webhooker/internal/healthcheck/healthcheck.go

// Package healthcheck provides application health status reporting.
package healthcheck

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

	"go.uber.org/fx"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/globals"
	"sneak.berlin/go/webhooker/internal/logger"
)

//nolint:revive // HealthcheckParams is a standard fx naming convention.
type HealthcheckParams struct {
	fx.In

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

// Healthcheck tracks application uptime and reports health status.
type Healthcheck struct {
	StartupTime time.Time
	log         *slog.Logger
	params      *HealthcheckParams
}

// New creates a Healthcheck that records the startup time on fx
// start.
func New(
	lc fx.Lifecycle,
	params HealthcheckParams,
) (*Healthcheck, error) {
	s := new(Healthcheck)
	s.params = &params
	s.log = params.Logger.Get()

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

			return nil
		},
		OnStop: func(_ context.Context) error {
			return nil
		},
	})

	return s, nil
}

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

	return resp
}

// Response contains the JSON-serialised health status.
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"`
}

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