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{- |
Open Graph metadata, as described at <https://ogp.me/>. This
implementation supports the following properties:
+------------------+----------------------------------------------------+
| @og:type@ | __Hardcoded__ value @"article"@ |
+------------------+----------------------------------------------------+
| @og:url@ | __Required__ concatenation of @root@ and @url@ |
| | context fields, both of which are required. |
+------------------+----------------------------------------------------+
| @og:title@ | __Required__ title of article, from @title@ field. |
+------------------+----------------------------------------------------+
| @og:description@ | __Optional__ brief description taken from context |
| | field @og-description@, if set. |
+------------------+----------------------------------------------------+
| @og:image@ | __Optional__ image URL taken from context |
| | field @og-image@, if set. |
+------------------+----------------------------------------------------+
To use, add 'openGraphField' to the template context:
@
let
context = 'defaultContext' <> …
postContext = context <> 'openGraphField' "opengraph" context
@
and update the template:
@
\<head>
\<title>$title$</title>
\<link rel="stylesheet" type="text\/css" href="\/css\/default.css" />
$if(opengraph)$$opengraph$$endif$
\</head>
@
See also "Hakyll.Web.Meta.TwitterCard".
-}
module Hakyll.Web.Meta.OpenGraph
( openGraphField
) where
import Hakyll.Core.Compiler
import Hakyll.Core.Item
import Hakyll.Web.Template
import Hakyll.Web.Template.Context
openGraphField :: String -> Context String -> Context String
openGraphField k ctx = functionField k $ \_args i -> do
template <- openGraphTemplate
itemBody <$> applyTemplate template ctx i
openGraphTemplate :: Compiler Template
openGraphTemplate = do
makeItem openGraphTemplateString >>= compileTemplateItem
openGraphTemplateString :: String
openGraphTemplateString =
"<meta property=\"og:type\" content=\"article\" />\
\<meta property=\"og:url\" content=\"$root$$url$\" />\
\<meta property=\"og:title\" content=\"$title$\" />\
\$if(og-description)$\
\<meta property=\"og:description\" content=\"$og-description$\" />\
\$endif$\
\$if(og-image)$\
\<meta property=\"og:image\" content=\"$og-image$\" />\
\$endif$\
\"
|
