package wspay

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

type Service struct {
	ShopId     string
	ShopSecret string
	BackendUrl string
}

func (s *Service) UpdatePayment(entry database.PaymentEntry) (updatedEntry database.PaymentEntry, err error) {
	var request = StatusCheckRequest{
		Version:        "2.0",
		ShopId:         s.ShopId,
		ShoppingCartId: entry.Id.String(),
		Signature:      CalculateStatusCheckSignature(s.ShopId, s.ShopSecret, entry.Id.String()),
	}

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

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

	if CompareStatusCheckReturnSignature(response.Signature, s.ShopId, s.ShopSecret, response.ActionSuccess, response.ApprovalCode, entry.Id.String()) != nil {
		entry.Amount = &response.Amount
		newState := determineState(response)

		if entry.State != newState && newState != "" {
			log.Printf("Updated state for %s: %s -> %s", entry.Id.String(), entry.State, newState)
			entry.State = newState
		}

		entry.State = state.StateCompleted
	} else {
		return database.PaymentEntry{}, errors.New("invalid signature")
	}
	return entry, nil
}

func determineState(response StatusCheckResponse) state.PaymentState {
	if response.Completed == "1" {
		return state.StateCompleted
	} else if response.Voided == "1" {
		return state.StateVoided
	} else if response.Refunded == "1" {
		return state.StateVoided
	} else if response.Authorized == "1" {
		return state.StateAccepted
	} else {
		return state.StateInitialized
	}
}

func (s *Service) CreatePaymentUrl(entry database.PaymentEntry) (database.PaymentEntry, string, error) {
	entry, url, err := s.InitializePayment(entry)
	if err != nil {
		return entry, "", err
	}
	return entry, url, 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) (database.PaymentEntry, string, error) {
	formattedAmount := fmt.Sprintf("%d,%02d", entry.TotalAmount/100, entry.TotalAmount%100)

	var request = CreateTransaction{
		ShopID:         s.ShopId,
		ShoppingCardID: entry.Id.String(),
		Version:        "2.0",
		TotalAmount:    formattedAmount,
		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),
	}

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

	var response TransactionResponse
	err = readResponse(httpResponse, &response)
	if err != nil {
		return database.PaymentEntry{}, "", err
	}
	if response.TransactionId == nil {
		return database.PaymentEntry{}, "", errors.New("received bad response")
	}

	entry.State = state.StateInitialized

	return entry, *response.PaymentFormUrl, nil
}

func (s *Service) HandleSuccessResponse(c *gin.Context, provider *database.PaymentEntryProvider) (string, error) {
	response := FormReturn{}
	if err := c.ShouldBind(&response); err != nil {
		return "", err
	}
	entry, err := 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 := provider.UpdateEntry(entry); err != nil {
		return "", err
	}

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

func (s *Service) HandleErrorResponse(c *gin.Context, provider *database.PaymentEntryProvider, paymentState state.PaymentState) (string, error) {
	response := FormError{}
	if err := c.ShouldBind(&response); err != nil {
		return "", err
	}
	entry, err := 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 := 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 CompareStatusCheckReturnSignature(signature string, shopId string, secret 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
	ActionSuccess
	ApprovalCode
	SecretKey
	ShopID
	ApprovalCode
	WsPayOrderId
	*/
	calculatedSignature := shopId + secret + actionSuccess + approvalCode + secret + shopId + 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 CalculateStatusCheckSignature(shopId string, secret string, cartId string) string {
	/**
	Represents a signature created from string formatted from following values in a following order using
	SHA512 algorithm:
	ShopID
	SecretKey
	ShoppingCartID
	SecretKey
	ShopID
	ShoppingCartID
	*/
	signature := shopId + secret + cartId + secret + shopId + cartId
	hash := sha512.New()
	hash.Write([]byte(signature))
	return hex.EncodeToString(hash.Sum(nil))
}

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
}