package viva

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"errors"
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"io"
	"log"
	"net/http"
	"net/url"
	"payment-poc/database"
	"payment-poc/state"
	"strconv"
	"time"
)

type Service struct {
	Provider     *database.PaymentEntryProvider
	ClientId     string
	ClientSecret string
	SourceCode   string

	MerchantId string
	ApiKey     string

	token      string
	expiration time.Time
}

func (s *Service) CreatePaymentUrl(amount int64) (url string, err error) {
	entry, err := s.Provider.CreateEntry(database.PaymentEntry{
		Gateway:     state.GatewayVivaWallet,
		State:       state.StateInitialized,
		TotalAmount: amount,
	})
	if err != nil {
		return "", err
	}
	entry, err = s.InitializePayment(entry)
	if err != nil {
		return "", err
	}
	entry, err = s.Provider.UpdateEntry(entry)
	if err != nil {
		return "", err
	}
	return "https://demo.vivapayments.com/web/checkout?ref=" + string(*entry.OrderId), nil
}

func (s *Service) InitializePayment(entry database.PaymentEntry) (database.PaymentEntry, error) {
	token, err := s.oAuthToken()
	if err != nil {
		return database.PaymentEntry{}, err
	}

	request := OrderRequest{
		Amount:              entry.TotalAmount,
		Description:         "Example payment",
		MerchantDescription: "Example payment",
		PreAuth:             true,
		AllowRecurring:      false,
		Source:              s.SourceCode,
	}

	httpResponse, err := createRequest(
		"POST",
		"https://demo-api.vivapayments.com/checkout/v2/orders",
		map[string]string{"authorization": "Bearer " + token, "content-type": "application/json"},
		toJson(request),
	)
	if err != nil {
		return database.PaymentEntry{}, err
	}

	var response OrderResponse
	err = readResponse(httpResponse, &response)
	if err != nil {
		return database.PaymentEntry{}, err
	}
	entry.OrderId = &response.OrderId
	return entry, nil
}

func (s *Service) CompleteTransaction(entry database.PaymentEntry, amount int64) (database.PaymentEntry, error) {
	completionRequest := TransactionCompleteRequest{
		Amount:              amount,
		CustomerDescription: "Example transaction",
	}
	httpResponse, err := createRequest(
		"POST",
		"https://demo.vivapayments.com/api/transactions/"+entry.TransactionId.String(),
		map[string]string{"authorization": "Bearer " + s.basicAuth(),
			"content-type": "application/json",
		},
		toJson(completionRequest),
	)
	if err != nil {
		return database.PaymentEntry{}, err
	}

	var response TransactionResponse
	err = readResponse(httpResponse, &response)
	if err != nil {
		return database.PaymentEntry{}, err
	}
	if response.StatusId == "F" {
		paidAmount := int64(response.Amount * 100)
		entry.Amount = &paidAmount
		entry.State = state.StateCompleted
	} else {
		return database.PaymentEntry{}, errors.New("received invalid status = " + response.StatusId)
	}
	return entry, nil
}

func (s *Service) CancelTransaction(entry database.PaymentEntry) (database.PaymentEntry, error) {
	httpResponse, err := createRequest(
		"DELETE",
		"https://demo.vivapayments.com/api/transactions/"+entry.TransactionId.String(),
		map[string]string{"authorization": "Bearer " + s.basicAuth(),
			"content-type": "application/json",
		},
		nil,
	)
	if err != nil {
		return database.PaymentEntry{}, err
	}

	var response TransactionResponse
	err = readResponse(httpResponse, &response)
	if err != nil {
		return database.PaymentEntry{}, err
	}
	if response.StatusId == "F" {
		paidAmount := int64(0)
		entry.Amount = &paidAmount
		entry.State = state.StateVoided
	} else {
		return database.PaymentEntry{}, errors.New("received invalid status = " + response.StatusId)
	}
	return entry, nil
}

func (s *Service) oAuthToken() (string, error) {
	if s.token != "" && s.expiration.After(time.Now()) {
		return s.token, nil
	}
	return s.fetchOAuthToken()
}

func readResponse[T any](httpResponse *http.Response, response T) error {
	if httpResponse.StatusCode == http.StatusOK {
		content, err := io.ReadAll(httpResponse.Body)
		if err != nil {
			return err
		}
		return json.Unmarshal(content, response)
	} else {
		return errors.New("received wrong status, expected 200 received " + strconv.FormatInt(int64(httpResponse.StatusCode), 10))
	}
}

func createRequest(method string, url string, headers map[string]string, content []byte) (*http.Response, error) {
	request, err := http.NewRequest(method, url, bytes.NewReader(content))
	if err != nil {
		return nil, err
	}
	for key, value := range headers {
		request.Header.Add(key, value)
	}
	return http.DefaultClient.Do(request)
}

func toJson[T any](request T) []byte {
	response, err := json.Marshal(request)
	if err != nil {
		panic(err)
	}
	return response
}

func (s *Service) fetchOAuthToken() (string, error) {
	form := url.Values{
		"grant_type": []string{"client_credentials"},
	}
	httpResponse, err := createRequest(
		"POST",
		"https://demo-accounts.vivapayments.com/connect/token",
		map[string]string{"content-type": "application/x-www-form-urlencoded", "authorization": "Basic " + base64.StdEncoding.EncodeToString([]byte(s.ClientId+":"+s.ClientSecret))},
		[]byte(form.Encode()),
	)
	var response OAuthResponse

	err = readResponse(httpResponse, &response)
	if err != nil {
		return "", err
	}
	s.token = response.AccessToken
	s.expiration = time.Now().Add(time.Duration(response.ExpiresIn) * time.Second)

	return s.token, nil
}

func (s *Service) basicAuth() string {
	return base64.StdEncoding.EncodeToString([]byte(s.MerchantId + ":" + s.ApiKey))
}

func (s *Service) HandleResponse(c *gin.Context, expectedState state.PaymentState) (string, error) {
	transactionId := uuid.MustParse(c.Query("t"))
	orderId := database.OrderId(c.Query("s"))
	lang := c.Query("lang")
	eventId := c.Query("eventId")
	eci := c.Query("eci")

	log.Printf("Received error response for viva payment %s", orderId)
	entry, err := s.Provider.FetchByOrderId(orderId)
	if err != nil {
		log.Printf("Couldn't find payment info for viva payment %s", orderId)
		return "", err
	}

	entry.State = expectedState
	entry.ECI = &eci
	entry.Lang = &lang
	entry.EventId = &eventId
	entry.TransactionId = &transactionId

	if _, err := s.Provider.UpdateEntry(entry); err != nil {
		return "", err
	}

	log.Printf("Viva payment %s received correctly, returning redirect", orderId)
	return "/entries/" + entry.Id.String(), nil
}