// SPDX-FileCopyrightText: 2026 Coffey Labs
// SPDX-License-Identifier: GPL-3.0-or-later

package preflight

import (
	"context"
	"os"
	"os/exec"

	"github.com/LINUXexpert-org/stalwart-migrator/internal/service"
)

// DeploymentKind is how a Stalwart instance appears to be run, which
// determines how cutover restarts it. It's an alias for
// service.Kind rather than a parallel type: detection here and control
// there have to agree on the same vocabulary, and one definition can't
// drift from itself.
type DeploymentKind = service.Kind

const (
	DeploymentSystemd = service.Systemd
	DeploymentDocker  = service.Docker
	DeploymentUnknown = service.Unknown
)

var systemdUnitPaths = []string{
	"/etc/systemd/system/stalwart.service",
	"/lib/systemd/system/stalwart.service",
	"/usr/lib/systemd/system/stalwart.service",
}

// DetectDeploymentKind makes a best-effort guess at how Stalwart is run
// here. It's deliberately conservative and cheap (file stats, one docker
// inspect) rather than exhaustive - an operator-supplied override should
// always be able to win over this, since the cost of guessing wrong here is
// cutover targeting the wrong thing.
func DetectDeploymentKind(ctx context.Context, containerName string) DeploymentKind {
	for _, p := range systemdUnitPaths {
		if _, err := os.Stat(p); err == nil {
			return DeploymentSystemd
		}
	}
	if containerName == "" {
		containerName = "stalwart"
	}
	if _, err := exec.LookPath("docker"); err == nil {
		if err := exec.CommandContext(ctx, "docker", "inspect", containerName).Run(); err == nil {
			return DeploymentDocker
		}
	}
	return DeploymentUnknown
}