@@ -1,27 +1,5 @@
1−-- | This module provides 'Context's which are used to expand expressions in
2−-- templates and allow for arbitrary customisation.
3−--
4−-- 'Template's define a small expression DSL which consists of strings,
5−-- identifiers and function application. There is no type system, every value is
6−-- a string and on the top level they get substituted verbatim into the page.
7−--
8−-- For example, you can build a context that contains
9−--
10−-- > … <> functionField "concat" (const . concat) <> …
11−--
12−-- which will allow you to use the @concat@ identifier as a function that takes
13−-- arbitrarily many stings and concatenates them to a new string:
14−--
15−-- > $partial(concat("templates/categories/", category))$
16−--
17−-- This will evaluate the @category@ field in the context, then prepend he path,
18−-- and include the referenced file as a template.
19−
20−
211--------------------------------------------------------------------------------
22−{-# LANGUAGE CPP #-}
232{-# LANGUAGE ExistentialQuantification #-}
24−{-# LANGUAGE RankNTypes #-}
253module Hakyll.Web.Template.Context
264 ( ContextField (..)
275 , Context (..)
@@ -39,31 +17,30 @@ module Hakyll.Web.Template.Context
3917 , urlField
4018 , pathField
4119 , titleField
42− , snippetField
4320 , dateField
4421 , dateFieldWith
4522 , getItemUTC
46− , getItemModificationTime
4723 , modificationTimeField
4824 , modificationTimeFieldWith
4925 , teaserField
5026 , teaserFieldWithSeparator
5127 , missingField
52− , bindItem
5328 ) where
5429
5530
5631--------------------------------------------------------------------------------
57−import Control.Applicative (Alternative (..))
32+import Control.Applicative (Alternative (..), pure, (<$>))
5833import Control.Monad (msum)
59−import Data.List (intercalate, tails)
60−#if MIN_VERSION_base(4,9,0)
61−import Data.Semigroup (Semigroup (..))
62−#endif
34+import Data.List (intercalate)
35+import qualified Data.Map as M
36+import Data.Monoid (Monoid (..))
6337import Data.Time.Clock (UTCTime (..))
64−import Data.Time.Format (formatTime)
65−import qualified Data.Time.Format as TF
66−import Data.Time.Locale.Compat (TimeLocale, defaultTimeLocale)
38+import Data.Time.Format (TimeLocale, defaultTimeLocale,
39+ formatTime, parseTime)
40+import System.FilePath (splitDirectories, takeBaseName)
41+
42+
43+--------------------------------------------------------------------------------
6744import Hakyll.Core.Compiler
6845import Hakyll.Core.Compiler.Internal
6946import Hakyll.Core.Identifier
@@ -72,16 +49,12 @@ import Hakyll.Core.Metadata
7249import Hakyll.Core.Provider
7350import Hakyll.Core.Util.String (needlePrefix, splitAll)
7451import Hakyll.Web.Html
75−import Prelude hiding (id)
76−import System.FilePath (dropExtension, splitDirectories,
77− takeBaseName)
7852
7953
8054--------------------------------------------------------------------------------
8155-- | Mostly for internal usage
8256data ContextField
83− = EmptyField
84− | StringField String
57+ = StringField String
8558 | forall a. ListField (Context a) [Item a]
8659
8760
@@ -106,140 +79,72 @@ newtype Context a = Context
10679
10780
10881--------------------------------------------------------------------------------
109−-- | Tries to find a key in the left context,
110−-- or when that fails in the right context.
111−#if MIN_VERSION_base(4,9,0)
112−instance Semigroup (Context a) where
113− (<>) (Context f) (Context g) = Context $ \k a i -> f k a i <|> g k a i
114−
115−instance Monoid (Context a) where
116− mempty = missingField
117− mappend = (<>)
118−#else
11982instance Monoid (Context a) where
12083 mempty = missingField
12184 mappend (Context f) (Context g) = Context $ \k a i -> f k a i <|> g k a i
122−#endif
12385
12486
12587--------------------------------------------------------------------------------
12688field' :: String -> (Item a -> Compiler ContextField) -> Context a
127−field' key value = Context $ \k _ i ->
128− if k == key
129− then value i
130− else noResult $ "Tried field " ++ key
89+field' key value = Context $ \k _ i -> if k == key then value i else empty
13190
13291
13392--------------------------------------------------------------------------------
134−-- | Constructs a new field for a 'Context'.
