# HG changeset patch
# User Franz Glasner <fzglas.hg@dom66.de>
# Date 1556868716 -7200
# Node ID e87fa5bd68e77a9dc1292f89c4fef7991a6de765
# Parent  62db35db89391053a87163777cb259656c46e8de
Implemented "try_determine_filemode()" to determine a file-mode from an Emacs-compatible declaration

diff -r 62db35db8939 -r e87fa5bd68e7 configmix/__init__.py
--- a/configmix/__init__.py	Thu May 02 10:32:36 2019 +0200
+++ b/configmix/__init__.py	Fri May 03 09:31:56 2019 +0200
@@ -21,11 +21,14 @@
 __all__ = ["load", "safe_load",
            "set_loader", "get_loader",
            "get_default_loader",
-           "Configuration"]
+           "Configuration",
+           "try_determine_filemode"]
 
 
 import fnmatch
 import copy
+import io
+import re
 
 from .compat import u, u2fs
 from .config import Configuration
@@ -116,6 +119,35 @@
     return ini.load(filename)
 
 
+EMACS_MODELINE = re.compile(r"-\*-(.*?)-\*-")
+EMACS_MODE = re.compile(r"(?:\A\s*|;\s*)mode[:=]\s*([-_.a-zA-Z0-9]+)")
+
+
+def try_determine_filemode(filename):
+    """Try to determine an explicitely given filemode from an Emacs-compatible
+    mode declaration (e.g. ``mode=python``).
+
+    :param str filename:
+    :return: the found mode string or `None`
+    :rtype: str or None
+
+    Only the first two lines are searched for.
+
+    """
+    with io.open(filename, encoding="ascii", errors="replace") as f:
+        idx = 0
+        for l in f:
+            idx += 1
+            mo = EMACS_MODELINE.search(l)
+            if mo:
+                mo = EMACS_MODE.search(mo.group(1))
+                if mo:
+                    return mo.group(1)
+            if idx >= 2:
+                break
+    return None
+
+
 DEFAULT_MODE_LOADERS = {
     "python": _load_py,
     "yaml": _load_yaml,