1 files changed, 117 insertions, 0 deletions
diff --git a/browser/fsm.py b/browser/fsm.py
new file mode 100644
index 0000000..eccfc6e
--- /dev/null
+++ b/browser/fsm.py
@@ -0,0 +1,117 @@
+import html
+import sys
+import urllib.parse
+
+
+class StackFSM(object):
+    """
+    Implement a finite state machine that uses a stack to
+    manage state.
+    """
+
+    def __init__(self):
+        self._state_stack = []
+
+    def _current_state(self):
+        if len(self._state_stack) > 0:
+            return self._state_stack[-1]
+        return None
+
+    def update(self):
+        fn = self._current_state()
+        if fn is not None:
+            fn()
+
+    def push_state(self, state):
+        self._state_stack.append(state)
+
+    def pop_state(self):
+        return self._state_stack.pop()
+
+
+class Parser(object):
+
+    def __init__(self, document, output=None):
+        self._document = document
+        if output is None:
+            output = sys.stdout
+        self._output = output
+        self._offset = 0
+        self._blanks = 0
+        self._fsm = StackFSM()
+
+    def parse(self):
+        self._fsm.push_state(self.text_state)
+        while self._fsm._current_state() is not None and len(self._document) > self._offset:
+            self._fsm.update()
+
+    def text_state(self):
+        line = self._document[self._offset]
+        if line.strip() == '':
+            self._blanks += 1
+        else:
+            self._blanks = 0
+        if line.startswith('```'):
+            self._fsm.push_state(self.pre_state)
+            self._output.write('<pre>\n')
+            self._offset += 1
+        elif line.startswith('* '):
+            self._fsm.push_state(self.list_state)
+            self._output.write('<ul>\n')
+        elif line.startswith('=>'):
+            self._fsm.push_state(self.link_state)
+            self._output.write('<ul>\n')
+        else:
+            if line.startswith('# '):
+                self._output.write('<h1>{}</h1>\n'.format(html.escape(line[2:])))
+            elif line.startswith('## '):
+                self._output.write('<h2>{}</h2>\n'.format(html.escape(line[3:])))
+            elif line.startswith('### '):
+                self._output.write('<h3>{}</h3>\n'.format(html.escape(line[4:])))
+            elif line.startswith('> '):
+                self._output.write('<blockquote>{}</blockquote>\n'.format(html.escape(line[2:])))
+            elif line.strip() == '':
+                if self._blanks > 1:
+                    self._output.write('<br/>\n')
+            else:
+                self._output.write('<p>{}</p>\n'.format(html.escape(line)))
+            self._offset += 1
+
+    def pre_state(self):
+        line = self._document[self._offset]
+        if line.startswith('```'):
+            self._fsm.pop_state()
+            self._output.write('</pre>\n')
+            self._offset += 1
+        else:
+            self._output.write(line + '\n')
+            self._offset += 1
+
+    def list_state(self):
+        line = self._document[self._offset]
+        if line.startswith('* '):
+            self._output.write('<li>{}</li>\n'.format(html.escape(line[2:])))
+            self._offset += 1
+        else:
+            self._fsm.pop_state()
+            self._output.write('</ul>\n')
+
+    def link_state(self):
+        line = self._document[self._offset]
+        if line.startswith('=>'):
+            parts = line[2:].split(None, 1)
+            url = parts[0]
+            url_parts = urllib.parse.urlsplit(url)
+            if url_parts.scheme in ('gemini', ''):
+                external = ''
+            else:
+                external = open('external_link.svg').read()
+            if len(parts) == 1:
+                text = url
+            else:
+                text = html.escape(parts[1])
+            self._output.write('<li class="link"><a href="{}">{}</a>{}</li>\n'.format(url, text, external))
+            self._offset += 1
+        else:
+            self._fsm.pop_state()
+            self._output.write('</ul>\n')