135−-- If the key matches, the compiler is run and its result is substituted in the
136−-- template.
137−--
138−-- If the compiler fails, the field will be considered non-existent
139−-- in an @$if()$@ macro or ultimately break the template application
140−-- (unless the key is found in another context when using '<>').
141−-- Use 'empty' or 'noResult' for intentional failures of fields used in
142−-- @$if()$@, to distinguish them from exceptions thrown with 'fail'.
93+-- | Constructs a new field in the 'Context.'
14394field
14495 :: String -- ^ Key
14596 -> (Item a -> Compiler String) -- ^ Function that constructs a value based
146− -- on the item (e.g. accessing metadata)
97+ -- on the item
14798 -> Context a
14899field key value = field' key (fmap StringField . value)
149100
150101
151102--------------------------------------------------------------------------------
152103-- | Creates a 'field' to use with the @$if()$@ template macro.
153−-- Attempting to substitute the field into the template will cause an error.
154104boolField
155105 :: String
156106 -> (Item a -> Bool)
157107 -> Context a
158−boolField name f = field' name (\i -> if f i
159− then return EmptyField
160− else noResult $ "Field " ++ name ++ " is false")
108+boolField name f = field name (\i -> if f i
109+ then pure (error $ unwords ["no string value for bool field:",name])
110+ else empty)
161111
162112
163113--------------------------------------------------------------------------------
164−-- | Creates a 'field' that does not depend on the 'Item' but always yields
165−-- the same string
166−constField :: String -- ^ Key
167− -> String -- ^ Value
168− -> Context a
114+-- | Creates a 'field' that does not depend on the 'Item'
115+constField :: String -> String -> Context a
169116constField key = field key . const . return
170117
171118
172119--------------------------------------------------------------------------------
173−-- | Creates a list field to be consumed by a @$for(…)$@ expression.
174−-- The compiler returns multiple items which are rendered in the loop body
175−-- with the supplied context.
176120listField :: String -> Context a -> Compiler [Item a] -> Context b
177121listField key c xs = listFieldWith key c (const xs)
178122
179123
180124--------------------------------------------------------------------------------
181−-- | Produces a new 'Context' which has list field 'key'. All fields from
182−-- 'c' are also accessible from the produced context.
183−-- Be careful when doing @listFieldWith k ca f <> cb@ as any fields in @ca@
184−-- will override fields in @cb@ with the same name.
185−-- Creates a list field like 'listField', but supplies the current page
186−-- to the compiler.
187125listFieldWith
188126 :: String -> Context a -> (Item b -> Compiler [Item a]) -> Context b
189127listFieldWith key c f = field' key $ fmap (ListField c) . f
190128
191129
192130--------------------------------------------------------------------------------
193−-- | Creates a variadic function field.
194−--
195−-- The function will be called with the dynamically evaluated string arguments
196−-- from the template as well as the page that is currently rendered.
197−functionField :: String -- ^ Key
198− -> ([String] -> Item a -> Compiler String) -- ^ Function
199− -> Context a
131+functionField :: String -> ([String] -> Item a -> Compiler String) -> Context a
200132functionField name value = Context $ \k args i ->
201133 if k == name
202134 then StringField <$> value args i
203− else noResult $ "Tried function field " ++ name
135+ else empty
204136
205137
206138--------------------------------------------------------------------------------
207−-- | Transform the respective string results of all fields in a context.
