package imgcache

import (
	"testing"
)

// TestComputeDefaultMaxBytesCountsWhatTheCacheHolds verifies that the
// default limit is 75% of the free space plus what the cache already
// holds, so a cache filled to its limit keeps that limit across a
// restart instead of shrinking to 75% of the space left free.
func TestComputeDefaultMaxBytesCountsWhatTheCacheHolds(t *testing.T) {
	t.Parallel()

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

	// Empty cache, 4 GiB free -> 3 GiB default.
	got, err := cache.computeDefaultMaxBytes(t.Context(),
		func(string) (uint64, error) { return 4294967296, nil })
	if err != nil {
		t.Fatalf("computeDefaultMaxBytes returned error: %v", err)
	}

	t.Logf("default for an empty cache with 4 GiB free: %d", got)

	if got != 3221225472 {
		t.Errorf("default for an empty cache = %d, want 3221225472 (75%% of 4 GiB)",
			got)
	}

	// The cache now holds those 3 GiB, which leaves 1 GiB free.
	_, err = cache.db.ExecContext(t.Context(),
		`INSERT INTO variant_content (cache_key, size_bytes, content_type)
		 VALUES (?, ?, ?)`,
		string(testVariantKeyOne), 3221225472, testContentTypeWebP,
	)
	if err != nil {
		t.Fatalf("failed to insert variant accounting row: %v", err)
	}

	got, err = cache.computeDefaultMaxBytes(t.Context(),
		func(string) (uint64, error) { return 1073741824, nil })
	if err != nil {
		t.Fatalf("computeDefaultMaxBytes returned error: %v", err)
	}

	t.Logf("default for a cache holding 3 GiB with 1 GiB free: %d", got)

	if got != 3221225472 {
		t.Errorf("default for a cache holding 3 GiB with 1 GiB free = %d, "+
			"want 3221225472 (75%% of 1 GiB + 3 GiB)", got)
	}
}