package imgcache

import (
	"bytes"
	"errors"
	"fmt"
	"image/color"
	"io"
	"os"
	"testing"
	"time"

	"sneak.berlin/go/pixa/internal/imageprocessor"
	"sneak.berlin/go/pixa/internal/imagerequest"
	"sneak.berlin/go/pixa/internal/magic"
)

// TestGetVariant_ContentTypeFromFirstBytes stores an image in each output
// format as a variant, recorded with the content type text/plain, and checks
// that GetVariant serves it whole with the content type of its format, read
// from the file.
func TestGetVariant_ContentTypeFromFirstBytes(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<30)
	processor := imageprocessor.New(imageprocessor.Params{})
	source := generateTestJPEG(t, 40, 30, color.RGBA{200, 40, 40, 255})

	for _, format := range []imagerequest.Format{
		imagerequest.FormatJPEG, imagerequest.FormatPNG, imagerequest.FormatGIF,
		imagerequest.FormatWebP, imagerequest.FormatAVIF, imagerequest.FormatJXL,
	} {
		result, err := processor.Process(t.Context(), bytes.NewReader(source),
			&imagerequest.Transform{
				Size:    imagerequest.Size{Width: 20, Height: 15},
				Format:  format,
				Quality: 85,
				FitMode: imagerequest.FitCover,
			})
		if err != nil {
			t.Fatalf("making a %s image: %v", format, err)
		}

		image, err := io.ReadAll(result.Content)
		if err != nil {
			t.Fatalf("reading the %s image: %v", format, err)
		}

		key := imagerequest.VariantKey("aabbccdd10" + string(format))

		err = cache.StoreVariant(t.Context(), key, bytes.NewReader(image), "text/plain")
		if err != nil {
			t.Fatalf("StoreVariant(%s) error = %v", format, err)
		}

		reader, size, contentType, err := cache.GetVariant(key)
		if err != nil {
			t.Fatalf("GetVariant(%s) error = %v", format, err)
		}

		served, err := io.ReadAll(reader)
		_ = reader.Close()

		if err != nil {
			t.Fatalf("reading the %s variant: %v", format, err)
		}

		t.Logf("%s: %d bytes served as %s", format, size, contentType)

		if want := imageprocessor.FormatToMIME(format); contentType != want {
			t.Errorf("%s variant content type = %q, want %q", format, contentType, want)
		}

		if size != int64(len(image)) || !bytes.Equal(served, image) {
			t.Errorf("%s variant served %d bytes, size %d, want the %d bytes stored",
				format, len(served), size, len(image))
		}
	}
}

// TestGetVariant_RefusesFileOfNoOutputFormat checks that GetVariant refuses
// a variant file whose first bytes are not those of an output format, with
// an error other than ErrNotFound, and that a variant with no file, or any
// variant of a disabled cache, is ErrNotFound.
func TestGetVariant_RefusesFileOfNoOutputFormat(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<30)
	jpegImage := generateTestJPEG(t, 10, 10, color.RGBA{0, 0, 255, 255})

	tests := []struct {
		name    string
		content []byte
		wantErr error
	}{
		{"text", []byte("this is text, not an image"), magic.ErrUnknownFormat},
		{"SVG", []byte(`<svg xmlns="http://www.w3.org/2000/svg"></svg>`),
			errNotAnOutputFormat},
		{"JPEG cut to 10 bytes", jpegImage[:10], io.EOF},
		{"empty", nil, io.EOF},
	}

	for i, tt := range tests {
		key := imagerequest.VariantKey(fmt.Sprintf("aabbccdd20%02d", i))

		_, err := cache.variants.Store(key, bytes.NewReader(tt.content))
		if err != nil {
			t.Fatalf("%s: storing the variant file: %v", tt.name, err)
		}

		reader, _, contentType, err := cache.GetVariant(key)
		t.Logf("%s: GetVariant() error = %v", tt.name, err)

		if reader != nil || contentType != "" || !errors.Is(err, tt.wantErr) {
			t.Errorf("%s: GetVariant() = reader %v, content type %q, error %v; "+
				"want no reader and %v", tt.name, reader, contentType, err, tt.wantErr)
		}
	}

	reader, _, _, err := cache.GetVariant(testVariantKeyFour)
	if reader != nil || !errors.Is(err, ErrNotFound) {
		t.Errorf("GetVariant() of a variant with no file = reader %v, error %v; "+
			"want no reader and %v", reader, err, ErrNotFound)
	}

	disabled, _ := newEvictionTestCache(t, 0)

	reader, _, _, err = disabled.GetVariant(testVariantKeyOne)
	if reader != nil || !errors.Is(err, ErrNotFound) {
		t.Errorf("GetVariant() on a disabled cache = reader %v, error %v; "+
			"want no reader and %v", reader, err, ErrNotFound)
	}
}

