dnswatcher/internal/healthcheck/healthcheck.go

// Package healthcheck provides application health status.
package healthcheck

import (
	"context"
	"log/slog"
	"time"

	"go.uber.org/fx"

	"sneak.berlin/go/dnswatcher/internal/config"
	"sneak.berlin/go/dnswatcher/internal/globals"
	"sneak.berlin/go/dnswatcher/internal/logger"
)

// Params contains dependencies for Healthcheck.
type Params struct {
	fx.In

	Globals *globals.Globals
	Config  *config.Config
	Logger  *logger.Logger
}

// Healthcheck provides health status information.
type Healthcheck struct {
	StartupTime time.Time
	log         *slog.Logger
	params      *Params
}

// Response is the health check response structure.
type Response struct {
	Status        string `json:"status"`
	Now           string `json:"now"`
	UptimeSeconds int64  `json:"uptimeSeconds"`
	UptimeHuman   string `json:"uptimeHuman"`
	Version       string `json:"version"`
	Appname       string `json:"appname"`
	Maintenance   bool   `json:"maintenanceMode"`
}

// New creates a new Healthcheck instance.
func New(
	lifecycle fx.Lifecycle,
	params Params,
) (*Healthcheck, error) {
	healthcheck := &Healthcheck{
		log:    params.Logger.Get(),
		params: &params,
	}

	lifecycle.Append(fx.Hook{
		OnStart: func(_ context.Context) error {
			healthcheck.StartupTime = time.Now()

			return nil
		},
	})

	return healthcheck, nil
}

// Check returns the current health status.
func (h *Healthcheck) Check() *Response {
	return &Response{
		Status:        "ok",
		Now:           time.Now().UTC().Format(time.RFC3339Nano),
		UptimeSeconds: int64(h.uptime().Seconds()),
		UptimeHuman:   h.uptime().String(),
		Appname:       h.params.Globals.Appname,
		Version:       h.params.Globals.Version,
		Maintenance:   h.params.Config.MaintenanceMode,
	}
}

func (h *Healthcheck) uptime() time.Duration {
	return time.Since(h.StartupTime)
}