billboard/internal/tui/tui.go

package tui

import (
	"bufio"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"billboard/internal/state"

	"golang.org/x/term"
)

type Display struct {
	server string
	client *http.Client
	state  state.Snapshot
	tick   int
	out    *os.File
}

func Run(serverAddr, ttyPath string) error {
	d := &Display{
		server: strings.TrimRight(serverAddr, "/"),
		client: &http.Client{Timeout: 10 * time.Second},
		out:    os.Stdout,
	}
	if ttyPath != "" {
		f, err := os.OpenFile(ttyPath, os.O_RDWR, 0)
		if err != nil {
			return fmt.Errorf("open tty: %w", err)
		}
		defer f.Close()
		d.out = f
	}
	if err := d.fetch(); err != nil {
		return fmt.Errorf("initial fetch: %w", err)
	}

	d.out.WriteString("\x1b[?1049h\x1b%G\x1b[?25l\x1b[2J")
	restore := func() { fmt.Fprint(d.out, "\x1b[0m\x1b[?25h\x1b[?1049l") }
	defer restore()

	quit := make(chan os.Signal, 1)
	signal.Notify(quit, os.Interrupt, syscall.SIGTERM)
	resize := make(chan os.Signal, 1)
	signal.Notify(resize, syscall.SIGWINCH)

	changed := make(chan struct{}, 1)
	go d.listen(changed)

	ticker := time.NewTicker(100 * time.Millisecond)
	defer ticker.Stop()
	poll := time.NewTicker(5 * time.Second)
	defer poll.Stop()
	dirty := true
	for {
		select {
		case <-quit:
			return nil
		case <-resize:
			fmt.Fprint(d.out, "\x1b[2J")
			dirty = true
		case <-changed:
			d.fetch()
			d.debug("update via SSE")
			dirty = true
		case <-poll.C:
			if d.fetchIfChanged() {
				dirty = true
			}
		case <-ticker.C:
			d.tick++
			if d.tick%2 == 0 && d.narrow() {
				dirty = true
			}
		}
		if dirty {
			d.render()
			dirty = false
		}
	}
}

func (d *Display) debug(msg string) {
	if os.Getenv("BILLBOARD_DEBUG") != "" {
		fmt.Fprintf(os.Stderr, "%s %s\n", time.Now().Format("15:04:05"), msg)
	}
}

func (d *Display) fetchIfChanged() bool {
	before, _ := json.Marshal(d.state)
	if err := d.fetch(); err != nil {
		return false
	}
	after, _ := json.Marshal(d.state)
	return string(before) != string(after)
}

func (d *Display) narrow() bool {
	w, _, err := term.GetSize(int(d.out.Fd()))
	return err != nil || w < 50
}

func (d *Display) fetch() error {
	resp, err := d.client.Get(d.server + "/api/state")
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	var snap state.Snapshot
	if err := json.NewDecoder(resp.Body).Decode(&snap); err != nil {
		return err
	}
	d.state = snap
	nonzero := 0
	for _, row := range snap.Pixels {
		for _, c := range row {
			if c != 0 {
				nonzero++
			}
		}
	}
	d.debug(fmt.Sprintf("fetch: %dx%d nonzero=%d msgs=%d", snap.Width, snap.Height, nonzero, len(snap.Messages)))
	return nil
}

func (d *Display) listen(changed chan<- struct{}) {
	notify := func() {
		select {
		case changed <- struct{}{}:
		default:
		}
	}
	for {
		req, err := http.NewRequest("GET", d.server+"/api/events", nil)
		if err != nil {
			return
		}
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			d.pollFallback(changed)
			return
		}
		scanner := bufio.NewScanner(resp.Body)
		for scanner.Scan() {
			if strings.HasPrefix(scanner.Text(), "event:") &&
				!strings.Contains(scanner.Text(), "hello") {
				notify()
			}
		}
		resp.Body.Close()
		if err := scanner.Err(); err != nil && err != io.EOF {
			time.Sleep(2 * time.Second)
		}
	}
}

func (d *Display) pollFallback(changed chan<- struct{}) {
	last := d.state
	for {
		time.Sleep(2 * time.Second)
		if err := d.fetch(); err != nil {
			continue
		}
		a, _ := json.Marshal(last)
		b, _ := json.Marshal(d.state)
		if string(a) != string(b) {
			last = d.state
			select {
			case changed <- struct{}{}:
			default:
			}
		}
	}
}

func (d *Display) render() {
	w, h, err := term.GetSize(int(d.out.Fd()))
	if err != nil || w <= 0 || h <= 0 {
		w, h = 80, 24
	}
	snap := d.state
	if snap.Width == 0 {
		return
	}

	var lines []string
	if w >= 50 {
		lines = d.wideLines(w, h)
	} else {
		lines = d.narrowLines(w, h)
	}

	var b strings.Builder
	for i, line := range lines {
		fmt.Fprintf(&b, "\x1b[%d;1H", i+1)
		b.WriteString(line)
	}
	b.WriteString("\x1b[0m\x1b[J")
	fmt.Fprint(d.out, b.String())
}

