/[james]/factorcss/FactorCSS.hs
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revision 61 by james, Sun Dec 19 22:10:41 2004 UTC revision 67 by james, Thu Dec 30 23:22:02 2004 UTC
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1    --
2    -- This file is part of FactorCSS
3    -- Licensed under the MIT License,
4    --                http://www.opensource.org/licenses/mit-license
5    -- Copyright 2004 James Bursa <james@semichrome.net>
6    --
7    
8    -- Factor a CSS stylesheet.
9    --
10    -- This tool takes a CSS stylesheet on input and produces an almost equivalent
11    -- stylesheet on output, but with rulesets split, combined, and reordered to
12    -- "factor out" common declarations. This helps reveal shared components. The
13    -- resulting stylesheet may also be smaller.
14    --
15    -- The only known case where the output is not equivalent to the input is when
16    -- the stylesheet depends on the order of rules (see CSS 2.1 6.4.1).
17    
18    import List
19    import System
20  import Tokeniser  import Tokeniser
21  import Parser  import Parser
22  import CSS  import CSS
23    
24    -- Program entry function.
25    main :: IO ()
26  main = do  main = do
27          s <- getContents          args <- getArgs
28  --      print (alexScanTokens s)          interact (run args)
29  --      print (parser (alexScanTokens s))  
30          putStr (unlines (show_stylesheet (parser (alexScanTokens s))))  -- Produce output from arguments and input.
31    run :: [String] -> String -> String
32    run args input
33            | argument "help" args          = usage
34            | null args                     = go factor
35            | argument "factor" args        = go factor
36            | argument "explode" args       = go (concatMap explode)
37            | argument "identity" args      = go id
38            | argument "tree" args          = show stylesheet ++ "\n"
39            | argument "statistics" args    = stats stylesheet ++ "\n"
40            | otherwise                     = usage
41            where   go f = (unlines . show_stylesheet . process f) stylesheet
42                    stylesheet = (parser . alexScanTokens) input
43    
44    -- Check an argument list for an argument in short or long form.
45    argument :: String -> [String] -> Bool
46    argument long args = elem short shorts || elem ("--" ++ long) args
47                    where   short = head long
48                            shorts = (concat . filter is_short) args
49                            is_short ('-':'-':_) = False
50                            is_short ('-':_) = True
51                            is_short _ = False
52    
53    -- Usage help string.
54    usage :: String
55    usage = unlines ["Usage: factorcss [OPTION]... <FILE",
56                    "\"Factor out\" common declarations in a CSS stylesheet by splitting, reordering,",
57                    "and combining rulesets.",
58                    "The stylesheet is read from standard input, and the result is produced on",
59                    "standard output.",
60                    "",
61                    "Output mode:",
62                    "  -f, --factor      factor out common declarations (default)",
63                    "  -e, --explode     produce rulesets with one selector and declaration each",
64                    "  -i, --identity    just parse and output unmodified",
65                    "  -t, --tree        parse and display parse tree",
66                    "  -s, --statistics  count rulesets, selectors, and declarations",
67                    "",
68                    "  -h, --help        display this help and exit"]
69    
70    -- Process a Stylesheet.
71    process :: ([Statement] -> [Statement]) -> Stylesheet -> Stylesheet
72    process f (Stylesheet charset imports stmts) =
73                    Stylesheet charset imports (process_stmts f stmts)
74    
75    -- Process a list of Statements.
76    process_stmts :: ([Statement] -> [Statement]) -> [Statement] -> [Statement]
77    process_stmts f stmts = (f . filter is_ruleset) stmts ++
78                    (map (process_media f) . filter is_media) stmts ++
79                    filter is_page stmts
80    
81    -- Process a Media Statement.
82    process_media :: ([Statement] -> [Statement]) -> Statement -> Statement
83    process_media f (Media media stmts) = Media media (f stmts)
84    
85    -- Factor a list of Ruleset Statements.
86    factor :: [Statement] -> [Statement]
87    factor = map implode_sel . groupBy eq_sel .
88                    sortBy cmp_sel .
89                    map implode_decl . groupBy eq_decl .
90                    sortBy cmp_decl . sortBy cmp_sel .
91                    concat . map explode
92    
93    -- Explode a Ruleset Statement into an equivalent list of Ruleset Statements
94    -- with one Selector and one Declaration per Ruleset.
