package handler

import (
	"fmt"
	"net/http"

	"github.com/labstack/echo/v4"
	"github.com/labstack/gommon/log"
	"github.com/rs/xid"

	"github.com/ngoduykhanh/wireguard-ui/opnsense"
	"github.com/ngoduykhanh/wireguard-ui/store"
)

// maxOPNsenseUploadSize caps the accepted config.xml upload size.
const maxOPNsenseUploadSize = 5 << 20 // 5 MiB

// PreviewOPNsenseImport handler accepts an uploaded OPNsense config.xml,
// parses and maps its WireGuard server/client definitions, and returns the
// staged (admin-editable) preview as JSON. It never touches the store -
// nothing is written, nothing is applied. Admin-only.
func PreviewOPNsenseImport(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		fileHeader, err := c.FormFile("config")
		if err != nil {
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please upload a config.xml file"})
		}
		if fileHeader.Size > maxOPNsenseUploadSize {
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "config.xml is too large (max 5 MiB)"})
		}

		src, err := fileHeader.Open()
		if err != nil {
			log.Error("Cannot open uploaded OPNsense config.xml: ", err)
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Cannot read uploaded file"})
		}
		defer src.Close()

		parsed, err := opnsense.Parse(src)
		if err != nil {
			log.Error("Cannot parse OPNsense config.xml: ", err)
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, fmt.Sprintf("Cannot parse config.xml: %v", err)})
		}

		existingServers, err := db.GetServers()
		if err != nil {
			log.Error("Cannot list existing servers: ", err)
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot list existing servers"})
		}
		existingIDs := make([]string, 0, len(existingServers))
		for _, s := range existingServers {
			existingIDs = append(existingIDs, s.ID)
		}

		preview := opnsense.ToPreview(parsed, existingIDs)
		return c.JSON(http.StatusOK, preview)
	}
}

// CommitOPNsenseImport handler accepts the (possibly admin-edited) preview
// JSON produced by PreviewOPNsenseImport - not the original XML - and
// writes the corresponding model.Server/ServerSetting/Client records via
// the store. Servers/clients that fail validation, or clients whose public
// key collides with one already in the store, are skipped and reported;
// the rest of the batch still commits. This never applies the resulting
// WireGuard config (no wg-quick/systemctl calls) - that remains a separate,
// manual "Apply" step elsewhere in the app. Admin-only.
func CommitOPNsenseImport(db store.IStore) echo.HandlerFunc {
	return func(c echo.Context) error {
		var payload opnsense.PreviewResult
		if err := c.Bind(&payload); err != nil {
			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Bad post data"})
		}

		existingClients, err := db.GetClients(false)
		if err != nil {
			log.Error("Cannot list existing clients for duplicate check: ", err)
			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot list existing clients"})
		}
		knownPublicKeys := make(map[string]bool, len(existingClients))
		for _, cd := range existingClients {
			knownPublicKeys[cd.Client.PublicKey] = true
		}

		type serverResult struct {
			ID             string   `json:"id"`
			Imported       bool     `json:"imported"`
			Error          string   `json:"error,omitempty"`
			ClientsCreated int      `json:"clients_created"`
			ClientsSkipped []string `json:"clients_skipped,omitempty"`
		}
		results := make([]serverResult, 0, len(payload.Servers))

		for _, ps := range payload.Servers {
			res := serverResult{ID: ps.ID}

			server, settings, clients, err := opnsense.ToModel(ps)
			if err != nil {
				res.Error = err.Error()
				results = append(results, res)
				continue
			}

			if _, err := db.GetServerByID(server.ID); err == nil {
				res.Error = "a server with this ID already exists"
				results = append(results, res)
				continue
			}

			if err := db.CreateServer(server); err != nil {
				res.Error = fmt.Sprintf("cannot create server: %v", err)
				results = append(results, res)
				continue
			}
			if err := db.SaveServerSettings(server.ID, settings); err != nil {
				log.Errorf("Server %s created but settings failed: %v", server.ID, err)
			}

			for _, client := range clients {
				if knownPublicKeys[client.PublicKey] {
					res.ClientsSkipped = append(res.ClientsSkipped, fmt.Sprintf("%s (duplicate public key)", client.Name))
					continue
				}
				client.ID = xid.New().String()
				if err := db.SaveClient(client); err != nil {
					res.ClientsSkipped = append(res.ClientsSkipped, fmt.Sprintf("%s (%v)", client.Name, err))
					continue
				}
				knownPublicKeys[client.PublicKey] = true
				res.ClientsCreated++
			}

			res.Imported = true
			log.Infof("Imported server %s from OPNsense config (%d clients)", server.ID, res.ClientsCreated)
			results = append(results, res)
		}

		return c.JSON(http.StatusOK, results)
	}
}