feat: add navigation and window size handlers with corresponding tests

internal/handlers/downNavigationHandler_test.go

@@ -0,0 +1,111 @@
+package handlers_test
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/StevanFreeborn/term-tier/internal/core"
+	"github.com/StevanFreeborn/term-tier/internal/handlers"
+	"github.com/StevanFreeborn/term-tier/internal/state"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+func TestNewDownNavigationHandler(t *testing.T) {
+	h := handlers.NewDownNavigationHandler()
+
+	if h.Description() != "Move down" {
+		t.Errorf("Expected description 'Move down', got %q", h.Description())
+	}
+
+	keys := h.KeysHandled()
+
+	if !slices.Contains(keys, "down") || !slices.Contains(keys, "j") {
+		t.Errorf("Expected keys ['down', 'j'], got %v", keys)
+	}
+}
+
+func TestDownNavigationHandler_Match(t *testing.T) {
+	h := handlers.NewDownNavigationHandler()
+
+	tests := []struct {
+		name     string
+		mode     state.Mode
+		key      string
+		expected bool
+	}{
+		{
+			name:     "Matches 'down' in Navigation Mode",
+			mode:     state.NavigationMode,
+			key:      "down",
+			expected: true,
+		},
+		{
+			name:     "Matches 'j' in Navigation Mode",
+			mode:     state.NavigationMode,
+			key:      "j",
+			expected: true,
+		},
+		{
+			name:     "Ignores 'down' in Input Mode",
+			mode:     state.InputMode,
+			key:      "down",
+			expected: false,
+		},
+		{
+			name:     "Ignores 'j' in Input Mode",
+			mode:     state.InputMode,
+			key:      "j",
+			expected: false,
+		},
+		{
+			name:     "Ignores other keys in Navigation Mode",
+			mode:     state.NavigationMode,
+			key:      "up",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := state.New(state.WithMode(tt.mode))
+			msg := tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune(tt.key)}
+
+			if tt.key == "down" {
+				msg = tea.KeyMsg{Type: tea.KeyDown}
+			}
+
+			if got := h.Match(s, msg); got != tt.expected {
+				t.Errorf("Match() = %v, want %v", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestDownNavigationHandler_Handle(t *testing.T) {
+	h := handlers.NewDownNavigationHandler()
+
+	fullTiers := make([]core.Tier, 6)
+	fullTiers[0] = core.Tier{Name: "S", Items: []core.Item{"1", "2", "3"}}
+	fullTiers[1] = core.Tier{Name: "A", Items: []core.Item{"4"}}
+
+	s := state.New(
+		state.WithTiers(fullTiers),
+		state.WithCursor(0, 2), // Start at the end of Row 0
+		state.WithMode(state.NavigationMode),
+	)
+
+	msg := tea.KeyMsg{Type: tea.KeyDown}
+	cmd := h.Handle(s, msg)
+
+	if s.CursorRow() != 1 {
+		t.Errorf("Expected cursor to move to Row 1, got %d", s.CursorRow())
+	}
+
+	if s.CursorCol() != 0 {
+		t.Errorf("Expected cursor column to clamp to 0, got %d", s.CursorCol())
+	}
+
+	if cmd != nil {
+		t.Error("Expected Handle to return nil, got a command")
+	}
+}