package mediaapi

import (
	"bytes"
	"context"
	"errors"
	"image"
	"image/color"
	"image/gif"
	"image/jpeg"
	"image/png"
	"io"
	"log/slog"
	"net/http"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/dariuszjaniak/warp/server/internal/config"
	"github.com/dariuszjaniak/warp/server/internal/federation"
	"github.com/dariuszjaniak/warp/server/internal/storage"
	_ "github.com/dariuszjaniak/warp/server/internal/storage/drivers"
	"github.com/dariuszjaniak/warp/server/internal/storage/filestore"
)

const (
	serverName = "warp.example"
	alice      = "@alice:warp.example"
	bob        = "@bob:warp.example"
)

// fakeRemote stands in for the federation client.
type fakeRemote struct {
	mu        sync.Mutex
	media     map[string]federation.MediaResponse
	content   map[string][]byte
	thumbs    map[string][]byte
	err       error
	downloads atomic.Int32
	thumbAsks atomic.Int32
	// gate, when set, holds every download until it is closed.
	gate chan struct{}
}

func (f *fakeRemote) DownloadMedia(_ context.Context, origin, mediaID string, _ time.Duration) (federation.MediaResponse, error) {
	f.downloads.Add(1)
	if f.gate != nil {
		<-f.gate
	}
	if f.err != nil {
		return federation.MediaResponse{}, f.err
	}
	f.mu.Lock()
	defer f.mu.Unlock()
	resp, ok := f.media[origin+"/"+mediaID]
	if !ok {
		return federation.MediaResponse{}, &federation.HTTPError{Status: http.StatusNotFound, Code: "M_NOT_FOUND"}
	}
	resp.Body = io.NopCloser(bytes.NewReader(f.content[origin+"/"+mediaID]))
	return resp, nil
}

func (f *fakeRemote) MediaThumbnail(_ context.Context, origin, mediaID string, req federation.ThumbnailRequest, _ time.Duration) (federation.MediaResponse, error) {
	f.thumbAsks.Add(1)
	f.mu.Lock()
	defer f.mu.Unlock()
	data, ok := f.thumbs[origin+"/"+mediaID]
	if !ok {
		return federation.MediaResponse{}, &federation.HTTPError{Status: http.StatusNotFound, Code: "M_NOT_FOUND"}
	}
	return federation.MediaResponse{ContentType: "image/png", Body: io.NopCloser(bytes.NewReader(data))}, nil
}

type testAPI struct {
	*API
	store  storage.MediaStore
	remote *fakeRemote
	now    *atomic.Int64
}

func newTestAPI(t *testing.T, tweak func(*config.Media)) *testAPI {
	t.Helper()
	dir := t.TempDir()
	db, err := storage.Open(t.Context(), storage.Config{
		Driver:           storage.DriverSQLite,
		ConnectionString: "file:" + filepath.ToSlash(filepath.Join(dir, "warp.db")) + "?_pragma=busy_timeout(5000)",
		MaxOpenConns:     4,
	}, slog.New(slog.DiscardHandler))
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = db.Close() })
	if err := db.Migrate(t.Context()); err != nil {
		t.Fatal(err)
	}
	blobs, err := filestore.New(filepath.Join(dir, "media"))
	if err != nil {
		t.Fatal(err)
	}

	cfg := config.Default().Media
	if tweak != nil {
		tweak(&cfg)
	}
	now := &atomic.Int64{}
	now.Store(time.Date(2026, 10, 16, 12, 0, 0, 0, time.UTC).UnixMilli())
	remote := &fakeRemote{media: map[string]federation.MediaResponse{}, content: map[string][]byte{}, thumbs: map[string][]byte{}}
	api, err := New(Options{
		ServerName: serverName,
		Store:      db.Media(),
		Blobs:      blobs,
		Remote:     remote,
		Config:     cfg,
		Logger:     slog.New(slog.DiscardHandler),
		Now:        func() time.Time { return time.UnixMilli(now.Load()) },
	})
	if err != nil {
		t.Fatal(err)
	}
	return &testAPI{API: api, store: db.Media(), remote: remote, now: now}
}

