refactor: fold auth and crypto into deezer domain

internal/deezer/blowfish.go

@@ -0,0 +1,39 @@
+package deezer
+
+import (
+	"crypto/cipher"
+	"crypto/md5"
+	"encoding/hex"
+
+	"golang.org/x/crypto/blowfish"
+)
+
+var (
+	blowfishIV        = []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07}
+	blowfishSecretKey = []byte("g4el58wc0zvf9na1")
+)
+
+func BlowfishKey(trackID string) []byte {
+	hash := md5.Sum([]byte(trackID))
+	hashHex := hex.EncodeToString(hash[:])
+
+	key := make([]byte, len(blowfishSecretKey))
+	copy(key, blowfishSecretKey)
+	for i := range len(hash) {
+		key[i] = key[i] ^ hashHex[i] ^ hashHex[i+16]
+	}
+
+	return key
+}
+
+func DecryptBlowfish(data, key []byte) ([]byte, error) {
+	block, err := blowfish.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	decrypted := make([]byte, len(data))
+	cipher.NewCBCDecrypter(block, blowfishIV).CryptBlocks(decrypted, data)
+
+	return decrypted, nil
+}