package pipeline

import (
	"bytes"
	"fmt"
	"image"
	"image/jpeg"
	"image/png"
	"strings"

	"golang.org/x/image/tiff"
	_ "golang.org/x/image/webp" // decode-only; we re-encode webp as png
)

// RotateImage rotates src clockwise by angle (must be 0/90/180/270).
func RotateImage(src image.Image, angle int) image.Image {
	angle = ((angle % 360) + 360) % 360
	if angle == 0 {
		return src
	}
	b := src.Bounds()
	w, h := b.Dx(), b.Dy()
	switch angle {
	case 180:
		dst := image.NewRGBA(image.Rect(0, 0, w, h))
		for y := 0; y < h; y++ {
			for x := 0; x < w; x++ {
				dst.Set(w-1-x, h-1-y, src.At(b.Min.X+x, b.Min.Y+y))
			}
		}
		return dst
	case 90:
		dst := image.NewRGBA(image.Rect(0, 0, h, w))
		for y := 0; y < h; y++ {
			for x := 0; x < w; x++ {
				dst.Set(h-1-y, x, src.At(b.Min.X+x, b.Min.Y+y))
			}
		}
		return dst
	case 270:
		dst := image.NewRGBA(image.Rect(0, 0, h, w))
		for y := 0; y < h; y++ {
			for x := 0; x < w; x++ {
				dst.Set(y, w-1-x, src.At(b.Min.X+x, b.Min.Y+y))
			}
		}
		return dst
	}
	return src
}

// EncodeImage re-encodes img using format hint from the original filename / detected format.
// Falls back to PNG when format is not directly writable.
func EncodeImage(img image.Image, format string) ([]byte, string, error) {
	var buf bytes.Buffer
	switch strings.ToLower(format) {
	case "jpeg", "jpg":
		if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 92}); err != nil {
			return nil, "", err
		}
		return buf.Bytes(), "jpg", nil
	case "tiff", "tif":
		if err := tiff.Encode(&buf, img, &tiff.Options{Compression: tiff.Deflate}); err != nil {
			return nil, "", err
		}
		return buf.Bytes(), "tiff", nil
	case "png", "":
		if err := png.Encode(&buf, img); err != nil {
			return nil, "", err
		}
		return buf.Bytes(), "png", nil
	case "webp":
		// Re-encode to PNG (no webp encoder in stdlib/x/image).
		if err := png.Encode(&buf, img); err != nil {
			return nil, "", err
		}
		return buf.Bytes(), "png", nil
	}
	return nil, "", fmt.Errorf("unsupported format: %s", format)
}