package wincmd

import (
	"errors"
	"fmt"
	"strings"
	"syscall"
	"time"

	"golang.org/x/sys/windows"
	"golang.org/x/sys/windows/svc"
	"golang.org/x/sys/windows/svc/eventlog"
	"golang.org/x/sys/windows/svc/mgr"
)

const (
	defaultServiceWaitTimeout = 15 * time.Second
	servicePollInterval       = 200 * time.Millisecond
)

// WaitServiceStatus waits until a service reaches the target state.
func WaitServiceStatus(name string, target SvcStatus, timeout time.Duration) error {
	name = strings.TrimSpace(name)
	if name == "" {
		return wrapInputError("empty service name")
	}
	if timeout <= 0 {
		timeout = defaultServiceWaitTimeout
	}

	service, err := OpenService(name)
	if err != nil {
		return err
	}
	defer service.Close()

	return waitServiceStatus(service.Service, svc.State(target), timeout)
}

// RestartService stops and starts a service, then waits for Running state.
func RestartService(name string, timeout time.Duration) error {
	name = strings.TrimSpace(name)
	if name == "" {
		return wrapInputError("empty service name")
	}
	if timeout <= 0 {
		timeout = defaultServiceWaitTimeout
	}

	service, err := OpenService(name)
	if err != nil {
		return err
	}
	defer service.Close()

	status, err := service.Query()
	if err != nil {
		return err
	}
	if status.State != svc.Stopped {
		if _, err := service.Control(svc.Stop); err != nil {
			if errno, ok := err.(syscall.Errno); !ok || errno != windows.ERROR_SERVICE_NOT_ACTIVE {
				return err
			}
		}
		if err := waitServiceStatus(service.Service, svc.Stopped, timeout); err != nil {
			return err
		}
	}

	if err := service.Start(); err != nil {
		return err
	}
	if err := waitServiceStatus(service.Service, svc.Running, timeout); err != nil {
		return err
	}
	return nil
}

// EnsureService creates the service when missing, or updates mutable config fields when it exists.
func EnsureService(spec WinSvcInput) (created bool, updated bool, err error) {
	name := strings.TrimSpace(spec.Name)
	if name == "" {
		return false, false, wrapInputError("empty service name")
	}
	elevated, elevErr := IsElevated()
	if elevErr != nil {
		return false, false, wrapPermissionError("query elevation", elevErr)
	}
	if !elevated {
		return false, false, wrapPermissionError("admin required for service operations", nil)
	}

	winmgr, err := mgr.Connect()
	if err != nil {
		return false, false, err
	}
	defer winmgr.Disconnect()

	service, err := winmgr.OpenService(name)
	if err != nil {
		if !isServiceNotExists(err) {
			return false, false, err
		}
		if strings.TrimSpace(spec.ExecPath) == "" {
			return false, false, wrapInputError("empty executable path")
		}
		cfg := mgr.Config{
			DisplayName:      spec.DisplayName,
			StartType:        normalizeStartType(spec.StartType),
			DelayedAutoStart: spec.DelayedAutoStart,
			Description:      spec.Description,
		}
		gsvc, err := winmgr.CreateService(name, spec.ExecPath, cfg, spec.Args...)
		if err != nil {
			return false, false, err
		}
		defer gsvc.Close()
		if err := eventlog.InstallAsEventCreate(name, eventlog.Error|eventlog.Warning|eventlog.Info); err != nil {
			_ = gsvc.Delete()
			return false, false, fmt.Errorf("install event log source: %w", err)
		}
		if _, err := applyServiceRecoverySettings(gsvc, spec); err != nil {
			_ = eventlog.Remove(name)
			_ = gsvc.Delete()
			return false, false, err
		}
		return true, false, nil
	}
	defer service.Close()

	current, err := service.Config()
	if err != nil {
		return false, false, err
	}
	want := current

	if spec.DisplayName != "" && current.DisplayName != spec.DisplayName {
		want.DisplayName = spec.DisplayName
		updated = true
	}
	if spec.Description != "" && current.Description != spec.Description {
		want.Description = spec.Description
		updated = true
	}
	if spec.StartType != 0 {
		normalized := normalizeStartType(spec.StartType)
		if current.StartType != normalized {
			want.StartType = normalized
			updated = true
		}
		if spec.DelayedAutoStart != current.DelayedAutoStart {
			want.DelayedAutoStart = spec.DelayedAutoStart
			updated = true
		}
	} else if spec.DelayedAutoStart && !current.DelayedAutoStart {
		want.DelayedAutoStart = true
		updated = true
	}