func sgr16(fg, bg uint8) string {
	f, b := int(fg), int(bg)
	if f < 8 {
		f += 30
	} else {
		f += 82 // 90-97
	}
	if b < 8 {
		b += 40
	} else {
		b += 92 // 100-107
	}
	return fmt.Sprintf("\x1b[%d;%dm", f, b)
}

func (d *Display) canvasLines(areaW, areaH int) []string {
	snap := d.state
	scaleX := float64(areaW) / float64(snap.Width)
	scaleY := float64(areaH*2) / float64(snap.Height)
	scale := min(scaleX, scaleY)
	if scale <= 0 {
		return nil
	}
	dispW := max(1, min(int(float64(snap.Width)*scale), areaW))
	dispH := max(1, min(int(float64(snap.Height)*scale), areaH*2))
	cellRows := (dispH + 1) / 2

	src := func(x, y int) uint8 {
		sx := min(int(float64(x)/scale), snap.Width-1)
		sy := min(int(float64(y)/scale), snap.Height-1)
		return snap.Pixels[sy][sx]
	}

	padLeft := strings.Repeat(" ", (areaW-dispW)/2)
	padRight := areaW - dispW - len(padLeft)
	blank := strings.Repeat(" ", areaW)

	lines := make([]string, 0, areaH)
	for row := 0; row < cellRows; row++ {
		var line strings.Builder
		line.WriteString(padLeft)
		for x := 0; x < dispW; x++ {
			fg := src(x, row*2)
			bg := uint8(0)
			if row*2+1 < dispH {
				bg = src(x, row*2+1)
			}
			line.WriteString(sgr16(fg, bg))
			line.WriteString("▀")
		}
		line.WriteString("\x1b[0m")
		line.WriteString(strings.Repeat(" ", padRight))
		lines = append(lines, line.String())
	}
	for len(lines) < areaH {
		lines = append(lines, blank)
	}
	top := (areaH - cellRows) / 2
	out := make([]string, areaH)
	copy(out[top:], lines)
	for i := range out {
		if out[i] == "" {
			out[i] = blank
		}
	}
	return out
}

func sanitize(s string) string {
	return strings.Map(func(r rune) rune {
		if r < 0x20 || r == 0x7f {
			return -1
		}
		return r
	}, s)
}

func wrapText(text string, width int) []string {
	if width <= 0 {
		return nil
	}
	var lines []string
	runes := []rune(text)
	for len(runes) > width {
		cut := width
		if i := strings.LastIndex(string(runes[:cut]), " "); i > 0 {
			cut = len([]rune(string(runes[:cut])[:i])) + 1
		}
		lines = append(lines, strings.TrimRight(string(runes[:cut]), " "))
		runes = []rune(strings.TrimLeft(string(runes[cut:]), " "))
	}
	return append(lines, string(runes))
}

func (d *Display) sidebarLines(msgW, h int) []string {
	blank := strings.Repeat(" ", msgW)
	msgs := d.state.Messages
	var lines []string
	for i := len(msgs) - 1; i >= 0 && len(lines) < h; i-- {
		text := msgs[i].At.Local().Format("15:04") + " " + sanitize(msgs[i].Text)
		wrapped := wrapText(text, msgW)
		for j := len(wrapped) - 1; j >= 0 && len(lines) < h; j-- {
			lines = append(lines, fmt.Sprintf("%-*s", msgW, wrapped[j]))
		}
	}
	for i, j := 0, len(lines)-1; i < j; i, j = i+1, j-1 {
		lines[i], lines[j] = lines[j], lines[i]
	}
	for len(lines) < h {
		lines = append([]string{blank}, lines...)
	}
	return lines
}

func (d *Display) wideLines(w, h int) []string {
	msgW := min(40, w/3)
	areaW := w - msgW - 1
	canvas := d.canvasLines(areaW, h)
	sidebar := d.sidebarLines(msgW, h)
	lines := make([]string, h)
	for row := 0; row < h; row++ {
		lines[row] = canvas[row] + "│" + sidebar[row]
	}
	return lines
}

func (d *Display) narrowLines(w, h int) []string {
	availRows := h - 2
	lines := d.canvasLines(w, availRows)
	lines = append(lines, strings.Repeat(" ", w))
	lines = append(lines, d.tickerLine(w))
	return lines
}

func (d *Display) tickerLine(w int) string {
	msgs := d.state.Messages
	if len(msgs) == 0 {
		return "\x1b[2mno messages yet — POST /api/message {\"text\":\"...\"}\x1b[0m"
	}
	parts := make([]string, 0, len(msgs))
	for i := len(msgs) - 1; i >= 0 && len(parts) < 10; i-- {
		parts = append(parts, sanitize(msgs[i].Text))
	}
	feed := strings.Join(parts, "  •  ") + "  •  "
	runes := []rune(feed)
	if len(runes) <= w {
		return feed
	}
	offset := (d.tick / 2) % len(runes)
	rotated := append(append([]rune{}, runes[offset:]...), runes[:offset]...)
	return string(rotated[:w])
}