🚚 Move Slug/Hash Generators to own file

gen_file.go

@@ -0,0 +1,81 @@
+package nomino
+
+import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"hash"
+
+	"github.com/gosimple/slug"
+)
+
+// ErrMissingOriginal is the error returned by Slug if there is no filename
+var ErrMissingOriginal = errors.New("missing original filename")
+
+func getOriginal(c *Config) (string, error) {
+	if c.original == "" {
+		return "", ErrMissingOriginal
+	}
+	name := c.original
+	c.original = ""
+	return name, nil
+}
+
+// Slug generates a name from the original filename.
+// When this is used, the original filename will be removed from the final filename.
+// If a language is specified, that may affect the resulting slug.
+func Slug(lang ...string) Generator {
+	ret := slug.Make
+	if len(lang) > 0 {
+		ret = func(in string) string {
+			return slug.MakeLang(in, lang[0])
+		}
+	}
+	return func(c *Config) (string, error) {
+		name, err := getOriginal(c)
+		return ret(name), err
+	}
+}
+
+// HashingFunc is a function that generates a hash.Hash
+type HashingFunc func() hash.Hash
+
+//go:generate stringer -type=HashType -trimprefix=Hash
+
+// HashType represents a particular hashing algorithm
+type HashType uint8
+
+const (
+	HashMD5 HashType = iota + 1
+	HashSHA1
+	HashSHA256
+)
+
+// 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{
+	HashMD5:    md5.New,
+	HashSHA1:   sha1.New,
+	HashSHA256: 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
+	}
+}