package main

import (
	"context"
	"image"
	"image/color"
	"image/png"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"testing"
)

func TestDownloaderConvertsImageToJPEG(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "image/png")
		img := image.NewRGBA(image.Rect(0, 0, 2, 2))
		img.Set(0, 0, color.RGBA{R: 255, A: 255})
		_ = png.Encode(w, img)
	}))
	defer server.Close()

	destination := filepath.Join(t.TempDir(), "wallpaper.jpg")
	if err := newDownloader().download(context.Background(), server.URL, destination); err != nil {
		t.Fatal(err)
	}
	f, err := os.Open(destination)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	_, format, err := image.Decode(f)
	if err != nil {
		t.Fatal(err)
	}
	if format != "jpeg" {
		t.Fatalf("expected jpeg, got %s", format)
	}
}

func TestDownloaderRejectsNonImage(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		_, _ = w.Write([]byte("not an image"))
	}))
	defer server.Close()

	err := newDownloader().download(context.Background(), server.URL, filepath.Join(t.TempDir(), "wallpaper.jpg"))
	if err == nil {
		t.Fatal("expected non-image response to fail")
	}
}