package bucket

import (
	"errors"
	"fmt"
	"mime"
	"net/url"
	"sort"
	"strings"
)

type Preview string

const previewPrefix = "preview/"

var ErrorInvalidPreview = errors.New("invalid preview")

func (p Preview) Validate() error {
	if !strings.HasPrefix(string(p), previewPrefix) {
		return fmt.Errorf("%w: %v", ErrorInvalidPreview, p)
	}
	return nil
}

func (p Preview) String() string {
	return string(p)
}

func (p Preview) Path() string {
	u := url.URL{
		Path: string(p),
	}
	return u.String()
}

func (p Preview) Format() PhotoFormat {
	extIndex := strings.LastIndex(string(p), ".")
	return PhotoFormat(mime.TypeByExtension(string(p)[extIndex:]))
}

type PreviewOption struct {
	Height int
	//Width int
	Format  PhotoFormat
	Quality int
}

type PhotoFormat string

const (
	PhotoFormatJPEG PhotoFormat = "image/jpeg"
	PhotoFormatWEBP PhotoFormat = "image/webp"
	PhotoFormatHEIF PhotoFormat = "image/heif"
	PhotoFormatPNG  PhotoFormat = "image/png"
	PhotoFormatGIF  PhotoFormat = "image/gif"
	PhotoFormatTIFF PhotoFormat = "image/tiff"
)

func (f PhotoFormat) ContentType() string {
	return string(f)
}

var SupportedFormats = []PhotoFormat{
	PhotoFormatJPEG,
	PhotoFormatWEBP,
	PhotoFormatHEIF,
	PhotoFormatPNG,
	PhotoFormatGIF,
	PhotoFormatTIFF,
}

type PhotoQualityLevel int

const (
	PhotoQualityLevelThumbnail PhotoQualityLevel = 0
	PhotoQualityLevelBasic     PhotoQualityLevel = 1
	PhotoQualityLevelNormal    PhotoQualityLevel = 2
	PhotoQualityLevelExtreme   PhotoQualityLevel = 3
)

func (f PhotoFormat) Quality(level PhotoQualityLevel) int {
	if f == PhotoFormatJPEG || f == PhotoFormatWEBP {
		return 34 + int(level)*18
	}
	if f == PhotoFormatHEIF {
		return 10 + int(level)*10
	}
	return 0
}

func (p Photo) GetPreview(option PreviewOption) Preview {
	objectBase := strings.Replace(string(p), photoPrefix, previewPrefix, 1)
	extIndex := strings.LastIndex(objectBase, ".")
	base := objectBase[:extIndex]
	res := fmt.Sprintf("_h%dq%d", option.Height, option.Quality)
	exts, err := mime.ExtensionsByType(option.Format.ContentType())
	if err != nil {
		panic(err)
	}
	sort.Strings(exts)
	if len(exts) < 1 {
		panic("missing MIME type to extension mapping, please configure within your operating system")
	}
	return Preview(base + res + exts[len(exts)-1])
}

var defaultSizes = []int{640, 320, 160, 80}
var defaultSizesThumb = []int{60, 30}
var defaultFormats = []PhotoFormat{
	PhotoFormatWEBP,
	PhotoFormatJPEG,
}

func DefaultPreviewOptions() []PreviewOption {
	options := make([]PreviewOption, 0)
	for _, size := range defaultSizes {
		for _, format := range defaultFormats {
			options = append(options, PreviewOption{
				Height:  size,
				Format:  format,
				Quality: format.Quality(PhotoQualityLevelNormal),
			})
		}
	}
	for _, size := range defaultSizesThumb {
		for _, format := range defaultFormats {
			options = append(options, PreviewOption{
				Height:  size,
				Format:  format,
				Quality: format.Quality(PhotoQualityLevelThumbnail),
			})
		}
	}
	return options
}