package wspay

import (
	"bytes"
	"crypto/sha512"
	"encoding/hex"
	"encoding/json"
	"errors"
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"io"
	"net/http"
	"payment-poc/database"
	"payment-poc/state"
	"strconv"
)

type Service struct {
	Provider   *database.PaymentEntryProvider
	ShopId     string
	ShopSecret string
	BackendUrl string
}

func (s *Service) CreatePaymentUrl(amount int64) (string, error) {
	entry, err := s.Provider.CreateEntry(database.PaymentEntry{
		Gateway:     state.GatewayWsPay,
		State:       state.StateInitialized,
		TotalAmount: amount,
	})
	if err != nil {
		return "", err
	}
	return "/wspay/initialize/" + entry.Id.String(), nil
}

func (s *Service) CompleteTransaction(entry database.PaymentEntry, amount int64) (database.PaymentEntry, error) {
	if entry.State == state.StateAccepted {
		var request = CompletionRequest{
			Version:      "2.0",
			WsPayOrderId: entry.Id.String(),
			ShopId:       s.ShopId,
			ApprovalCode: *entry.ApprovalCode,
			STAN:         *entry.STAN,
			Amount:       amount,
			Signature:    CalculateCompletionSignature(s.ShopId, s.ShopSecret, entry.Id.String(), *entry.STAN, *entry.ApprovalCode, amount),
		}

		httpResponse, err := createRequest(
			"POST",
			"https://test.wspay.biz/api/services/completion",
			map[string]string{"content-type": "application/json"},
			toJson(request),
		)
		if err != nil {
			return database.PaymentEntry{}, err
		}

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

		if CompareCompletionReturnSignature(response.Signature, s.ShopId, s.ShopSecret, entry.Id.String(), *entry.STAN, response.ActionSuccess, response.ApprovalCode) != nil {
			entry.Amount = &amount
			entry.State = state.StateCompleted
		} else {
			return database.PaymentEntry{}, errors.New("invalid signature")
		}
		return entry, nil
	} else {
		return database.PaymentEntry{}, errors.New("payment is in invalid state")
	}
}

func (s *Service) CancelTransaction(entry database.PaymentEntry) (database.PaymentEntry, error) {
	if entry.State == state.StateAccepted {
		var request = CompletionRequest{
			Version:      "2.0",
			WsPayOrderId: entry.Id.String(),
			ShopId:       s.ShopId,
			ApprovalCode: *entry.ApprovalCode,
			STAN:         *entry.STAN,
			Amount:       entry.TotalAmount,
			Signature:    CalculateCompletionSignature(s.ShopId, s.ShopSecret, entry.Id.String(), *entry.STAN, *entry.ApprovalCode, entry.TotalAmount),
		}

		httpResponse, err := createRequest(
			"POST",
			"https://test.wspay.biz/api/services/void",
			map[string]string{"content-type": "application/json"},
			toJson(request),
		)
		if err != nil {
			return database.PaymentEntry{}, err
		}

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

		if CompareCompletionReturnSignature(response.Signature, s.ShopId, s.ShopSecret, entry.Id.String(), *entry.STAN, response.ActionSuccess, response.ApprovalCode) != nil {
			entry.State = state.StateCanceled
		} else {
			return database.PaymentEntry{}, errors.New("invalid signature")
		}
		return entry, nil
	} else {
		return database.PaymentEntry{}, errors.New("payment is in invalid state")
	}
}

func (s *Service) InitializePayment(entry database.PaymentEntry) Form {
	form := Form{
		ShopID:         s.ShopId,
		ShoppingCartID: entry.Id.String(),
		Version:        "2.0",
		TotalAmount:    entry.TotalAmount,
		ReturnURL:      s.BackendUrl + "/wspay/success",
		ReturnErrorURL: s.BackendUrl + "/wspay/error",
		CancelURL:      s.BackendUrl + "/wspay/cancel",
		Signature:      CalculateFormSignature(s.ShopId, s.ShopSecret, entry.Id.String(), entry.TotalAmount),
	}
	return form
}

func (s *Service) HandleSuccessResponse(c *gin.Context) (string, error) {
	response := FormReturn{}
	if err := c.ShouldBind(&response); err != nil {
		return "", err
	}
	entry, err := s.Provider.FetchById(uuid.MustParse(response.ShoppingCartID))
	if err != nil {
		return "", err
	}

	if err := CompareFormReturnSignature(response.Signature, s.ShopId, s.ShopSecret, response.ShoppingCartID, response.Success, response.ApprovalCode); err != nil {
		return "", err
	}

	entry.Lang = &response.Lang
	entry.ECI = &response.ECI
	entry.STAN = &response.STAN
	entry.Success = &response.Success
	entry.ApprovalCode = &response.ApprovalCode
	entry.State = state.StateAccepted

