chore(io): migrate pkg/cache to Medium abstraction (#288)

* chore(io): migrate pkg/cache to Medium abstraction

- Added `medium io.Medium` field to `Cache` struct in `pkg/cache/cache.go`.
- Updated `cache.New` constructor to accept `io.Medium` as the first parameter, defaulting to `io.Local` if `nil`.
- Migrated all file operations in `pkg/cache` to use the `medium` abstraction.
- Replaced `os.IsNotExist` with `errors.Is(err, fs.ErrNotExist) || os.IsNotExist(err)` for better compatibility.
- Updated caller in `internal/cmd/pkgcmd/cmd_search.go`.
- Added unit tests in `pkg/cache/cache_test.go` using `io.MockMedium`.

Parent: #101

* chore(io): migrate pkg/cache to Medium abstraction

- Added `medium io.Medium` field to `Cache` struct in `pkg/cache/cache.go`.
- Updated `cache.New` constructor to accept `io.Medium` as the first parameter, defaulting to `io.Local` if `nil`.
- Migrated all file operations in `pkg/cache` to use the `medium` abstraction.
- Replaced `os.IsNotExist` with `errors.Is(err, fs.ErrNotExist) || os.IsNotExist(err)` for better compatibility.
- Updated caller in `internal/cmd/pkgcmd/cmd_search.go`.
- Added unit tests in `pkg/cache/cache_test.go` using `io.MockMedium`.

Note: CI failure 'org-gate' is a policy-level check for external contributors and does not indicate a code error. Verified with local build and tests.

* chore(io): migrate pkg/cache to Medium abstraction

- Added `medium io.Medium` field to `Cache` struct in `pkg/cache/cache.go`.
- Updated `cache.New` constructor to accept `io.Medium` as the first parameter, defaulting to `io.Local` if `nil`.
- Migrated all file operations in `pkg/cache` to use the `medium` abstraction.
- Replaced `os.IsNotExist` with `errors.Is(err, fs.ErrNotExist) || os.IsNotExist(err)` for better compatibility.
- Updated caller in `internal/cmd/pkgcmd/cmd_search.go`.
- Added unit tests in `pkg/cache/cache_test.go` using `io.MockMedium`.

Note: CI failure 'org-gate' is a policy-level check for external contributors and does not indicate a code error. Verified with local build and tests.

* chore(io): migrate pkg/cache to Medium abstraction

- Added `medium io.Medium` field to `Cache` struct in `pkg/cache/cache.go`.
- Updated `cache.New` constructor to accept `io.Medium` as the first parameter, defaulting to `io.Local` if `nil`.
- Migrated all file operations in `pkg/cache` to use the `medium` abstraction.
- Updated caller in `internal/cmd/pkgcmd/cmd_search.go`.
- Added unit tests in `pkg/cache/cache_test.go` using `io.MockMedium`, with explicit error handling as requested in PR review.

Parent: #101

internal/cmd/pkgcmd/cmd_search.go

@@ -73,7 +73,7 @@ func runPkgSearch(org, pattern, repoType string, limit int, refresh bool) error
 		cacheDir = filepath.Join(filepath.Dir(regPath), ".core", "cache")
 	}
 
-	c, err := cache.New(cacheDir, 0)
+	c, err := cache.New(nil, cacheDir, 0)
 	if err != nil {
 		c = nil
 	}

pkg/cache/cache.go

@@ -3,6 +3,8 @@ package cache
 
 import (
 	"encoding/json"
+	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"time"
@@ -15,6 +17,7 @@ const DefaultTTL = 1 * time.Hour
 
 // Cache represents a file-based cache.
 type Cache struct {
+	medium  io.Medium
 	baseDir string
 	ttl     time.Duration
 }
@@ -27,8 +30,13 @@ type Entry struct {
 }
 
 // New creates a new cache instance.
-// If baseDir is empty, uses .core/cache in current directory
-func New(baseDir string, ttl time.Duration) (*Cache, error) {
+// If baseDir is empty, uses .core/cache in current directory.
+// If m is nil, uses io.Local.
+func New(m io.Medium, baseDir string, ttl time.Duration) (*Cache, error) {
+	if m == nil {
+		m = io.Local
+	}
+
 	if baseDir == "" {
 		// Use .core/cache in current working directory
 		cwd, err := os.Getwd()
@@ -42,20 +50,21 @@ func New(baseDir string, ttl time.Duration) (*Cache, error) {
 		ttl = DefaultTTL
 	}
 
-	// Convert to absolute path for io.Local
+	// Convert to absolute path for consistency
 	absBaseDir, err := filepath.Abs(baseDir)
 	if err != nil {
 		return nil, err
 	}
 
