package assets

import (
	"bytes"
	"os"
	"path/filepath"
	"testing"
)

func TestUpscalePNGUsesBackend(t *testing.T) {
	// A fake backend binary on PATH so look() resolves it.
	binDir := t.TempDir()
	fake := filepath.Join(binDir, "upscayl-bin")
	if err := os.WriteFile(fake, []byte("#!/bin/sh\n"), 0o755); err != nil {
		t.Fatal(err)
	}
	t.Setenv("PATH", binDir)

	// Stub runner: emulate `-i in -o out -s scale` by copying in->out.
	orig := runner
	defer func() { runner = orig }()
	var gotScale string
	runner = func(dir string, env []string, name string, args ...string) ([]byte, error) {
		var in, out string
		for i := 0; i < len(args)-1; i++ {
			switch args[i] {
			case "-i":
				in = args[i+1]
			case "-o":
				out = args[i+1]
			case "-s":
				gotScale = args[i+1]
			}
		}
		data, err := os.ReadFile(in)
		if err != nil {
			return nil, err
		}
		return nil, os.WriteFile(out, data, 0o644)
	}

	dir := t.TempDir()
	src := filepath.Join(dir, "tex.png")
	if err := os.WriteFile(src, []byte("pngdata"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := runUpscale([]string{"--scale", "2", dir}, &stdout, &stderr); code != exitOK {
		t.Fatalf("upscale exit = %d\n%s", code, stderr.String())
	}
	if gotScale != "2" {
		t.Fatalf("scale passed to backend = %q, want 2", gotScale)
	}
	if data, _ := os.ReadFile(src); string(data) != "pngdata" {
		t.Fatalf("upscaled file content = %q, want the backend output", data)
	}
}

func TestUpscaleNoBackendFailsClosed(t *testing.T) {
	t.Setenv("PATH", t.TempDir()) // empty PATH: no backend resolvable
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "tex.png"), []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := runUpscale([]string{dir}, &stdout, &stderr); code != exitTool {
		t.Fatalf("no-backend exit = %d, want %d", code, exitTool)
	}
}