// TestService_Get_MakesAgainVariantOfNoOutputFormat replaces a cached
// variant's file with text, and checks that the next request is a miss
// answered with the variant made again, and the one after a hit.
func TestService_Get_MakesAgainVariantOfNoOutputFormat(t *testing.T) {
	t.Parallel()

	svc, fixtures := SetupTestService(t)
	req := photoVariant(fixtures, 85, imagerequest.FitCover)

	want, _ := getImage(t, svc, req)

	path := svc.cache.variants.keyToPath(imagerequest.CacheKey(req))

	err := os.WriteFile(path, []byte("this is text, not an image"), StorageFilePerm)
	if err != nil {
		t.Fatalf("replacing the variant file: %v", err)
	}

	got, status := getImage(t, svc, req)
	t.Logf("after the replacement: %d bytes, %s", len(got), status)

	if status != CacheMiss || !bytes.Equal(got, want) {
		t.Errorf("after the replacement: Get() = %d bytes, %s; want the %d bytes "+
			"made again, %s", len(got), status, len(want), CacheMiss)
	}

	got, status = getImage(t, svc, req)

	if status != CacheHit || !bytes.Equal(got, want) {
		t.Errorf("next request: Get() = %d bytes, %s; want the %d bytes, %s",
			len(got), status, len(want), CacheHit)
	}
}

// TestService_Get_HitWaitsForNoDatabaseWrite holds the database's one
// connection while a cached variant is requested. The hit must be answered
// while the connection is still held, and its access time and hit count
// must reach the database once it is free.
func TestService_Get_HitWaitsForNoDatabaseWrite(t *testing.T) {
	t.Parallel()

	svc, fixtures := SetupTestService(t)
	req := photoVariant(fixtures, 85, imagerequest.FitCover)
	key := imagerequest.CacheKey(req)

	getImage(t, svc, req)
	waitForPendingCountsWritten(t, svc.cache)

	anHourAgo := time.Now().Add(-time.Hour)
	setVariantLastAccessed(t, svc.cache, key, anHourAgo)

	want := readCacheStatsCounters(t, svc.cache)
	want.hitCount++

	releaseDatabase := holdDatabase(t, svc.cache)
	defer releaseDatabase()

	results := startGet(t.Context(), svc, req)

	select {
	case got := <-results:
		if got.err != nil {
			t.Fatalf("Get() of the cached variant error = %v", got.err)
		}
	case <-time.After(pendingCountsWait):
		t.Fatal("the cache hit waited for the database")
	}

	releaseDatabase()

	waitForCounters(t, svc.cache, want)

	deadline := time.Now().Add(pendingCountsWait)

	for countRows(t, svc.cache, `
		SELECT COUNT(*) FROM variant_content
		WHERE cache_key = ? AND last_accessed_at > ?
	`, string(key), anHourAgo.UTC().Format(sqliteTimestampFormat)) == 0 {
		if time.Now().After(deadline) {
			t.Fatal("the hit's access time was not written")
		}

		time.Sleep(10 * time.Millisecond)
	}
}

// TestTouchVariantAndTouchSourceContent_DropAccessTimesPastTheLimit hands one
// more access time of a variant, and one more of a source, than may wait to
// be written. touchVariant and touchSourceContent must return each time
// without waiting, and the last of each must be dropped.
func TestTouchVariantAndTouchSourceContent_DropAccessTimesPastTheLimit(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<30)

	done := make(chan struct{})

	go func() {
		defer close(done)

		for range maxPendingAccessTimes + 1 {
			cache.touchVariant(testVariantKeyOne)
			cache.touchSourceContent("aabbccdd3001")
		}
	}()

	select {
	case <-done:
	case <-time.After(pendingCountsWait):
		t.Fatal("touchVariant or touchSourceContent waited once the access " +
			"times reached the limit")
	}

	if waiting := len(cache.pendingVariantAccessTimes); waiting != maxPendingAccessTimes {
		t.Errorf("%d access times of variants wait to be written, want %d",
			waiting, maxPendingAccessTimes)
	}

	if waiting := len(cache.pendingSourceAccessTimes); waiting != maxPendingAccessTimes {
		t.Errorf("%d access times of sources wait to be written, want %d",
			waiting, maxPendingAccessTimes)
	}
}

// TestStopPendingCountWrites_WritesPendingAccessTimes hands the access time
// of one of two variants, three times, then stops the goroutine that writes
// them, which never started. The stop must write that access time and
// leave the other variant's.
func TestStopPendingCountWrites_WritesPendingAccessTimes(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<30)
	anHourAgo := time.Now().Add(-time.Hour)

	for _, key := range []imagerequest.VariantKey{testVariantKeyOne, testVariantKeyTwo} {
		storeEvictionTestVariant(t, cache, key, []byte("variant bytes"))
		setVariantLastAccessed(t, cache, key, anHourAgo)
	}

	for range 3 {
		cache.touchVariant(testVariantKeyOne)
	}

	err := cache.StopPendingCountWrites(t.Context())
	if err != nil {
		t.Fatalf("StopPendingCountWrites() error = %v", err)
	}

	for key, wantTouched := range map[imagerequest.VariantKey]int{
		testVariantKeyOne: 1, testVariantKeyTwo: 0,
	} {
		touched := countRows(t, cache, `
			SELECT COUNT(*) FROM variant_content
			WHERE cache_key = ? AND last_accessed_at > ?
		`, string(key), anHourAgo.UTC().Format(sqliteTimestampFormat))
		if touched != wantTouched {
			t.Errorf("variant %s: %d rows with a new access time, want %d",
				key, touched, wantTouched)
		}
	}

	if waiting := len(cache.pendingVariantAccessTimes); waiting != 0 {
		t.Errorf("%d access times still wait to be written, want 0", waiting)
	}
}