package proxmox

import (
	"bytes"
	"context"
	"crypto/sha256"
	"crypto/subtle"
	"crypto/tls"
	"crypto/x509"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"

	"forgejo.digital-droplets.de/philschlo/proxui/platform/cluster"
)

const defaultTimeout = 15 * time.Second

type Client struct {
	baseURL     *url.URL
	tokenID     string
	tokenSecret string
	httpClient  *http.Client
	retries     int
}

type Option func(*clientConfig)

type clientConfig struct {
	timeout time.Duration
	retries int
	rootCAs *x509.CertPool
}

func WithTimeout(timeout time.Duration) Option {
	return func(cfg *clientConfig) {
		cfg.timeout = timeout
	}
}

func WithRetries(retries int) Option {
	return func(cfg *clientConfig) {
		cfg.retries = retries
	}
}

func WithRootCAs(rootCAs *x509.CertPool) Option {
	return func(cfg *clientConfig) {
		cfg.rootCAs = rootCAs
	}
}

func NewClient(cluster cluster.Cluster, opts ...Option) (*Client, error) {
	baseURL, err := url.Parse(strings.TrimRight(cluster.APIEndpoint, "/"))
	if err != nil {
		return nil, fmt.Errorf("parse proxmox api endpoint: %w", err)
	}
	if baseURL.Scheme != "https" || baseURL.Host == "" {
		return nil, fmt.Errorf("proxmox api endpoint must be an https url")
	}
	if strings.TrimSpace(cluster.TokenID) == "" {
		return nil, fmt.Errorf("proxmox token id is required")
	}
	if strings.TrimSpace(cluster.TokenSecret) == "" {
		return nil, fmt.Errorf("proxmox token secret is required")
	}

	fingerprint, err := normalizeFingerprint(cluster.TLSFingerprint)
	if err != nil {
		return nil, err
	}

	cfg := clientConfig{
		timeout: defaultTimeout,
		retries: 2,
	}
	for _, opt := range opts {
		opt(&cfg)
	}
	if cfg.timeout <= 0 {
		return nil, fmt.Errorf("timeout must be greater than 0")
	}
	if cfg.retries < 0 {
		return nil, fmt.Errorf("retries must not be negative")
	}

	return &Client{
		baseURL:     baseURL,
		tokenID:     cluster.TokenID,
		tokenSecret: cluster.TokenSecret,
		httpClient: &http.Client{
			Timeout: cfg.timeout,
			Transport: &http.Transport{
				Proxy: http.ProxyFromEnvironment,
				TLSClientConfig: &tls.Config{
					MinVersion: tls.VersionTLS12,
					RootCAs:    cfg.rootCAs,
					VerifyConnection: func(state tls.ConnectionState) error {
						return verifyFingerprint(state, fingerprint)
					},
				},
			},
		},
		retries: cfg.retries,
	}, nil
}

func (c *Client) Get(ctx context.Context, path string) (*http.Response, error) {
	return c.Do(ctx, http.MethodGet, path, nil)
}

func (c *Client) Post(ctx context.Context, path string, body []byte) (*http.Response, error) {
	return c.Do(ctx, http.MethodPost, path, body)
}

func (c *Client) Put(ctx context.Context, path string, body []byte) (*http.Response, error) {
	return c.Do(ctx, http.MethodPut, path, body)
}

func (c *Client) Delete(ctx context.Context, path string) (*http.Response, error) {
	return c.Do(ctx, http.MethodDelete, path, nil)
}

type TaskStatus struct {
	Status     string
	ExitStatus string
}

type VMStatus struct {
	Status string
}

func (c *Client) GetTaskStatus(ctx context.Context, node string, upid string) (TaskStatus, error) {
	response, err := c.Get(ctx, fmt.Sprintf(
		"/nodes/%s/tasks/%s/status",
		url.PathEscape(node),
		url.PathEscape(upid),
	))
	if err != nil {
		return TaskStatus{}, err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return TaskStatus{}, fmt.Errorf("proxmox returned %s", response.Status)
	}

	var body struct {
		Data struct {
			Status     string `json:"status"`
			ExitStatus string `json:"exitstatus"`
		} `json:"data"`
	}
	if err := json.NewDecoder(response.Body).Decode(&body); err != nil {
		return TaskStatus{}, err
	}

