Add new module for preview renderers

src/rstpreview/controllers.py

@@ -1,4 +1,4 @@
-import docutils.core
+from . import markup
 import jinja2
 import milla.controllers
 
@@ -37,7 +37,7 @@ class IndexController(BaseController):
         response = request.ResponseClass()
         try:
             content = request.POST['content']
-            preview = PreviewController.rst2html(content)
+            preview = markup.get_previewer(content).preview()
         except KeyError:
             content = preview = ''
         response.text = self.render('index.html.j2', **dict(
@@ -49,24 +49,13 @@ class IndexController(BaseController):
 
 class PreviewController(BaseController):
 
-    DOCUTILS_SETTINGS = {
-        'syntax_highlight': 'short',
-    }
-
     allowed_methods = ('HEAD', 'POST')
 
     def __call__(self, request):
         return getattr(self, request.method)(request)
 
-    @classmethod
-    def rst2html(cls, source):
-        return docutils.core.publish_parts(
-            source=source,
-            writer_name='html4css1',
-            settings_overrides=cls.DOCUTILS_SETTINGS,
-        )['html_body']
-
     def POST(self, request):
         response = request.ResponseClass()
-        response.text = self.rst2html(request.text)
+        previewer = markup.get_previewer(request.text)
+        response.text = previewer.preview()
         return response

src/rstpreview/markup.py

@@ -0,0 +1,72 @@
+import markupsafe
+try:
+    import docutils.core
+except ImportError:
+    docutils = None
+
+
+def get_previewer(source):
+    lines = source.splitlines()
+    for previewer in PreviewerMeta.previewers:
+        if previewer.detect(lines):
+            return previewer(source)
+    return DefaultPreviewer(source)
+
+
+class PreviewerMeta(type):
+
+    previewers = []
+
+    def __new__(mcs, name, bases, attrs):
+        cls = type.__new__(mcs, name, bases, attrs)
+        if hasattr(cls, 'detect'):
+            mcs.previewers.append(cls)
+        return cls
+
+
+Previewer = PreviewerMeta('Previewer', (), {})
+
+
+class BasePreviewer(Previewer):
+
+    def __init__(self, source):
+        self.source = source
+
+
+class ReStructuredTextPreviewer(BasePreviewer):
+    DOCUTILS_SETTINGS = {
+        'syntax_highlight': 'short',
+    }
+
+    @classmethod
+    def detect(cls, lines):
+        if docutils is None:
+            return False
+        for idx, line in enumerate(lines):
+            if line.startswith('.. '):  # directives, comments
+                return True
+            if line.endswith('::'):  # directive, literal block
+                return True
+            if '``' in line:  # default role
+                return True
+            if ':`' in line:  # role
+                return True
+
+    def preview(self):
+        return docutils.core.publish_parts(
+            source=self.source,
+            writer_name='html4css1',
+            settings_overrides=self.DOCUTILS_SETTINGS,
+        )['html_body']
+
+
+class PlainTextPreviewer(BasePreviewer):
+
+    def preview(self):
+        return '<pre>{0}</pre>'.format(markupsafe.escape(self.source))
+
+
+if docutils is not None:
+    DefaultPreviewer = ReStructuredTextPreviewer
+else:
+    DefaultPreviewer = PlainTextPreviewer