Adding context based parameters

.gitignore

@@ -1,3 +1,4 @@
 /_example/_example
 /_example/cache/
+/.cache/
 *.txt

diskcache.go

@@ -13,6 +13,7 @@ package diskcache
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"crypto/sha256"
 	"errors"
 	"fmt"
@@ -176,7 +177,7 @@ func (c *Cache) EvictKey(key string) error {
 // or if the cached response is stale the request will be executed and cached.
 func (c *Cache) Fetch(key string, p Policy, req *http.Request, force bool) (bool, time.Time, *http.Response, error) {
 	// check stale
-	stale, mod, err := c.Stale(key, p.TTL)
+	stale, mod, err := c.Stale(req.Context(), key, p.TTL)
 	if err != nil {
 		return false, time.Time{}, nil, err
 	}
@@ -213,14 +214,17 @@ func (c *Cache) Mod(key string) (time.Time, error) {
 }
 
 // Stale returns whether or not the key is stale, based on ttl.
-func (c *Cache) Stale(key string, ttl time.Duration) (bool, time.Time, error) {
+func (c *Cache) Stale(ctx context.Context, key string, ttl time.Duration) (bool, time.Time, error) {
 	mod, err := c.Mod(key)
 	switch {
 	case err != nil && errors.Is(err, fs.ErrNotExist):
 		return true, mod, nil
 	case err != nil:
 		return false, time.Time{}, err
 	}
+	if d, ok := TTL(ctx); ok {
+		ttl = d
+	}
 	return ttl != 0 && time.Now().After(mod.Add(ttl)), mod, nil
 }
 
@@ -230,7 +234,7 @@ func (c *Cache) Cached(req *http.Request) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	stale, _, err := c.Stale(key, p.TTL)
+	stale, _, err := c.Stale(req.Context(), key, p.TTL)
 	if err != nil {
 		return false, err
 	}
@@ -347,3 +351,22 @@ func UserCacheDir(paths ...string) (string, error) {
 	}
 	return filepath.Join(append([]string{dir}, paths...)...), nil
 }
+
+// contextKey is a context key.
+type contextKey string
+
+// context keys.
+const (
+	ttlKey contextKey = "ttl"
+)
+
+// WithContextTTL adds the ttl to the context.
+func WithContextTTL(parent context.Context, ttl time.Duration) context.Context {
+	return context.WithValue(parent, ttlKey, ttl)
+}
+
+// TTL returns the ttl from the context.
+func TTL(ctx context.Context) (time.Duration, bool) {
+	ttl, ok := ctx.Value(ttlKey).(time.Duration)
+	return ttl, ok
+}

diskcache_test.go

@@ -0,0 +1,97 @@
+package diskcache
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestWithContextTTL(t *testing.T) {
+	// set up simple test server for demonstration
+	var count uint64
+	s := httptest.NewServer(http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+		fmt.Fprintf(res, "%d\n", atomic.AddUint64(&count, 1))
+	}))
+	defer s.Close()
+	baseDir := setupDir(t, "test-with-context-ttl")
+	// create disk cache
+	c, err := New(
+		WithBasePathFs(baseDir),
+		WithErrorTruncator(),
+		WithTTL(365*24*time.Hour),
+	)
+	if err != nil {
+		t.Fatalf("expected no error, got: %v", err)
+	}
+	cl := &http.Client{
+		Transport: c,
+	}
+	ctx := context.Background()
+	for i := 0; i < 3; i++ {
+		v, err := doReq(ctx, cl, s.URL)
+		switch {
+		case err != nil:
+			t.Fatalf("expected no error, got: %v", err)
+		case v != 1:
+			t.Errorf("expected %d, got: %d", 1, v)
+		}
+	}
+	if count != 1 {
+		t.Fatalf("expected count == %d, got: %d", 1, count)
+	}
+	for i := 1; i < 5; i++ {
+		v, err := doReq(WithContextTTL(ctx, 1*time.Millisecond), cl, s.URL)
+		switch {
+		case err != nil:
+			t.Fatalf("expected no error, got: %v", err)
+		case v != i+1:
+			t.Errorf("expected %d, got: %d", i+1, v)
+		}
+		<-time.After(2 * time.Millisecond)
+	}
+}
+
+func doReq(ctx context.Context, cl *http.Client, urlstr string) (int, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", urlstr, nil)
+	if err != nil {
+		return -1, err
+	}
+	res, err := cl.Do(req)
+	if err != nil {
+		return -1, err
+	}
+	defer res.Body.Close()
+	buf, err := io.ReadAll(res.Body)
+	if err != nil {
+		return -1, err
+	}
+	return strconv.Atoi(string(bytes.TrimSpace(buf)))
+}
+
+func setupDir(t *testing.T, name string) string {
+	t.Helper()
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("expected no error, got: %v", err)
+	}
+	dir := filepath.Join(wd, ".cache", name)
+	switch err := os.RemoveAll(dir); {
+	case errors.Is(err, os.ErrNotExist):
+	case err != nil:
+		t.Fatalf("expected no error, got: %v", err)
+	}
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatalf("expected no error, got: %v", err)
+	}
+	return dir
+}