1 files changed, 44 insertions, 0 deletions
diff --git a/src/pymdvar/pymdvar.py b/src/pymdvar/pymdvar.py
new file mode 100644
index 0000000..b6ea344
--- /dev/null
+++ b/src/pymdvar/pymdvar.py
@@ -0,0 +1,44 @@
+from os import getenv
+from markdown.extensions import Extension
+from markdown.inlinepatterns import Pattern
+
+VARIABLE_RE = r'(\$\{)([a-zA-Z_]*)(\})'
+
+
+class VariablePattern(Pattern):
+    # need to redefine as an extra attribute needs to be passed
+    def __init__(self, pattern, variables, enable_env, md=None):
+        self.variables = variables
+        self.enable_env = enable_env
+        super().__init__(pattern, md)
+
+    def handleMatch(self, m):
+        # for some reason the group is offest by 1
+        variable = m.group(3)
+        value = ''
+
+        if variable in self.variables:
+            value = self.variables[variable]
+        else:
+            if self.enable_env:
+                value = getenv(variable, '')
+        return value
+
+
+class VariableExtension(Extension):
+    def __init__(self, **kwargs):
+        self.config = {
+            'enable_env': [False, 'Enable environment variables parsing.'],
+            'variables': [dict(), 'Dictionary holding variables to be used.']
+        }
+        super().__init__(**kwargs)
+
+    def extendMarkdown(self, md):
+        variables = self.getConfig('variables', dict())
+        enable_env = self.getConfig('enable_env', False)
+        variable_pattern = VariablePattern(VARIABLE_RE, variables, enable_env)
+        md.inlinePatterns.register(variable_pattern, 'variable', 175)
+
+
+def makeExtension(*args, **kwargs):
+    return VariableExtension(*args, **kwargs)