208−-- For example,
209−--
210−-- > mapContext (++"c") (constField "x" "a" <> constField "y" "b")
211−--
212−-- is equivalent to
213−--
214−-- > constField "x" "ac" <> constField "y" "bc"
215−--
216139mapContext :: (String -> String) -> Context a -> Context a
217140mapContext f (Context c) = Context $ \k a i -> do
218141 fld <- c k a i
219142 case fld of
220− EmptyField -> wrongType "boolField"
221143 StringField str -> return $ StringField (f str)
222− _ -> wrongType "ListField"
223− where
224− wrongType typ = fail $ "Hakyll.Web.Template.Context.mapContext: " ++
225− "can't map over a " ++ typ ++ "!"
144+ ListField _ _ -> fail $
145+ "Hakyll.Web.Template.Context.mapContext: " ++
146+ "can't map over a ListField!"
226147
227−--------------------------------------------------------------------------------
228−-- | A context that allows snippet inclusion. In processed file, use as:
229−--
230−-- > ...
231−-- > $snippet("path/to/snippet/")$
232−-- > ...
233−--
234−-- The contents of the included file will not be interpolated like @partial@
235−-- does it.
236−--
237−snippetField :: Context String
238−snippetField = functionField "snippet" f
239− where
240− f [contentsPath] _ = loadBody (fromFilePath contentsPath)
241− f [] _ = fail "No argument to function 'snippet()'"
242− f _ _ = fail "Too many arguments to function 'snippet()'"
243148
244149--------------------------------------------------------------------------------
245150-- | A context that contains (in that order)
@@ -259,7 +164,8 @@ defaultContext =
259164 metadataField `mappend`
260165 urlField "url" `mappend`
261166 pathField "path" `mappend`
262− titleField "title"
167+ titleField "title" `mappend`
168+ missingField
263169
264170
265171--------------------------------------------------------------------------------
@@ -277,20 +183,15 @@ bodyField key = field key $ return . itemBody
277183-- | Map any field to its metadata value, if present
278184metadataField :: Context a
279185metadataField = Context $ \k _ i -> do
280− let id = itemIdentifier i
281− empty' = noResult $ "No '" ++ k ++ "' field in metadata " ++
282− "of item " ++ show id
283− value <- getMetadataField id k
284− maybe empty' (return . StringField) value
186+ value <- getMetadataField (itemIdentifier i) k
187+ maybe empty (return . StringField) value
285188
286189
287190--------------------------------------------------------------------------------
288191-- | Absolute url to the resulting item
289192urlField :: String -> Context a
290−urlField key = field key $ \i -> do
291− let id = itemIdentifier i
292− empty' = fail $ "No route url found for item " ++ show id
293− fmap (maybe empty' toUrl) $ getRoute id
193+urlField key = field key $
194+ fmap (maybe empty toUrl) . getRoute . itemIdentifier
294195
295196
296197--------------------------------------------------------------------------------
@@ -341,12 +242,6 @@ titleField = mapContext takeBaseName . pathField
341242-- that begins with @yyyy-mm-dd@ . For example:
342243-- @folder//yyyy-mm-dd-title//dist//main.extension@ .
343244-- In case of multiple matches, the rightmost one is used.
344−--
345−-- As another alternative, if none of the above matches, and the file has a
346−-- path which contains nested directories specifying a date, then that date
347−-- will be used. In other words, if the path is of the form
348−-- @**//yyyy//mm//dd//**//main.extension@ .
349−-- As above, in case of multiple matches, the rightmost one is used.
350245
351246dateField :: String -- ^ Key in which the rendered date should be placed
352247 -> String -- ^ Format to use on the date
@@ -357,7 +252,7 @@ dateField = dateFieldWith defaultTimeLocale
357252--------------------------------------------------------------------------------
358253-- | This is an extended version of 'dateField' that allows you to
359254-- specify a time locale that is used for outputting the date. For more
360−-- details, see 'dateField' and 'formatTime'.
255+-- details, see 'dateField'.
