source/factorcss/FactorCSS.hs

--
-- This file is part of FactorCSS
-- Licensed under the MIT License,
--                http://www.opensource.org/licenses/mit-license
-- Copyright 2004 James Bursa <james@semichrome.net>
--

-- Factor a CSS stylesheet.
--
-- This tool takes a CSS stylesheet on input and produces an almost equivalent
-- stylesheet on output, but with rulesets split, combined, and reordered to
-- "factor out" common declarations. This helps reveal shared components. The
-- resulting stylesheet may also be smaller.
--
-- The only known case where the output is not equivalent to the input is when
-- the stylesheet depends on the order of rules (see CSS 2.1 6.4.1).

import List
import System
import Tokeniser
import Parser
import CSS

-- Program entry function.
main :: IO ()
main = do
        args <- getArgs
        interact (run args)

-- Produce output from arguments and input.
run :: [String] -> String -> String
run args input
        | argument "help" args          = usage
        | null args                     = go factor
        | argument "factor" args        = go factor
        | argument "explode" args       = go (concatMap explode)
        | argument "identity" args      = go id
        | argument "tree" args          = show stylesheet ++ "\n"
        | argument "statistics" args    = stats stylesheet ++ "\n"
        | otherwise                     = usage
        where   go f = (unlines . show_stylesheet . process f) stylesheet
                stylesheet = (parser . alexScanTokens) input

-- Check an argument list for an argument in short or long form.
argument :: String -> [String] -> Bool
argument long args = elem short shorts || elem ("--" ++ long) args
                where   short = head long
                        shorts = (concat . filter is_short) args
                        is_short ('-':'-':_) = False
                        is_short ('-':_) = True
                        is_short _ = False

-- Usage help string.
usage :: String
usage = unlines ["Usage: factorcss [OPTION]... <FILE",
                "\"Factor out\" common declarations in a CSS stylesheet by splitting, reordering,",
                "and combining rulesets.",
                "The stylesheet is read from standard input, and the result is produced on",
                "standard output.",
                "",
                "Output mode:",
                "  -f, --factor      factor out common declarations (default)",
                "  -e, --explode     produce rulesets with one selector and declaration each",
                "  -i, --identity    just parse and output unmodified",
                "  -t, --tree        parse and display parse tree",
                "  -s, --statistics  count rulesets, selectors, and declarations",
                "",
                "  -h, --help        display this help and exit"]

-- Process a Stylesheet.
process :: ([Statement] -> [Statement]) -> Stylesheet -> Stylesheet
process f (Stylesheet charset imports stmts) =
                Stylesheet charset imports (process_stmts f stmts)

-- Process a list of Statements.
process_stmts :: ([Statement] -> [Statement]) -> [Statement] -> [Statement]
process_stmts f stmts = (f . filter is_ruleset) stmts ++
                (map (process_media f) . filter is_media) stmts ++
                filter is_page stmts

-- Process a Media Statement.
process_media :: ([Statement] -> [Statement]) -> Statement -> Statement
process_media f (Media media stmts) = Media media (f stmts)

-- Factor a list of Ruleset Statements.
factor :: [Statement] -> [Statement]
factor = map implode_sel . groupBy eq_sel .
                sortBy cmp_sel .
                map implode_decl . groupBy eq_decl .
                sortBy cmp_decl . sortBy cmp_sel .
                concat . map explode

-- Explode a Ruleset Statement into an equivalent list of Ruleset Statements
-- with one Selector and one Declaration per Ruleset.
--
-- For example (in CSS syntax),
--   explode "h1, em { color: red; background-color: blue }" =
--       "h1 { color: red }
--        h1 { background-color: blue }
--        em { color: red }
--        em { background-color: blue }"
--
-- [length (explode (Ruleset sels decls)) == length sels * length decls]
explode :: Statement -> [Statement]
explode (Ruleset sels decls) =
                concat (map (\s -> map (\d -> Ruleset [s] [d]) decls) sels)

-- Compare two Ruleset Statements by the Selectors in each.
cmp_sel :: Statement -> Statement -> Ordering
cmp_sel (Ruleset sels0 decls0) (Ruleset sels1 decls1)
        | a < b         = LT
        | a == b        = EQ
        | a > b         = GT
        where   a = show_selectors sels0
                b = show_selectors sels1

-- Compare two Ruleset Statements by the first Declaration in each.
cmp_decl :: Statement -> Statement -> Ordering
cmp_decl (Ruleset sels0 (decl0:decls0)) (Ruleset sels1 (decl1:decls1))
        | a < b         = LT
        | a == b        = EQ
        | a > b         = GT
        where   a = show_declaration decl0
                b = show_declaration decl1

