loader logic revised

pkg/connector/connector.go

@@ -1,6 +1,10 @@
 package connector
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
 	"galaxy/model/client"
 	"galaxy/model/report"
 )
@@ -29,7 +33,72 @@ type UIConnector interface {
 }
 
 type VersionInfo struct {
-	OS      string `json:"os"`      // Operating System name (unix, darwin, windows, etc.)
-	Version string `json:"version"` // Semver format: X.Y.Z
-	URL     string `json:"url"`     // Artifact download URL for this version
+	OS       string       `json:"os"`      // Operating System name (unix, darwin, windows, etc.)
+	Version  string       `json:"version"` // Semver format: X.Y.Z
+	URL      string       `json:"url"`     // Artifact download URL for this version
+	Checksum SHA256Digest `json:"sha256"`  // Base64 SHA-256 checksum for artifact binary data
+}
+
+// SHA256Digest represents a SHA-256 digest in raw binary form.
+//
+// Internally it stores the exact 32-byte digest.
+// In JSON it is encoded as a lowercase hexadecimal string of 64 characters.
+type SHA256Digest [32]byte
+
+// NewSHA256Digest calculates SHA-256 for the provided byte slice
+// and returns the digest as SHA256Digest.
+//
+// The function does not modify the input data.
+func NewSHA256Digest(data []byte) SHA256Digest {
+	sum := sha256.Sum256(data)
+	return SHA256Digest(sum)
+}
+
+// String returns the lowercase hexadecimal representation
+// of the digest.
+//
+// The returned string always contains exactly 64 characters.
+func (d SHA256Digest) String() string {
+	return hex.EncodeToString(d[:])
+}
+
+// MarshalJSON encodes the digest as a JSON string containing
+// the lowercase hexadecimal SHA-256 value.
+//
+// Example JSON value:
+//
+//	"b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9"
+func (d SHA256Digest) MarshalJSON() ([]byte, error) {
+	return json.Marshal(d.String())
+}
+
+// UnmarshalJSON decodes a JSON string containing a lowercase or uppercase
+// hexadecimal SHA-256 value into the digest.
+//
+// The input must be a JSON string with exactly 64 hexadecimal characters.
+func (d *SHA256Digest) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return fmt.Errorf("sha256 digest must be a JSON string: %w", err)
+	}
+
+	if len(s) != hex.EncodedLen(len(d)) {
+		return fmt.Errorf("invalid SHA-256 hex length: got %d, want %d", len(s), hex.EncodedLen(len(d)))
+	}
+
+	decoded, err := hex.DecodeString(s)
+	if err != nil {
+		return fmt.Errorf("invalid SHA-256 hex value: %w", err)
+	}
+
+	copy(d[:], decoded)
+	return nil
+}
+
+// Equal returns true when both digests are identical.
+//
+// Since SHA256Digest is based on a fixed-size array, direct value comparison
+// is efficient and idiomatic for non-constant-time equality checks.
+func (d SHA256Digest) Equal(other SHA256Digest) bool {
+	return d == other
 }