361256dateFieldWith :: TimeLocale -- ^ Output time locale
362257 -> String -- ^ Destination key
363258 -> String -- ^ Format to use on the date
@@ -377,18 +272,17 @@ getItemUTC :: MonadMetadata m
377272 -> m UTCTime -- ^ Parsed UTCTime
378273getItemUTC locale id' = do
379274 metadata <- getMetadata id'
380− let tryField k fmt = lookupString k metadata >>= parseTime' fmt
381− paths = splitDirectories $ (dropExtension . toFilePath) id'
275+ let tryField k fmt = M.lookup k metadata >>= parseTime' fmt
276+ paths = splitDirectories $ toFilePath id'
382277
383278 maybe empty' return $ msum $
384279 [tryField "published" fmt | fmt <- formats] ++
385280 [tryField "date" fmt | fmt <- formats] ++
386− [parseTime' "%Y-%m-%d" $ intercalate "-" $ take 3 $ splitAll "-" fnCand | fnCand <- reverse paths] ++
387− [parseTime' "%Y-%m-%d" $ intercalate "-" $ fnCand | fnCand <- map (take 3) $ reverse . tails $ paths]
281+ [parseTime' "%Y-%m-%d" $ intercalate "-" $ take 3 $ splitAll "-" fnCand | fnCand <- reverse paths]
388282 where
389283 empty' = fail $ "Hakyll.Web.Template.Context.getItemUTC: " ++
390284 "could not parse time for " ++ show id'
391− parseTime' = parseTimeM True locale
285+ parseTime' = parseTime locale
392286 formats =
393287 [ "%a, %d %b %Y %H:%M:%S %Z"
394288 , "%Y-%m-%dT%H:%M:%S%Z"
@@ -401,33 +295,20 @@ getItemUTC locale id' = do
401295
402296
403297--------------------------------------------------------------------------------
404−-- | Get the time on which the actual file was last modified. This only works if
405−-- there actually is an underlying file, of couse.
406−getItemModificationTime
407− :: Identifier
408− -> Compiler UTCTime
409−getItemModificationTime identifier = do
410− provider <- compilerProvider <$> compilerAsk
411− return $ resourceModificationTime provider identifier
412−
413−
414−--------------------------------------------------------------------------------
415−-- | Creates a field with the last modification date of the underlying item.
416298modificationTimeField :: String -- ^ Key
417299 -> String -- ^ Format
418− -> Context a -- ^ Resulting context
300+ -> Context a -- ^ Resuting context
419301modificationTimeField = modificationTimeFieldWith defaultTimeLocale
420302
421303
422304--------------------------------------------------------------------------------
423−-- | Creates a field with the last modification date of the underlying item
424−-- in a custom localisation format (see 'formatTime').
425305modificationTimeFieldWith :: TimeLocale -- ^ Time output locale
426306 -> String -- ^ Key
427307 -> String -- ^ Format
428308 -> Context a -- ^ Resulting context
429309modificationTimeFieldWith locale key fmt = field key $ \i -> do
430− mtime <- getItemModificationTime $ itemIdentifier i
310+ provider <- compilerProvider <$> compilerAsk
311+ let mtime = resourceModificationTime provider $ itemIdentifier i
431312 return $ formatTime locale fmt mtime
432313
433314
@@ -460,22 +341,7 @@ teaserFieldWithSeparator separator key snapshot = field key $ \item -> do
460341
461342
462343--------------------------------------------------------------------------------
463−-- | Constantly reports any field as missing. Mostly for internal usage,
464−-- it is the last choice in every context used in a template application.
465344missingField :: Context a
466−missingField = Context $ \k _ _ -> noResult $
467− "Missing field '" ++ k ++ "' in context"
468−
469−parseTimeM :: Bool -> TimeLocale -> String -> String -> Maybe UTCTime
470−#if MIN_VERSION_time(1,5,0)
471−parseTimeM = TF.parseTimeM
472−#else
473−parseTimeM _ = TF.parseTime
474−#endif
475−
476−--------------------------------------------------------------------------------
477−
478−-- | Binds an 'Item' to a given 'Context', allowing it to be combined with any
479−-- other 'Context' of any type.
480−bindItem :: Context a -> Item a -> forall b. Context b
481−bindItem (Context ctx) ia = Context $ \k args _ -> ctx k args ia
345+missingField = Context $ \k _ i -> fail $
346+ "Missing field $" ++ k ++ "$ in context for item " ++
347+ show (itemIdentifier i)