func readAll(t *testing.T, c Content) []byte {
	t.Helper()
	defer func() { _ = c.Body.Close() }()
	data, err := io.ReadAll(c.Body)
	if err != nil {
		t.Fatal(err)
	}
	return data
}

func mediaIDOf(t *testing.T, mxc string) string {
	t.Helper()
	rest, ok := strings.CutPrefix(mxc, "mxc://"+serverName+"/")
	if !ok || !ValidMediaID(rest) {
		t.Fatalf("bad mxc URI %q", mxc)
	}
	return rest
}

func TestUploadAndDownload(t *testing.T) {
	api := newTestAPI(t, nil)
	ctx := t.Context()

	mxc, err := api.Upload(ctx, Upload{
		UserID: alice, ContentType: "text/plain; charset=utf-8", FileName: "hello.txt",
		Body: strings.NewReader("hello, world"),
	})
	if err != nil {
		t.Fatalf("Upload: %v", err)
	}
	id := mediaIDOf(t, mxc)

	c, err := api.Download(ctx, serverName, id, FetchOptions{})
	if err != nil {
		t.Fatalf("Download: %v", err)
	}
	if got := readAll(t, c); string(got) != "hello, world" {
		t.Errorf("content = %q", got)
	}
	if c.ContentType != "text/plain; charset=utf-8" || c.FileName != "hello.txt" || c.Size != 12 || len(c.SHA256) != 64 {
		t.Errorf("content metadata = %+v", c)
	}

	for _, bad := range []struct{ origin, id string }{
		{serverName, "nope"},
		{serverName, "../etc"},
		{"bad/server", id},
	} {
		if _, err := api.Download(ctx, bad.origin, bad.id, FetchOptions{}); !errors.Is(err, ErrNotFound) {
			t.Errorf("Download(%s, %s) = %v, want ErrNotFound", bad.origin, bad.id, err)
		}
	}
}

func TestUploadNormalisesContentType(t *testing.T) {
	for raw, want := range map[string]string{
		"":                      "application/octet-stream",
		"not a type;;":          "application/octet-stream",
		"Image/PNG":             "image/png",
		"text/plain; charset=x": "text/plain; charset=x",
	} {
		if got := normaliseContentType(raw); got != want {
			t.Errorf("normaliseContentType(%q) = %q, want %q", raw, got, want)
		}
	}
}

func TestUploadTooLarge(t *testing.T) {
	api := newTestAPI(t, func(m *config.Media) { m.MaxUploadBytes = 10 })
	_, err := api.Upload(t.Context(), Upload{UserID: alice, Body: strings.NewReader("eleven bytes")})
	if !errors.Is(err, ErrTooLarge) {
		t.Fatalf("Upload = %v, want ErrTooLarge", err)
	}
}

func TestMediaIDs(t *testing.T) {
	seen := map[string]bool{}
	for range 1000 {
		id := newMediaID()
		if len(id) != mediaIDLength || !ValidMediaID(id) {
			t.Fatalf("bad media ID %q", id)
		}
		if seen[id] {
			t.Fatalf("media ID %q generated twice", id)
		}
		seen[id] = true
	}
}

func TestCreateAndUploadTo(t *testing.T) {
	api := newTestAPI(t, func(m *config.Media) { m.MaxPendingUploads = 2 })
	ctx := t.Context()

	mxc, expires, err := api.Create(ctx, alice)
	if err != nil {
		t.Fatalf("Create: %v", err)
	}
	if want := api.now.Load() + (24 * time.Hour).Milliseconds(); expires != want {
		t.Errorf("expires = %d, want %d", expires, want)
	}
	id := mediaIDOf(t, mxc)

