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-- |
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-- This file is part of FactorCSS |
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-- Licensed under the MIT License, |
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-- http://www.opensource.org/licenses/mit-license |
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-- Copyright 2004 James Bursa <james@semichrome.net> |
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-- |
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-- Factor a CSS stylesheet. |
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-- |
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-- This tool takes a CSS stylesheet on input and produces an almost equivalent |
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-- stylesheet on output, but with rulesets split, combined, and reordered to |
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-- "factor out" common declarations. This helps reveal shared components. The |
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-- resulting stylesheet may also be smaller. |
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-- |
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-- The only known case where the output is not equivalent to the input is when |
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-- the stylesheet depends on the order of rules (see CSS 2.1 6.4.1). |
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import List |
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import Tokeniser |
import Tokeniser |
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import Parser |
import Parser |
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import CSS |
import CSS |
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main = do |
main = do |
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s <- getContents |
s <- getContents |
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-- print (alexScanTokens s) |
-- print (alexScanTokens s) |
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-- print (parser (alexScanTokens s)) |
-- (print . process . parser . alexScanTokens) s |
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putStr (unlines (show_stylesheet (parser (alexScanTokens s)))) |
(putStr . unlines . show_stylesheet . process . |
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parser . alexScanTokens) s |
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-- Process a Stylesheet. |
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process :: Stylesheet -> Stylesheet |
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process (Stylesheet charset imports stmts) = |
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Stylesheet charset imports (process_stmts stmts) |
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-- Process a list of Statements. |
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process_stmts :: [Statement] -> [Statement] |
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process_stmts stmts = (factor . filter is_ruleset) stmts ++ |
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(map process_media . filter is_media) stmts ++ |
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filter is_page stmts |
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-- Process a Media Statement. |
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process_media :: Statement -> Statement |
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process_media (Media media stmts) = Media media (factor stmts) |
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-- Factor a list of Ruleset Statements. |
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factor :: [Statement] -> [Statement] |
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factor = map implode_sel . groupBy eq_sel . |
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sortBy cmp_sel . |
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map implode_decl . groupBy eq_decl . |
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sortBy cmp_decl . sortBy cmp_sel . |
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concat . map explode |
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-- Explode a Ruleset Statement into an equivalent list of Ruleset Statements |
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-- with one Selector and one Declaration per Ruleset. |
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-- |
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-- For example (in CSS syntax), |
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-- explode "h1, em { color: red; background-color: blue }" = |
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-- "h1 { color: red } |
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-- h1 { background-color: blue } |
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-- em { color: red } |
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-- em { background-color: blue }" |
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-- |
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-- [length (explode (Ruleset sels decls)) == length sels * length decls] |
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explode :: Statement -> [Statement] |
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explode (Ruleset sels decls) = |
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concat (map (\s -> map (\d -> Ruleset [s] [d]) decls) sels) |
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-- Compare two Ruleset Statements by the Selectors in each. |
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cmp_sel :: Statement -> Statement -> Ordering |
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cmp_sel (Ruleset sels0 decls0) (Ruleset sels1 decls1) |
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| a < b = LT |
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| a == b = EQ |
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| a > b = GT |
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where a = show_selectors sels0 |
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b = show_selectors sels1 |
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-- Compare two Ruleset Statements by the first Declaration in each. |
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cmp_decl :: Statement -> Statement -> Ordering |
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cmp_decl (Ruleset sels0 (decl0:decls0)) (Ruleset sels1 (decl1:decls1)) |
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| a < b = LT |
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| a == b = EQ |
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| a > b = GT |
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where a = show_declaration decl0 |
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b = show_declaration decl1 |
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-- Compare two Ruleset Statements for equality by the Selectors in each. |
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eq_sel :: Statement -> Statement -> Bool |
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eq_sel z = (== EQ) . cmp_sel z |
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-- Compare two Ruleset Statements for equality by the first declaration in each. |
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eq_decl :: Statement -> Statement -> Bool |
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eq_decl z = (== EQ) . cmp_decl z |
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-- Implode a list of Ruleset Statements with equal lists of Selectors to a |
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-- single equivalent Ruleset Statement. |
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-- |
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-- For example, |
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-- implode_sel "h1, em { color: red } |
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-- h1, em { background-color: blue }" = |
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-- "h1, em { color: red; background-color: blue }" |
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implode_sel :: [Statement] -> Statement |
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implode_sel ((Ruleset sels decls):stmts) = |
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Ruleset sels (concat (decls:(map declarations stmts))) |
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where declarations :: Statement -> [Declaration] |
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declarations (Ruleset s d) = d |
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-- Implode a list of Ruleset Statements with equal lists of Declarations to a |
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-- single equivalent Ruleset Statement. |
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-- |
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-- For example, |
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-- implode_decl "h1 { color: red } |
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-- em { color: red }" = |
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-- "h1, em { color: red }" |
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implode_decl :: [Statement] -> Statement |
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implode_decl ((Ruleset sels decls):stmts) = |
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Ruleset (concat (sels:(map selectors stmts))) decls |
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where selectors :: Statement -> [Selector] |
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selectors (Ruleset s d) = s |
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