package media

import (
	"fmt"

	"github.com/davidbyttow/govips/v2/vips"
)

// ConvertAndResize loads the image at src, optionally resizes it to width pixels
// wide (maintaining aspect ratio), and exports it in the requested format.
//
// width <= 0 means no resize. format must be "webp" or "jpeg".
func ConvertAndResize(src string, width int, format string) ([]byte, error) {
	img, err := vips.NewImageFromFile(src)
	if err != nil {
		return nil, fmt.Errorf("load image %s: %w", src, err)
	}
	defer img.Close()

	if width > 0 && width < img.Width() {
		scale := float64(width) / float64(img.Width())
		if err := img.Resize(scale, vips.KernelLanczos3); err != nil {
			return nil, fmt.Errorf("resize: %w", err)
		}
	}

	switch format {
	case "webp":
		buf, _, err := img.ExportWebp(vips.NewWebpExportParams())
		if err != nil {
			return nil, fmt.Errorf("export webp: %w", err)
		}
		return buf, nil
	case "jpeg":
		buf, _, err := img.ExportJpeg(vips.NewJpegExportParams())
		if err != nil {
			return nil, fmt.Errorf("export jpeg: %w", err)
		}
		return buf, nil
	default:
		return nil, fmt.Errorf("unsupported format %q: must be webp or jpeg", format)
	}
}