	// Not there yet: a download that does not wait is told so.
	if _, err := api.Download(ctx, serverName, id, FetchOptions{}); !errors.Is(err, ErrNotYetUploaded) {
		t.Errorf("Download of pending media = %v, want ErrNotYetUploaded", err)
	}

	up := func(user, body string) error {
		return api.UploadTo(ctx, serverName, id, Upload{UserID: user, ContentType: "text/plain", Body: strings.NewReader(body)})
	}
	if err := up(bob, "bob's"); !errors.Is(err, ErrNotYours) {
		t.Errorf("UploadTo by another user = %v, want ErrNotYours", err)
	}
	if err := up(alice, "alice's"); err != nil {
		t.Fatalf("UploadTo: %v", err)
	}
	if err := up(alice, "again"); !errors.Is(err, ErrCannotOverwrite) {
		t.Errorf("second UploadTo = %v, want ErrCannotOverwrite", err)
	}
	c, err := api.Download(ctx, serverName, id, FetchOptions{})
	if err != nil {
		t.Fatalf("Download: %v", err)
	}
	if got := readAll(t, c); string(got) != "alice's" {
		t.Errorf("content = %q", got)
	}

	// The limit counts reservations without content.
	if _, _, err := api.Create(ctx, alice); err != nil {
		t.Fatal(err)
	}
	if _, _, err := api.Create(ctx, alice); err != nil {
		t.Fatal(err)
	}
	if _, _, err := api.Create(ctx, alice); !errors.Is(err, ErrTooManyPending) {
		t.Errorf("third pending Create = %v, want ErrTooManyPending", err)
	}
	if _, _, err := api.Create(ctx, bob); err != nil {
		t.Errorf("another user's Create: %v", err)
	}

	// A day later the reservations have lapsed: they no longer count,
	// and their IDs no longer take content.
	lapsed, _, _ := api.Create(ctx, bob)
	api.now.Add((25 * time.Hour).Milliseconds())
	err = api.UploadTo(ctx, serverName, mediaIDOf(t, lapsed), Upload{UserID: bob, Body: strings.NewReader("late")})
	if !errors.Is(err, ErrNotFound) {
		t.Errorf("UploadTo a lapsed ID = %v, want ErrNotFound", err)
	}
	if _, _, err := api.Create(ctx, alice); err != nil {
		t.Errorf("Create after the reservations lapsed: %v", err)
	}
}

func TestDownloadWaitsForPendingContent(t *testing.T) {
	api := newTestAPI(t, nil)
	ctx := t.Context()
	// The wait uses the real clock for its timer; only the deadline is
	// computed from the API's clock, which this test leaves running.
	api.API.now = time.Now

	mxc, _, err := api.Create(ctx, alice)
	if err != nil {
		t.Fatal(err)
	}
	id := mediaIDOf(t, mxc)

	done := make(chan error, 1)
	go func() {
		c, err := api.Download(ctx, serverName, id, FetchOptions{Wait: 10 * time.Second})
		if err == nil {
			_ = c.Body.Close()
		}
		done <- err
	}()
	time.Sleep(50 * time.Millisecond)
	if err := api.UploadTo(ctx, serverName, id, Upload{UserID: alice, Body: strings.NewReader("now")}); err != nil {
		t.Fatal(err)
	}
	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("waiting Download = %v", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("the upload did not wake the waiting download")
	}

	// A wait that runs out is ErrNotYetUploaded.
	other, _, _ := api.Create(ctx, alice)
	start := time.Now()
	_, err = api.Download(ctx, serverName, mediaIDOf(t, other), FetchOptions{Wait: 100 * time.Millisecond})
	if !errors.Is(err, ErrNotYetUploaded) {
		t.Errorf("Download after the wait = %v, want ErrNotYetUploaded", err)
	}
	if time.Since(start) < 100*time.Millisecond {
		t.Error("Download did not wait")
	}
}

func TestRemoteMediaIsFetchedOnceAndCached(t *testing.T) {
	api := newTestAPI(t, nil)
	ctx := t.Context()
	api.remote.media["remote.example/abc"] = federation.MediaResponse{
		ContentType: "image/png", ContentDisposition: `inline; filename="dir/cat.png"`,
	}
	api.remote.content["remote.example/abc"] = []byte("png bytes")
	api.remote.gate = make(chan struct{})

