feat: compress HTML

ssg/src/Main.hs

@@ -1,12 +1,15 @@
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 import Control.Monad (forM_)
 import Data.List (isPrefixOf, isSuffixOf)
 import Data.Maybe (fromMaybe)
+import qualified Data.Set as S
 import qualified Data.Text as T
 import qualified Data.Text.Slugger as Slugger
 import Hakyll
 import System.FilePath (takeFileName)
+import qualified Text.HTML.TagSoup as TS
 import Text.Pandoc
   ( Extension (Ext_fenced_code_attributes, Ext_footnotes, Ext_gfm_auto_identifiers, Ext_implicit_header_references, Ext_smart),
     Extensions,
@@ -17,7 +20,7 @@ import Text.Pandoc
     readerExtensions,
     writerExtensions,
   )
-import Text.Pandoc.Highlighting (Style, breezeDark, styleToCss)
+import Text.Pandoc.Highlighting (Style, breezeDark)
 
 --------------------------------------------------------------------------------
 -- PERSONALIZATION
@@ -100,6 +103,7 @@ main = hakyllWith config $ do
         >>= saveSnapshot "content"
         >>= loadAndApplyTemplate "templates/post.html" ctx
         >>= loadAndApplyTemplate "templates/default.html" ctx
+        >>= compressHtmlCompiler
 
   match "new-zealand/**" $ do
     let ctx = constField "type" "article" <> postCtx
@@ -109,6 +113,7 @@ main = hakyllWith config $ do
         >>= saveSnapshot "content"
         >>= loadAndApplyTemplate "templates/info.html" ctx
         >>= loadAndApplyTemplate "templates/default.html" ctx
+        >>= compressHtmlCompiler
 
   match "index.html" $ do
     route idRoute
@@ -124,6 +129,7 @@ main = hakyllWith config $ do
       getResourceBody
         >>= applyAsTemplate indexCtx
         >>= loadAndApplyTemplate "templates/default.html" indexCtx
+        >>= compressHtmlCompiler
 
   match "templates/*" $ compile templateBodyCompiler
 
@@ -153,9 +159,44 @@ main = hakyllWith config $ do
 --------------------------------------------------------------------------------
 -- COMPILER HELPERS
 
-makeStyle :: Style -> Compiler (Item String)
-makeStyle =
-  makeItem . compressCss . styleToCss
+compressHtmlCompiler :: Item String -> Compiler (Item String)
+compressHtmlCompiler = pure . fmap compressHtml
+
+compressHtml :: String -> String
+compressHtml = withTagList compressTags
+
+compressTags :: [TS.Tag String] -> [TS.Tag String]
+compressTags = go S.empty
+  where
+    go :: S.Set String -> [TS.Tag String] -> [TS.Tag String]
+    go stack =
+      \case [] -> []
+            ((TS.TagComment _):rest) -> go stack rest
+            (tag@(TS.TagOpen name _):rest) -> tag : go (S.insert name stack) rest
+            (tag@(TS.TagClose name):rest) -> tag : go (S.delete name stack) rest
+            (tag@(TS.TagText _):rest)
+              | stackHasExclusion stack -> tag : go stack rest
+              | otherwise -> fmap cleanTag tag : go stack rest
+            (tag:rest) -> tag : go stack rest
+
+    stackHasExclusion :: S.Set String -> Bool
+    stackHasExclusion stack =
+      any (`S.member` stack) ["pre", "style", "textarea"]
+
+    replaceTab :: Char -> Char
+    replaceTab '\t' = ' '
+    replaceTab s    = s
+
+    isNewLineIsh :: Char -> Bool
+    isNewLineIsh = (`elem` ("\f\n\r\v" :: String))
+
+    cleanTag :: String -> String
+    cleanTag = filter (not . isNewLineIsh) . fmap replaceTab . trim
+
+-- https://rebeccaskinner.net/posts/2021-01-31-hakyll-syntax-highlighting.html
+--makeStyle :: Style -> Compiler (Item String)
+--makeStyle =
+--  makeItem . compressCss . styleToCss
 
 --------------------------------------------------------------------------------
 -- CONTEXT

ssg/ssg.cabal

@@ -11,9 +11,11 @@ executable hakyll-site
   hs-source-dirs:    src
   build-depends:     base >= 4.8
                    , hakyll >= 4.14
+                   , containers >= 0.6.5.1
                    , filepath >= 1.0
                    , pandoc >= 2.11
                    , slugger >= 0.1.0.1
+                   , tagsoup >= 0.14.8
                    , text >= 1 && < 1.3
   ghc-options:       -Wall -threaded
   default-language:  Haskell2010