package photos

import (
	"bytes"
	"image"

	"github.com/disintegration/imaging"
	"github.com/gen2brain/webp"
)

// Object roles holding the non-destructive edited version of a photo. They
// mirror the base roles and are bound in addition to them.
const (
	RoleEdit        = "edit"
	RoleEditThumb   = "edit_thumb"
	RoleEditMedium  = "edit_medium"
	RoleEditPreview = "edit_preview"
)

// applyLight renders the light adjustments into a copy of the image. The
// original pixels are never modified in place.
func applyLight(src image.Image, p LightParams) *image.NRGBA {
	// Clone returns a fresh NRGBA copy, so the source stays untouched.
	dst := imaging.Clone(src)

	master := curveLUT(p.Curve.RGB)
	red := curveLUT(p.Curve.Red)
	green := curveLUT(p.Curve.Green)
	blue := curveLUT(p.Curve.Blue)

	width := dst.Rect.Dx()
	for y := 0; y < dst.Rect.Dy(); y++ {
		row := dst.Pix[y*dst.Stride : y*dst.Stride+width*4]
		for i := 0; i+3 < len(row); i += 4 {
			if row[i+3] == 0 {
				continue
			}
			row[i] = uint8(adjustChannel(float64(row[i]), p, &master, &red))
			row[i+1] = uint8(adjustChannel(float64(row[i+1]), p, &master, &green))
			row[i+2] = uint8(adjustChannel(float64(row[i+2]), p, &master, &blue))
		}
	}
	return dst
}

// buildEditedVariants renders the edited version of a photo: the full-size
// image plus the thumb, medium and preview variants. The variants mirror the
// base ones, so the grid and the viewer can switch to them transparently.
func buildEditedVariants(data []byte, p EditParams) (thumb, medium, preview, full []byte, err error) {
	img, err := imaging.Decode(bytes.NewReader(data), imaging.AutoOrientation(true))
	if err != nil {
		return nil, nil, nil, nil, err
	}
	edited := applyLight(img, p.Light)

	thumbImg := imaging.Fill(edited, 200, 200, imaging.Center, imaging.Lanczos)
	mediumImg := imaging.Fill(edited, 800, 800, imaging.Center, imaging.Lanczos)
	previewImg := imaging.Fit(edited, 1200, 1200, imaging.Lanczos)

	opts := webp.Options{Quality: 82}
	var buf bytes.Buffer
	if err := webp.Encode(&buf, thumbImg, opts); err != nil {
		return nil, nil, nil, nil, err
	}
	thumb = buf.Bytes()

	buf.Reset()
	if err := webp.Encode(&buf, mediumImg, opts); err != nil {
		return nil, nil, nil, nil, err
	}
	medium = buf.Bytes()

	buf.Reset()
	if err := webp.Encode(&buf, previewImg, opts); err != nil {
		return nil, nil, nil, nil, err
	}
	preview = buf.Bytes()

	buf.Reset()
	if err := webp.Encode(&buf, edited, opts); err != nil {
		// Полноразмерная версия не обязательна: превью и миниатюры уже
		// готовы, поэтому ошибку кодирования полной версии не считаем
		// фатальной.
		full = nil
	} else {
		full = buf.Bytes()
	}
	return thumb, medium, preview, full, nil
}