poc of functions

internal/cache/key.go

@@ -0,0 +1,34 @@
+package cache
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"os"
+)
+
+// HashFile computes the SHA-256 hex digest of the file at path.
+func HashFile(path string) (string, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
+}
+
+// AnalysisKey builds a cache key for FFF or SLA analysis.
+// Format: "<endpoint>:<filehash>:scale=<scale>"
+// scale uses %.6g so "1.50" and "1.5" map to the same key.
+func AnalysisKey(endpoint, fileHash string, scale float64) string {
+	return fmt.Sprintf("%s:%s:scale=%.6g", endpoint, fileHash, scale)
+}
+
+// ThumbnailKey builds a cache key for thumbnail generation.
+func ThumbnailKey(fileHash string) string {
+	return "thumbnail:" + fileHash
+}