package productDescriptionService

import (
	"context"
	"encoding/xml"
	"fmt"
	"io"
	"log"
	"os"
	"slices"
	"strings"

	"git.ma-al.com/goc_daniel/b2b/app/config"
	"git.ma-al.com/goc_daniel/b2b/app/db"
	"git.ma-al.com/goc_daniel/b2b/app/model"
	"git.ma-al.com/goc_daniel/b2b/app/service/langsService"
	"git.ma-al.com/goc_daniel/b2b/app/utils/responseErrors"
	"google.golang.org/api/option"
	"gorm.io/gorm"

	// [START translate_v3_import_client_library]
	"cloud.google.com/go/auth/credentials"
	translate "cloud.google.com/go/translate/apiv3"
	"cloud.google.com/go/translate/apiv3/translatepb"
	// [END translate_v3_import_client_library]
)

type ProductDescriptionService struct {
	db        *gorm.DB
	ctx       context.Context
	googleCli translate.TranslationClient
	// projectID is the Google Cloud project ID used as the "parent" in API calls,
	// e.g. "projects/my-project-123/locations/global"
	projectID string
}

// New creates a ProductDescriptionService and authenticates against the
// Google Cloud Translation API using a service account key file.
//
// Required configuration (set in .env or environment):
//
//	GOOGLE_APPLICATION_CREDENTIALS  – absolute path to the service account JSON key file
//	GOOGLE_CLOUD_PROJECT_ID         – your Google Cloud project ID
//
// The service account must have the "Cloud Translation API User" role
// (roles/cloudtranslate.user) granted in Google Cloud IAM.
func New() *ProductDescriptionService {
	ctx := context.Background()
	cfg := config.Get()

	// Read the service account key file whose path comes from config / env.
	data, err := os.ReadFile(cfg.GoogleTranslate.CredentialsFile)
	if err != nil {
		log.Fatalf("productDescriptionService: cannot read credentials file %q: %v",
			cfg.GoogleTranslate.CredentialsFile, err)
	}

	// Build OAuth2 credentials scoped to the Cloud Translation API.
	// The correct scope for Cloud Translation v3 is "cloud-translation".
	creds, err := credentials.DetectDefault(&credentials.DetectOptions{
		Scopes:          []string{"https://www.googleapis.com/auth/cloud-translation"},
		CredentialsJSON: data,
	})
	if err != nil {
		log.Fatalf("productDescriptionService: cannot build Google credentials: %v", err)
	}

	googleCli, err := translate.NewTranslationClient(ctx, option.WithAuthCredentials(creds))
	if err != nil {
		log.Fatalf("productDescriptionService: cannot create Translation client: %v", err)
	}

	return &ProductDescriptionService{
		db:        db.Get(),
		ctx:       ctx,
		googleCli: *googleCli,
		projectID: cfg.GoogleTranslate.ProjectID,
	}
}

// We assume that any user has access to all product descriptions
func (s *ProductDescriptionService) GetProductDescription(userID uint, productID uint, productShopID uint, productLangID uint) (*model.ProductDescription, error) {
	var ProductDescription model.ProductDescription

	err := s.db.
		Table("ps_product_lang").
		Where("id_product = ? AND id_shop = ? AND id_lang = ?", productID, productShopID, productLangID).
		First(&ProductDescription).Error
	if err != nil {
		return nil, fmt.Errorf("database error: %w", err)
	}

	return &ProductDescription, nil
}

// Updates relevant fields with the "updates" map
func (s *ProductDescriptionService) SaveProductDescription(userID uint, productID uint, productShopID uint, productLangID uint, updates map[string]string) error {
	// only some fields can be affected
	allowedFields := []string{"description", "description_short", "meta_description", "meta_title", "name", "available_now", "available_later", "usage"}
	for key := range updates {
		if !slices.Contains(allowedFields, key) {
			return responseErrors.ErrBadField
		}
	}

	// check that fields description, description_short and usage, if they exist, have a valid html format
	mustBeHTML := []string{"description", "description_short", "usage"}
	for i := 0; i < len(mustBeHTML); i++ {
		if text, exists := updates[mustBeHTML[i]]; exists {
			if !isValidXHTML(text) {
				return responseErrors.ErrInvalidXHTML
			}
		}
	}

	record := model.ProductDescription{
		ProductID: productID,
		ShopID:    productShopID,
		LangID:    productLangID,
	}

	err := s.db.
		Table("ps_product_lang").
		Where("id_product = ? AND id_shop = ? AND id_lang = ?", productID, productShopID, productLangID).
		FirstOrCreate(&record).Error
	if err != nil {
		return fmt.Errorf("database error: %w", err)
	}

	if len(updates) == 0 {
		return nil
	}
	updatesIface := make(map[string]interface{}, len(updates))
	for k, v := range updates {
		updatesIface[k] = v
	}

