Add templating support for generating config files

 - Remove unneeded method
 - Write result to a file and not STDOUT
 - Add documentation
 - Remove trailing whitespace
 - Documentation corrections

Change-Id: I7532222d3512380c4f1129bd05dc2ba37b409dc2
Signed-off-by: Peter Barabas <peter.barabas@ericsson.com>

1 files changed, 169 insertions, 0 deletions

diff --git a/deploy/templater.py b/deploy/templater.py
new file mode 100755
index 000000000..2ad6e05ba
--- /dev/null
+++ b/deploy/templater.py
@@ -0,0 +1,169 @@
+#!/usr/bin/env python
+###############################################################################
+# Copyright (c) 2016 Ericsson AB and others.
+# peter.barabas@ericsson.com
+# All rights reserved. This program and the accompanying materials
+# are made available under the terms of the Apache License, Version 2.0
+# which accompanies this distribution, and is available at
+# http://www.apache.org/licenses/LICENSE-2.0
+###############################################################################
+
+
+import io
+import re
+import yaml
+from common import(
+    err,
+    ArgParser,
+)
+
+
+TAG_START = '%{'
+TAG_END = '}'
+DELIMITER = '/'
+
+
+class Templater(object):
+    def __init__(self, base_file, template_file, output_file):
+        self.template_file = template_file
+        self.output_file = output_file
+        self.base = self.load_yaml(base_file)
+
+    def load_yaml(self, filename):
+        try:
+            with io.open(filename) as yaml_file:
+                return yaml.load(yaml_file)
+        except Exception as error:
+            err('Error opening YAML file: %s' % error)
+
+    def save_yaml(self, filename, content):
+        try:
+            with io.open(filename, 'w') as yaml_file:
+                yaml_file.write(content)
+        except Exception as error:
+            err('Error writing YAML file: %s' % error)
+
+    def get_indent(self, line):
+        return len(line) - len(line.lstrip(' '))
+
+    def format_fragment(self, fragment, indent):
+        result = ''
+        is_first_line = True
+
+        for line in fragment.splitlines():
+            # Skip indenting the first line as it is already indented
+            if is_first_line:
+                line += '\n'
+                is_first_line = False
+            else:
+                line = ' ' * indent + line + '\n'
+
+            result += line
+
+        return result.rstrip('\n')
+
+    def format_substitution(self, string):
+        if isinstance(string, basestring):
+            return string
+        else:
+            return yaml.dump(string, default_flow_style=False)
+
+    def parse_interface_tag(self, tag):
+        # Remove 'interface(' prefix, trailing ')' and split arguments
+        args = tag[len('interface('):].rstrip(')').split(',')
+
+        if len(args) == 1 and not args[0]:
+            err('No arguments for interface().')
+        elif len(args) == 2 and (not args[0] or not args[1]):
+            err('Empty argument for interface().')
+        elif len(args) > 2:
+            err('Too many arguments for interface().')
+        else:
+            return args
+
+    def get_interface_from_network(self, interfaces, network):
+        nics = self.base[interfaces]
+        for nic in nics:
+            if network in nics[nic]:
+                return nic
+
+        err('Network not found: %s' % network)
+
+    def get_role_interfaces(self, role):
+        nodes = self.base['nodes']
+        for node in nodes:
+            if role in node['role']:
+                return node['interfaces']
+
+        err('Role not found: %s' % role)
+
+    def lookup_interface(self, args):
+        nodes = self.base['nodes']
+
+        if len(args) == 1:
+            interfaces = nodes[0]['interfaces']
+        if len(args) == 2:
+            interfaces = self.get_role_interfaces(args[1])
+
+        return self.get_interface_from_network(interfaces, args[0])
+
+    def parse_tag(self, tag, indent):
+        fragment = ''
+
+        if 'interface(' in tag:
+            args = self.parse_interface_tag(tag)
+            fragment = self.lookup_interface(args)
+        else:
+            path = tag.split(DELIMITER)
+            fragment = self.base
+            for i in path:
+                if i in fragment:
+                    fragment = fragment.get(i)
+                else:
+                    err('Error: key "%s" does not exist in base YAML file' % i)
+
+            fragment = self.format_substitution(fragment)
+
+        return self.format_fragment(fragment, indent)
+
+    def run(self):
+        result = ''
+
+        regex = re.compile(re.escape(TAG_START) + r'([a-z].+)' + re.escape(TAG_END),
+                           flags=re.IGNORECASE)
+        with io.open(self.template_file) as f:
+            for line in f:
+                indent = self.get_indent(line)
+                result += re.sub(regex,
+                                 lambda match: self.parse_tag(match.group(1), indent),
+                                 line)
+
+        self.save_yaml(self.output_file, result)
+
+
+def parse_arguments():
+    description = '''Process 'template_file' using 'base_file' as source for
+template variable substitution and write the results to 'output_file'.'''
+
+    parser = ArgParser(prog='python %s' % __file__,
+                       description=description)
+    parser.add_argument('base_file',
+                        help='Base YAML filename')
+    parser.add_argument('template_file',
+                        help='Fragment filename')
+    parser.add_argument('output_file',
+                        help='Output filename')
+
+    args = parser.parse_args()
+    return(args.base_file, args.template_file, args.output_file)
+
+
+def main():
+    base_file, template_file, output_file = parse_arguments()
+
+    templater = Templater(base_file, template_file, output_file)
+    templater.run()
+
+
+if __name__ == '__main__':
+    main()