	const callers = 5
	var wg sync.WaitGroup
	errs := make(chan error, callers)
	for range callers {
		wg.Go(func() {
			c, err := api.Download(ctx, "remote.example", "abc", FetchOptions{})
			if err != nil {
				errs <- err
				return
			}
			if got := readAll(t, c); string(got) != "png bytes" {
				errs <- errors.New("wrong content: " + string(got))
			}
			if c.FileName != "cat.png" {
				errs <- errors.New("file name kept its directory: " + c.FileName)
			}
		})
	}
	time.Sleep(50 * time.Millisecond)
	close(api.remote.gate)
	wg.Wait()
	close(errs)
	for err := range errs {
		t.Error(err)
	}
	if n := api.remote.downloads.Load(); n != 1 {
		t.Errorf("%d downloads for %d concurrent requests, want 1", n, callers)
	}

	// Cached: served without asking again, even with federation off.
	api.remote.err = federation.ErrDisabled
	c, err := api.Download(ctx, "remote.example", "abc", FetchOptions{})
	if err != nil {
		t.Fatalf("cached Download: %v", err)
	}
	_ = c.Body.Close()
	if n := api.remote.downloads.Load(); n != 1 {
		t.Errorf("cached media was fetched again (%d downloads)", n)
	}

	// Another server asking for it is not served a third server's media.
	if _, err := api.Download(ctx, "remote.example", "abc", FetchOptions{LocalOnly: true}); !errors.Is(err, ErrNotFound) {
		t.Errorf("LocalOnly Download of remote media = %v, want ErrNotFound", err)
	}
}

func TestRemoteErrors(t *testing.T) {
	for name, tc := range map[string]struct {
		err  error
		want error
	}{
		"federation off":  {federation.ErrDisabled, ErrFederationDisabled},
		"not allowed":     {federation.ErrNotAllowed, ErrFederationDisabled},
		"not found":       {&federation.HTTPError{Status: 404, Code: "M_NOT_FOUND"}, ErrNotFound},
		"not uploaded":    {&federation.HTTPError{Status: 504, Code: "M_NOT_YET_UPLOADED"}, ErrNotYetUploaded},
		"too large":       {&federation.HTTPError{Status: 413, Code: "M_TOO_LARGE"}, ErrTooLarge},
		"server error":    {&federation.HTTPError{Status: 500}, ErrRemote},
		"network failure": {errors.New("connection refused"), ErrRemote},
	} {
		t.Run(name, func(t *testing.T) {
			api := newTestAPI(t, nil)
			api.remote.err = tc.err
			_, err := api.Download(t.Context(), "remote.example", "abc", FetchOptions{})
			if !errors.Is(err, tc.want) {
				t.Errorf("Download = %v, want %v", err, tc.want)
			}
		})
	}

	api := newTestAPI(t, nil)
	api.remote.content["remote.example/big"] = bytes.Repeat([]byte("x"), 100)
	api.remote.media["remote.example/big"] = federation.MediaResponse{ContentType: "text/plain"}
	api.cfg.MaxUploadBytes = 10
	if _, err := api.Download(t.Context(), "remote.example", "big", FetchOptions{}); !errors.Is(err, ErrTooLarge) {
		t.Errorf("Download of oversized remote media = %v, want ErrTooLarge", err)
	}
}

