package swapcfg

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

	"gopkg.in/yaml.v2"

	"edge-infra.dev/pkg/k8s/runtime/controller/reconcile"
	v1ien "edge-infra.dev/pkg/sds/ien/k8s/apis/v1"
	"edge-infra.dev/pkg/sds/ien/k8s/controllers/nodeagent/config"
)

const (
	swapConfigFilePath             = "/zynstra/config/swapcfg.yaml"
	filePerms          os.FileMode = 0644
)

type Plugin struct{}

var (
	ErrSwapFieldNotFound = errors.New("swap enabled field not found")
)

type swapConfig struct {
	Swap Swap `yaml:"swap"`
}

type Swap struct {
	Enabled bool `yaml:"enabled"`
}

// Updates the swap configuration file on the node
func (swapCfgPlugin Plugin) Reconcile(_ context.Context, ienode *v1ien.IENode, conf config.Config) (reconcile.Result, error) {
	if ienode.Spec.SwapEnabled == nil {
		return reconcile.ResultEmpty, nil
	}
	if err := modifySwapConfig(ienode, filepath.Join(conf.GetNodeRootPath(), swapConfigFilePath)); err != nil {
		return reconcile.ResultRequeue, err
	}
	return reconcile.ResultSuccess, nil
}

func modifySwapConfig(ien *v1ien.IENode, configPath string) error {
	currentSwapBytes, err := readConfig(configPath)
	if err != nil {
		return err
	}

	targetSwapBytes, err := generateSwapConfig(ien)
	if err != nil {
		return err
	}

	if bytes.Equal(currentSwapBytes, targetSwapBytes) {
		return nil
	}
	return os.WriteFile(configPath, targetSwapBytes, filePerms)
}

func readConfig(configPath string) ([]byte, error) {
	if _, err := os.Stat(configPath); err != nil && !os.IsNotExist(err) {
		return nil, err
	} else if !os.IsNotExist(err) {
		return os.ReadFile(configPath)
	}
	return nil, nil
}

func generateSwapConfig(ien *v1ien.IENode) ([]byte, error) {
	targetSwapCfg := &swapConfig{
		Swap: Swap{
			Enabled: *ien.Spec.SwapEnabled,
		},
	}
	return yaml.Marshal(&targetSwapCfg)
}