package console

import (
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"time"

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

	"proxui/backend/internal/auth"
	"proxui/backend/internal/rbac"
)

type ClusterRepository interface {
	GetCluster(ctx context.Context, id string) (cluster.Cluster, bool, error)
}

type VMRepository interface {
	GetVM(ctx context.Context, profileID string, vmID string) (VMInfo, bool, error)
}

type VMInfo struct {
	ID             string
	TenantID       string
	ClusterID      string
	ProxmoxVMID    int
	Node           string
	MembershipRole string
}

type ProxyClientFactory func(cluster.Cluster) (ProxyClient, error)

type ProxyClient interface {
	GetVNCTicket(ctx context.Context, node string, vmid int) (proxmox.VNCInfo, error)
}

type Handler struct {
	clusters     ClusterRepository
	vmRepo       VMRepository
	clientFactory ProxyClientFactory
	signingKey   []byte
}

func NewHandler(clusters ClusterRepository, vmRepo VMRepository, clientFactory ProxyClientFactory, signingKey string) Handler {
	return Handler{
		clusters:      clusters,
		vmRepo:        vmRepo,
		clientFactory: clientFactory,
		signingKey:    []byte(signingKey),
	}
}

func (h Handler) CreateConsoleTicket(w http.ResponseWriter, r *http.Request) {
	principal, ok := auth.PrincipalFromRequest(r)
	if !ok {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}

	vmID := r.PathValue("vmID")
	if vmID == "" {
		writeError(w, http.StatusBadRequest, "vm_id_required")
		return
	}

	vm, found, err := h.vmRepo.GetVM(r.Context(), principal.Subject, vmID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "vm_get_failed")
		return
	}
	if !found {
		writeError(w, http.StatusNotFound, "vm_not_found")
		return
	}

	if !rbac.Can(rbac.Role(vm.MembershipRole), rbac.ActionVMConsole) {
		writeError(w, http.StatusForbidden, "forbidden")
		return
	}

	cluster, found, err := h.clusters.GetCluster(r.Context(), vm.ClusterID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "cluster_get_failed")
		return
	}
	if !found {
		writeError(w, http.StatusBadGateway, "cluster_not_found")
		return
	}

	client, err := h.clientFactory(cluster)
	if err != nil {
		writeError(w, http.StatusBadGateway, "proxmox_client_failed")
		return
	}

	vncInfo, err := client.GetVNCTicket(r.Context(), vm.Node, vm.ProxmoxVMID)
	if err != nil {
		writeError(w, http.StatusBadGateway, "proxmox_vnc_ticket_failed")
		return
	}

	proxyTicket, err := h.signProxyTicket(proxyTicketPayload{
		ClusterID:  vm.ClusterID,
		Node:       vm.Node,
		VMID:       vm.ProxmoxVMID,
		TenantID:   vm.TenantID,
		Endpoint:   cluster.APIEndpoint,
		VNC:        vncTicket{VNCInfo: vncInfo},
		ExpiresAt:  time.Now().Add(15 * time.Minute),
	})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "ticket_sign_failed")
		return
	}

	writeJSON(w, http.StatusOK, consoleResponse{
		Ticket: proxyTicket,
	})
}

type vncTicket struct {
	proxmox.VNCInfo
}

type proxyTicketPayload struct {
	ClusterID string    `json:"cluster_id"`
	Node      string    `json:"node"`
	VMID      int       `json:"vmid"`
	TenantID  string    `json:"tenant_id"`
	Endpoint  string    `json:"endpoint"`
	VNC       vncTicket `json:"vnc"`
	ExpiresAt time.Time `json:"expires_at"`
	Signature string    `json:"signature"`
}

func (h Handler) signProxyTicket(payload proxyTicketPayload) (string, error) {
	payload.Signature = ""
	data, err := json.Marshal(payload)
	if err != nil {
		return "", err
	}

	mac := hmac.New(sha256.New, h.signingKey)
	mac.Write(data)
	payload.Signature = base64.RawURLEncoding.EncodeToString(mac.Sum(nil))

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

	return base64.RawURLEncoding.EncodeToString(result), nil
}

func VerifyProxyTicket(ticket string, signingKey []byte) (proxyTicketPayload, error) {
	data, err := base64.RawURLEncoding.DecodeString(ticket)
	if err != nil {
		return proxyTicketPayload{}, fmt.Errorf("invalid ticket encoding")
	}

	var payload proxyTicketPayload
	if err := json.Unmarshal(data, &payload); err != nil {
		return proxyTicketPayload{}, fmt.Errorf("invalid ticket payload")
	}

	if time.Now().After(payload.ExpiresAt) {
		return proxyTicketPayload{}, fmt.Errorf("ticket expired")
	}

	receivedSig := payload.Signature
	payload.Signature = ""
	dataToVerify, _ := json.Marshal(payload)

	mac := hmac.New(sha256.New, signingKey)
	mac.Write(dataToVerify)
	expectedSig := base64.RawURLEncoding.EncodeToString(mac.Sum(nil))

	if !hmac.Equal([]byte(receivedSig), []byte(expectedSig)) {
		return proxyTicketPayload{}, fmt.Errorf("invalid ticket signature")
	}

	payload.Signature = receivedSig
	return payload, nil
}

type consoleResponse struct {
	Ticket string `json:"ticket"`
}

func DefaultProxyClientFactory(cluster cluster.Cluster) (ProxyClient, error) {
	return proxmox.NewClient(cluster)
}

func writeJSON(w http.ResponseWriter, status int, body any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(body)
}

func writeError(w http.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]string{"error": message})
}