// --- thumbnails ---------------------------------------------------------------

func testImage(w, h int) *image.RGBA {
	img := image.NewRGBA(image.Rect(0, 0, w, h))
	for y := range h {
		for x := range w {
			img.Set(x, y, color.RGBA{uint8(x), uint8(y), 128, 255})
		}
	}
	return img
}

func encodePNG(t *testing.T, img image.Image) []byte {
	t.Helper()
	var buf bytes.Buffer
	if err := png.Encode(&buf, img); err != nil {
		t.Fatal(err)
	}
	return buf.Bytes()
}

func uploadBytes(t *testing.T, api *testAPI, contentType string, data []byte) string {
	t.Helper()
	mxc, err := api.Upload(t.Context(), Upload{UserID: alice, ContentType: contentType, Body: bytes.NewReader(data)})
	if err != nil {
		t.Fatal(err)
	}
	return mediaIDOf(t, mxc)
}

func decodeThumbnail(t *testing.T, c Content) image.Image {
	t.Helper()
	img, _, err := image.Decode(bytes.NewReader(readAll(t, c)))
	if err != nil {
		t.Fatalf("thumbnail does not decode: %v", err)
	}
	return img
}

func TestThumbnails(t *testing.T) {
	api := newTestAPI(t, nil)
	ctx := t.Context()
	id := uploadBytes(t, api, "image/png", encodePNG(t, testImage(1000, 500)))

	for _, tc := range []struct {
		req          ThumbnailRequest
		wantW, wantH int
	}{
		// The smallest crop size that covers 50 × 50 is 96 × 96.
		{ThumbnailRequest{Width: 50, Height: 50, Method: MethodCrop}, 96, 96},
		{ThumbnailRequest{Width: 20, Height: 20, Method: MethodCrop}, 32, 32},
		// 320 × 240 scaled from 2:1 keeps the ratio: 320 × 160.
		{ThumbnailRequest{Width: 300, Height: 200, Method: MethodScale}, 320, 160},
		// Larger than every size: the largest, 800 × 600 → 800 × 400.
		{ThumbnailRequest{Width: 2000, Height: 2000, Method: MethodScale}, 800, 400},
	} {
		c, err := api.Thumbnail(ctx, serverName, id, tc.req, FetchOptions{})
		if err != nil {
			t.Fatalf("Thumbnail(%+v): %v", tc.req, err)
		}
		if c.ContentType != "image/png" {
			t.Errorf("Thumbnail(%+v) is %s, want image/png", tc.req, c.ContentType)
		}
		b := decodeThumbnail(t, c).Bounds()
		if b.Dx() != tc.wantW || b.Dy() != tc.wantH {
			t.Errorf("Thumbnail(%+v) is %d × %d, want %d × %d", tc.req, b.Dx(), b.Dy(), tc.wantW, tc.wantH)
		}
	}

	// The second ask for a size is answered from the stored thumbnail.
	first, _ := api.store.Thumbnail(ctx, serverName, id, 96, 96, MethodCrop)
	c, err := api.Thumbnail(ctx, serverName, id, ThumbnailRequest{Width: 96, Height: 96, Method: MethodCrop}, FetchOptions{})
	if err != nil {
		t.Fatal(err)
	}
	_ = c.Body.Close()
	if c.SHA256 != first.SHA256 {
		t.Error("the stored thumbnail was not reused")
	}
}

func TestThumbnailOfSmallImageIsTheOriginal(t *testing.T) {
	api := newTestAPI(t, nil)
	original := encodePNG(t, testImage(100, 50))
	id := uploadBytes(t, api, "image/png", original)

	c, err := api.Thumbnail(t.Context(), serverName, id, ThumbnailRequest{Width: 640, Height: 480, Method: MethodScale}, FetchOptions{})
	if err != nil {
		t.Fatal(err)
	}
	if got := readAll(t, c); !bytes.Equal(got, original) {
		t.Error("a thumbnail larger than the image was not the image itself")
	}

	// A crop of a small image is never enlarged: 100 × 50 cropped to a
	// square is 50 × 50.
	c, err = api.Thumbnail(t.Context(), serverName, id, ThumbnailRequest{Width: 96, Height: 96, Method: MethodCrop}, FetchOptions{})
	if err != nil {
		t.Fatal(err)
	}
	if b := decodeThumbnail(t, c).Bounds(); b.Dx() != 50 || b.Dy() != 50 {
		t.Errorf("crop of a small image is %d × %d, want 50 × 50", b.Dx(), b.Dy())
	}
}

