feat: extract cache package from core/go pkg/cache
File-based cache with TTL, JSON serialisation, go-io Medium backend. Moved from forge.lthn.ai/core/go/pkg/cache to standalone module. Co-Authored-By: Virgil <virgil@lethean.io>
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commit
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4 changed files with 294 additions and 0 deletions
171
cache.go
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171
cache.go
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// Package cache provides a file-based cache for GitHub API responses.
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package cache
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import (
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"encoding/json"
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"errors"
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"os"
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"path/filepath"
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"time"
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"forge.lthn.ai/core/go-io"
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)
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// DefaultTTL is the default cache expiry time.
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const DefaultTTL = 1 * time.Hour
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// Cache represents a file-based cache.
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type Cache struct {
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medium io.Medium
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baseDir string
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ttl time.Duration
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}
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// Entry represents a cached item with metadata.
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type Entry struct {
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Data json.RawMessage `json:"data"`
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CachedAt time.Time `json:"cached_at"`
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ExpiresAt time.Time `json:"expires_at"`
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}
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// New creates a new cache instance.
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// If medium is nil, uses io.Local (filesystem).
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// If baseDir is empty, uses .core/cache in current directory.
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func New(medium io.Medium, baseDir string, ttl time.Duration) (*Cache, error) {
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if medium == nil {
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medium = io.Local
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}
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if baseDir == "" {
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// Use .core/cache in current working directory
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cwd, err := os.Getwd()
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if err != nil {
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return nil, err
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}
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baseDir = filepath.Join(cwd, ".core", "cache")
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}
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if ttl == 0 {
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ttl = DefaultTTL
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}
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// Ensure cache directory exists
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if err := medium.EnsureDir(baseDir); err != nil {
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return nil, err
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}
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return &Cache{
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medium: medium,
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baseDir: baseDir,
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ttl: ttl,
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}, nil
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}
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// Path returns the full path for a cache key.
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func (c *Cache) Path(key string) string {
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return filepath.Join(c.baseDir, key+".json")
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}
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// Get retrieves a cached item if it exists and hasn't expired.
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func (c *Cache) Get(key string, dest any) (bool, error) {
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path := c.Path(key)
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dataStr, err := c.medium.Read(path)
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if err != nil {
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if errors.Is(err, os.ErrNotExist) {
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return false, nil
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}
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return false, err
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}
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var entry Entry
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if err := json.Unmarshal([]byte(dataStr), &entry); err != nil {
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// Invalid cache file, treat as miss
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return false, nil
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}
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// Check expiry
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if time.Now().After(entry.ExpiresAt) {
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return false, nil
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}
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// Unmarshal the actual data
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if err := json.Unmarshal(entry.Data, dest); err != nil {
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return false, err
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}
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return true, nil
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}
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// Set stores an item in the cache.
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func (c *Cache) Set(key string, data any) error {
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path := c.Path(key)
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// Ensure parent directory exists
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if err := c.medium.EnsureDir(filepath.Dir(path)); err != nil {
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return err
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}
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// Marshal the data
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dataBytes, err := json.Marshal(data)
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if err != nil {
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return err
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}
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entry := Entry{
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Data: dataBytes,
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CachedAt: time.Now(),
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ExpiresAt: time.Now().Add(c.ttl),
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}
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entryBytes, err := json.MarshalIndent(entry, "", " ")
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if err != nil {
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return err
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}
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return c.medium.Write(path, string(entryBytes))
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}
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// Delete removes an item from the cache.
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func (c *Cache) Delete(key string) error {
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path := c.Path(key)
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err := c.medium.Delete(path)
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if errors.Is(err, os.ErrNotExist) {
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return nil
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}
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return err
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}
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// Clear removes all cached items.
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func (c *Cache) Clear() error {
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return c.medium.DeleteAll(c.baseDir)
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}
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// Age returns how old a cached item is, or -1 if not cached.
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func (c *Cache) Age(key string) time.Duration {
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path := c.Path(key)
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dataStr, err := c.medium.Read(path)
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if err != nil {
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return -1
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}
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var entry Entry
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if err := json.Unmarshal([]byte(dataStr), &entry); err != nil {
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return -1
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}
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return time.Since(entry.CachedAt)
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}
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// GitHub-specific cache keys
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// GitHubReposKey returns the cache key for an org's repo list.
