1 files changed, 123 insertions, 0 deletions
diff --git a/sqlglot/helper.py b/sqlglot/helper.py
new file mode 100644
index 0000000..5d90c49
--- /dev/null
+++ b/sqlglot/helper.py
@@ -0,0 +1,123 @@
+import logging
+import re
+from contextlib import contextmanager
+from enum import Enum
+
+CAMEL_CASE_PATTERN = re.compile("(?<!^)(?=[A-Z])")
+logger = logging.getLogger("sqlglot")
+
+
+class AutoName(Enum):
+    def _generate_next_value_(name, _start, _count, _last_values):
+        return name
+
+
+def list_get(arr, index):
+    try:
+        return arr[index]
+    except IndexError:
+        return None
+
+
+def ensure_list(value):
+    if value is None:
+        return []
+    return value if isinstance(value, (list, tuple, set)) else [value]
+
+
+def csv(*args, sep=", "):
+    return sep.join(arg for arg in args if arg)
+
+
+def apply_index_offset(expressions, offset):
+    if not offset or len(expressions) != 1:
+        return expressions
+
+    expression = expressions[0]
+
+    if expression.is_int:
+        expression = expression.copy()
+        logger.warning("Applying array index offset (%s)", offset)
+        expression.args["this"] = str(int(expression.args["this"]) + offset)
+        return [expression]
+    return expressions
+
+
+def camel_to_snake_case(name):
+    return CAMEL_CASE_PATTERN.sub("_", name).upper()
+
+
+def while_changing(expression, func):
+    while True:
+        start = hash(expression)
+        expression = func(expression)
+        if start == hash(expression):
+            break
+    return expression
+
+
+def tsort(dag):
+    result = []
+
+    def visit(node, visited):
+        if node in result:
+            return
+        if node in visited:
+            raise ValueError("Cycle error")
+
+        visited.add(node)
+
+        for dep in dag.get(node, []):
+            visit(dep, visited)
+
+        visited.remove(node)
+        result.append(node)
+
+    for node in dag:
+        visit(node, set())
+
+    return result
+
+
+def open_file(file_name):
+    """
+    Open a file that may be compressed as gzip and return in newline mode.
+    """
+    with open(file_name, "rb") as f:
+        gzipped = f.read(2) == b"\x1f\x8b"
+
+    if gzipped:
+        import gzip
+
+        return gzip.open(file_name, "rt", newline="")
+
+    return open(file_name, "rt", encoding="utf-8", newline="")
+
+
+@contextmanager
+def csv_reader(table):
+    """
+    Returns a csv reader given the expression READ_CSV(name, ['delimiter', '|', ...])
+
+    Args:
+        expression (Expression): An anonymous function READ_CSV
+
+    Returns:
+        A python csv reader.
+    """
+    file, *args = table.this.expressions
+    file = file.name
+    file = open_file(file)
+
+    delimiter = ","
+    args = iter(arg.name for arg in args)
+    for k, v in zip(args, args):
+        if k == "delimiter":
+            delimiter = v
+
+    try:
+        import csv as csv_
+
+        yield csv_.reader(file, delimiter=delimiter)
+    finally:
+        file.close()