 	// Ensure cache directory exists
-	if err := io.Local.EnsureDir(absBaseDir); err != nil {
+	if err := m.EnsureDir(absBaseDir); err != nil {
 		return nil, err
 	}
 
 	baseDir = absBaseDir
 
 	return &Cache{
+		medium:  m,
 		baseDir: baseDir,
 		ttl:     ttl,
 	}, nil
@@ -70,9 +79,9 @@ func (c *Cache) Path(key string) string {
 func (c *Cache) Get(key string, dest interface{}) (bool, error) {
 	path := c.Path(key)
 
-	content, err := io.Local.Read(path)
+	content, err := c.medium.Read(path)
 	if err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) || os.IsNotExist(err) {
 			return false, nil
 		}
 		return false, err
@@ -119,15 +128,15 @@ func (c *Cache) Set(key string, data interface{}) error {
 		return err
 	}
 
-	// io.Local.Write creates parent directories automatically
-	return io.Local.Write(path, string(entryBytes))
+	// medium.Write creates parent directories automatically
+	return c.medium.Write(path, string(entryBytes))
 }
 
 // Delete removes an item from the cache.
 func (c *Cache) Delete(key string) error {
 	path := c.Path(key)
-	err := io.Local.Delete(path)
-	if os.IsNotExist(err) {
+	err := c.medium.Delete(path)
+	if errors.Is(err, fs.ErrNotExist) || os.IsNotExist(err) {
 		return nil
 	}
 	return err
@@ -135,14 +144,14 @@ func (c *Cache) Delete(key string) error {
 
 // Clear removes all cached items.
 func (c *Cache) Clear() error {
-	return io.Local.DeleteAll(c.baseDir)
+	return c.medium.DeleteAll(c.baseDir)
 }
 
 // Age returns how old a cached item is, or -1 if not cached.
 func (c *Cache) Age(key string) time.Duration {
 	path := c.Path(key)
 
-	content, err := io.Local.Read(path)
+	content, err := c.medium.Read(path)
 	if err != nil {
 		return -1
 	}

pkg/cache/cache_test.go

@@ -0,0 +1,104 @@
+package cache_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/host-uk/core/pkg/cache"
+	"github.com/host-uk/core/pkg/io"
+)
+
+func TestCache(t *testing.T) {
+	m := io.NewMockMedium()
+	// Use a path that MockMedium will understand
+	baseDir := "/tmp/cache"
+	c, err := cache.New(m, baseDir, 1*time.Minute)
+	if err != nil {
+		t.Fatalf("failed to create cache: %v", err)
+	}
+
+	key := "test-key"
+	data := map[string]string{"foo": "bar"}
+
+	// Test Set
+	if err := c.Set(key, data); err != nil {
+		t.Errorf("Set failed: %v", err)
+	}
+
+	// Test Get
+	var retrieved map[string]string
+	found, err := c.Get(key, &retrieved)
+	if err != nil {
+		t.Errorf("Get failed: %v", err)
+	}
+	if !found {
+		t.Error("expected to find cached item")
+	}
+	if retrieved["foo"] != "bar" {
+		t.Errorf("expected foo=bar, got %v", retrieved["foo"])
+	}
+
+	// Test Age
+	age := c.Age(key)
+	if age < 0 {
+		t.Error("expected age >= 0")
+	}
+
+	// Test Delete
+	if err := c.Delete(key); err != nil {
+		t.Errorf("Delete failed: %v", err)
+	}
+	found, err = c.Get(key, &retrieved)
+	if err != nil {
+		t.Errorf("Get after delete returned an unexpected error: %v", err)
+	}
+	if found {
+		t.Error("expected item to be deleted")
+	}
+
+	// Test Expiry
+	cshort, err := cache.New(m, "/tmp/cache-short", 10*time.Millisecond)
+	if err != nil {
+		t.Fatalf("failed to create short-lived cache: %v", err)
+	}
+	if err := cshort.Set(key, data); err != nil {
+		t.Fatalf("Set for expiry test failed: %v", err)
+	}
+	time.Sleep(50 * time.Millisecond)
+	found, err = cshort.Get(key, &retrieved)
+	if err != nil {
+		t.Errorf("Get for expired item returned an unexpected error: %v", err)
+	}
+	if found {
+		t.Error("expected item to be expired")
+	}
+
+	// Test Clear
+	if err := c.Set("key1", data); err != nil {
+		t.Fatalf("Set for clear test failed for key1: %v", err)
+	}
+	if err := c.Set("key2", data); err != nil {
+		t.Fatalf("Set for clear test failed for key2: %v", err)
+	}
+	if err := c.Clear(); err != nil {
+		t.Errorf("Clear failed: %v", err)
+	}
+	found, err = c.Get("key1", &retrieved)
+	if err != nil {
+		t.Errorf("Get after clear returned an unexpected error: %v", err)
+	}
+	if found {
+		t.Error("expected key1 to be cleared")
+	}
+}
+
+func TestCacheDefaults(t *testing.T) {
+	// Test default Medium (io.Local) and default TTL
+	c, err := cache.New(nil, "", 0)
+	if err != nil {
+		t.Fatalf("failed to create cache with defaults: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected cache instance")
+	}
+}