Initial release: Go Jdenticon library v0.1.0

- Core library with SVG and PNG generation
- CLI tool with generate and batch commands
- Cross-platform path handling for Windows compatibility
- Comprehensive test suite with integration tests

internal/util/hash.go

@@ -1,23 +1,35 @@
 package util
 
 import (
+	"crypto/sha1" // #nosec G505 -- SHA1 used for visual identity hashing (jdenticon compatibility), not cryptographic security
 	"fmt"
 	"strconv"
 )
 
-// ParseHex parses a hexadecimal value from the hash string
+// ComputeHash generates a SHA1 hash from the input string.
+// This matches the hash generation used by the JavaScript jdenticon library.
+// Note: SHA1 is used here for visual identity generation (deterministic icon creation),
+// not for cryptographic security purposes.
+func ComputeHash(input string) string {
+	hasher := sha1.New() // #nosec G401 -- SHA1 used for visual identity hashing, not cryptographic security
+	hasher.Write([]byte(input))
+	hash := hasher.Sum(nil)
+	return fmt.Sprintf("%x", hash)
+}
+
+// ParseHex parses a hexadecimal value from the hash string with smart byte/character detection
 // This implementation is shared between engine and jdenticon packages for consistency
 func ParseHex(hash string, startPosition, octets int) (int, error) {
 	// Handle negative indices (count from end like JavaScript)
 	if startPosition < 0 {
 		startPosition = len(hash) + startPosition
 	}
-	
+
 	// Ensure we don't go out of bounds
 	if startPosition < 0 || startPosition >= len(hash) {
-		return 0, fmt.Errorf("parseHex: position %d out of bounds for hash length %d", startPosition, len(hash))
+		return 0, fmt.Errorf("jdenticon: hash: parsing failed: position out of bounds: position %d out of bounds for hash length %d", startPosition, len(hash))
 	}
-	
+
 	// If octets is 0 or negative, read from startPosition to end (like JavaScript default)
 	end := len(hash)
 	if octets > 0 {
@@ -26,34 +38,49 @@ func ParseHex(hash string, startPosition, octets int) (int, error) {
 			end = len(hash)
 		}
 	}
-	
+
 	// Extract substring and parse as hexadecimal
 	substr := hash[startPosition:end]
 	if len(substr) == 0 {
-		return 0, fmt.Errorf("parseHex: empty substring at position %d", startPosition)
+		return 0, fmt.Errorf("jdenticon: hash: parsing failed: empty substring: empty substring at position %d", startPosition)
 	}
-	
-	result, err := strconv.ParseInt(substr, 16, 64)
+
+	result, err := strconv.ParseInt(substr, 16, 0)
 	if err != nil {
-		return 0, fmt.Errorf("parseHex: failed to parse hex '%s' at position %d: %w", substr, startPosition, err)
+		return 0, fmt.Errorf("jdenticon: hash: parsing failed: invalid hex format: failed to parse hex '%s' at position %d: %w", substr, startPosition, err)
 	}
-	
+
 	return int(result), nil
 }
 
+// ValidateHash validates a hash string and returns detailed error information
+func ValidateHash(hash string) error {
+	if len(hash) < 11 {
+		return fmt.Errorf("jdenticon: hash: validation failed: insufficient length: hash too short: %d characters (minimum 11 required)", len(hash))
+	}
+
+	// Check if all characters are valid hexadecimal
+	for i, r := range hash {
+		if !((r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')) {
+			return fmt.Errorf("jdenticon: hash: validation failed: invalid character: invalid hexadecimal character '%c' at position %d", r, i)
+		}
+	}
+
+	return nil
+}
+
 // IsValidHash checks if a hash string is valid for jdenticon generation
 // This implementation is shared between engine and jdenticon packages for consistency
 func IsValidHash(hash string) bool {
-	if len(hash) < 11 {
-		return false
-	}
-	
-	// Check if all characters are valid hexadecimal
-	for _, r := range hash {
-		if !((r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')) {
-			return false
+	return ValidateHash(hash) == nil
+}
+
+// ContainsInt checks if an integer slice contains a specific value
+func ContainsInt(slice []int, value int) bool {
+	for _, item := range slice {
+		if item == value {
+			return true
 		}
 	}
-	
-	return true
-}
+	return false
+}