package app

import (
	"strings"
)

func (transportSystemdBackend) Health(client TransportClient) transportBackendHealthResult {
	units, errCode, errMsg := transportSystemdHealthUnits(client)
	if len(units) == 0 {
		return transportBackendHealthResult{
			OK:      false,
			Code:    errCode,
			Message: errMsg,
			Status:  TransportClientDown,
		}
	}

	active := 0
	starting := 0
	inactive := 0
	failed := 0
	unknown := 0
	issues := make([]string, 0, len(units))
	for _, unit := range units {
		stdout, stderr, _, _ := transportRunCommand(transportBackendHealthTimeout, "systemctl", "is-active", unit)
		state := strings.ToLower(strings.TrimSpace(stdout))
		switch state {
		case "active":
			active++
		case "activating", "reloading":
			starting++
		case "inactive", "deactivating":
			inactive++
		case "failed":
			failed++
			msg := strings.TrimSpace(stderr)
			if msg == "" {
				msg = "systemd unit failed"
			}
			issues = append(issues, unit+": "+msg)
		default:
			unknown++
			msg := strings.TrimSpace(stderr)
			if msg == "" {
				msg = strings.TrimSpace(stdout)
			}
			if msg == "" {
				msg = "status unknown"
			}
			issues = append(issues, unit+": "+msg)
		}
	}

	total := len(units)
	if active == total {
		res := transportBackendHealthResult{OK: true, Status: TransportClientUp}
		if latency, _ := transportProbeClientLatency(client); latency > 0 {
			res.LatencyMS = latency
		}
		return res
	}
	if active+starting == total {
		return transportBackendHealthResult{OK: true, Status: TransportClientStarting}
	}
	if inactive == total {
		return transportBackendHealthResult{OK: true, Status: TransportClientDown}
	}
	msg := strings.TrimSpace(strings.Join(issues, "; "))
	if msg == "" {
		msg = "backend units are not synchronized"
	}
	status := TransportClientDegraded
	if active == 0 && failed == 0 && unknown == 0 {
		status = TransportClientDown
	}
	return transportBackendHealthResult{
		OK:        false,
		Code:      "TRANSPORT_BACKEND_HEALTH_FAILED",
		Message:   msg,
		Status:    status,
		Retryable: true,
	}
}