refactor: major project restructure

internal/crypto/blowfish.go

@@ -0,0 +1,34 @@
+package crypto
+
+import (
+	"crypto/cipher"
+	"crypto/md5"
+	"fmt"
+
+	"golang.org/x/crypto/blowfish"
+)
+
+func GetKey(secretKey, songID string) []byte {
+	hash := md5.Sum([]byte(songID))
+	hashHex := fmt.Sprintf("%x", hash)
+
+	key := []byte(secretKey)
+	for i := 0; i < len(hash); i++ {
+		key[i] = key[i] ^ hashHex[i] ^ hashHex[i+16]
+	}
+
+	return key
+}
+
+func Decrypt(data, key, iv []byte) ([]byte, error) {
+	block, err := blowfish.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	mode := cipher.NewCBCDecrypter(block, iv)
+	decrypted := make([]byte, len(data))
+	mode.CryptBlocks(decrypted, data)
+
+	return decrypted, nil
+}