package k8sapi

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"regexp"
	"time"

	"github.com/edgelesssys/constellation/coordinator/kubernetes/k8sapi/resources"
	kubeadm "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3"
)

const (
	// kubeConfig is the path to the Kubernetes admin config (used for authentication).
	kubeConfig = "/etc/kubernetes/admin.conf"
	// kubeletStartTimeout is the maximum time given to the kubelet service to (re)start.
	kubeletStartTimeout = 10 * time.Minute
)

var (
	kubernetesKeyRegexp = regexp.MustCompile("[a-f0-9]{64}")
	providerIDRegex     = regexp.MustCompile(`^azure:///subscriptions/([^/]+)/resourceGroups/([^/]+)/providers/Microsoft.Compute/virtualMachineScaleSets/([^/]+)/virtualMachines/([^/]+)$`)
)

// Client provides the functionality of `kubectl apply`.
type Client interface {
	Apply(resources resources.Marshaler, forceConflicts bool) error
	SetKubeconfig(kubeconfig []byte)
	// TODO: add tolerations
}

// KubernetesUtil provides low level management of the kubernetes cluster.
type KubernetesUtil struct {
	inst installer
}

// NewKubernetesUtils creates a new KubernetesUtil.
func NewKubernetesUtil() *KubernetesUtil {
	return &KubernetesUtil{
		inst: newOSInstaller(),
	}
}

// InstallComponents installs kubernetes components in the version specified.
func (k *KubernetesUtil) InstallComponents(ctx context.Context, version string) error {
	var versionConf kubernetesVersion
	var ok bool
	if versionConf, ok = versionConfigs[version]; !ok {
		return fmt.Errorf("unsupported kubernetes version %q", version)
	}
	if err := versionConf.installK8sComponents(ctx, k.inst); err != nil {
		return err
	}

	return enableSystemdUnit(ctx, kubeletServiceEtcPath)
}

func (k *KubernetesUtil) InitCluster(ctx context.Context, initConfig []byte) error {
	// TODO: audit policy should be user input
	auditPolicy, err := resources.NewDefaultAuditPolicy().Marshal()
	if err != nil {
		return fmt.Errorf("failed to generate default audit policy: %w", err)
	}
	if err := os.WriteFile(auditPolicyPath, auditPolicy, 0o644); err != nil {
		return fmt.Errorf("failed to write default audit policy: %w", err)
	}

	initConfigFile, err := os.CreateTemp("", "kubeadm-init.*.yaml")
	if err != nil {
		return fmt.Errorf("failed to create init config file %v: %w", initConfigFile.Name(), err)
	}
	defer os.Remove(initConfigFile.Name())

	if _, err := initConfigFile.Write(initConfig); err != nil {
		return fmt.Errorf("writing kubeadm init yaml config %v failed: %w", initConfigFile.Name(), err)
	}

	cmd := exec.CommandContext(ctx, kubeadmPath, "init", "--config", initConfigFile.Name())
	_, err = cmd.Output()
	if err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			return fmt.Errorf("kubeadm init failed (code %v) with: %s", exitErr.ExitCode(), exitErr.Stderr)
		}
		return fmt.Errorf("kubeadm init failed: %w", err)
	}
	return nil
}

type SetupPodNetworkInput struct {
	CloudProvider     string
	NodeName          string
	FirstNodePodCIDR  string
	SubnetworkPodCIDR string
	ProviderID        string
}

// SetupPodNetwork sets up the cilium pod network.
func (k *KubernetesUtil) SetupPodNetwork(ctx context.Context, in SetupPodNetworkInput) error {
	switch in.CloudProvider {
	case "gcp":
		return k.setupGCPPodNetwork(ctx, in.NodeName, in.FirstNodePodCIDR, in.SubnetworkPodCIDR)
	case "azure":
		return k.setupAzurePodNetwork(ctx, in.ProviderID, in.SubnetworkPodCIDR)
	case "qemu":
		return k.setupQemuPodNetwork(ctx)
	default:
		return fmt.Errorf("unsupported cloud provider %q", in.CloudProvider)
	}
}

func (k *KubernetesUtil) setupAzurePodNetwork(ctx context.Context, providerID, subnetworkPodCIDR string) error {
	matches := providerIDRegex.FindStringSubmatch(providerID)
	if len(matches) != 5 {
		return fmt.Errorf("error splitting providerID %q", providerID)
	}