	return TaskStatus{
		Status:     body.Data.Status,
		ExitStatus: body.Data.ExitStatus,
	}, nil
}

func (c *Client) PowerVM(ctx context.Context, node string, vmid int, action string) (string, error) {
	response, err := c.Post(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d/status/%s",
		url.PathEscape(node),
		vmid,
		url.PathEscape(action),
	), nil)
	if err != nil {
		return "", err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return "", fmt.Errorf("proxmox returned %s", response.Status)
	}

	var body struct {
		Data string `json:"data"`
	}
	if err := json.NewDecoder(response.Body).Decode(&body); err != nil {
		return "", err
	}
	if body.Data == "" {
		return "", fmt.Errorf("proxmox response missing UPID")
	}

	return body.Data, nil
}

func (c *Client) GetVMStatus(ctx context.Context, node string, vmid int) (VMStatus, error) {
	response, err := c.Get(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d/status/current",
		url.PathEscape(node),
		vmid,
	))
	if err != nil {
		return VMStatus{}, err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return VMStatus{}, fmt.Errorf("proxmox returned %s", response.Status)
	}

	var body struct {
		Data struct {
			Status string `json:"status"`
		} `json:"data"`
	}
	if err := json.NewDecoder(response.Body).Decode(&body); err != nil {
		return VMStatus{}, err
	}
	if body.Data.Status == "" {
		return VMStatus{}, fmt.Errorf("proxmox response missing VM status")
	}

	return VMStatus{Status: body.Data.Status}, nil
}

func (c *Client) CloneVM(ctx context.Context, node string, templateVMID int, newVMID int, name string) (string, error) {
	requestBody := map[string]any{
		"newid": newVMID,
		"name":  name,
	}
	body, err := json.Marshal(requestBody)
	if err != nil {
		return "", err
	}

	response, err := c.Post(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d/clone",
		url.PathEscape(node),
		templateVMID,
	), body)
	if err != nil {
		return "", err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return "", fmt.Errorf("proxmox returned %s", response.Status)
	}

	return decodeUPID(response.Body)
}

func (c *Client) ConfigureCloudInit(ctx context.Context, node string, vmid int, cfg CloudInitConfig) (string, error) {
	requestBody := map[string]any{
		"ciuser": cfg.CIUser,
	}
	if cfg.SSHKeys != "" {
		requestBody["sshkeys"] = cfg.SSHKeys
	}
	if cfg.IPConfig0 != "" {
		requestBody["ipconfig0"] = cfg.IPConfig0
	}
	if cfg.Hostname != "" {
		requestBody["searchdomain"] = cfg.Hostname
	}

	body, err := json.Marshal(requestBody)
	if err != nil {
		return "", err
	}

	response, err := c.Post(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d/config",
		url.PathEscape(node),
		vmid,
	), body)
	if err != nil {
		return "", err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return "", fmt.Errorf("proxmox returned %s", response.Status)
	}

	return decodeUPID(response.Body)
}

func (c *Client) StartVM(ctx context.Context, node string, vmid int) (string, error) {
	return c.PowerVM(ctx, node, vmid, "start")
}

func (c *Client) StopVM(ctx context.Context, node string, vmid int) (string, error) {
	return c.PowerVM(ctx, node, vmid, "stop")
}

func (c *Client) DeleteVM(ctx context.Context, node string, vmid int) (string, error) {
	response, err := c.Delete(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d",
		url.PathEscape(node),
		vmid,
	))
	if err != nil {
		return "", err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return "", fmt.Errorf("proxmox returned %s", response.Status)
	}

	return decodeUPID(response.Body)
}

type CloudInitConfig struct {
	CIUser    string `json:"ciuser"`
	SSHKeys   string `json:"sshkeys,omitempty"`
	IPConfig0 string `json:"ipconfig0,omitempty"`
	Hostname  string `json:"hostname,omitempty"`
}

func decodeUPID(body io.Reader) (string, error) {
	var response struct {
		Data string `json:"data"`
	}
	if err := json.NewDecoder(body).Decode(&response); err != nil {
		return "", err
	}
	if response.Data == "" {
		return "", fmt.Errorf("proxmox response missing UPID")
	}
	return response.Data, nil
}

