fbcode_builder: getdeps: add platform type tuple helper

Summary:
This will feed into the manifest context for system
dependent manifest sections.  This is essentially the same
code borrowed from the watchman and eden getdeps.py.

Reviewed By: simpkins

Differential Revision: D14690997

fbshipit-source-id: 3d3ae146237a2cd49609aaa2bd0e785ebe21f02c

build/fbcode_builder/getdeps/platform.py

@@ -0,0 +1,98 @@
+# Copyright (c) 2019-present, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree. An additional grant
+# of patent rights can be found in the PATENTS file in the same directory.
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import re
+import shlex
+import sys
+
+
+def is_windows():
+    """ Returns true if the system we are currently running on
+    is a Windows system """
+    return sys.platform.startswith("win")
+
+
+def get_linux_type():
+    try:
+        with open("/etc/os-release") as f:
+            data = f.read()
+    except EnvironmentError:
+        return (None, None)
+
+    os_vars = {}
+    for line in data.splitlines():
+        parts = line.split("=", 1)
+        if len(parts) != 2:
+            continue
+        key = parts[0].strip()
+        value_parts = shlex.split(parts[1].strip())
+        if not value_parts:
+            value = ""
+        else:
+            value = value_parts[0]
+        os_vars[key] = value
+
+    name = os_vars.get("NAME")
+    if name:
+        name = name.lower()
+        name = re.sub("linux", "", name)
+        name = name.strip()
+
+    return "linux", name, os_vars.get("VERSION_ID").lower()
+
+
+class HostType(object):
+    def __init__(self, ostype=None, distro=None, distrovers=None):
+        if ostype is None:
+            distro = None
+            distrovers = None
+            if sys.platform.startswith("linux"):
+                ostype, distro, distrovers = get_linux_type()
+            elif sys.platform.startswith("darwin"):
+                ostype = "darwin"
+            elif is_windows():
+                ostype = "windows"
+                distrovers = str(sys.getwindowsversion().major)
+            else:
+                ostype = sys.platform
+
+        # The operating system type
+        self.ostype = ostype
+        # The distribution, if applicable
+        self.distro = distro
+        # The OS/distro version if known
+        self.distrovers = distrovers
+
+    def is_windows(self):
+        return self.ostype == "windows"
+
+    def is_darwin(self):
+        return self.ostype == "darwin"
+
+    def is_linux(self):
+        return self.ostype == "linux"
+
+    def as_tuple_string(self):
+        return "%s-%s-%s" % (
+            self.ostype,
+            self.distro or "none",
+            self.distrovers or "none",
+        )
+
+    @staticmethod
+    def from_tuple_string(s):
+        ostype, distro, distrovers = s.split("-")
+        return HostType(ostype=ostype, distro=distro, distrovers=distrovers)
+
+    def __eq__(self, b):
+        return (
+            self.ostype == b.ostype
+            and self.distro == b.distro
+            and self.distrovers == b.distrovers
+        )