Evaluation of Python code in content files

_src/build.py

@@ -12,6 +12,7 @@ import frontmatter # from package python-frontmatter
 import datetime
 import re
 from functools import partial
+import evaluations # from itself
 
 def link_this(src: str, dest: str):
     """Creates symlink to source at destination
@@ -87,8 +88,28 @@ def save_this(path: str, content: str):
     with open(path, 'w') as fp:
         fp.write(content)
 
-def evaluate_content(match: re.Match, frontmatter_data: dict) -> str:
-    return '{evaluation goes here!}'
+def evaluate_content(match: re.Match, frontmatter_data: dict, path: str) -> str:
+    global config
+    
+    match = match.group(1)
+    print('  '+match)
+    
+    # prepare globals (environment) for the evaluation
+    environment = {}
+    extension = vars(evaluations.Content)
+    for i in extension.keys():
+        if i.startswith('_'): continue
+        environment[i] = extension[i]
+    environment.update(config['variables'])
+    environment['path'] = path
+    environment.update(frontmatter_data)
+    # this trick let the evaluation functions access our environment
+    evaluations.environment = environment
+    # now execute the command!
+    try:
+        return str(eval(match, environment))
+    except Exception as error:
+        print('\033[31m   ', error, '\033[m', file=sys.stderr)
 
 
 if __name__ == '__main__':
@@ -101,6 +122,7 @@ if __name__ == '__main__':
     # load config
     config = configparser.ConfigParser(interpolation=configparser.ExtendedInterpolation())
     config.read('config.ini')
+    evaluations.config = config # pass the config to evaluations module, so functions can read it
     
     # scan source files
     content_files = scan_dir('content')
@@ -135,12 +157,11 @@ if __name__ == '__main__':
         
         # evaluate {python code} in braces in content files, pass frontmatter_data to the function
         content = re.sub(r'\{([^\s}]+([^}]*[^\s}])?)\}',
-            partial(evaluate_content, frontmatter_data=frontmatter_data),
-            content, flags=re.DOTALL)
+            partial(evaluate_content, frontmatter_data=frontmatter_data, path=path),
+            content)
         
         # load template
         if template := template_for(path):
-            print('  template:', template)
             if template not in template_cache:
                 with open('templates/'+template) as fp:
                     template_cache[template] = fp.read()

_src/evaluations.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+import os
+import urllib.parse
+
+class Content:
+    def log(dest: str) -> str:
+        return 'gemlog/'+dest+'.gmi'
+
+    def article(dest):
+        return 'articles/'+dest+'.gmi'
+
+    def res(dest, label=None):
+        path = os.path.splitext(environment['path'])[0]
+        path += '/'+dest
+        
+        if not os.path.exists('static/'+path):
+            raise Exception(f'Resource {dest} for {path} not found')
+        
+        path = os.path.relpath(path, start=os.path.dirname(os.path.dirname(path)))
+        path = urllib.parse.quote(path)
+        if label:
+            return path+' '+label
+        else:
+            return path