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

	return "/entries/" + entry.Id.String(), nil
}

func (s *Service) HandleErrorResponse(c *gin.Context, paymentState state.PaymentState) (string, error) {
	response := FormError{}
	if err := c.ShouldBind(&response); err != nil {
		return "", err
	}
	entry, err := s.Provider.FetchById(uuid.MustParse(response.ShoppingCartID))
	if err != nil {
		return "", err
	}

	if err := CompareFormReturnSignature(response.Signature, s.ShopId, s.ShopSecret, response.ShoppingCartID, response.Success, response.ApprovalCode); err != nil {
		return "", err
	}

	entry.Lang = &response.Lang
	entry.ECI = &response.ECI
	entry.Success = &response.Success
	entry.ApprovalCode = &response.ApprovalCode
	entry.Error = &response.ErrorMessage
	entry.State = paymentState

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

	return "/entries/" + entry.Id.String(), nil
}

func CalculateFormSignature(shopId string, secret string, cartId string, amount int64) string {
	/**
	Represents a signature created from string formatted from following values in a following order using
	SHA512 algorithm:
	ShopID
	SecretKey
	ShoppingCartID
	SecretKey
	TotalAmount
	SecretKey
	*/
	signature := shopId + secret + cartId + secret + strconv.FormatInt(amount, 10) + secret
	hash := sha512.New()
	hash.Write([]byte(signature))
	return hex.EncodeToString(hash.Sum(nil))
}

func CalculateCompletionSignature(shopId string, secret string, cartId string, stan string, approvalCode string, amount int64) string {
	/**
	Represents a signature created from string formatted from following values in a following order using
	SHA512 algorithm:
	ShopID
	WsPayOrderId
	SecretKey
	STAN
	SecretKey
	ApprovalCode
	SecretKey
	Amount
	SecretKey
	WsPayOrderId
	*/
	signature := shopId + cartId + secret + stan + secret + approvalCode + secret + strconv.FormatInt(amount, 10) + secret + cartId
	hash := sha512.New()
	hash.Write([]byte(signature))
	return hex.EncodeToString(hash.Sum(nil))
}

func CompareFormReturnSignature(signature string, shopId string, secret string, cartId string, success int, approvalCode string) error {
	/**
	Represents a signature created from string formatted from following values in a following order using
	SHA512 algorithm:
	ShopID
	SecretKey
	ShoppingCartID
	SecretKey
	Success
	SecretKey
	ApprovalCode
	SecretKey
	Merchant should validate this signature to make sure that the request is originating from WSPayForm.
	*/
	calculatedSignature := shopId + secret + cartId + secret + strconv.FormatInt(int64(success), 10) + secret + approvalCode + secret
	hash := sha512.New()
	hash.Write([]byte(calculatedSignature))
	if hex.EncodeToString(hash.Sum(nil)) == signature {
		return nil
	} else {
		return errors.New("signature mismatch")
	}
}

func CompareCompletionReturnSignature(signature string, shopId string, secret string, stan string, actionSuccess string, approvalCode string, cartId string) error {
	/**
	Represents a signature created from string formatted from following values in a following order using
	SHA512 algorithm:
	ShopID
	SecretKey
	STAN
	ActionSuccess
	SecretKey
	ApprovalCode
	WsPayOrderId
	Merchant should validate this signature to make sure that the request is originating from WSPayForm.
	*/
	calculatedSignature := shopId + secret + stan + actionSuccess + secret + approvalCode + cartId
	hash := sha512.New()
	hash.Write([]byte(calculatedSignature))
	if hex.EncodeToString(hash.Sum(nil)) == signature {
		return nil
	} else {
		return errors.New("signature mismatch")
	}
}

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
}