package assets

import (
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

var upscaleBackends = []string{"upscayl-bin", "upscayl", "realesrgan-ncnn-vulkan", "waifu2x-ncnn-vulkan"}

// runUpscale upscales textures in place through an installed ncnn-vulkan
// backend. DDS inputs are bridged through PNG so the NWN flip stays correct.
func runUpscale(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("upscale", flag.ContinueOnError)
	fs.SetOutput(stderr)
	scale := fs.Int("scale", 4, "upscale factor")
	backend := fs.String("backend", "", "override the upscaler binary")
	nonRecursive := fs.Bool("non-recursive", false, "do not descend into subdirectories")
	if err := fs.Parse(args); err != nil {
		return exitUsage
	}
	dirs := fs.Args()
	if len(dirs) == 0 {
		fmt.Fprintln(stderr, "assets upscale: usage: upscale [--scale N] <dir>...")
		return exitUsage
	}

	candidates := upscaleBackends
	if *backend != "" {
		candidates = []string{*backend}
	}
	tool := look(candidates...)
	if tool == "" {
		fmt.Fprintf(stderr, "assets upscale: no upscaler found — install one of: %s\n", strings.Join(upscaleBackends, ", "))
		return exitTool
	}

	files, err := walk(dirs, textureExts, !*nonRecursive)
	if err != nil {
		fmt.Fprintln(stderr, "assets upscale:", err)
		return exitUsage
	}

	// magick is only needed if a .dds input is present; resolve lazily.
	magick := ""
	failed := false
	for _, src := range files {
		var upErr error
		if strings.EqualFold(filepath.Ext(src), ".dds") {
			if magick == "" {
				if magick = look("magick"); magick == "" {
					fmt.Fprintln(stderr, "assets upscale: .dds input needs ImageMagick (magick) for the png bridge")
					return exitTool
				}
			}
			upErr = upscaleDDS(tool, magick, src, *scale)
		} else {
			upErr = upscaleImage(tool, src, src, *scale)
		}
		if upErr != nil {
			fmt.Fprintf(stderr, "assets upscale: %s: %v\n", src, upErr)
			failed = true
		}
	}
	if failed {
		return exitFail
	}
	return exitOK
}

// upscaleImage runs the ncnn-vulkan backend to upscale src into dst (may be the
// same path).
func upscaleImage(tool, src, dst string, scale int) error {
	tmp := dst + ".upscaled.png"
	out, err := runner("", nil, tool, "-i", src, "-o", tmp, "-s", strconv.Itoa(scale))
	if err != nil {
		return fmt.Errorf("%s: %v: %s", filepath.Base(tool), err, strings.TrimSpace(string(out)))
	}
	return os.Rename(tmp, dst)
}

// upscaleDDS bridges a DDS through PNG: dds->png (flip), upscale, png->dds
// (flip back), yielding a correctly-flipped upscaled DDS.
func upscaleDDS(tool, magick, src string, scale int) error {
	tmpPNG := src + ".bridge.png"
	if err := ddsToPNG(magick, src, tmpPNG); err != nil {
		return err
	}
	defer os.Remove(tmpPNG)
	if err := upscaleImage(tool, tmpPNG, tmpPNG, scale); err != nil {
		return err
	}
	return pngToDDS(magick, tmpPNG, src)
}