package imgcache

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"sync"
	"testing"
	"time"
)

// webpRequest returns a request for a 100x100 WebP variant of path.
func webpRequest(path string) *ImageRequest {
	return &ImageRequest{
		SourceHost: testHostCDN,
		SourcePath: path,
		Size:       Size{Width: 100, Height: 100},
		Format:     FormatWebP,
		Quality:    85,
		FitMode:    FitCover,
	}
}

// assertVariantServed checks that GetVariant serves key with the given
// content and the image/webp content type storeEvictionTestVariant stores.
func assertVariantServed(t *testing.T, cache *Cache, key VariantKey, content []byte) {
	t.Helper()

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

	defer func() { _ = reader.Close() }()

	got, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("reading variant %s: %v", key, err)
	}

	if !bytes.Equal(got, content) {
		t.Errorf("GetVariant(%s) content = %q, want %q", key, got, content)
	}

	if size != int64(len(content)) {
		t.Errorf("GetVariant(%s) size = %d, want %d", key, size, len(content))
	}

	if contentType != testContentTypeWebP {
		t.Errorf("GetVariant(%s) content type = %q, want %q",
			key, contentType, testContentTypeWebP)
	}
}

// assertVariantNotFound checks that GetVariant refuses key with
// ErrNotFound.
func assertVariantNotFound(t *testing.T, cache *Cache, key VariantKey) {
	t.Helper()

	reader, _, _, err := cache.GetVariant(key)
	if err == nil {
		_ = reader.Close()
	}

	if !errors.Is(err, ErrNotFound) {
		t.Errorf("GetVariant(%s) error = %v, want ErrNotFound", key, err)
	}
}

// assertLookupMisses checks that Lookup reports request as a miss.
func assertLookupMisses(t *testing.T, cache *Cache, request *ImageRequest) {
	t.Helper()

	lookup, err := cache.Lookup(t.Context(), request)
	if err != nil {
		t.Fatalf("Lookup(%s) error = %v", request.SourcePath, err)
	}

	if lookup.Hit {
		t.Errorf("Lookup(%s) is a hit, want a miss", request.SourcePath)
	}
}

// TestSecondHitDoesNotReadMetaFile checks that once a variant has been
// stored or read, a hit takes its content type from memory: with the
// .meta file deleted, GetVariant must still return the stored content
// type rather than the application/octet-stream it uses without one.
func TestSecondHitDoesNotReadMetaFile(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<20)
	content := []byte("webp variant bytes")

	storeEvictionTestVariant(t, cache, testVariantKeyOne, content)

	// A second Cache on the same state directory starts with nothing in
	// memory, as pixad does after a restart, so its first read uses the
	// .meta file.
	restarted, err := NewCache(cache.db, cache.config)
	if err != nil {
		t.Fatalf("NewCache() error = %v", err)
	}

	assertVariantServed(t, restarted, testVariantKeyOne, content)

	err = os.Remove(cache.variants.keyToPath(testVariantKeyOne) + ".meta")
	if err != nil {
		t.Fatalf("removing .meta file: %v", err)
	}

	assertVariantServed(t, cache, testVariantKeyOne, content)
	assertVariantServed(t, restarted, testVariantKeyOne, content)
}

// TestReadDuringStoreKeepsStoredContentType checks that a GetVariant
// which began before StoreVariant finished cannot replace the content
// type the store kept in memory. Such a read can find the variant file
// but not yet its .meta file, and so gets application/octet-stream. The
// test deletes the .meta file after the store, then runs the part of
// GetVariant that comes after its check of memory.
func TestReadDuringStoreKeepsStoredContentType(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<20)
	content := []byte("webp variant bytes")

	storeEvictionTestVariant(t, cache, testVariantKeyOne, content)

	err := os.Remove(cache.variants.keyToPath(testVariantKeyOne) + ".meta")
	if err != nil {
		t.Fatalf("removing .meta file: %v", err)
	}

	reader, _, contentType, err := cache.loadVariantWithMeta(testVariantKeyOne)
	if err != nil {
		t.Fatalf("loadVariantWithMeta(%s) error = %v", testVariantKeyOne, err)
	}

	_ = reader.Close()

	t.Logf("the read without a .meta file got content type %q", contentType)

	assertVariantServed(t, cache, testVariantKeyOne, content)
}

// TestEvictedVariantIsNotServed checks that a variant the evictor
// removed is a miss and cannot be read, although it had been stored
// and served before.
func TestEvictedVariantIsNotServed(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1500)

	oldRequest := webpRequest("/old.jpg")
	newRequest := webpRequest("/new.jpg")
	oldKey := CacheKey(oldRequest)
	newKey := CacheKey(newRequest)
	oldContent := bytes.Repeat([]byte{0x01}, 1000)
	newContent := bytes.Repeat([]byte{0x02}, 1000)

	storeEvictionTestVariant(t, cache, oldKey, oldContent)
	storeEvictionTestVariant(t, cache, newKey, newContent)
	assertVariantServed(t, cache, oldKey, oldContent)
	setVariantLastAccessed(t, cache, oldKey, time.Now().Add(-time.Hour))

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

	assertLookupMisses(t, cache, oldRequest)
	assertVariantNotFound(t, cache, oldKey)
	assertVariantServed(t, cache, newKey, newContent)
}

// TestVariantDeletedFromDiskIsNotServed checks that a variant whose
// file was deleted by something other than the evictor cannot be read,
// and is a miss afterwards.
func TestVariantDeletedFromDiskIsNotServed(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<20)

	request := webpRequest("/deleted.jpg")
	key := CacheKey(request)
	content := []byte("webp variant bytes")

	storeEvictionTestVariant(t, cache, key, content)
	assertVariantServed(t, cache, key, content)

	err := os.Remove(cache.variants.keyToPath(key))
	if err != nil {
		t.Fatalf("removing variant file: %v", err)
	}

	assertVariantNotFound(t, cache, key)
	assertLookupMisses(t, cache, request)
}

// TestConcurrentVariantStoreReadAndEvict stores, reads and evicts
// variants from several goroutines at once, for the race detector.
func TestConcurrentVariantStoreReadAndEvict(t *testing.T) {
	t.Parallel()

	cache, _ := newEvictionTestCache(t, 1<<20)
	ctx := t.Context()

	var wg sync.WaitGroup

	for goroutine := range 8 {
		wg.Go(func() {
			key := VariantKey(fmt.Sprintf("aabbccdd01%02d", goroutine))
			content := []byte(key)

			for range 20 {
				err := cache.StoreVariant(
					ctx, key, bytes.NewReader(content), testContentTypeWebP)
				if err != nil {
					t.Errorf("StoreVariant(%s) error = %v", key, err)

					return
				}

				reader, _, contentType, err := cache.GetVariant(key)
				if err != nil {
					t.Errorf("GetVariant(%s) error = %v", key, err)

					return
				}

				_ = reader.Close()

				if contentType != testContentTypeWebP {
					t.Errorf("GetVariant(%s) content type = %q, want %q",
						key, contentType, testContentTypeWebP)
				}

				err = cache.evictVariant(ctx, key)
				if err != nil {
					t.Errorf("evictVariant(%s) error = %v", key, err)

					return
				}

				assertVariantNotFound(t, cache, key)
			}
		})
	}

	wg.Wait()
}