.
-
-
-[green]Available search filters[white]
-
-%s
-`
+	//go:embed help-pages/development.txt
+	developmentHelpText string
+)
 
 type HelpPage struct {
 	*tview.Box
-	view *tview.TextView
+	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(),
-		view: tview.NewTextView(),
+		Box:         tview.NewBox(),
+		filters:     filters,
+		filterHints: hints,
 	}
 
-	filtersText := strings.Builder{}
+	page := tview.NewTextView()
+	page.SetDynamicColors(true)
+	page.SetText(navigationHelpText)
+	hp.addPage(page)
 
-	lastIndex := len(filters) - 1
-	for index, filter := range filters {
-		filtersText.WriteString("- ")
-		filtersText.WriteString(filter)
-		filtersText.WriteRune(' ')
-		filtersText.WriteString(hints[filter])
-		if index != lastIndex {
-			filtersText.WriteRune('\n')
-		}
-	}
+	page = tview.NewTextView()
+	page.SetDynamicColors(true)
+	page.SetText(fmt.Sprintf(searchingHelpText, hp.getFiltersText()))
+	hp.addPage(page)
 
-	hp.view.SetDynamicColors(true)
-	hp.view.SetText(fmt.Sprintf(text, filtersText.String()))
+	page = tview.NewTextView()
+	page.SetDynamicColors(true)
+	page.SetText(developmentHelpText)
+	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 "\tNo filters defined.\n"
+	}
+
+	filtersText := strings.Builder{}
+	gapSize := 4
+
+	tagMaxWidth := 3
+	for _, filter := range hp.filters {
+		tagMaxWidth = max(tagMaxWidth, len(filter))
+	}
+	filtersText.WriteString("\t[yellow::b]Tag")
+	filtersText.WriteString(strings.Repeat(" ", gapSize))
+	filtersText.WriteString("\tArgs[white::-]\n\n")
+
+	for _, filter := range hp.filters {
+		filtersText.WriteRune('\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.view.SetRect(x, y, width, height)
-	hp.view.Draw(screen)
+	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)) {
-		hp.view.InputHandler()(event, 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/tuiutil/ui.go

@@ -102,7 +102,7 @@ func NewUI(ctx context.Context, app *tview.Application, db *bbolt.DB) *UI {
 
 	ui.helpBar.SetBackgroundColor(barBackgroundColor)
 	ui.helpBar.SetTextColor(barTextColor)
-	ui.helpBar.SetText(" Press Escape to quit")
+	ui.helpBar.SetText(" Press Enter for next page or Escape to exit help ")
 
 	ui.searchErrorBar.SetBackgroundColor(barTextColor)
 	ui.searchErrorBar.SetTextColor(barAlertTextColor)