// Package collage makes a pic collage
package collage

import (
	"errors"
	"fmt"
	"image"
	"io"
	"io/fs"
)

type Dimension struct {
	Width  uint `json:"width"`
	Height uint `json:"height"`
}

type Point struct {
	X uint `json:"x"`
	Y uint `json:"y"`
}

type Rectangle struct {
	Start Point `json:"start"`
	End   Point `json:"end"`
}

func (r Rectangle) ToImgRect() image.Rectangle {
	return image.Rectangle{
		Min: image.Point{int(r.Start.X), int(r.Start.Y)},
		Max: image.Point{int(r.End.X), int(r.End.Y)},
	}
}

type Request struct {
	BackgroundImage string    `json:"background_image"`
	Aspect          Dimension `json:"aspect"`
	Dimension       Dimension `json:"dimension"`
	Photos          []struct {
		ImageName string    `json:"image"`
		Crop      Rectangle `json:"crop"`
		Frame     Rectangle `json:"frame"`
	} `json:"photos"`
}

func Make(req Request, source fs.FS, output io.Writer) {
	rec := image.Rect(0, 0, int(req.Aspect.Width), int(req.Aspect.Height))
	canvas := image.NewRGBA64(rec)
	for photo := range req.Photos {
		fmt.Println(photo)
	}
	fmt.Println(canvas)
}

type HasSubImage interface {
	SubImage(r image.Rectangle) image.Image
}

func Crop(img image.Image, r Rectangle) (image.Image, error) {
	if imgHS, ok := img.(HasSubImage); ok {
		return imgHS.SubImage(r.ToImgRect()), nil
	}
	return nil, errors.New("image does not support cropping")
}

func GetImage(source fs.FS, imageName string) (image.Image, error) {
	imgF, err := source.Open(imageName)
	if err != nil {
		return nil, err
	}
	img, _, err := image.Decode(imgF)
	return img, err
}