func TestThumbnailOfGIFIsStill(t *testing.T) {
	api := newTestAPI(t, nil)
	pal := image.NewPaletted(image.Rect(0, 0, 10, 10), []color.Color{color.Black, color.White})
	var buf bytes.Buffer
	if err := gif.EncodeAll(&buf, &gif.GIF{Image: []*image.Paletted{pal, pal}, Delay: []int{10, 10}}); err != nil {
		t.Fatal(err)
	}
	id := uploadBytes(t, api, "image/gif", buf.Bytes())
	c, err := api.Thumbnail(t.Context(), serverName, id, ThumbnailRequest{Width: 32, Height: 32, Method: MethodScale, Animated: true}, FetchOptions{})
	if err != nil {
		t.Fatal(err)
	}
	_ = c.Body.Close()
	if c.ContentType != "image/png" {
		t.Errorf("thumbnail of a GIF is %s, want a still image/png", c.ContentType)
	}
}

func TestThumbnailRefusals(t *testing.T) {
	api := newTestAPI(t, func(m *config.Media) { m.MaxThumbnailPixels = 100 * 100 })
	ctx := t.Context()
	req := ThumbnailRequest{Width: 32, Height: 32, Method: MethodCrop}

	text := uploadBytes(t, api, "text/plain", []byte("not an image"))
	if _, err := api.Thumbnail(ctx, serverName, text, req, FetchOptions{}); !errors.Is(err, ErrCannotThumbnail) {
		t.Errorf("thumbnail of text = %v, want ErrCannotThumbnail", err)
	}
	liar := uploadBytes(t, api, "image/png", []byte("not a png"))
	if _, err := api.Thumbnail(ctx, serverName, liar, req, FetchOptions{}); !errors.Is(err, ErrCannotThumbnail) {
		t.Errorf("thumbnail of a broken PNG = %v, want ErrCannotThumbnail", err)
	}
	huge := uploadBytes(t, api, "image/png", encodePNG(t, testImage(200, 200)))
	if _, err := api.Thumbnail(ctx, serverName, huge, req, FetchOptions{}); !errors.Is(err, ErrCannotThumbnail) {
		t.Errorf("thumbnail past the pixel limit = %v, want ErrCannotThumbnail", err)
	}

	none := newTestAPI(t, func(m *config.Media) { m.ThumbnailSizes = nil })
	id := uploadBytes(t, none, "image/png", encodePNG(t, testImage(10, 10)))
	if _, err := none.Thumbnail(ctx, serverName, id, req, FetchOptions{}); !errors.Is(err, ErrCannotThumbnail) {
		t.Errorf("thumbnail with no sizes configured = %v, want ErrCannotThumbnail", err)
	}
}

func TestRemoteThumbnail(t *testing.T) {
	api := newTestAPI(t, nil)
	ctx := t.Context()
	thumb := encodePNG(t, testImage(96, 96))
	api.remote.thumbs["remote.example/pic"] = thumb

	req := ThumbnailRequest{Width: 90, Height: 90, Method: MethodCrop}
	for range 2 {
		c, err := api.Thumbnail(ctx, "remote.example", "pic", req, FetchOptions{})
		if err != nil {
			t.Fatalf("Thumbnail: %v", err)
		}
		if got := readAll(t, c); !bytes.Equal(got, thumb) {
			t.Error("remote thumbnail content differs")
		}
	}
	if n := api.remote.thumbAsks.Load(); n != 1 {
		t.Errorf("remote thumbnail fetched %d times, want once", n)
	}
	if n := api.remote.downloads.Load(); n != 0 {
		t.Errorf("the original was downloaded %d times to make a thumbnail", n)
	}
}