	ciliumInstall := exec.CommandContext(ctx, "cilium", "install", "--azure-resource-group", matches[2], "--encryption", "wireguard", "--ipam", "azure",
		"--helm-set",
		"tunnel=disabled,enableIPv4Masquerade=true,azure.enabled=true,debug.enabled=true,ipv4NativeRoutingCIDR="+subnetworkPodCIDR+
			",endpointRoutes.enabled=true,encryption.enabled=true,encryption.type=wireguard,l7Proxy=false,egressMasqueradeInterfaces=eth0")
	ciliumInstall.Env = append(os.Environ(), "KUBECONFIG="+kubeConfig)
	out, err := ciliumInstall.CombinedOutput()
	if err != nil {
		err = errors.New(string(out))
		return err
	}
	return nil
}

func (k *KubernetesUtil) setupGCPPodNetwork(ctx context.Context, nodeName, nodePodCIDR, subnetworkPodCIDR string) error {
	out, err := exec.CommandContext(ctx, kubectlPath, "--kubeconfig", kubeConfig, "patch", "node", nodeName, "-p", "{\"spec\":{\"podCIDR\": \""+nodePodCIDR+"\"}}").CombinedOutput()
	if err != nil {
		err = errors.New(string(out))
		return err
	}

	// allow coredns to run on uninitialized nodes (required by cloud-controller-manager)
	err = exec.CommandContext(ctx, kubectlPath, "--kubeconfig", kubeConfig, "-n", "kube-system", "patch", "deployment", "coredns", "--type", "json", "-p", "[{\"op\":\"add\",\"path\":\"/spec/template/spec/tolerations/-\",\"value\":{\"key\":\"node.cloudprovider.kubernetes.io/uninitialized\",\"value\":\"true\",\"effect\":\"NoSchedule\"}},{\"op\":\"add\",\"path\":\"/spec/template/spec/nodeSelector\",\"value\":{\"node-role.kubernetes.io/control-plane\":\"\"}}]").Run()
	if err != nil {
		return err
	}

	err = exec.CommandContext(ctx, kubectlPath, "--kubeconfig", kubeConfig, "-n", "kube-system", "patch", "deployment", "coredns", "--type", "json", "-p", "[{\"op\":\"add\",\"path\":\"/spec/template/spec/tolerations/-\",\"value\":{\"key\":\"node.kubernetes.io/network-unavailable\",\"value\":\"\",\"effect\":\"NoSchedule\"}}]").Run()
	if err != nil {
		return err
	}

	ciliumInstall := exec.CommandContext(ctx, "cilium", "install", "--encryption", "wireguard", "--ipam", "kubernetes", "--ipv4-native-routing-cidr", subnetworkPodCIDR, "--helm-set", "endpointRoutes.enabled=true,tunnel=disabled")
	ciliumInstall.Env = append(os.Environ(), "KUBECONFIG="+kubeConfig)
	out, err = ciliumInstall.CombinedOutput()
	if err != nil {
		err = errors.New(string(out))
		return err
	}
	return nil
}

func (k *KubernetesUtil) setupQemuPodNetwork(ctx context.Context) error {
	ciliumInstall := exec.CommandContext(ctx, "cilium", "install", "--encryption", "wireguard", "--helm-set", "ipam.operator.clusterPoolIPv4PodCIDRList=10.244.0.0/16,endpointRoutes.enabled=true")
	ciliumInstall.Env = append(os.Environ(), "KUBECONFIG="+kubeConfig)
	out, err := ciliumInstall.CombinedOutput()
	if err != nil {
		err = errors.New(string(out))
		return err
	}
	return nil
}

// SetupAutoscaling deploys the k8s cluster autoscaler.
func (k *KubernetesUtil) SetupAutoscaling(kubectl Client, clusterAutoscalerConfiguration resources.Marshaler, secrets resources.Marshaler) error {
	if err := kubectl.Apply(secrets, true); err != nil {
		return fmt.Errorf("applying cluster-autoscaler Secrets failed: %w", err)
	}
	return kubectl.Apply(clusterAutoscalerConfiguration, true)
}

// SetupCloudControllerManager deploys the k8s cloud-controller-manager.
func (k *KubernetesUtil) SetupCloudControllerManager(kubectl Client, cloudControllerManagerConfiguration resources.Marshaler, configMaps resources.Marshaler, secrets resources.Marshaler) error {
	if err := kubectl.Apply(configMaps, true); err != nil {
		return fmt.Errorf("applying ccm ConfigMaps failed: %w", err)
	}
	if err := kubectl.Apply(secrets, true); err != nil {
		return fmt.Errorf("applying ccm Secrets failed: %w", err)
	}
	if err := kubectl.Apply(cloudControllerManagerConfiguration, true); err != nil {
		return fmt.Errorf("applying ccm failed: %w", err)
	}
	return nil
}

// SetupCloudNodeManager deploys the k8s cloud-node-manager.
func (k *KubernetesUtil) SetupCloudNodeManager(kubectl Client, cloudNodeManagerConfiguration resources.Marshaler) error {
	return kubectl.Apply(cloudNodeManagerConfiguration, true)
}

