handle indented snippets

zpp

@@ -51,8 +51,6 @@ def main(args):
     # So I think it makes the most sense to break the input text by "/*/"?
     # and then depending on whether a snippet has a newline, we handle it
     # differently?
-    # The trouble with that appoarch, is that we won't preserve the indentation.
-        # I'm not sure that really matters.
 
     divisions = entire_input.split("/*/")
 
@@ -64,13 +62,58 @@ def main(args):
         if passthrough:
             ostream.write(division);
         elif "\n" in division:
-            # this would be a multi-line snippet, so we'll run the source
-            # altogether and capture the output:
+            # This would be a multi-line snippet, so we'll run the source
+            # altogether and capture the output.
+            # Python is funny about indentation, so we will have to strip off
+            # the initial left indentation of each of the lines of the snippet.
+            # So step 1 is figuring out how much indentation we need to remove.
+            # We'll look at the first line for that.
+            
+            # bonus points if we can support tabs too!
+            
+            lines = division.split('\n');
+            
+            first_nonempty_line = None;
+            
+            # let's find the first non-empty line:
+            for line in lines:
+                if line.strip():
+                    first_nonempty_line = line;
+                    break;
+            
+            if first_nonempty_line is None:
+                print(f"zpp: error! empty snippet!");
+                return 1;
+            
+            # and just build up the string the whitespace:
+            indentation = '';
+            
+            for c in first_nonempty_line:
+                if c.isspace():
+                    indentation += c
+                else:
+                    break;
+            
+            # now that we know how many spaces to eliminate, let's go through
+            # each line and remove them. lines of just whitespace can be
+            # passed through with getting processed.
+            
+            source = "";
+            
+            for line in lines:
+                if not line.strip():
+                    source += line + '\n';
+                elif line.startswith(indentation):
+                    source += line[len(indentation):] + '\n';
+                else:
+                    print(f"zpp: error! mixed indentation in snippet!");
+                    return 1;
+            
             real_stdout = sys.stdout
             
             sys.stdout = captured_stdout = io.StringIO()
             
-            eval(compile(division, "<zog-snippet>", "exec"), snippet_globals);
+            eval(compile(source, "<zog-snippet>", "exec"), snippet_globals);
             
             sys.stdout = real_stdout