func TestPickSize(t *testing.T) {
	api := newTestAPI(t, nil)
	for _, tc := range []struct {
		req  ThumbnailRequest
		want thumbnailSize
	}{
		{ThumbnailRequest{Width: 1, Height: 1, Method: MethodCrop}, thumbnailSize{Width: 32, Height: 32, Method: MethodCrop}},
		{ThumbnailRequest{Width: 33, Height: 10, Method: MethodCrop}, thumbnailSize{Width: 96, Height: 96, Method: MethodCrop}},
		{ThumbnailRequest{Width: 500, Height: 500, Method: MethodCrop}, thumbnailSize{Width: 96, Height: 96, Method: MethodCrop}},
		{ThumbnailRequest{Width: 640, Height: 100, Method: MethodScale}, thumbnailSize{Width: 640, Height: 480, Method: MethodScale}},
		{ThumbnailRequest{Width: 641, Height: 100, Method: MethodScale}, thumbnailSize{Width: 800, Height: 600, Method: MethodScale}},
	} {
		got, ok := api.pickSize(tc.req)
		if !ok || got != tc.want {
			t.Errorf("pickSize(%+v) = %+v, want %+v", tc.req, got, tc.want)
		}
	}

	scaleOnly := newTestAPI(t, func(m *config.Media) {
		m.ThumbnailSizes = []config.ThumbnailSize{{Width: 100, Height: 100, Method: MethodScale}}
	})
	if got, ok := scaleOnly.pickSize(ThumbnailRequest{Width: 32, Height: 32, Method: MethodCrop}); !ok || got.Method != MethodScale {
		t.Errorf("crop with only scale sizes = %+v, %v; want the scale size", got, ok)
	}
}

func TestFit(t *testing.T) {
	for _, tc := range []struct {
		srcW, srcH, boxW, boxH int
		method                 string
		outW, outH             int
		crop                   image.Rectangle
	}{
		{1000, 500, 96, 96, MethodCrop, 96, 96, image.Rect(250, 0, 750, 500)},
		{500, 1000, 96, 96, MethodCrop, 96, 96, image.Rect(0, 250, 500, 750)},
		{1000, 500, 320, 240, MethodScale, 320, 160, image.Rect(0, 0, 1000, 500)},
		{50, 20, 320, 240, MethodScale, 50, 20, image.Rect(0, 0, 50, 20)},
		{40, 80, 96, 96, MethodCrop, 40, 40, image.Rect(0, 20, 40, 60)},
	} {
		outW, outH, crop := fit(tc.srcW, tc.srcH, tc.boxW, tc.boxH, tc.method)
		if outW != tc.outW || outH != tc.outH || crop != tc.crop {
			t.Errorf("fit(%d×%d into %d×%d %s) = %d×%d from %v, want %d×%d from %v",
				tc.srcW, tc.srcH, tc.boxW, tc.boxH, tc.method, outW, outH, crop, tc.outW, tc.outH, tc.crop)
		}
	}
}

// jpegWithOrientation makes a JPEG with an EXIF orientation tag, the way a
// phone camera writes a portrait photo: landscape pixels, and a tag saying
// which way is up.
func jpegWithOrientation(t *testing.T, img image.Image, orientation int, bigEndian bool) []byte {
	t.Helper()
	var plain bytes.Buffer
	if err := jpeg.Encode(&plain, img, nil); err != nil {
		t.Fatal(err)
	}

	var tiff []byte
	if bigEndian {
		tiff = []byte{'M', 'M', 0, 42, 0, 0, 0, 8, 0, 1, 0x01, 0x12, 0, 3, 0, 0, 0, 1, 0, byte(orientation), 0, 0, 0, 0, 0, 0}
	} else {
		tiff = []byte{'I', 'I', 42, 0, 8, 0, 0, 0, 1, 0, 0x12, 0x01, 3, 0, 1, 0, 0, 0, byte(orientation), 0, 0, 0, 0, 0, 0, 0}
	}
	payload := append([]byte("Exif\x00\x00"), tiff...)
	length := len(payload) + 2
	app1 := append([]byte{0xFF, 0xE1, byte(length >> 8), byte(length)}, payload...)

