mfd-monitor-agent/internal/httpapi/server.go

package httpapi

import (
	"encoding/json"
	"net/http"

	"mfd-monitor-agent/internal/status"
)

// Provider supplies the latest cached HostStatus to HTTP handlers.
type Provider interface {
	// Get returns the latest snapshot and whether a snapshot is ready.
	Get() (status.HostStatus, bool)
}

// StaticProvider is a test provider with a fixed snapshot response.
type StaticProvider struct {
	Snapshot status.HostStatus
	OK       bool
}

// Get returns the configured static snapshot and readiness flag.
func (p StaticProvider) Get() (status.HostStatus, bool) {
	return p.Snapshot, p.OK
}

// New creates the HTTP API handler for health and status endpoints.
func New(provider Provider) http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		snapshot, ok := provider.Get()
		if !ok {
			writeJSON(w, http.StatusServiceUnavailable, map[string]any{
				"status": "starting",
			})
			return
		}
		writeJSON(w, http.StatusOK, map[string]any{
			"status":          "ok",
			"version":         snapshot.Agent.Version,
			"snapshot_at":     snapshot.Agent.SnapshotAt,
			"snapshot_status": snapshot.Agent.SnapshotStatus,
		})
	})
	mux.HandleFunc("/status", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		snapshot, ok := provider.Get()
		if !ok {
			http.Error(w, "snapshot not ready", http.StatusServiceUnavailable)
			return
		}
		writeJSON(w, http.StatusOK, snapshot)
	})
	return mux
}

// writeJSON serializes value as JSON with a response status code.
func writeJSON(w http.ResponseWriter, code int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(value)
}