1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
--------------------------------------------------------------------------------
-- | Provides utilities to manipulate HTML pages
module Hakyll.Web.Html
( -- * Generic
withTags
-- * Headers
, demoteHeaders
-- * Url manipulation
, getUrls
, withUrls
, toUrl
, toSiteRoot
, isExternal
-- * Stripping/escaping
, stripTags
, escapeHtml
) where
--------------------------------------------------------------------------------
import Data.Char (digitToInt, intToDigit,
isDigit, toLower)
import Data.List (isPrefixOf)
import qualified Data.Set as S
import System.FilePath (joinPath, splitPath,
takeDirectory)
import Text.Blaze.Html (toHtml)
import Text.Blaze.Html.Renderer.String (renderHtml)
import qualified Text.HTML.TagSoup as TS
--------------------------------------------------------------------------------
-- | Map over all tags in the document
withTags :: (TS.Tag String -> TS.Tag String) -> String -> String
withTags f = renderTags' . map f . TS.parseTags
--------------------------------------------------------------------------------
-- | Map every @h1@ to an @h2@, @h2@ to @h3@, etc.
demoteHeaders :: String -> String
demoteHeaders = withTags $ \tag -> case tag of
TS.TagOpen t a -> TS.TagOpen (demote t) a
TS.TagClose t -> TS.TagClose (demote t)
t -> t
where
demote t@['h', n]
| isDigit n = ['h', intToDigit (min 6 $ digitToInt n + 1)]
| otherwise = t
demote t = t
--------------------------------------------------------------------------------
isUrlAttribute :: String -> Bool
isUrlAttribute = (`elem` ["src", "href", "data"])
--------------------------------------------------------------------------------
getUrls :: [TS.Tag String] -> [String]
getUrls tags = [v | TS.TagOpen _ as <- tags, (k, v) <- as, isUrlAttribute k]
--------------------------------------------------------------------------------
-- | Apply a function to each URL on a webpage
withUrls :: (String -> String) -> String -> String
withUrls f = withTags tag
where
tag (TS.TagOpen s a) = TS.TagOpen s $ map attr a
tag x = x
attr (k, v) = (k, if isUrlAttribute k then f v else v)
--------------------------------------------------------------------------------
-- | Customized TagSoup renderer. The default TagSoup renderer escape CSS
-- within style tags, and doesn't properly minimize.
renderTags' :: [TS.Tag String] -> String
renderTags' = TS.renderTagsOptions TS.renderOptions
{ TS.optRawTag = (`elem` ["script", "style"]) . map toLower
, TS.optMinimize = (`S.member` minimize) . map toLower
}
where
-- A list of elements which must be minimized
minimize = S.fromList
[ "area", "br", "col", "embed", "hr", "img", "input", "meta", "link"
, "param"
]
--------------------------------------------------------------------------------
-- | Convert a filepath to an URL starting from the site root
--
-- Example:
--
-- > toUrl "foo/bar.html"
--
-- Result:
--
-- > "/foo/bar.html"
toUrl :: FilePath -> String
toUrl ('/' : xs) = '/' : xs
toUrl url = '/' : url
--------------------------------------------------------------------------------
-- | Get the relative url to the site root, for a given (absolute) url
toSiteRoot :: String -> String
toSiteRoot = emptyException . joinPath . map parent
. filter relevant . splitPath . takeDirectory
where
parent = const ".."
emptyException [] = "."
emptyException x = x
relevant "." = False
relevant "/" = False
relevant _ = True
--------------------------------------------------------------------------------
-- | Check if an URL links to an external HTTP(S) source
isExternal :: String -> Bool
isExternal url = any (flip isPrefixOf url) ["http://", "https://", "//"]
--------------------------------------------------------------------------------
-- | Strip all HTML tags from a string
--
-- Example:
--
-- > stripTags "<p>foo</p>"
--
-- Result:
--
-- > "foo"
--
-- This also works for incomplete tags
--
-- Example:
--
-- > stripTags "<p>foo</p"
--
-- Result:
--
-- > "foo"
stripTags :: String -> String
stripTags [] = []
stripTags ('<' : xs) = stripTags $ drop 1 $ dropWhile (/= '>') xs
stripTags (x : xs) = x : stripTags xs
--------------------------------------------------------------------------------
-- | HTML-escape a string
--
-- Example:
--
-- > escapeHtml "Me & Dean"
--
-- Result:
--
-- > "Me & Dean"
escapeHtml :: String -> String
escapeHtml = renderHtml . toHtml
|