	err = s.db.
		Table("ps_product_lang").
		Where("id_product = ? AND id_shop = ? AND id_lang = ?", productID, productShopID, productLangID).
		Updates(updatesIface).Error
	if err != nil {
		return fmt.Errorf("database error: %w", err)
	}

	return nil
}

// TranslateProductDescription fetches the product description for productFromLangID,
// translates every text field into productToLangID using the Google Cloud
// Translation API (v3 TranslateText), and returns the translated record.
//
// The Google Cloud project must have the Cloud Translation API enabled and the
// service account must hold the "Cloud Translation API User" role.
func (s *ProductDescriptionService) TranslateProductDescription(userID uint, productID uint, productShopID uint, productFromLangID uint, productToLangID uint) (*model.ProductDescription, error) {
	var ProductDescription model.ProductDescription

	err := s.db.
		Table("ps_product_lang").
		Where("id_product = ? AND id_shop = ? AND id_lang = ?", productID, productShopID, productFromLangID).
		First(&ProductDescription).Error
	if err != nil {
		return nil, fmt.Errorf("database error: %w", err)
	}
	ProductDescription.LangID = productToLangID

	// we translate all changeable fields, and we keep the exact same HTML structure in relevant fields.
	lang, err := langsService.LangSrv.GetLanguageById(productToLangID)
	if err != nil {
		return nil, err
	}

	fields := []*string{&ProductDescription.Description,
		&ProductDescription.DescriptionShort,
		&ProductDescription.MetaDescription,
		&ProductDescription.MetaTitle,
		&ProductDescription.Name,
		&ProductDescription.AvailableNow,
		&ProductDescription.AvailableLater,
		&ProductDescription.Usage,
	}
	keys := []string{"translation_of_product_description",
		"translation_of_product_short_description",
		"translation_of_product_meta_description",
		"translation_of_product_meta_title",
		"translation_of_product_name",
		"translation_of_product_available_now",
		"translation_of_product_available_later",
		"translation_of_product_usage",
	}

	request := "Translate to " + lang.ISOCode + " without changing the html structure.\n"
	for i := 0; i < len(keys); i++ {
		request += "\n<" + keys[i] + ">"
		request += *fields[i]
		request += "</" + keys[i] + ">\n"
	}
	request = cleanForPrompt(request)

	// TranslateText is the standard Cloud Translation v3 endpoint.
	// "parent" must be "projects/<PROJECT_ID>/locations/global" (or a specific region).
	// MimeType "text/plain" is used because cleanForPrompt strips HTML attributes;
	// switch to "text/html" if you want Google to preserve HTML tags automatically.
	req := &translatepb.TranslateTextRequest{
		Parent:             fmt.Sprintf("projects/%s/locations/global", s.projectID),
		TargetLanguageCode: lang.ISOCode,
		MimeType:           "text/plain",
		Contents:           []string{request},
	}
	responseGoogle, err := s.googleCli.TranslateText(s.ctx, req)
	if err != nil {
		fmt.Println(err)
		return nil, err
	}

	// TranslateText returns one Translation per input string.
	if len(responseGoogle.GetTranslations()) == 0 {
		return nil, responseErrors.ErrOpenAIBadOutput
	}
	response := responseGoogle.GetTranslations()[0].GetTranslatedText()

	for i := 0; i < len(keys); i++ {
		success, resolution := resolveResponse(*fields[i], response, keys[i])
		if !success {
			return nil, responseErrors.ErrOpenAIBadOutput
		}
		*fields[i] = resolution

		fmt.Println("resolution: ", resolution)
	}

	return &ProductDescription, nil
}

// isValidXHTML checks if the string obeys the XHTML format
func isValidXHTML(s string) bool {
	r := strings.NewReader(s)
	d := xml.NewDecoder(r)

	// Configure the decoder for HTML; leave off strict and autoclose for XHTML
	d.Strict = true
	d.AutoClose = xml.HTMLAutoClose
	d.Entity = xml.HTMLEntity
	for {
		_, err := d.Token()
		switch err {
		case io.EOF:
			return true // We're done, it's valid!
		case nil:
		default:
			return false // Oops, something wasn't right
		}
	}
}

func cleanForPrompt(s string) string {
	r := strings.NewReader(s)
	d := xml.NewDecoder(r)

	prompt := ""