// JoinCluster joins existing Kubernetes cluster using kubeadm join.
func (k *KubernetesUtil) JoinCluster(ctx context.Context, joinConfig []byte) error {
	// TODO: audit policy should be user input
	auditPolicy, err := resources.NewDefaultAuditPolicy().Marshal()
	if err != nil {
		return fmt.Errorf("failed to generate default audit policy: %w", err)
	}
	if err := os.WriteFile(auditPolicyPath, auditPolicy, 0o644); err != nil {
		return fmt.Errorf("failed to write default audit policy: %w", err)
	}

	joinConfigFile, err := os.CreateTemp("", "kubeadm-join.*.yaml")
	if err != nil {
		return fmt.Errorf("failed to create join config file %v: %w", joinConfigFile.Name(), err)
	}
	defer os.Remove(joinConfigFile.Name())

	if _, err := joinConfigFile.Write(joinConfig); err != nil {
		return fmt.Errorf("writing kubeadm init yaml config %v failed: %w", joinConfigFile.Name(), err)
	}

	// run `kubeadm join` to join a worker node to an existing Kubernetes cluster
	cmd := exec.CommandContext(ctx, kubeadmPath, "join", "--config", joinConfigFile.Name())
	if _, err := cmd.Output(); err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			return fmt.Errorf("kubeadm join failed (code %v) with: %s", exitErr.ExitCode(), exitErr.Stderr)
		}
		return fmt.Errorf("kubeadm join failed: %w", err)
	}
	return nil
}

// SetupKMS deploys the KMS deployment.
func (k *KubernetesUtil) SetupKMS(kubectl Client, kmsConfiguration resources.Marshaler) error {
	if err := kubectl.Apply(kmsConfiguration, true); err != nil {
		return fmt.Errorf("applying KMS configuration failed: %w", err)
	}
	return nil
}

// StartKubelet enables and starts the kubelet systemd unit.
func (k *KubernetesUtil) StartKubelet() error {
	ctx, cancel := context.WithTimeout(context.TODO(), kubeletStartTimeout)
	defer cancel()
	if err := enableSystemdUnit(ctx, kubeletServiceEtcPath); err != nil {
		return fmt.Errorf("enabling kubelet systemd unit failed: %w", err)
	}
	return startSystemdUnit(ctx, "kubelet.service")
}

// RestartKubelet restarts a kubelet.
func (k *KubernetesUtil) RestartKubelet() error {
	ctx, cancel := context.WithTimeout(context.TODO(), kubeletStartTimeout)
	defer cancel()
	return restartSystemdUnit(ctx, "kubelet.service")
}

// GetControlPlaneJoinCertificateKey return the key which can be used in combination with the joinArgs
// to join the Cluster as control-plane.
func (k *KubernetesUtil) GetControlPlaneJoinCertificateKey(ctx context.Context) (string, error) {
	// Key will be valid for 1h (no option to reduce the duration).
	// https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-init-phase/#cmd-phase-upload-certs
	output, err := exec.CommandContext(ctx, kubeadmPath, "init", "phase", "upload-certs", "--upload-certs").Output()
	if err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			return "", fmt.Errorf("kubeadm upload-certs failed (code %v) with: %s", exitErr.ExitCode(), exitErr.Stderr)
		}
		return "", fmt.Errorf("kubeadm upload-certs failed: %w", err)
	}
	// Example output:
	/*
		[upload-certs] Storing the certificates in ConfigMap "kubeadm-certs" in the "kube-system" Namespace
		[upload-certs] Using certificate key:
		9555b74008f24687eb964bd90a164ecb5760a89481d9c55a77c129b7db438168
	*/
	key := kubernetesKeyRegexp.FindString(string(output))
	if key == "" {
		return "", fmt.Errorf("failed to parse kubeadm output: %s", string(output))
	}
	return key, nil
}

// CreateJoinToken creates a new bootstrap (join) token.
func (k *KubernetesUtil) CreateJoinToken(ctx context.Context, ttl time.Duration) (*kubeadm.BootstrapTokenDiscovery, error) {
	output, err := exec.CommandContext(ctx, kubeadmPath, "token", "create", "--ttl", ttl.String(), "--print-join-command").Output()
	if err != nil {
		return nil, fmt.Errorf("kubeadm token create failed: %w", err)
	}
	// `kubeadm token create [...] --print-join-command` outputs the following format:
	// kubeadm join [API_SERVER_ENDPOINT] --token [TOKEN] --discovery-token-ca-cert-hash [DISCOVERY_TOKEN_CA_CERT_HASH]
	return ParseJoinCommand(string(output))
}