-- Compare two Ruleset Statements for equality by the Selectors in each.
eq_sel :: Statement -> Statement -> Bool
eq_sel z = (== EQ) . cmp_sel z

-- Compare two Ruleset Statements for equality by the first declaration in
-- each.
eq_decl :: Statement -> Statement -> Bool
eq_decl z = (== EQ) . cmp_decl z

-- Implode a list of Ruleset Statements with equal lists of Selectors to a
-- single equivalent Ruleset Statement.
--
-- For example,
--   implode_sel "h1, em { color: red }
--        h1, em { background-color: blue }" =
--       "h1, em { color: red; background-color: blue }"
implode_sel :: [Statement] -> Statement
implode_sel ((Ruleset sels decls):stmts) =
                Ruleset sels (concat (decls:(map declarations stmts)))

-- Implode a list of Ruleset Statements with equal lists of Declarations to a
-- single equivalent Ruleset Statement.
--
-- For example,
--   implode_decl "h1 { color: red }
--        em { color: red }" =
--       "h1, em { color: red }"
implode_decl :: [Statement] -> Statement
implode_decl ((Ruleset sels decls):stmts) =
                Ruleset (concat (sels:(map selectors stmts))) decls

-- Count rulesets, selectors, and declarations in a Stylesheet.
stats :: Stylesheet -> String
stats (Stylesheet charset imports stmts)
        | n == 0        = "0 rulesets"
        | otherwise     = "rulesets " ++ show n ++
                          ", selectors min " ++ show s0 ++
                          " max " ++ show s1 ++
                          " mean " ++ take 5 (
                                show (fromIntegral sn / fromIntegral n)) ++
                          ", declarations min " ++ show d0 ++
                          " max " ++ show d1 ++
                          " mean " ++ take 5 (
                                show (fromIntegral dn / fromIntegral n))
        where [n, s0, s1, sn, d0, d1, dn] = stats_stmts stmts

-- Count rulesets, selectors, and declarations in a list of Statements.
stats_stmts :: [Statement] -> [Int]
stats_stmts stmts = stats_rulesets (filter is_ruleset stmts ++
                (concatMap get_stmts (filter is_media stmts)))
                where   get_stmts (Media media stmts) = stmts

-- Count rulesets, selectors, and declarations in a list of Ruleset Statements.
stats_rulesets :: [Statement] -> [Int]
stats_rulesets stmts = [length stmts,
                minimum sel_lengths, maximum sel_lengths, sum sel_lengths,
                minimum decl_lengths, maximum decl_lengths, sum decl_lengths]
                where   sel_lengths = map (length . selectors) stmts
                        decl_lengths = map (length . declarations) stmts

-- Extract the list of Selectors from a Ruleset Statement.
selectors :: Statement -> [Selector]
selectors (Ruleset s d) = s

-- Extract the list of Declarations from a Ruleset Statement.
declarations :: Statement -> [Declaration]
declarations (Ruleset s d) = d
1	james	63	--
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	james	62
8	james	63	-- 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	james	62	import List
19	james	66	import System
20	james	61	import Tokeniser
21			import Parser
22			import CSS
23
24	james	66	-- Program entry function.
25			main :: IO ()
26	james	61	main = do
27	james	66	args <- getArgs
28			interact (run args)
29	james	62
30	james	66	-- 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	james	67	\| argument "identity" args = go id
38			\| argument "tree" args = show stylesheet ++ "\n"
39			\| argument "statistics" args = stats stylesheet ++ "\n"
40	james	66	\| otherwise = usage
41	james	67	where go f = (unlines . show_stylesheet . process f) stylesheet
42			stylesheet = (parser . alexScanTokens) input
43	james	66
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	james	67	" -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	james	66	"",
68	james	67	" -h, --help display this help and exit"]
69	james	66
70	james	62	-- Process a Stylesheet.
71	james	66	process :: ([Statement] -> [Statement]) -> Stylesheet -> Stylesheet
72			process f (Stylesheet charset imports stmts) =
73			Stylesheet charset imports (process_stmts f stmts)
74	james	62
75			-- Process a list of Statements.
76	james	66	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	james	62	filter is_page stmts
80
81			-- Process a Media Statement.
82	james	66	process_media :: ([Statement] -> [Statement]) -> Statement -> Statement
83			process_media f (Media media stmts) = Media media (f stmts)
84	james	62
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	james	66	-- Compare two Ruleset Statements for equality by the first declaration in
131			-- each.
132	james	62	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	james	67
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