	// Configure the decoder for HTML; leave off strict and autoclose for XHTML
	d.Strict = true
	d.AutoClose = xml.HTMLAutoClose
	d.Entity = xml.HTMLEntity
	for {
		token, err := d.Token()
		if err == io.EOF {
			break
		}

		switch v := token.(type) {
		case xml.StartElement:
			prompt += "<" + AttrName(v.Name)

			for _, attr := range v.Attr {
				if v.Name.Local == "img" && attr.Name.Local == "alt" {
					prompt += fmt.Sprintf(` %s="%s"`, AttrName(attr.Name), attr.Value)
				}
			}

			prompt += ">"
		case xml.EndElement:
			prompt += "</" + AttrName(v.Name) + ">"
		case xml.CharData:
			prompt += string(v)
		case xml.Comment:
		case xml.ProcInst:
		case xml.Directive:
		}
	}

	return prompt
}

func resolveResponse(original string, response string, key string) (bool, string) {
	success, match := GetStringInBetween(response, "<"+key+">", "</"+key+">")
	if !success || !isValidXHTML(match) {
		return false, ""
	}

	success, resolution := RebuildFromResponse("<"+key+">"+original+"</"+key+">", "<"+key+">"+match+"</"+key+">")
	if !success {
		return false, ""
	}

	return true, resolution[2+len(key) : len(resolution)-3-len(key)]
}

// GetStringInBetween returns empty string if no start or end string found
func GetStringInBetween(str string, start string, end string) (success bool, result string) {
	s := strings.Index(str, start)
	if s == -1 {
		return false, ""
	}
	s += len(start)
	e := strings.Index(str[s:], end)
	if e == -1 {
		return false, ""
	}

	return true, str[s : s+e]
}

// Rebuilds HTML using the original HTML as a template and the response as a source
// Assumes that both original and response have the exact same XML structure
func RebuildFromResponse(s_original string, s_response string) (bool, string) {

	r_original := strings.NewReader(s_original)
	d_original := xml.NewDecoder(r_original)

	r_response := strings.NewReader(s_response)
	d_response := xml.NewDecoder(r_response)

	result := ""

	// Configure the decoder for HTML; leave off strict and autoclose for XHTML
	d_original.Strict = true
	d_original.AutoClose = xml.HTMLAutoClose
	d_original.Entity = xml.HTMLEntity

	d_response.Strict = true
	d_response.AutoClose = xml.HTMLAutoClose
	d_response.Entity = xml.HTMLEntity

	token_original, err_original := d_original.Token()
	token_response, err_response := d_response.Token()

	for {
		// err_original can only be EOF or nil.
		if err_original != nil || err_response != nil {
			if err_original != err_response {
				return false, ""
			}
			return true, result
		}

		switch v_original := token_original.(type) {
		case xml.StartElement:
			switch v_response := token_response.(type) {
			case xml.StartElement:
				if v_original.Name.Space != v_response.Name.Space || v_original.Name.Local != v_response.Name.Local {
					return false, ""
				}

				result += "<" + AttrName(v_original.Name)

				for _, attr := range v_original.Attr {
					if v_original.Name.Local != "img" || attr.Name.Local != "alt" {
						result += fmt.Sprintf(` %s="%s"`, AttrName(attr.Name), attr.Value)
					}
				}

				for _, attr := range v_response.Attr {
					if v_response.Name.Local == "img" && attr.Name.Local == "alt" {
						result += fmt.Sprintf(` %s="%s"`, AttrName(attr.Name), attr.Value)
					}
				}
				result += ">"

			case xml.CharData:
				result += string(v_response)
				token_response, err_response = d_response.Token()
				continue

			default:
				return false, ""
			}

		case xml.EndElement:
			switch v_response := token_response.(type) {
			case xml.EndElement:
				if v_original.Name.Space != v_response.Name.Space || v_original.Name.Local != v_response.Name.Local {
					return false, ""
				}

				if v_original.Name.Local != "img" {
					result += "</" + AttrName(v_original.Name) + ">"
				}

			case xml.CharData:
				result += string(v_response)
				token_response, err_response = d_response.Token()
				continue

			default:
				return false, ""
			}

		case xml.CharData:
			switch v_response := token_response.(type) {
			case xml.CharData:
				result += string(v_response)

			case xml.StartElement:
				result += string(v_original)
				token_original, err_original = d_original.Token()
				continue

			case xml.EndElement:
				result += string(v_original)
				token_original, err_original = d_original.Token()
				continue

			default:
				return false, ""
			}

		case xml.Comment:
			result += "<!--" + string(v_original) + "-->"
			token_original, err_original = d_original.Token()
			continue

		case xml.ProcInst:
			if len(v_original.Inst) == 0 {
				result += "<?" + v_original.Target + "?>"
			} else {
				result += "<?" + v_original.Target + " " + string(v_original.Inst) + "?>"
			}
			token_original, err_original = d_original.Token()
			continue

		case xml.Directive:
			result += "<!" + string(v_original) + ">"
			token_original, err_original = d_original.Token()
			continue
		}

		token_original, err_original = d_original.Token()
		token_response, err_response = d_response.Token()
	}
}

func AttrName(name xml.Name) string {
	if name.Space == "" {
		return name.Local
	} else {
		return name.Space + ":" + name.Local
	}
}