1 files changed, 143 insertions, 0 deletions
diff --git a/src/aristaproto/casing.py b/src/aristaproto/casing.py
new file mode 100644
index 0000000..f7d0832
--- /dev/null
+++ b/src/aristaproto/casing.py
@@ -0,0 +1,143 @@
+import keyword
+import re
+
+
+# Word delimiters and symbols that will not be preserved when re-casing.
+# language=PythonRegExp
+SYMBOLS = "[^a-zA-Z0-9]*"
+
+# Optionally capitalized word.
+# language=PythonRegExp
+WORD = "[A-Z]*[a-z]*[0-9]*"
+
+# Uppercase word, not followed by lowercase letters.
+# language=PythonRegExp
+WORD_UPPER = "[A-Z]+(?![a-z])[0-9]*"
+
+
+def safe_snake_case(value: str) -> str:
+    """Snake case a value taking into account Python keywords."""
+    value = snake_case(value)
+    value = sanitize_name(value)
+    return value
+
+
+def snake_case(value: str, strict: bool = True) -> str:
+    """
+    Join words with an underscore into lowercase and remove symbols.
+
+    Parameters
+    -----------
+    value: :class:`str`
+        The value to convert.
+    strict: :class:`bool`
+        Whether or not to force single underscores.
+
+    Returns
+    --------
+    :class:`str`
+        The value in snake_case.
+    """
+
+    def substitute_word(symbols: str, word: str, is_start: bool) -> str:
+        if not word:
+            return ""
+        if strict:
+            delimiter_count = 0 if is_start else 1  # Single underscore if strict.
+        elif is_start:
+            delimiter_count = len(symbols)
+        elif word.isupper() or word.islower():
+            delimiter_count = max(
+                1, len(symbols)
+            )  # Preserve all delimiters if not strict.
+        else:
+            delimiter_count = len(symbols) + 1  # Extra underscore for leading capital.
+
+        return ("_" * delimiter_count) + word.lower()
+
+    snake = re.sub(
+        f"(^)?({SYMBOLS})({WORD_UPPER}|{WORD})",
+        lambda groups: substitute_word(groups[2], groups[3], groups[1] is not None),
+        value,
+    )
+    return snake
+
+
+def pascal_case(value: str, strict: bool = True) -> str:
+    """
+    Capitalize each word and remove symbols.
+
+    Parameters
+    -----------
+    value: :class:`str`
+        The value to convert.
+    strict: :class:`bool`
+        Whether or not to output only alphanumeric characters.
+
+    Returns
+    --------
+    :class:`str`
+        The value in PascalCase.
+    """
+
+    def substitute_word(symbols, word):
+        if strict:
+            return word.capitalize()  # Remove all delimiters
+
+        if word.islower():
+            delimiter_length = len(symbols[:-1])  # Lose one delimiter
+        else:
+            delimiter_length = len(symbols)  # Preserve all delimiters
+
+        return ("_" * delimiter_length) + word.capitalize()
+
+    return re.sub(
+        f"({SYMBOLS})({WORD_UPPER}|{WORD})",
+        lambda groups: substitute_word(groups[1], groups[2]),
+        value,
+    )
+
+
+def camel_case(value: str, strict: bool = True) -> str:
+    """
+    Capitalize all words except first and remove symbols.
+
+    Parameters
+    -----------
+    value: :class:`str`
+        The value to convert.
+    strict: :class:`bool`
+        Whether or not to output only alphanumeric characters.
+
+    Returns
+    --------
+    :class:`str`
+        The value in camelCase.
+    """
+    return lowercase_first(pascal_case(value, strict=strict))
+
+
+def lowercase_first(value: str) -> str:
+    """
+    Lower cases the first character of the value.
+
+    Parameters
+    ----------
+    value: :class:`str`
+        The value to lower case.
+
+    Returns
+    -------
+    :class:`str`
+        The lower cased string.
+    """
+    return value[0:1].lower() + value[1:]
+
+
+def sanitize_name(value: str) -> str:
+    # https://www.python.org/dev/peps/pep-0008/#descriptive-naming-styles
+    if keyword.iskeyword(value):
+        return f"{value}_"
+    if not value.isidentifier():
+        return f"_{value}"
+    return value