package handler

import (
	"fmt"
	"net/http"
	"strings"

	"github.com/labstack/echo/v4"
	"github.com/labstack/gommon/log"
	"github.com/ngoduykhanh/wireguard-ui/model"
	"github.com/ngoduykhanh/wireguard-ui/store"
	"github.com/ngoduykhanh/wireguard-ui/util"
	"github.com/rs/xid"
)

// MyAccessClientView is the display-friendly shape returned to the
// "My Access" self-service portal page - it deliberately omits any secret
// key material (private key, preshared key) since non-admins must never
// see those in the frontend.
type MyAccessClientView struct {
	ID           string   `json:"id"`
	Name         string   `json:"name"`
	Email        string   `json:"email"`
	ServerID     string   `json:"server_id"`
	ServerName   string   `json:"server_name"`
	Interface    string   `json:"interface"`
	AllocatedIPs []string `json:"allocated_ips"`
	Enabled      bool     `json:"enabled"`
}

// visibleClientsForUser computes the set of clients a given (possibly
// non-admin) user is allowed to see on the self-service "My Access" portal:
//
//	(clients whose ServerID is in user.ServerIDs) UNION (clients whose own
//	ID is in user.ClientIDs)
//
// Admins bypass the filter entirely and see every client.
func visibleClientsForUser(db store.IStore, user model.User, admin bool) ([]model.ClientData, error) {
	allClients, err := db.GetClients(false)
	if err != nil {
		return nil, err
	}

	if admin {
		return allClients, nil
	}

	allowedServers := make(map[string]bool, len(user.ServerIDs))
	for _, id := range user.ServerIDs {
		allowedServers[id] = true
	}
	allowedClients := make(map[string]bool, len(user.ClientIDs))
	for _, id := range user.ClientIDs {
		allowedClients[id] = true
	}

	var visible []model.ClientData
	for _, cd := range allClients {
		if allowedServers[cd.Client.ServerID] || allowedClients[cd.Client.ID] {
			visible = append(visible, cd)
		}
	}
	return visible, nil
}

// clientAuthorizedForUser reports whether the given user (admin or not) may
// access the single client identified by clientData, per the same union
// rule used by visibleClientsForUser.
func clientAuthorizedForUser(user model.User, admin bool, clientData model.ClientData) bool {
	if admin {
		return true
	}
	for _, id := range user.ServerIDs {
		if id == clientData.Client.ServerID {
			return true
		}
	}
	for _, id := range user.ClientIDs {
		if id == clientData.Client.ID {
			return true
		}
	}
	return false
}

// buildMyAccessViews resolves the server name/interface for each visible
// client and shapes them for display, skipping any client whose server
// cannot be resolved anymore (orphaned record).
func buildMyAccessViews(db store.IStore, clientDataList []model.ClientData) []MyAccessClientView {
	serverCache := make(map[string]model.Server)
	views := make([]MyAccessClientView, 0, len(clientDataList))

	for _, cd := range clientDataList {
		serverID := cd.Client.ServerID
		if serverID == "" {
			serverID = util.DefaultServerID
		}

		server, ok := serverCache[serverID]
		if !ok {
			s, err := db.GetServerByID(serverID)
			if err != nil {
				continue
			}
			server = s
			serverCache[serverID] = server
		}

		interfaceName := ""
		if server.Interface != nil {
			interfaceName = server.Interface.Name
		}

		views = append(views, MyAccessClientView{
			ID:           cd.Client.ID,
			Name:         cd.Client.Name,
			Email:        cd.Client.Email,
			ServerID:     serverID,
			ServerName:   server.Name,
			Interface:    interfaceName,
			AllocatedIPs: cd.Client.AllocatedIPs,
			Enabled:      cd.Client.Enabled,
		})
	}

	return views
}

// MyAccessPage renders the read-only, per-user self-service portal: a
// non-admin sees only their own assigned clients (via ServerIDs/ClientIDs),
// an admin sees every client. View + QR code + download only - no
// add/edit/delete controls live on this page.
func MyAccessPage(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		admin := isAdmin(c)

		user, err := db.GetUserByName(currentUser(c))
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot load current user"})
		}

		clientDataList, err := visibleClientsForUser(db, user, admin)
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{
				false, fmt.Sprintf("Cannot get client list: %v", err),
			})
		}

		views := buildMyAccessViews(db, clientDataList)

		return c.Render(http.StatusOK, "my_access.html", map[string]interface{}{
			"baseData": model.BaseData{Active: "my-access", CurrentUser: currentUser(c), Admin: admin},
			"clients":  views,
		})
	}
}

