package imageproc

import (
	"image"
	"image/color"

	xdraw "golang.org/x/image/draw"
)

func Crop(src image.Image, rect image.Rectangle) image.Image {
	b := src.Bounds()
	rect = rect.Intersect(b)
	if rect.Empty() {
		rect = b
	}
	dst := image.NewRGBA(image.Rect(0, 0, rect.Dx(), rect.Dy()))
	for y := rect.Min.Y; y < rect.Max.Y; y++ {
		for x := rect.Min.X; x < rect.Max.X; x++ {
			dst.Set(x-rect.Min.X, y-rect.Min.Y, src.At(x, y))
		}
	}
	return dst
}

func ResizeToMax(src image.Image, maxDim int) image.Image {
	if maxDim <= 0 {
		return src
	}
	b := src.Bounds()
	w, h := b.Dx(), b.Dy()
	if w <= maxDim && h <= maxDim {
		return normalizeRGBA(src)
	}
	nw, nh := w, h
	if w >= h {
		nw = maxDim
		nh = max(1, h*maxDim/w)
	} else {
		nh = maxDim
		nw = max(1, w*maxDim/h)
	}
	dst := image.NewRGBA(image.Rect(0, 0, nw, nh))
	xdraw.CatmullRom.Scale(dst, dst.Bounds(), src, b, xdraw.Over, nil)
	return dst
}

func ResizeToFill(src image.Image, width, height int) image.Image {
	if width <= 0 || height <= 0 {
		return normalizeRGBA(src)
	}
	b := src.Bounds()
	srcRatio := float64(b.Dx()) / float64(b.Dy())
	dstRatio := float64(width) / float64(height)
	crop := b
	if srcRatio > dstRatio {
		cropW := int(float64(b.Dy()) * dstRatio)
		x0 := b.Min.X + (b.Dx()-cropW)/2
		crop = image.Rect(x0, b.Min.Y, x0+cropW, b.Max.Y)
	} else if srcRatio < dstRatio {
		cropH := int(float64(b.Dx()) / dstRatio)
		y0 := b.Min.Y + (b.Dy()-cropH)/2
		crop = image.Rect(b.Min.X, y0, b.Max.X, y0+cropH)
	}
	dst := image.NewRGBA(image.Rect(0, 0, width, height))
	xdraw.CatmullRom.Scale(dst, dst.Bounds(), src, crop, xdraw.Over, nil)
	return dst
}

func normalizeRGBA(src image.Image) image.Image {
	b := src.Bounds()
	dst := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
	xdraw.Draw(dst, dst.Bounds(), src, b.Min, xdraw.Src)
	return dst
}

func rgba8(c color.Color) (int, int, int) {
	r, g, b, _ := c.RGBA()
	return int(r >> 8), int(g >> 8), int(b >> 8)
}