test(04-02): add i3bar formatting with TDD

- I3BarBlock struct for i3bar protocol JSON
- formatI3BarBlocks: compact format D-06/D-07/D-08
- 10 tests covering mixed states, colors, labels, markers

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

i3bar.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+// I3BarBlock represents a single block in the i3bar protocol.
+type I3BarBlock struct {
+	FullText  string `json:"full_text"`
+	ShortText string `json:"short_text,omitempty"`
+	Color     string `json:"color"`
+	Name      string `json:"name"`
+	Markup    string `json:"markup,omitempty"`
+}
+
+// formatI3BarBlocks builds the vmux status block for i3bar from session data.
+func formatI3BarBlocks(sessions []SessionInfo) []I3BarBlock {
+	if len(sessions) == 0 {
+		return []I3BarBlock{{FullText: "vmux: no sessions", Color: "#00ff00", Name: "vmux"}}
+	}
+
+	hasWaiting := false
+	parts := make([]string, 0, len(sessions))
+
+	for _, s := range sessions {
+		name := shortName(s)
+		switch s.State {
+		case "Needs Input":
+			parts = append(parts, name+"[!]")
+			hasWaiting = true
+		case "Working":
+			parts = append(parts, name+"[W]")
+		case "Idle":
+			parts = append(parts, name+"[I]")
+		}
+	}
+
+	var text string
+	if !hasWaiting {
+		text = fmt.Sprintf("vmux: all working (%d)", len(sessions))
+	} else {
+		text = "vmux: " + strings.Join(parts, " ")
+	}
+
+	color := "#00ff00"
+	if hasWaiting {
+		color = "#ff0000"
+	}
+
+	return []I3BarBlock{{FullText: text, Color: color, Name: "vmux"}}
+}

i3bar_test.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestFormatI3BarBlocks_MixedStates(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/home/pierre/Code/auth", State: "Needs Input"},
+		{Cwd: "/home/pierre/Code/portal", State: "Working"},
+		{Cwd: "/home/pierre/Code/neia", State: "Idle"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	if len(blocks) != 1 {
+		t.Fatalf("expected 1 block, got %d", len(blocks))
+	}
+	want := "vmux: auth[!] portal[W] neia[I]"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+	if blocks[0].Color != "#ff0000" {
+		t.Errorf("color = %q, want #ff0000", blocks[0].Color)
+	}
+}
+
+func TestFormatI3BarBlocks_AllWorking(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/a/b/one", State: "Working"},
+		{Cwd: "/a/b/two", State: "Working"},
+		{Cwd: "/a/b/three", State: "Working"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: all working (3)"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+	if blocks[0].Color != "#00ff00" {
+		t.Errorf("color = %q, want #00ff00", blocks[0].Color)
+	}
+}
+
+func TestFormatI3BarBlocks_NoSessions(t *testing.T) {
+	blocks := formatI3BarBlocks(nil)
+	want := "vmux: no sessions"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+	if blocks[0].Color != "#00ff00" {
+		t.Errorf("color = %q, want #00ff00", blocks[0].Color)
+	}
+}
+
+func TestFormatI3BarBlocks_ColorRed(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/a/b/x", State: "Working"},
+		{Cwd: "/a/b/y", State: "Needs Input"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	if blocks[0].Color != "#ff0000" {
+		t.Errorf("color = %q, want #ff0000", blocks[0].Color)
+	}
+}
+
+func TestFormatI3BarBlocks_ColorGreen(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/a/b/x", State: "Working"},
+		{Cwd: "/a/b/y", State: "Idle"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	if blocks[0].Color != "#00ff00" {
+		t.Errorf("color = %q, want #00ff00", blocks[0].Color)
+	}
+}
+
+func TestFormatI3BarBlocks_UsesLabel(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/home/pierre/Code/auth-service", Label: "auth", State: "Working"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: all working (1)"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+}
+
+func TestFormatI3BarBlocks_UsesLabelInMixed(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/home/pierre/Code/auth-service", Label: "auth", State: "Needs Input"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: auth[!]"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+}
+
+func TestFormatI3BarBlocks_UsesCwdBase(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/home/pierre/Code/vibe/vmux", State: "Needs Input"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: vmux[!]"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+}
+
+func TestFormatI3BarBlocks_NeedsInputMarker(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/a/proj", State: "Needs Input"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: proj[!]"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+}
+
+func TestFormatI3BarBlocks_IdleMarker(t *testing.T) {
+	sessions := []SessionInfo{
+		{Cwd: "/a/proj", State: "Idle"},
+		{Cwd: "/a/other", State: "Needs Input"},
+	}
+	blocks := formatI3BarBlocks(sessions)
+	want := "vmux: proj[I] other[!]"
+	if blocks[0].FullText != want {
+		t.Errorf("full_text = %q, want %q", blocks[0].FullText, want)
+	}
+}