package handlers

import (
	"context"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"

	"gitea.futuresens.co.uk/futuresens/cmstypes"
	"gitea.futuresens.co.uk/futuresens/hardlink/internal/mail"
	"gitea.futuresens.co.uk/futuresens/hardlink/internal/paymentsvc"
	"gitea.futuresens.co.uk/futuresens/hardlink/internal/printer"
	"gitea.futuresens.co.uk/futuresens/hardlink/internal/types"
	"gitea.futuresens.co.uk/futuresens/logging"
	"github.com/google/uuid"
	log "github.com/sirupsen/logrus"
)

type SalePaymentRequest struct {
	Reference string `json:"reference,omitempty"`
	ConfirmNo string `json:"confirmNo,omitempty"`
	Amount    int64  `json:"amount"`
	Currency  string `json:"currency,omitempty"`
}

type paymentStreamMessage struct {
	Type     string                `json:"type"`
	Code     string                `json:"code,omitempty"`
	Response *cmstypes.ResponseRec `json:"response,omitempty"`
}

func (app *App) salePayment(w http.ResponseWriter, r *http.Request) {
	const op = logging.Op("salePayment")

	response := cmstypes.ResponseRec{
		Status: cmstypes.StatusRec{
			Code:    http.StatusInternalServerError,
			Message: http.StatusText(http.StatusInternalServerError),
		},
	}

	setPaymentCORS(w)

	if r.Method == http.MethodOptions {
		w.WriteHeader(http.StatusNoContent)
		return
	}

	if r.Method != http.MethodPost {
		response.Data = buildPaymentFailureURL(types.ResultError, "Method not allowed; use POST")
		writeTransactionResult(w, http.StatusMethodNotAllowed, response)
		return
	}

	if app.paymentService == nil {
		mail.SendEmailOnError(
			app.cfg.Hotel,
			app.cfg.Kiosk,
			"Payment Service Not Configured",
			"Payment service is not configured; cannot process payment requests",
		)

		response.Data = buildPaymentFailureURL(types.ResultError, "Payment service is not configured")
		writeTransactionResult(w, http.StatusInternalServerError, response)
		return
	}

	if ct := r.Header.Get("Content-Type"); ct != "" && !strings.Contains(ct, "application/json") {
		response.Data = buildPaymentFailureURL(types.ResultError, "Content-Type must be application/json")
		writeTransactionResult(w, http.StatusUnsupportedMediaType, response)
		return
	}

	defer r.Body.Close()

	var req SalePaymentRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		logging.Error(
			types.ServiceName,
			err.Error(),
			"ReadJSON",
			string(op),
			"",
			app.cfg.Hotel,
			app.cfg.Kiosk,
		)

		response.Data = buildPaymentFailureURL(types.ResultError, "invalid JSON payload: "+err.Error())
		writeTransactionResult(w, http.StatusBadRequest, response)
		return
	}

	if req.Amount <= 0 {
		response.Data = buildPaymentFailureURL(types.ResultError, "Amount must be greater than zero")
		writeTransactionResult(w, http.StatusBadRequest, response)
		return
	}

	if req.Currency == "" {
		req.Currency = "GBP"
	}

	if req.Reference == "" {
		req.Reference = req.ConfirmNo
	}

	if req.Reference == "" {
		req.Reference = uuid.NewString()
	}

	requestID := buildPaymentRequestID(req.Reference)

	timeoutSeconds := app.cfg.TimeoutSeconds
	if timeoutSeconds <= 0 {
		timeoutSeconds = 300
	}

	ctx, cancel := context.WithTimeout(
		r.Context(),
		time.Duration(timeoutSeconds)*time.Second,
	)
	defer cancel()

	flusher, ok := w.(http.Flusher)
	if !ok {
		response.Data = buildPaymentFailureURL(
			types.ResultError,
			"Streaming payment updates are not supported",
		)
		writeTransactionResult(w, http.StatusInternalServerError, response)
		return
	}

	w.Header().Set("Content-Type", "application/x-ndjson; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("X-Content-Type-Options", "nosniff")

	encoder := json.NewEncoder(w)

	var streamMu sync.Mutex
	streamStarted := false
	streamFailed := false

	sendStreamMessage := func(message paymentStreamMessage) {
		streamMu.Lock()
		defer streamMu.Unlock()

		if streamFailed {
			return
		}

		if err := encoder.Encode(message); err != nil {
			streamFailed = true
			return
		}

		streamStarted = true
		flusher.Flush()
	}

	onStatus := func(update paymentsvc.StatusUpdate) {
		if update.Code == "" {
			return
		}