95    --
96    -- For example (in CSS syntax),
97    --   explode "h1, em { color: red; background-color: blue }" =
98    --       "h1 { color: red }
99    --        h1 { background-color: blue }
100    --        em { color: red }
101    --        em { background-color: blue }"
102    --
103    -- [length (explode (Ruleset sels decls)) == length sels * length decls]
104    explode :: Statement -> [Statement]
105    explode (Ruleset sels decls) =
106                    concat (map (\s -> map (\d -> Ruleset [s] [d]) decls) sels)
107    
108    -- Compare two Ruleset Statements by the Selectors in each.
109    cmp_sel :: Statement -> Statement -> Ordering
110    cmp_sel (Ruleset sels0 decls0) (Ruleset sels1 decls1)
111            | a < b         = LT
112            | a == b        = EQ
113            | a > b         = GT
114            where   a = show_selectors sels0
115                    b = show_selectors sels1
116    
117    -- Compare two Ruleset Statements by the first Declaration in each.
118    cmp_decl :: Statement -> Statement -> Ordering
119    cmp_decl (Ruleset sels0 (decl0:decls0)) (Ruleset sels1 (decl1:decls1))
120            | a < b         = LT
121            | a == b        = EQ
122            | a > b         = GT
123            where   a = show_declaration decl0
124                    b = show_declaration decl1
125    
126    -- Compare two Ruleset Statements for equality by the Selectors in each.
127    eq_sel :: Statement -> Statement -> Bool
128    eq_sel z = (== EQ) . cmp_sel z
129    
130    -- Compare two Ruleset Statements for equality by the first declaration in
131    -- each.
132    eq_decl :: Statement -> Statement -> Bool
133    eq_decl z = (== EQ) . cmp_decl z
134    
135    -- Implode a list of Ruleset Statements with equal lists of Selectors to a
136    -- single equivalent Ruleset Statement.
137    --
138    -- For example,
139    --   implode_sel "h1, em { color: red }
140    --        h1, em { background-color: blue }" =
141    --       "h1, em { color: red; background-color: blue }"
142    implode_sel :: [Statement] -> Statement
143    implode_sel ((Ruleset sels decls):stmts) =
144                    Ruleset sels (concat (decls:(map declarations stmts)))
145    
146    -- Implode a list of Ruleset Statements with equal lists of Declarations to a
147    -- single equivalent Ruleset Statement.
148    --
149    -- For example,
150    --   implode_decl "h1 { color: red }
151    --        em { color: red }" =
152    --       "h1, em { color: red }"
153    implode_decl :: [Statement] -> Statement
154    implode_decl ((Ruleset sels decls):stmts) =
155                    Ruleset (concat (sels:(map selectors stmts))) decls
156    
157    -- Count rulesets, selectors, and declarations in a Stylesheet.
158    stats :: Stylesheet -> String
159    stats (Stylesheet charset imports stmts)
160            | n == 0        = "0 rulesets"
161            | otherwise     = "rulesets " ++ show n ++
162                              ", selectors min " ++ show s0 ++
163                              " max " ++ show s1 ++
164                              " mean " ++ take 5 (
165                                    show (fromIntegral sn / fromIntegral n)) ++
166                              ", declarations min " ++ show d0 ++
167                              " max " ++ show d1 ++
168                              " mean " ++ take 5 (
169                                    show (fromIntegral dn / fromIntegral n))
170            where [n, s0, s1, sn, d0, d1, dn] = stats_stmts stmts
171    
172    -- Count rulesets, selectors, and declarations in a list of Statements.
173    stats_stmts :: [Statement] -> [Int]
174    stats_stmts stmts = stats_rulesets (filter is_ruleset stmts ++
175                    (concatMap get_stmts (filter is_media stmts)))
176                    where   get_stmts (Media media stmts) = stmts
177    
178    -- Count rulesets, selectors, and declarations in a list of Ruleset Statements.
179    stats_rulesets :: [Statement] -> [Int]
180    stats_rulesets stmts = [length stmts,
181                    minimum sel_lengths, maximum sel_lengths, sum sel_lengths,
182                    minimum decl_lengths, maximum decl_lengths, sum decl_lengths]
183                    where   sel_lengths = map (length . selectors) stmts
184                            decl_lengths = map (length . declarations) stmts
185    
186    -- Extract the list of Selectors from a Ruleset Statement.
187    selectors :: Statement -> [Selector]
188    selectors (Ruleset s d) = s
189    
190    -- Extract the list of Declarations from a Ruleset Statement.
191    declarations :: Statement -> [Declaration]
192    declarations (Ruleset s d) = d
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