login-app: use tcell/tview to make the form and add cinematic

pkg/login-app/cmd/stream.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/gdamore/tcell"
+)
+
+// Stream updates a StreamDisplay with new data updates
+type Stream struct {
+	display  *StreamDisplay
+	speed    int
+	length   int
+	headPos  int
+	tailPos  int
+	stopCh   chan bool
+	killCh   chan bool
+	headDone bool
+	fini     bool
+}
+
+func (s *Stream) run() {
+	blackStyle := tcell.StyleDefault.
+		Foreground(tcell.ColorBlack).
+		Background(tcell.ColorBlack)
+
+	midStyleA := blackStyle.Foreground(tcell.ColorGreen)
+	midStyleB := blackStyle.Foreground(tcell.ColorLime)
+	headStyleA := blackStyle.Foreground(tcell.ColorSilver)
+	headStyleB := blackStyle.Foreground(tcell.ColorWhite)
+
+	var lastRune rune
+STREAM:
+	for {
+		select {
+		case <-s.stopCh:
+			s.fini = true
+		case <-time.After(time.Duration(s.speed) * time.Millisecond):
+			// add a new rune if there is space in the stream
+			if !s.fini && !s.headDone && s.headPos <= curSizes.height {
+				newRune := characters[rand.Intn(len(characters))]
+
+				// Making most of the green characters bright/bold...
+				if rand.Intn(100) < 66 {
+					screen.SetCell(s.display.column, s.headPos-1, midStyleA, lastRune)
+				} else {
+					screen.SetCell(s.display.column, s.headPos-1, midStyleB, lastRune)
+				}
+
+				// ...and turning about a third of the heads from gray to white
+				if rand.Intn(100) < 33 {
+					screen.SetCell(s.display.column, s.headPos, headStyleA, newRune)
+				} else {
+					screen.SetCell(s.display.column, s.headPos, headStyleB, newRune)
+				}
+				lastRune = newRune
+				s.headPos++
+			} else {
+				if s.fini && (s.length <= 0 || s.headPos <= 0) {
+					break STREAM
+				} else if s.fini && s.headPos < s.length {
+					s.length = s.headPos
+				}
+				s.headDone = true
+			}
+
+			// clear rune at the tail of the stream
+			if s.tailPos > 0 || s.headPos >= s.length {
+				if s.tailPos == 0 && !s.fini {
+					// tail is being incremented for the first time. there is space for a new stream
+					s.display.newStream <- true
+				}
+				if s.tailPos < curSizes.height {
+					screen.SetCell(s.display.column, s.tailPos, blackStyle, ' ') //'\uFF60'
+					s.tailPos++
+				} else {
+					break STREAM
+				}
+			}
+		}
+	}
+
+	delete(s.display.streams, s)
+}
+
+// StreamDisplay represents a vertical line in the terminal on which `Stream`s are displayed.
+// StreamDisplay also creates the Streams themselves
+type StreamDisplay struct {
+	column      int
+	stopCh      chan bool
+	streams     map[*Stream]bool
+	streamsLock sync.Mutex
+	newStream   chan bool
+}
+
+func (sd *StreamDisplay) run() {
+	for {
+		select {
+		case <-sd.stopCh:
+			// lock this SD forever
+			sd.streamsLock.Lock()
+
+			// stop streams for this SD
+			for s := range sd.streams {
+				s.stopCh <- true
+			}
+
+			// close this goroutine
+			return
+
+		case <-sd.newStream:
+			// have some wait before the first stream starts..
+			time.Sleep(time.Duration(rand.Intn(9000)) * time.Millisecond)
+
+			// lock map
+			sd.streamsLock.Lock()
+
+			// create new stream instance
+			s := &Stream{
+				display: sd,
+				stopCh:  make(chan bool),
+				speed:   30 + rand.Intn(110),
+				length:  10 + rand.Intn(8), // length of a stream is between 10 and 18 runes
+			}
+
+			// store in streams map
+			sd.streams[s] = true
+
+			// run the stream in a goroutine
+			go s.run()
+
+			// unlock map
+			sd.streamsLock.Unlock()
+		}
+	}
+}