package useCases

import (
	"RenewCMS/internal/domain/image"
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"encoding/xml"
	stdimage "image"
	"io"

	_ "golang.org/x/image/webp"
	_ "image/jpeg"
	_ "image/png"
)

const svgRootElement = "svg"

var rasterFormats = map[string]string{
	"image/png":  "png",
	"image/jpeg": "jpeg",
	"image/webp": "webp",
}

type CreateImageUseCase struct {
	imageRepository image.Repository
}

func NewCreateImageUseCase(imageRepository image.Repository) *CreateImageUseCase {
	return &CreateImageUseCase{imageRepository}
}

func (g *CreateImageUseCase) CreateImage(input image.ImageInput) (image.Image, error) {
	if !image.IsAllowedContentType(input.ContentType) {
		return image.Image{}, image.ErrImageTypeNotAllowed
	}

	data, err := readWithinLimit(input.Content)
	if err != nil {
		return image.Image{}, err
	}

	width, height, err := measure(data, input.ContentType)
	if err != nil {
		return image.Image{}, err
	}

	checksum := sha256.Sum256(data)
	return g.imageRepository.Create(image.ImageInput{
		Content:      bytes.NewReader(data),
		Filename:     image.NormalizeUploadFilename(input.Filename, input.ContentType),
		Size:         int64(len(data)),
		ContentType:  input.ContentType,
		Width:        width,
		Height:       height,
		SHA256:       hex.EncodeToString(checksum[:]),
		UploadedByID: input.UploadedByID,
	})
}

func readWithinLimit(content io.Reader) ([]byte, error) {
	if content == nil {
		return nil, image.ErrImageUnreadable
	}
	data, err := io.ReadAll(io.LimitReader(content, image.MaxImageSize+1))
	if err != nil {
		return nil, err
	}
	if int64(len(data)) > image.MaxImageSize {
		return nil, image.ErrImageTooLarge
	}
	return data, nil
}

func measure(data []byte, contentType string) (int, int, error) {
	if contentType == "image/svg+xml" {
		if !hasSvgRoot(data) {
			return 0, 0, image.ErrImageUnreadable
		}
		return 0, 0, nil
	}

	config, format, err := stdimage.DecodeConfig(bytes.NewReader(data))
	if err != nil || format != rasterFormats[contentType] {
		return 0, 0, image.ErrImageUnreadable
	}
	return config.Width, config.Height, nil
}

func hasSvgRoot(data []byte) bool {
	decoder := xml.NewDecoder(bytes.NewReader(data))
	for {
		token, err := decoder.Token()
		if err != nil {
			return false
		}
		if start, ok := token.(xml.StartElement); ok {
			return start.Name.Local == svgRootElement
		}
	}
}