	if strings.TrimSpace(spec.ExecPath) != "" {
		binaryPath, buildErr := buildServiceBinaryPath(spec.ExecPath, spec.Args)
		if buildErr != nil {
			return false, false, buildErr
		}
		if current.BinaryPathName != binaryPath {
			want.BinaryPathName = binaryPath
			updated = true
		}
	}

	if updated {
		if err := service.UpdateConfig(want); err != nil {
			return false, false, err
		}
	}

	recoveryChanged, err := applyServiceRecoverySettings(service, spec)
	if err != nil {
		return false, false, err
	}
	updated = updated || recoveryChanged
	return false, updated, nil
}

func waitServiceStatus(service *mgr.Service, target svc.State, timeout time.Duration) error {
	if timeout <= 0 {
		timeout = defaultServiceWaitTimeout
	}
	var lastState svc.State
	err := waitUntil(timeout, servicePollInterval, "wait service status timeout", func() (bool, error) {
		status, err := service.Query()
		if err != nil {
			return false, err
		}
		lastState = status.State
		return status.State == target, nil
	})
	if err != nil {
		if errors.Is(err, ErrTimeout) {
			return wrapTimeoutError(fmt.Sprintf("wait service status timeout: current=%v target=%v", lastState, target))
		}
		return err
	}
	return nil
}

func isServiceNotExists(err error) bool {
	if err == nil {
		return false
	}
	if errno, ok := err.(syscall.Errno); ok {
		return errno == windows.ERROR_SERVICE_DOES_NOT_EXIST
	}
	return false
}

func normalizeStartType(startType uint32) uint32 {
	if startType == 0 {
		return StartManual
	}
	return startType
}

func buildServiceBinaryPath(execPath string, args []string) (string, error) {
	execPath = strings.TrimSpace(execPath)
	if execPath == "" {
		return "", wrapInputError("empty executable path")
	}
	parts := make([]string, 0, len(args)+1)
	parts = append(parts, windows.EscapeArg(execPath))
	for _, arg := range args {
		parts = append(parts, windows.EscapeArg(arg))
	}
	return strings.Join(parts, " "), nil
}

func applyServiceRecoverySettings(service *mgr.Service, spec WinSvcInput) (bool, error) {
	if service == nil {
		return false, nil
	}
	updated := false

	if spec.RecoveryActions != nil {
		currentActions, err := service.RecoveryActions()
		if err != nil {
			return false, err
		}
		currentResetSec, err := service.ResetPeriod()
		if err != nil {
			return false, err
		}
		if shouldUpdateRecoveryActions(currentActions, spec.RecoveryActions, currentResetSec, spec.RecoveryResetSec) {
			if len(spec.RecoveryActions) == 0 {
				if err := service.ResetRecoveryActions(); err != nil {
					return false, err
				}
			} else {
				if err := service.SetRecoveryActions(spec.RecoveryActions, spec.RecoveryResetSec); err != nil {
					return false, err
				}
			}
			updated = true
		}
	}

	if recoveryCommandSpecified(spec) {
		currentCmd, err := service.RecoveryCommand()
		if err != nil {
			return false, err
		}
		if currentCmd != spec.RecoveryCommand {
			if err := service.SetRecoveryCommand(spec.RecoveryCommand); err != nil {
				return false, err
			}
			updated = true
		}
	}

	if spec.RecoveryOnFail != nil {
		currentFlag, err := service.RecoveryActionsOnNonCrashFailures()
		if err != nil {
			return false, err
		}
		if currentFlag != *spec.RecoveryOnFail {
			if err := service.SetRecoveryActionsOnNonCrashFailures(*spec.RecoveryOnFail); err != nil {
				return false, err
			}
			updated = true
		}
	}

	return updated, nil
}

func shouldUpdateRecoveryActions(current []mgr.RecoveryAction, desired []mgr.RecoveryAction, currentResetSec uint32, desiredResetSec uint32) bool {
	if desired == nil {
		return false
	}
	if len(desired) == 0 {
		return len(current) != 0 || currentResetSec != 0
	}
	return !equalRecoveryActions(current, desired) || currentResetSec != desiredResetSec
}

func recoveryCommandSpecified(spec WinSvcInput) bool {
	return spec.RecoveryCommandSet || spec.RecoveryCommand != ""
}

func equalRecoveryActions(a, b []mgr.RecoveryAction) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i].Type != b[i].Type || a[i].Delay != b[i].Delay {
			return false
		}
	}
	return true
}