		sendStreamMessage(paymentStreamMessage{
			Type: "status",
			Code: update.Code,
		})
	}

	result, err := app.paymentService.Sale(
		ctx,
		paymentsvc.SaleRequest{
			RequestID: requestID,
			Reference: req.Reference,
			Amount:    req.Amount,
			Currency:  req.Currency,
		},
		onStatus,
	)

	if err != nil {
		status := http.StatusBadGateway
		if errors.Is(err, paymentsvc.ErrPaymentInProgress) {
			status = http.StatusConflict
		}

		logging.Error(
			types.ServiceName,
			err.Error(),
			"Payment provider error",
			string(op),
			req.Reference,
			app.cfg.Hotel,
			app.cfg.Kiosk,
		)

		response.Status.Code = status
		response.Status.Message = http.StatusText(status)
		response.Data = buildPaymentFailureURL(types.ResultError, err.Error())

		if !streamStarted {
			w.Header().Set("Content-Type", "application/json; charset=utf-8")
			writeTransactionResult(w, status, response)
			return
		}

		sendStreamMessage(paymentStreamMessage{
			Type:     "result",
			Response: &response,
		})
		return
	}

	if result == nil {
		response.Status.Code = http.StatusBadGateway
		response.Status.Message = "Empty payment result"
		response.Data = buildPaymentFailureURL(
			types.ResultError,
			"Payment provider returned an empty result",
		)

		if !streamStarted {
			w.Header().Set("Content-Type", "application/json; charset=utf-8")
			writeTransactionResult(w, http.StatusBadGateway, response)
			return
		}

		sendStreamMessage(paymentStreamMessage{
			Type:     "result",
			Response: &response,
		})
		return
	}

	response.Status.Code = http.StatusOK

	if result.Success && strings.EqualFold(result.Status, "APPROVED") {
		printer.PrintSaleReceipt(result.CustomerReceipt)

		response.Status.Message = result.Message
		response.Data = buildPaymentSuccessURL(result)

		sendStreamMessage(paymentStreamMessage{
			Type:     "result",
			Response: &response,
		})
		return
	}

	description := result.ErrorMessage
	if description == "" {
		description = result.Message
	}
	if description == "" {
		description = result.Status
	}

	log.Printf("Transaction failed: %s", description)
	printer.PrintSaleReceipt(result.CustomerReceipt)

	response.Status.Message = "Payment unsuccessful"
	response.Data = buildPaymentFailureURL(types.ResultError, description)

	sendStreamMessage(paymentStreamMessage{
		Type:     "result",
		Response: &response,
	})
}

func buildPaymentRequestID(reference string) string {
	const prefix = "REQ_"
	const maxLength = 60

	suffix := fmt.Sprintf("_%d", time.Now().UnixMilli())
	maxReferenceLength := maxLength - len(prefix) - len(suffix)

	runes := []rune(reference)
	if len(runes) > maxReferenceLength {
		runes = runes[:maxReferenceLength]
	}

	return prefix + string(runes) + suffix
}

func setPaymentCORS(w http.ResponseWriter) {
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS")
	w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
	w.Header().Set("Content-Type", "application/json")
}

func buildPaymentSuccessURL(result *paymentsvc.Result) string {
	// txnReference := result.ReferenceNumber
	// if txnReference == "" {
	// 	txnReference = result.TransactionID
	// }

	q := url.Values{}
	q.Set("CardNumber", hex.EncodeToString([]byte(result.CardNumber)))
	q.Set("CardType", hex.EncodeToString([]byte(result.CardType)))
	q.Set("ExpiryDate", hex.EncodeToString([]byte(result.ExpiryDate)))
	q.Set("TxnReference", result.RequestID)
	q.Set("CardHash", hex.EncodeToString([]byte(result.CardHash)))
	q.Set("CardReference", hex.EncodeToString([]byte(result.CardReference)))

	return (&url.URL{
		Path:     types.CheckinSuccessfulEndpoint,
		RawQuery: q.Encode(),
	}).String()
}

func buildPaymentFailureURL(msgType, description string) string {
	log.WithFields(log.Fields{
		types.LogFieldError:       msgType,
		types.LogFieldDescription: description,
	}).Error("Transaction failed")

	q := url.Values{}
	q.Set("MsgType", msgType)
	q.Set("Description", description)

	return (&url.URL{
		Path:     types.CheckinUnsuccessfulEndpoint,
		RawQuery: q.Encode(),
	}).String()
}