	data := plain.Bytes()
	out := append([]byte{}, data[:2]...)
	out = append(out, app1...)
	return append(out, data[2:]...)
}

func TestJPEGOrientation(t *testing.T) {
	img := testImage(40, 20)
	for _, bigEndian := range []bool{false, true} {
		for o := 1; o <= 8; o++ {
			data := jpegWithOrientation(t, img, o, bigEndian)
			if got := jpegOrientation(bytes.NewReader(data)); got != o {
				t.Errorf("orientation %d (big endian %v) read as %d", o, bigEndian, got)
			}
		}
	}
	if got := jpegOrientation(strings.NewReader("not a jpeg")); got != 1 {
		t.Errorf("orientation of garbage = %d, want 1", got)
	}
}

func TestThumbnailIsTurnedUpright(t *testing.T) {
	api := newTestAPI(t, nil)
	// Stored 1000 × 500, tagged "a quarter turn clockwise": upright it is
	// 500 × 1000, portrait.
	id := uploadBytes(t, api, "image/jpeg", jpegWithOrientation(t, testImage(1000, 500), 6, false))
	c, err := api.Thumbnail(t.Context(), serverName, id, ThumbnailRequest{Width: 320, Height: 240, Method: MethodScale}, FetchOptions{})
	if err != nil {
		t.Fatal(err)
	}
	if c.ContentType != "image/jpeg" {
		t.Errorf("thumbnail of a JPEG is %s", c.ContentType)
	}
	if b := decodeThumbnail(t, c).Bounds(); b.Dx() != 120 || b.Dy() != 240 {
		t.Errorf("upright thumbnail is %d × %d, want 120 × 240", b.Dx(), b.Dy())
	}
}

func TestOrient(t *testing.T) {
	// A 2 × 1 image, red then blue; orientation 6 turns it a quarter
	// clockwise, so red ends up on top.
	img := image.NewRGBA(image.Rect(0, 0, 2, 1))
	red, blue := color.RGBA{255, 0, 0, 255}, color.RGBA{0, 0, 255, 255}
	img.SetRGBA(0, 0, red)
	img.SetRGBA(1, 0, blue)

	out := orient(img, 6).(*image.RGBA)
	if out.Bounds().Dx() != 1 || out.Bounds().Dy() != 2 {
		t.Fatalf("turned image is %v", out.Bounds())
	}
	if out.RGBAAt(0, 0) != red || out.RGBAAt(0, 1) != blue {
		t.Errorf("turned pixels are %v, %v", out.RGBAAt(0, 0), out.RGBAAt(0, 1))
	}
	out = orient(img, 8).(*image.RGBA)
	if out.RGBAAt(0, 0) != blue || out.RGBAAt(0, 1) != red {
		t.Errorf("anticlockwise pixels are %v, %v", out.RGBAAt(0, 0), out.RGBAAt(0, 1))
	}
}

func TestContentDisposition(t *testing.T) {
	for _, tc := range []struct {
		contentType, name, want string
	}{
		{"image/png", "", "inline"},
		{"image/png; foo=bar", "cat.png", "inline; filename=cat.png"},
		{"text/html", "page.html", "attachment; filename=page.html"},
		{"image/svg+xml", "", "attachment"},
		{"application/octet-stream", "a b.bin", `attachment; filename="a b.bin"`},
		{"text/plain", "zażółć.txt", "inline; filename*=utf-8''za%C5%BC%C3%B3%C5%82%C4%87.txt"},
	} {
		if got := ContentDisposition(tc.contentType, tc.name); got != tc.want {
			t.Errorf("ContentDisposition(%q, %q) = %q, want %q", tc.contentType, tc.name, got, tc.want)
		}
	}
}

func TestFileNameFrom(t *testing.T) {
	for in, want := range map[string]string{
		"":                                        "",
		`attachment; filename="a.txt"`:            "a.txt",
		`inline; filename="../../etc/passwd"`:     "passwd",
		`inline; filename*=utf-8''%C5%BC.png`:     "ż.png",
		"this is not a disposition header at all": "",
	} {
		if got := fileNameFrom(in); got != want {
			t.Errorf("fileNameFrom(%q) = %q, want %q", in, got, want)
		}
	}
}