feat: implement load and save handlers with corresponding tests

internal/handlers/loadHandler.go

@@ -0,0 +1,48 @@
+package handlers
+
+import (
+	"slices"
+
+	"github.com/StevanFreeborn/term-tier/internal/core"
+	"github.com/StevanFreeborn/term-tier/internal/state"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+type loadHandler struct {
+	keys        []string
+	description string
+	saver       core.Saver
+}
+
+func NewLoadHandler(saver core.Saver) KeyMsgHandler {
+	return loadHandler{
+		keys:        []string{"ctrl+o"},
+		description: "Load tiers",
+		saver:       saver,
+	}
+}
+
+func (h loadHandler) KeysHandled() []string {
+	return h.keys
+}
+
+func (h loadHandler) Description() string {
+	return h.description
+}
+
+func (h loadHandler) Match(s state.State, msg tea.KeyMsg) bool {
+	return s.Mode() == state.NavigationMode && slices.Contains(h.keys, msg.String())
+}
+
+func (h loadHandler) Handle(s state.State, msg tea.KeyMsg) tea.Cmd {
+	return s.StartInputMode("Load tiers", func(val string, s state.State) tea.Cmd {
+		if data, err := h.saver.Load(val); err != nil {
+			s.SetStatus("Error: " + err.Error())
+		} else {
+			s.Load(data)
+			s.SetStatus("Loaded " + val)
+		}
+
+		return nil
+	})
+}