func (c *Client) GetVNCTicket(ctx context.Context, node string, vmid int) (VNCInfo, error) {
	requestBody := map[string]any{}
	body, err := json.Marshal(requestBody)
	if err != nil {
		return VNCInfo{}, err
	}

	response, err := c.Post(ctx, fmt.Sprintf(
		"/nodes/%s/qemu/%d/vncproxy",
		url.PathEscape(node),
		vmid,
	), body)
	if err != nil {
		return VNCInfo{}, err
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		_, _ = io.Copy(io.Discard, response.Body)
		return VNCInfo{}, fmt.Errorf("proxmox returned %s", response.Status)
	}

	var result struct {
		Data struct {
			Port     int    `json:"port"`
			Ticket   string `json:"ticket"`
			User     string `json:"user"`
			Cert     string `json:"cert"`
			UPID     string `json:"upid"`
		} `json:"data"`
	}
	if err := json.NewDecoder(response.Body).Decode(&result); err != nil {
		return VNCInfo{}, err
	}

	return VNCInfo{
		Port:   result.Data.Port,
		Ticket: result.Data.Ticket,
		User:   result.Data.User,
		Cert:   result.Data.Cert,
		UPID:   result.Data.UPID,
	}, nil
}

type VNCInfo struct {
	Port   int
	Ticket string
	User   string
	Cert   string
	UPID   string
}

func (c *Client) Do(ctx context.Context, method string, path string, body []byte) (*http.Response, error) {
	var lastErr error
	attempts := c.retries + 1
	for attempt := 0; attempt < attempts; attempt++ {
		response, err := c.doOnce(ctx, method, path, body)
		if err == nil && response.StatusCode < http.StatusInternalServerError {
			return response, nil
		}
		if err == nil {
			_, _ = io.Copy(io.Discard, response.Body)
			_ = response.Body.Close()
			lastErr = fmt.Errorf("proxmox returned %s", response.Status)
		} else {
			lastErr = err
		}

		if ctx.Err() != nil {
			return nil, ctx.Err()
		}
	}

	return nil, lastErr
}

func (c *Client) doOnce(ctx context.Context, method string, path string, body []byte) (*http.Response, error) {
	requestURL := c.resolvePath(path)
	request, err := http.NewRequestWithContext(ctx, method, requestURL, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	request.Header.Set("Authorization", fmt.Sprintf("PVEAPIToken=%s=%s", c.tokenID, c.tokenSecret))
	if body != nil {
		request.Header.Set("Content-Type", "application/json")
	}

	return c.httpClient.Do(request)
}

func (c *Client) resolvePath(path string) string {
	resolved := *c.baseURL
	resolved.Path = joinURLPath(c.baseURL.Path, path)
	return resolved.String()
}

func joinURLPath(basePath string, path string) string {
	basePath = strings.TrimRight(basePath, "/")
	path = strings.TrimLeft(path, "/")
	if path == "" {
		return basePath
	}
	return basePath + "/" + path
}

func normalizeFingerprint(fingerprint string) (string, error) {
	normalized := strings.NewReplacer(":", "", " ", "", "-", "").Replace(strings.TrimSpace(fingerprint))
	normalized = strings.ToLower(normalized)
	if len(normalized) != sha256.Size*2 {
		return "", fmt.Errorf("tls fingerprint must be a sha256 hex digest")
	}
	if _, err := hex.DecodeString(normalized); err != nil {
		return "", fmt.Errorf("tls fingerprint must be hex encoded: %w", err)
	}
	return normalized, nil
}

func verifyFingerprint(state tls.ConnectionState, expected string) error {
	if len(state.PeerCertificates) == 0 {
		return fmt.Errorf("server certificate missing")
	}

	sum := sha256.Sum256(state.PeerCertificates[0].Raw)
	actual := hex.EncodeToString(sum[:])
	if subtle.ConstantTimeCompare([]byte(actual), []byte(expected)) != 1 {
		return fmt.Errorf("server certificate fingerprint mismatch")
	}
	return nil
}