From 84f20675c4c858e0676acd930a7d8f65ffcd9ec9 Mon Sep 17 00:00:00 2001
From: Xevion <xevioni@yandex.com>
Date: Thu, 27 Aug 2020 00:06:02 -0500
Subject: [PATCH] helper functions for generating directory names, random
 strings, validating extensions and more

---
 phototag/helpers.py | 56 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 phototag/helpers.py

diff --git a/phototag/helpers.py b/phototag/helpers.py
new file mode 100644
index 0000000..c3fa222
--- /dev/null
+++ b/phototag/helpers.py
@@ -0,0 +1,56 @@
+"""
+helpers.py
+
+Simple helper functions and constants separated from the primary application functionality.
+"""
+import os
+import random
+import string
+
+from phototag import LOSSY_EXTS, RAW_EXTS
+
+ALL_EXTENSIONS = RAW_EXTS + LOSSY_EXTS
+
+
+def valid_extension(extension: str) -> bool:
+    """
+    :param extension: The extension you wish to test. Prepended dots are acceptable.
+    :return: A boolean describing the validity of the extension in the context of the phototag application.
+    """
+    return extension.lstrip('.') in ALL_EXTENSIONS
+
+
+def get_extension(filename: str) -> str:
+    """
+    :param filename: A filename or path with a file in it. Relative and absolute paths accepted. Must have an extension.
+    :return: The extension with the prepended dot removed and the extension in lowercase
+    """
+    return os.path.splitext(filename)[1][1:].lower()
+
+
+def random_characters(length: int) -> str:
+    """
+    :param length: A integer describing the intended length of the generated string.
+    :return: A random series of characters *length* characters long.
+    """
+    return ''.join(random.choices(string.ascii_letters, k=length))
+
+
+def get_temp_directory(directory: str, start: str = "temp", append_random: int = 0) -> str:
+    """
+    :param directory: A valid directory where the temporary directory is intended to be created.
+    :param start: The string the directory should start with.
+    :param append_random: Whether or not to always include a random series of characters.
+    :return: A valid path to a directory that has not yet been created.
+    """
+    temp: str = ""
+
+    # Generate directory names until one matches (usually first or second try)
+    while os.path.exists(temp):
+        temp = os.path.join(directory, (start + "_" + random_characters(append_random)) if append_random > 0 else start)
+        if append_random >= 128:
+            raise Exception(
+                "Could not find a valid temporary directory name. Please try again in a different directory."
+            )
+        append_random += (3 if append_random == 0 else 1)
+    return temp