// GetMyAccessClients returns the same filtered listing as JSON, for the
// page's client-side refresh (e.g. after a status change elsewhere).
func GetMyAccessClients(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		admin := isAdmin(c)

		user, err := db.GetUserByName(currentUser(c))
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot load current user"})
		}

		clientDataList, err := visibleClientsForUser(db, user, admin)
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{
				false, fmt.Sprintf("Cannot get client list: %v", err),
			})
		}

		return c.JSON(http.StatusOK, buildMyAccessViews(db, clientDataList))
	}
}

// GetMyAccessClientQRCode returns the QR code (as a data-URI, same shape
// produced elsewhere in the app) for a single client, provided the
// requesting user is authorized to see it per the ServerIDs/ClientIDs union
// rule - independent of whether the route-level RequireServerAccess
// middleware would have allowed it, since a ClientIDs-only grant may cover a
// client on a server the user otherwise has no access to at all.
func GetMyAccessClientQRCode(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		clientID := c.Param("cid")
		if _, err := xid.FromString(clientID); err != nil {
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
		}

		admin := isAdmin(c)
		user, err := db.GetUserByName(currentUser(c))
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot load current user"})
		}

		qrCodeSettings := model.QRCodeSettings{
			Enabled:    true,
			IncludeDNS: true,
			IncludeMTU: true,
		}

		clientData, err := db.GetClientByID(clientID, qrCodeSettings)
		if err != nil {
			return c.JSON(http.StatusNotFound, jsonHTTPResponse{false, "Client not found"})
		}

		if !clientAuthorizedForUser(user, admin, clientData) {
			return c.JSON(http.StatusForbidden, jsonHTTPResponse{false, "Access denied"})
		}

		return c.JSON(http.StatusOK, util.FillClientSubnetRange(clientData))
	}
}

// GetMyAccessClientDownload streams the client's WireGuard config file,
// same content as the existing DownloadClient handler, but authorized via
// the ServerIDs/ClientIDs union rule instead of a server-scoped route
// parameter.
func GetMyAccessClientDownload(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		clientID := c.Param("cid")
		if _, err := xid.FromString(clientID); err != nil {
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
		}

		admin := isAdmin(c)
		user, err := db.GetUserByName(currentUser(c))
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot load current user"})
		}

		clientData, err := db.GetClientByID(clientID, model.QRCodeSettings{Enabled: false})
		if err != nil {
			log.Errorf("Cannot generate client id %s config file for downloading: %v", clientID, err)
			return c.JSON(http.StatusNotFound, jsonHTTPResponse{false, "Client not found"})
		}

		if !clientAuthorizedForUser(user, admin, clientData) {
			return c.JSON(http.StatusForbidden, jsonHTTPResponse{false, "Access denied"})
		}

		clientServerID := clientData.Client.ServerID
		if clientServerID == "" {
			clientServerID = util.DefaultServerID
		}
		server, err := db.GetServerByID(clientServerID)
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, err.Error()})
		}
		globalSettings, err := buildEffectiveSettings(db, clientServerID)
		if err != nil {
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, err.Error()})
		}
		config := util.BuildClientConfig(*clientData.Client, server, globalSettings)

		reader := strings.NewReader(config)
		c.Response().Header().Set(echo.HeaderContentDisposition, fmt.Sprintf("attachment; filename=%s.conf", clientData.Client.Name))
		return c.Stream(http.StatusOK, "text/conf", reader)
	}
}