package k8sclient

import (
	"crypto/tls"
	"crypto/x509"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

// KubeConfig represents a parsed kubeconfig
type KubeConfig struct {
	APIVersion string `yaml:"apiVersion"`
	Clusters   []struct {
		Name    string `yaml:"name"`
		Cluster struct {
			Server                   string `yaml:"server"`
			CertificateAuthorityData string `yaml:"certificate-authority-data"`
			InsecureSkipTLSVerify    bool   `yaml:"insecure-skip-tls-verify"`
		} `yaml:"cluster"`
	} `yaml:"clusters"`
	Users []struct {
		Name string `yaml:"name"`
		User struct {
			ClientCertificateData string `yaml:"client-certificate-data"`
			ClientKeyData         string `yaml:"client-key-data"`
			Token                 string `yaml:"token"`
		} `yaml:"user"`
	} `yaml:"users"`
	Contexts []struct {
		Name    string `yaml:"name"`
		Context struct {
			Cluster string `yaml:"cluster"`
			User    string `yaml:"user"`
		} `yaml:"context"`
	} `yaml:"contexts"`
	CurrentContext string `yaml:"current-context"`
}

// Client wraps an HTTP client for K8s API calls
type Client struct {
	BaseURL    string
	HTTPClient *http.Client
}

// NewClient creates a K8s API client from kubeconfig YAML
func NewClient(kubeconfigYAML string) (*Client, error) {
	var kcfg KubeConfig
	if err := yaml.Unmarshal([]byte(kubeconfigYAML), &kcfg); err != nil {
		return nil, fmt.Errorf("parse kubeconfig: %w", err)
	}

	// Find current context
	ctxName := kcfg.CurrentContext
	var clusterName, userName string
	for _, ctx := range kcfg.Contexts {
		if ctx.Name == ctxName {
			clusterName = ctx.Context.Cluster
			userName = ctx.Context.User
			break
		}
	}
	if clusterName == "" {
		return nil, fmt.Errorf("current context %q not found", ctxName)
	}

	// Find cluster
	var server string
	var caData string
	for _, cl := range kcfg.Clusters {
		if cl.Name == clusterName {
			server = cl.Cluster.Server
			caData = cl.Cluster.CertificateAuthorityData
			break
		}
	}
	if server == "" {
		return nil, fmt.Errorf("cluster %q not found", clusterName)
	}

	// Build TLS config
	tlsCfg := &tls.Config{}
	if caData != "" {
		caBytes, err := base64.StdEncoding.DecodeString(caData)
		if err != nil {
			return nil, fmt.Errorf("decode CA cert: %w", err)
		}
		caPool := x509.NewCertPool()
		caPool.AppendCertsFromPEM(caBytes)
		tlsCfg.RootCAs = caPool
	} else {
		tlsCfg.InsecureSkipVerify = true
	}

	// Find user certs
	for _, u := range kcfg.Users {
		if u.Name == userName {
			if u.User.ClientCertificateData != "" && u.User.ClientKeyData != "" {
				certBytes, _ := base64.StdEncoding.DecodeString(u.User.ClientCertificateData)
				keyBytes, _ := base64.StdEncoding.DecodeString(u.User.ClientKeyData)
				cert, err := tls.X509KeyPair(certBytes, keyBytes)
				if err != nil {
					return nil, fmt.Errorf("parse client cert: %w", err)
				}
				tlsCfg.Certificates = []tls.Certificate{cert}
			}
			break
		}
	}

	httpClient := &http.Client{
		Timeout: 30 * time.Second,
		Transport: &http.Transport{
			TLSClientConfig: tlsCfg,
		},
	}

	return &Client{
		BaseURL:    strings.TrimRight(server, "/"),
		HTTPClient: httpClient,
	}, nil
}

// get performs a GET request to the K8s API
func (c *Client) get(path string, result interface{}) error {
	url := c.BaseURL + path
	resp, err := c.HTTPClient.Get(url)
	if err != nil {
		return fmt.Errorf("GET %s: %w", path, err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("read body: %w", err)
	}

	if resp.StatusCode >= 400 {
		return fmt.Errorf("K8s API error %d: %s", resp.StatusCode, string(body[:min(len(body), 200)]))
	}

	if err := json.Unmarshal(body, result); err != nil {
		return fmt.Errorf("unmarshal: %w (body: %s)", err, string(body[:min(len(body), 100)]))
	}
	return nil
}

// --- K8s API response types ---

// NodeList response
type NodeList struct {
	Items []NodeItem `json:"items"`
}

type NodeItem struct {
	Metadata ObjectMeta      `json:"metadata"`
	Status   NodeStatus      `json:"status"`
	Spec     NodeSpec        `json:"spec"`
}

type NodeSpec struct {
	PodCIDR string `json:"podCIDR"`
}

type NodeStatus struct {
	Capacity    ResourceList   `json:"capacity"`
	Allocatable ResourceList   `json:"allocatable"`
	Conditions  []NodeCondition `json:"conditions"`
	NodeInfo    NodeInfo       `json:"nodeInfo"`
	Addresses   []NodeAddress  `json:"addresses"`
}

type ResourceList map[string]string

type NodeCondition struct {
	Type   string `json:"type"`
	Status string `json:"status"`
}

type NodeInfo struct {
	KubeletVersion    string `json:"kubeletVersion"`
	OSImage           string `json:"osImage"`
	KernelVersion     string `json:"kernelVersion"`
	ContainerRuntimeVersion string `json:"containerRuntimeVersion"`
}

type NodeAddress struct {
	Type    string `json:"type"`
	Address string `json:"address"`
}

