add Rule.from_string() and Rule.to_string()

readme.markdown

@@ -5,6 +5,8 @@ This is a a CSS modeling utility written in pure Python.
 ## Usage ##
 
 ```python
+from css_parser.stylesheet import StyleSheet
+
 # parse css string
 text = 'body {margin:0;} p.indent{text-indent:1em;}'
 stylesheet = StyleSheet.from_string(text)
@@ -43,12 +45,44 @@ stylesheet.prepend_rule(newrule, existingrule)
 mediaquery = existingrule.get_mediaquery()
 newrule.set_mediaquery(mediaquery)
 stylesheet.append(newrule, mediaquery)
+
 '''
 If the media-queries don't match, the new rule 
 will be added before/after the media-query, 
 depending on whether prepend_rule or 
 append_rule is used.
 '''
+
+from css_parser.rule import Rule
+
+# create rule from string
+text = 'blockquote {margin:1em 5% 1em 5%;}'
+rule = Rule.from_string(text)
+
+# media-queries are retained
+text = '@media all {blockquote {margin:1em 5% 1em 5%;} }'
+rule = Rule.from_string(text)
+
+# multiple rules can be generated in this way, if desired
+text = '/* multiple rules */' \
+	'@media all {' \
+	'	blockquote {' \
+	'		margin:1em 5% 1em 5%;' \
+	'	}' \
+	'	p {' \
+	'		color:blue;' \
+	'	}' \
+	'}'
+rule = Rule.from_string(text)
+
+'''
+Note: If it is important that comments and whitespace be
+preserved, use StyleSheet.from_string() rather than Rule.from_string().
+'''
+
+# write single rule to string
+# includes media-query, if applicable
+rule.to_string()
 ```	
 
 ## Features
@@ -71,6 +105,7 @@ append_rule is used.
 
 ### Rule
 
+1. [ ] Create Rule from string
 1. [ ] Get declarations by property
 2. [ ] Append declaration
 3. [ ] Prepend declaration

src/css_parser/rule.py

@@ -1,11 +1,21 @@
 import re
+import stylesheet_reader
 
 class Rule:
 	def __init__(self, tokens=[]):
 		self.tokens = tokens
 		self.selector_tokens = []
 		self.declarations = []
 		self.mediaquery = None
+
+	@classmethod
+	def from_string(cls, text):
+		stylesheet = stylesheet_reader.StyleSheetReader.read_string(text)
+		if len(stylesheet.get_rules()) == 1:
+			return stylesheet.get_rules()[0]
+		if len(stylesheet.get_rules()) > 1:
+			return stylesheet.get_rules()
+		return None
 
 	def set_selector_tokens(self, tokens):
 		self.selector_tokens = tokens
@@ -32,3 +42,12 @@ def stringify_tokens(self, tokens):
 		txt = ''.join([str(t) for t in tokens])
 		return re.sub('\s+', ' ', txt).strip()
 
+	def to_string(self):
+		tokens = [t for t in self.tokens]
+		if self.mediaquery:
+			m = self.mediaquery
+			tokens = m.get_starttokens() + tokens + m.get_endtokens()
+		return ''.join([str(t) for t in tokens])
+
+	def __str__(self):
+		return ''.join([str(t) for t in self.tokens])

src/tests/test_rule.py

@@ -0,0 +1,82 @@
+import os
+import re
+from css_parser.stylesheet import StyleSheet
+from css_parser.rule import Rule
+
+class TestCases:
+
+	# ----------------------------------------
+
+	def test_from_string(self):
+		tests = [
+				# one rule
+				{'input': 'body{margin:0;}',
+				 'expected': 'body{margin:0;}'
+					},
+				# one rule, space around
+				{'input': ' p.indent {margin:0;} ',
+				 'expected': 'p.indent {margin:0;}'
+					},
+				# one rule, multilined
+				{'input': 'p.indent {' \
+						'	margin:0;' \
+						'}',
+				 'expected': 'p.indent {' \
+						'	margin:0;' \
+						'}'
+					},
+				# one rule, media-queried
+				{'input': '@media all {' \
+						'	p { margin:0;}' \
+						'}',
+				 'expected': '@media all {' \
+						'p { margin:0;}' \
+						'}'
+					}
+
+				]
+
+		for test in tests:
+			yield self.check_from_string, test
+
+	def check_from_string(self, test):
+		rule = Rule.from_string(test['input'])
+		observed = rule.to_string()
+		for k in test:
+			print '%s: %s' % (k, test[k])
+		print 'observed: %s' % (observed)
+		assert observed == test['expected']
+
+	# ----------------------------------------
+
+	def test_from_string_multiple_rules(self):
+		tests = [
+				# two rules
+				{'input': 'body{margin:0;} p {padding:0 }',
+				 'expected': ['body{margin:0;}', 'p {padding:0 }']
+					},
+				# two rules, media-queried
+				{'input': '@media all {' \
+						'	p { margin:0;}' \
+						'	span { margin:0;}' \
+						'}',
+				 'expected': ['@media all {p { margin:0;}}', 
+					 '@media all {span { margin:0;}}']
+					}
+				]
+
+		for test in tests:
+			yield self.check_from_string_multiple_rules, test
+
+	def check_from_string_multiple_rules(self, test):
+		rules = Rule.from_string(test['input'])
+		observed = [r.to_string() for r in rules]
+		for k in test:
+			print '%s: %s' % (k, test[k])
+		print 'observed: %s' % (observed)
+		assert observed == test['expected']
+
+	# ----------------------------------------
+
+
+