Add hostname editing feature to agent detail page

- Create enhanced agent detail template with all stats and hostname edit form
- Add UpdateHostname method to store for agent hostname updates
- Add UpdateAgentHostname handler in UI for web form submissions
- Add UpdateHostname endpoint in API handler for JSON requests
- Register new POST /agents/{id}/hostname route for hostname updates
- Improve agent detail page layout with Settings and Danger Zone sections
- Add error handling for missing agents and empty hostname values

internal/api/api.go

@@ -73,3 +73,32 @@ func (h *Handler) DeleteAgent(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(map[string]string{"status": "deleted"})
 }
+
+// UpdateHostname updates the hostname for an agent.
+func (h *Handler) UpdateHostname(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	agentID := r.PathValue("id")
+	if agentID == "" {
+		http.Error(w, "missing agent id", http.StatusBadRequest)
+		return
+	}
+
+	hostname := r.FormValue("hostname")
+	if hostname == "" {
+		http.Error(w, "missing hostname", http.StatusBadRequest)
+		return
+	}
+
+	err := h.store.UpdateHostname(agentID, hostname)
+	if err != nil {
+		http.Error(w, "agent not found", http.StatusNotFound)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]string{"status": "updated"})
+}

internal/store/store.go

@@ -1,12 +1,18 @@
 package store
 
 import (
+	"errors"
 	"sync"
 	"time"
 
 	"nerd-monitor/internal/stats"
 )
 
+var (
+	// ErrAgentNotFound is returned when an agent is not found.
+	ErrAgentNotFound = errors.New("agent not found")
+)
+
 // AgentStats represents the latest stats for an agent.
 type AgentStats struct {
 	ID        string
@@ -76,3 +82,17 @@ func (s *Store) DeleteAgent(id string) {
 
 	delete(s.agents, id)
 }
+
+// UpdateHostname updates the hostname for an agent.
+func (s *Store) UpdateHostname(id string, hostname string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	agent, exists := s.agents[id]
+	if !exists {
+		return ErrAgentNotFound
+	}
+
+	agent.Hostname = hostname
+	return nil
+}

internal/ui/handlers.go

@@ -133,6 +133,30 @@ func (h *Handler) DeleteAgent(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/", http.StatusSeeOther)
 }
 
+// UpdateAgentHostname handles hostname updates for agents.
+func (h *Handler) UpdateAgentHostname(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	agentID := r.PathValue("id")
+	hostname := r.FormValue("hostname")
+
+	if hostname == "" {
+		http.Error(w, "Hostname cannot be empty", http.StatusBadRequest)
+		return
+	}
+
+	err := h.store.UpdateHostname(agentID, hostname)
+	if err != nil {
+		http.NotFound(w, r)
+		return
+	}
+
+	http.Redirect(w, r, "/agents/"+agentID, http.StatusSeeOther)
+}
+
 // getStaleAgents returns agents that haven't reported in 6 months.
 func (h *Handler) getStaleAgents() []*store.AgentStats {
 	const staleThreshold = 6 * 30 * 24 * time.Hour