// PodList response
type PodList struct {
	Items []PodItem `json:"items"`
}

type PodItem struct {
	Metadata ObjectMeta `json:"metadata"`
	Status   PodStatus  `json:"status"`
	Spec     PodSpec    `json:"spec"`
}

type PodSpec struct {
	NodeName  string      `json:"nodeName"`
	Containers []Container `json:"containers"`
}

type Container struct {
	Image string `json:"image"`
}

type PodStatus struct {
	Phase        string              `json:"phase"`
	PodIP        string              `json:"podIP"`
	ContainerStatuses []ContainerStatus `json:"containerStatuses"`
}

type ContainerStatus struct {
	RestartCount int  `json:"restartCount"`
	Ready        bool `json:"ready"`
}

// DeploymentList response
type DeploymentList struct {
	Items []DeploymentItem `json:"items"`
}

type DeploymentItem struct {
	Metadata ObjectMeta       `json:"metadata"`
	Spec     DeploymentSpec   `json:"spec"`
	Status   DeploymentStatus `json:"status"`
}

type DeploymentSpec struct {
	Replicas int                `json:"replicas"`
	Template DeploymentTemplate `json:"template"`
}

type DeploymentTemplate struct {
	Spec PodSpec `json:"spec"`
}

type DeploymentStatus struct {
	Replicas          int `json:"replicas"`
	AvailableReplicas int `json:"availableReplicas"`
	ReadyReplicas     int `json:"readyReplicas"`
}

// ServiceList response
type ServiceList struct {
	Items []ServiceItem `json:"items"`
}

type ServiceItem struct {
	Metadata ObjectMeta    `json:"metadata"`
	Spec     ServiceSpec   `json:"spec"`
}

type ServiceSpec struct {
	Type      string            `json:"type"`
	ClusterIP string            `json:"clusterIP"`
	Ports     []ServicePort     `json:"ports"`
	Selector  map[string]string `json:"selector"`
}

type ServicePort struct {
	Name       string `json:"name"`
	Port       int    `json:"port"`
	TargetPort interface{} `json:"targetPort"`
	NodePort   int    `json:"nodePort"`
	Protocol   string `json:"protocol"`
}

// IngressList response
type IngressList struct {
	Items []IngressItem `json:"items"`
}

type IngressItem struct {
	Metadata ObjectMeta    `json:"metadata"`
	Spec     IngressSpec   `json:"spec"`
}

type IngressSpec struct {
	TLS   []IngressTLS   `json:"tls"`
	Rules []IngressRule  `json:"rules"`
}

type IngressTLS struct {
	Hosts []string `json:"hosts"`
}

type IngressRule struct {
	Host string `json:"host"`
}

// ObjectMeta
type ObjectMeta struct {
	Name        string            `json:"name"`
	Namespace   string            `json:"namespace"`
	Labels      map[string]string `json:"labels"`
	Annotations map[string]string `json:"annotations"`
	CreationTimestamp string      `json:"creationTimestamp"`
}

// SyncResult holds sync counts
type SyncResult struct {
	Nodes       int `json:"nodes"`
	Pods        int `json:"pods"`
	Deployments int `json:"deployments"`
	Services    int `json:"services"`
	Ingresses   int `json:"ingresses"`
}

// GetServerVersion returns K8s server version
func (c *Client) GetServerVersion() (string, error) {
	var result struct {
		GitVersion string `json:"gitVersion"`
	}
	if err := c.get("/version", &result); err != nil {
		return "", err
	}
	return result.GitVersion, nil
}

// ListNodes fetches all nodes
func (c *Client) ListNodes() (*NodeList, error) {
	var result NodeList
	if err := c.get("/api/v1/nodes", &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ListPods fetches all pods across namespaces
func (c *Client) ListPods() (*PodList, error) {
	var result PodList
	if err := c.get("/api/v1/pods", &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ListDeployments fetches all deployments across namespaces
func (c *Client) ListDeployments() (*DeploymentList, error) {
	var result DeploymentList
	if err := c.get("/apis/apps/v1/deployments", &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ListServices fetches all services across namespaces
func (c *Client) ListServices() (*ServiceList, error) {
	var result ServiceList
	if err := c.get("/api/v1/services", &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ListIngresses fetches all ingresses across namespaces
func (c *Client) ListIngresses() (*IngressList, error) {
	var result IngressList
	if err := c.get("/apis/networking.k8s.io/v1/ingresses", &result); err != nil {
		return nil, err
	}
	return &result, nil
}