✨ Add Hash generator

generators.go

@@ -1,8 +1,12 @@
 package nomino
 
 import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
 	"errors"
 	"fmt"
+	"hash"
 	"strconv"
 	"time"
 
@@ -185,3 +189,44 @@ func SlugWithLang(lang string) Generator {
 		return slug.MakeLang(name, lang), err
 	}
 }
+
+// HashingFunc is a function that generates a hash.Hash
+type HashingFunc func() hash.Hash
+
+//go:generate stringer -type=HashType
+
+// HashType represents a particular hashing algorithm
+type HashType uint8
+
+const (
+	MD5 HashType = iota + 1
+	SHA1
+	SHA256
+)
+
+// ErrInvalidHashType is returned by the Hash generator when an invalid HashType is passed
+var ErrInvalidHashType = errors.New("invalid hash type")
+
+var hashMap = map[HashType]HashingFunc{
+	MD5:    md5.New,
+	SHA1:   sha1.New,
+	SHA256: sha256.New,
+}
+
+// Hash generates a name from a hash of the filename.
+// When this is used, the original filename will be removed from the final filename.
+func Hash(t HashType) Generator {
+	f, ok := hashMap[t]
+	return func(c *Config) (string, error) {
+		if !ok {
+			return "", fmt.Errorf("%w: %s", ErrInvalidHashType, t)
+		}
+		name, err := getOriginal(c)
+		if err != nil {
+			return "", err
+		}
+		hs := f()
+		hs.Write([]byte(name))
+		return fmt.Sprintf("%x", hs.Sum(nil)), nil
+	}
+}