Add setup_cosmos_modules to the repo

global/overlay/etc/puppet/setup_cosmos_modules

@@ -0,0 +1,160 @@
+#!/usr/bin/env python3
+""" Write out a puppet cosmos-modules.conf """
+
+import hashlib
+import os
+import os.path
+import platform
+import sys
+
+from debian import debian_support
+
+try:
+    from configobj import ConfigObj
+
+    OS_INFO = ConfigObj("/etc/os-release")
+except (IOError, ModuleNotFoundError):
+    OS_INFO = None
+
+
+def get_file_hash(modulesfile):
+    """
+    Based on https://github.com/python/cpython/pull/31930: should use
+    hashlib.file_digest() but it is only available in python 3.11
+    """
+    try:
+        with open(modulesfile, "rb") as fileobj:
+            digestobj = hashlib.sha256()
+            _bufsize = 2**18
+            buf = bytearray(_bufsize)  # Reusable buffer to reduce allocations.
+            view = memoryview(buf)
+            while True:
+                size = fileobj.readinto(buf)
+                if size == 0:
+                    break  # EOF
+                digestobj.update(view[:size])
+    except FileNotFoundError:
+        return ""
+
+    return digestobj.hexdigest()
+
+
+def get_list_hash(file_lines):
+    """Get hash of list contents"""
+
+    file_lines_hash = hashlib.sha256()
+    for line in file_lines:
+        file_lines_hash.update(line)
+
+    return file_lines_hash.hexdigest()
+
+
+def create_file_content(modules):
+    """
+    Write out the expected file contents to a list so we can check the
+    expected checksum before writing anything
+    """
+    file_lines = []
+    file_lines.append(
+        "# Generated by {}\n".format(  # pylint: disable=consider-using-f-string
+            os.path.basename(sys.argv[0])
+        ).encode("utf-8")
+    )
+    for key in modules:
+        file_lines.append(
+            "{0:11} {1} {2} {3}\n".format(  # pylint: disable=consider-using-f-string
+                key,
+                modules[key]["repo"],
+                modules[key]["upgrade"],
+                modules[key]["tag"],
+            ).encode("utf-8")
+        )
+
+    return file_lines
+
+
+def main():
+    """Starting point of the program"""
+
+    modulesfile: str = "/etc/puppet/cosmos-modules.conf"
+    modulesfile_tmp: str = modulesfile + ".tmp"
+
+    modules: dict = {
+        "sunet": {
+            "repo": "https://github.com/SUNET/puppet-sunet.git",
+            "upgrade": "yes",
+            "tag": "stable-2023v1-2*",
+        },
+        "augeas": {
+            "repo": "https://github.com/SUNET/puppet-augeas.git",
+            "upgrade": "yes",
+            "tag": "sunet-2*",
+        },
+        "concat": {
+            "repo": "https://github.com/SUNET/puppetlabs-concat.git",
+            "upgrade": "yes",
+            "tag": "sunet-2*",
+        },
+        "stdlib": {
+            "repo": "https://github.com/SUNET/puppetlabs-stdlib.git",
+            "upgrade": "yes",
+            "tag": "sunet-2*",
+        },
+        "apt": {
+            "repo": "https://github.com/SUNET/puppetlabs-apt.git",
+            "upgrade": "yes",
+            "tag": "sunet-2*",
+        },
+        "docker": {
+            "repo": "https://github.com/SUNET/garethr-docker.git",
+            "upgrade": "yes",
+            "tag": "sunet-2*",
+        },
+    }
+
+    if OS_INFO:
+        # Provided by Debian/Ubuntu via
+        # https://github.com/SUNET/multiverse/blob/main/global/pre-tasks.d/030puppet
+
+        if (OS_INFO["ID"] == "debian" and int(OS_INFO["VERSION_ID"]) >= 12) or (
+            OS_INFO["ID"] == "ubuntu"
+            and debian_support.version_compare(OS_INFO["VERSION_ID"], "24.04") >= 0
+        ):
+            del modules["augeas"]
+            del modules["apt"]
+            del modules["concat"]
+            del modules["stdlib"]
+
+        # Make test machines use special test branch of puppet-sunet:
+        if OS_INFO["ID"] == "ubuntu":
+            nodename = platform.node()
+            name_parts = nodename.split("-")
+            if len(name_parts) > 1:
+                if name_parts[1] == "test":
+                    modules["sunet"]["tag"] = "testing-2*"
+
+    # Build list of expected file content
+    file_lines = create_file_content(modules)
+
+    # Get hash of the list
+    list_hash = get_list_hash(file_lines)
+
+    # Get hash of the existing file on disk
+    file_hash = get_file_hash(modulesfile)
+
+    # Update the file if necessary
+    if list_hash != file_hash:
+        # Since we are reading the file with 'rb' when computing our hash use 'wb' when
+        # writing so we dont end up creating a file that does not match the
+        # expected hash
+        with open(modulesfile_tmp, "wb") as fileobj:
+            for line in file_lines:
+                fileobj.write(line)
+
+        # Rename it in place so the update is atomic for anything else trying to
+        # read the file
+        os.rename(modulesfile_tmp, modulesfile)
+
+
+if __name__ == "__main__":
+    main()