// Service lifecycle management (install / uninstall / start / stop) plus the
// service-hosted run loop. Uses kardianos/service so the same binary runs as a
// Windows service (SCM), a systemd/upstart/sysv daemon on Linux, or a launchd
// daemon on macOS, and can also run interactively (foreground / container).
package cli

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"github.com/Grace-Solutions/OrchestrAD/internal/config"
	"github.com/Grace-Solutions/OrchestrAD/internal/logging"
	"github.com/Grace-Solutions/OrchestrAD/internal/pki"
	"github.com/Grace-Solutions/OrchestrAD/internal/tlsmgr"
	"github.com/kardianos/service"
)

const (
	serviceName        = "OrchestrAD"
	serviceDisplayName = "OrchestrAD"
	serviceDescription = "OrchestrAD - Active Directory Rule Automation Platform"
)

// program adapts the server run loop to the service.Interface contract. Start
// must not block, so the server runs on a goroutine whose lifetime is bound to
// a context cancelled by Stop.
type program struct {
	cancel context.CancelFunc
	done   chan error
}

// Start is called by the service manager (or by Run when interactive). It
// launches the server without blocking.
func (p *program) Start(s service.Service) error {
	// When launched by a service manager the process inherits the manager's
	// working directory (e.g. C:\Windows\System32 on Windows), which would put a
	// relative ORCHESTRAD_DATA_PATH (default ./data) in the wrong place. Pin the
	// working directory to the executable's directory so data lands next to the
	// installed binary. Interactive runs (foreground / container) keep the
	// caller's working directory and any absolute data path they set.
	if !service.Interactive() {
		if exe, err := os.Executable(); err == nil {
			_ = os.Chdir(filepath.Dir(exe))
		}
	}

	ctx, cancel := context.WithCancel(context.Background())
	p.cancel = cancel
	p.done = make(chan error, 1)
	go func() {
		p.done <- runServer(ctx)
	}()
	return nil
}

// Stop is called on service stop / interactive interrupt. It cancels the run
// context and waits for the server to unwind so the process exits cleanly.
func (p *program) Stop(s service.Service) error {
	if p.cancel != nil {
		p.cancel()
	}
	if p.done != nil {
		return <-p.done
	}
	return nil
}

// serviceConfig builds the platform service definition. WorkingDirectory is
// pinned to the executable's directory so a relative ORCHESTRAD_DATA_PATH
// (default ./data) resolves next to the installed binary rather than wherever
// the service manager happens to launch it from. Arguments ["run"] make the
// service manager start the process in run mode, which routes back through
// service.Run.
func serviceConfig() (*service.Config, error) {
	exe, err := os.Executable()
	if err != nil {
		return nil, fmt.Errorf("resolving executable path: %w", err)
	}
	return &service.Config{
		Name:             serviceName,
		DisplayName:      serviceDisplayName,
		Description:      serviceDescription,
		Arguments:        []string{"run"},
		WorkingDirectory: filepath.Dir(exe),
	}, nil
}

// newService constructs the service handle and its program.
func newService() (service.Service, error) {
	cfg, err := serviceConfig()
	if err != nil {
		return nil, err
	}
	return service.New(&program{}, cfg)
}

// runService runs the server through the service framework. When launched by a
// service manager it speaks the manager's control protocol (required on
// Windows); when launched interactively it runs Start, blocks until an
// interrupt, then runs Stop. This is the single entry point used by the `run`
// command so foreground, container, and service execution share one path.
func runService() error {
	s, err := newService()
	if err != nil {
		return fmt.Errorf("creating service: %w", err)
	}
	return s.Run()
}

// controlService applies a single service control action (start or stop) using
// the platform service manager.
func controlService(action string) error {
	s, err := newService()
	if err != nil {
		return fmt.Errorf("creating service: %w", err)
	}
	if err := service.Control(s, action); err != nil {
		return fmt.Errorf("%s service: %w", action, err)
	}
	return nil
}

// initializeService idempotently ensures the service is installed and running.
// Re-running it is safe: an already-installed service is not reinstalled, and an
// already-running one is left alone. This backs the `initialize` (and `install`)
// command so provisioning is repeatable.
func initializeService() error {
	s, err := newService()
	if err != nil {
		return fmt.Errorf("creating service: %w", err)
	}

	status, err := s.Status()
	if errors.Is(err, service.ErrNotInstalled) {
		if err := s.Install(); err != nil {
			return fmt.Errorf("installing service: %w", err)
		}
		logging.Info("Service", "Service installed")
		status = service.StatusStopped
	} else if err != nil {
		return fmt.Errorf("querying service status: %w", err)
	} else {
		logging.Info("Service", "Service already installed")
	}

	ensureFirewall()

	if status == service.StatusRunning {
		logging.Info("Service", "Service already running")
		return nil
	}
	if err := s.Start(); err != nil {
		return fmt.Errorf("starting service: %w", err)
	}
	logging.Info("Service", "Service started")
	return nil
}

// ensureFirewall creates the inbound allow rule for the configured listen port.
// Best-effort: a failure (e.g. missing privileges) is logged but does not block
// service provisioning.
func ensureFirewall() {
	port := 18090
	if cfg, err := config.Load(); err == nil {
		port = cfg.Server.Port
	}
	if err := EnsureFirewallRule(port); err != nil {
		logging.Warn("Firewall", "Could not create inbound firewall rule (%v); open TCP %d manually if needed", err, port)
	}
}

// removeService idempotently ensures the service is stopped and removed.
// Re-running it is safe: a not-installed service is treated as already removed,
// and a stop failure on an already-stopped service does not block removal. This
// backs the `remove` (and `uninstall`) command.
func removeService() error {
	s, err := newService()
	if err != nil {
		return fmt.Errorf("creating service: %w", err)
	}

	status, err := s.Status()
	if errors.Is(err, service.ErrNotInstalled) {
		logging.Info("Service", "Service not installed; nothing to remove")
		return nil
	} else if err != nil {
		return fmt.Errorf("querying service status: %w", err)
	}

	if status == service.StatusRunning {
		if err := s.Stop(); err != nil {
			logging.Warn("Service", "Could not stop service before removal: %v", err)
		} else {
			logging.Info("Service", "Service stopped")
		}
	}
	if err := s.Uninstall(); err != nil {
		return fmt.Errorf("removing service: %w", err)
	}
	_ = RemoveFirewallRule()
	removeStoreCertificate()
	logging.Info("Service", "Service removed")
	return nil
}

// removeStoreCertificate deletes the self-managed leaf we published into the
// host's personal certificate store, so uninstalling does not leave an orphan
// behind. Best-effort: the certificate may never have been installed, and the
// data directory may already be gone.
func removeStoreCertificate() {
	cfg, err := config.Load()
	if err != nil {
		return
	}
	certPEM, err := os.ReadFile(filepath.Join(cfg.DataPath, "tls", "server.crt"))
	if err != nil {
		return
	}
	cert, err := pki.ParseCertPEM(certPEM)
	if err != nil {
		return
	}
	if err := tlsmgr.RemoveLeafFromMyStore(cert); err != nil {
		logging.Warn("Service", "Could not remove the server certificate from the host store: %v", err)
		return
	}
	logging.Info("Service", "Removed the server certificate from the host store")
}