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func GitHubReposKey(org string) string {
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return filepath.Join("github", org, "repos")
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}
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// GitHubRepoKey returns the cache key for a specific repo's metadata.
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func GitHubRepoKey(org, repo string) string {
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return filepath.Join("github", org, repo, "meta")
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}
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104
cache_test.go
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104
cache_test.go
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package cache_test
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import (
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"testing"
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"time"
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"forge.lthn.ai/core/go-cache"
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"forge.lthn.ai/core/go-io"
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)
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func TestCache(t *testing.T) {
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m := io.NewMockMedium()
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// Use a path that MockMedium will understand
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baseDir := "/tmp/cache"
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c, err := cache.New(m, baseDir, 1*time.Minute)
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if err != nil {
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t.Fatalf("failed to create cache: %v", err)
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}
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key := "test-key"
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data := map[string]string{"foo": "bar"}
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// Test Set
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if err := c.Set(key, data); err != nil {
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t.Errorf("Set failed: %v", err)
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}
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// Test Get
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var retrieved map[string]string
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found, err := c.Get(key, &retrieved)
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if err != nil {
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t.Errorf("Get failed: %v", err)
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}
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if !found {
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t.Error("expected to find cached item")
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}
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if retrieved["foo"] != "bar" {
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t.Errorf("expected foo=bar, got %v", retrieved["foo"])
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}
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// Test Age
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age := c.Age(key)
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if age < 0 {
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t.Error("expected age >= 0")
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}
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// Test Delete
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if err := c.Delete(key); err != nil {
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t.Errorf("Delete failed: %v", err)
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}
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found, err = c.Get(key, &retrieved)
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if err != nil {
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t.Errorf("Get after delete returned an unexpected error: %v", err)
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}
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if found {
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t.Error("expected item to be deleted")
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}
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// Test Expiry
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cshort, err := cache.New(m, "/tmp/cache-short", 10*time.Millisecond)
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if err != nil {
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t.Fatalf("failed to create short-lived cache: %v", err)
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}
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if err := cshort.Set(key, data); err != nil {
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t.Fatalf("Set for expiry test failed: %v", err)
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}
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time.Sleep(50 * time.Millisecond)
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found, err = cshort.Get(key, &retrieved)
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if err != nil {
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t.Errorf("Get for expired item returned an unexpected error: %v", err)
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}
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if found {
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t.Error("expected item to be expired")
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}
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// Test Clear
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if err := c.Set("key1", data); err != nil {
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t.Fatalf("Set for clear test failed for key1: %v", err)
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}
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if err := c.Set("key2", data); err != nil {
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t.Fatalf("Set for clear test failed for key2: %v", err)
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}
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if err := c.Clear(); err != nil {
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t.Errorf("Clear failed: %v", err)
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}
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found, err = c.Get("key1", &retrieved)
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if err != nil {
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t.Errorf("Get after clear returned an unexpected error: %v", err)
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}
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if found {
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t.Error("expected key1 to be cleared")
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}
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}
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func TestCacheDefaults(t *testing.T) {
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// Test default Medium (io.Local) and default TTL
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c, err := cache.New(nil, "", 0)
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if err != nil {
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t.Fatalf("failed to create cache with defaults: %v", err)
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}
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if c == nil {
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t.Fatal("expected cache instance")
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}
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}
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7
go.mod
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7
go.mod
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module forge.lthn.ai/core/go-cache
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go 1.26.0
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require forge.lthn.ai/core/go-io v0.0.3
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require forge.lthn.ai/core/go-log v0.0.1 // indirect
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12
go.sum
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12
go.sum
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forge.lthn.ai/core/go-io v0.0.3 h1:TlhYpGTyjPgAlbEHyYrVSeUChZPhJXcLZ7D/8IbFqfI=
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forge.lthn.ai/core/go-io v0.0.3/go.mod h1:ZlU9OQpsvNFNmTJoaHbFIkisZyc0eCq0p8znVWQLRf0=
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forge.lthn.ai/core/go-log v0.0.1 h1:x/E6EfF9vixzqiLHQOl2KT25HyBcMc9qiBkomqVlpPg=
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forge.lthn.ai/core/go-log v0.0.1/go.mod h1:r14MXKOD3LF/sI8XUJQhRk/SZHBE7jAFVuCfgkXoZPw=
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github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
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github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
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github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
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github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
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github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
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github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
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gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
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gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
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