Allow control of span linking

.gitignore

@@ -1,2 +1,6 @@
 /.stack-work
-/agda-reference-filter
+/agda-reference-filter
+
+/example/Agda*.html
+/example/*.agdai
+/example/*.css

README.md

@@ -4,9 +4,35 @@ A Pandoc filter for linking Agda identifiers in inline code blocks.
 
 ## Usage
 
-Compile your literate Agda file to Markdown (use `--html-highlight=auto`), then `pandoc --filter agda-reference-filter -i output.md -o output.html` to compile the Markdown to HTML. Inline code spans that are exactly the same as an identifier present in the raw HTML emitted by Agda (that is - either a definition or a reference) will be linked to the same place that Agda linked that identifier to.
+The filter operates on Markdown files generated by Agda's built-in
+literate programming support (use `--html-highlight=auto` to keep the
+Markdown), then call Pandoc with the filter:
 
 ```bash
 agda --html-highlight=auto --html example.lagda.md
 pandoc --filter agda-reference-filter -i example.md -o example.html
-```
+```
+
+The input file will be scanned, in source order, to build a variable
+name - HTML element association.
+
+Only the first reference is counted: if you have two identifiers called
+`go`, then `` `go` `` in Markdown will link to the first.
+
+### Controlling whether spans are linked
+
+Code spans in Markdown are only linked if they have the `agda` - **case
+insensitive** - class. In Pandoc syntax, you can attach a class to a
+code span like so:
+
+```
+`List`{.agda}
+```
+
+If you want a span to have the `agda` class but for it not to be linked,
+add the `nolink` class.
+
+### Controlling what spans are linked to
+
+If a span has the `ident` attribute, then the value of that attribute
+will be used as the identifier to link to instead of the span text.

example/example.html

@@ -1,4 +1,10 @@
-<p>This is a literate Agda file. This span - <span class="Agda"><a href="example.html#104" class="Record">span</a></span> - will be linked to the record below:</p>
-<pre class="Agda"><a id="97" class="Keyword">record</a> <a id="span"></a><a id="104" href="example.html#104" class="Record">span</a> <a id="109" class="Symbol">:</a> <a id="111" class="PrimitiveType">Set</a> <a id="115" class="Keyword">where</a>
-  <a id="123" class="Keyword">constructor</a> <a id="hey-look"></a><a id="135" href="example.html#135" class="InductiveConstructor">hey-look</a>
+<p>This is a literate Agda file.</p>
+<p>Here’s some inline code:</p>
+<ul class="incremental">
+<li>This is a link to the record below: <pre class="Agda"><a href="example.html#224" class="Record">Record</a></pre></li>
+<li>This is not: <code>Record</code></li>
+<li>This is a link with alternate text: <pre class="Agda"><a href="example.html#224" class="Record">also a link</a></pre></li>
+</ul>
+<pre class="Agda"><a id="217" class="Keyword">record</a> <a id="Record"></a><a id="224" href="example.html#224" class="Record">Record</a> <a id="231" class="Symbol">:</a> <a id="233" class="PrimitiveType">Set</a> <a id="237" class="Keyword">where</a>
+  <a id="245" class="Keyword">constructor</a> <a id="hey-look"></a><a id="257" href="example.html#257" class="InductiveConstructor">hey-look</a>
 </pre>

example/example.lagda.md

@@ -1,6 +1,12 @@
-This is a literate Agda file. This span - `span` - will be linked to the record below:
+This is a literate Agda file.
+
+Here's some inline code:
+
+- This is a link to the record below: `Record`{.agda}
+- This is not: `Record`
+- This is a link with alternate text: `also a link`{.agda ident=Record}
 
 ```agda
-record span : Set where
+record Record : Set where
   constructor hey-look
 ```

example/example.md

@@ -1,5 +1,11 @@
-This is a literate Agda file. This span - `span` - will be linked to the record below:
+This is a literate Agda file.
 
-<pre class="Agda"><a id="97" class="Keyword">record</a> <a id="span"></a><a id="104" href="example.html#104" class="Record">span</a> <a id="109" class="Symbol">:</a> <a id="111" class="PrimitiveType">Set</a> <a id="115" class="Keyword">where</a>
-  <a id="123" class="Keyword">constructor</a> <a id="hey-look"></a><a id="135" href="example.html#135" class="InductiveConstructor">hey-look</a>
+Here's some inline code:
+
+- This is a link to the record below: `Record`{.agda}
+- This is not: `Record`
+- This is a link with alternate text: `also a link`{.agda ident=Record}
+
+<pre class="Agda"><a id="217" class="Keyword">record</a> <a id="Record"></a><a id="224" href="example.html#224" class="Record">Record</a> <a id="231" class="Symbol">:</a> <a id="233" class="PrimitiveType">Set</a> <a id="237" class="Keyword">where</a>
+  <a id="245" class="Keyword">constructor</a> <a id="hey-look"></a><a id="257" href="example.html#257" class="InductiveConstructor">hey-look</a>
 </pre>

src/Main.hs

@@ -25,23 +25,62 @@ linkDocument (Pandoc meta blocks) =
   let hm = parseSymbolRefs blocks
    in Pandoc meta (walk (link hm) blocks)
 
-link :: HashMap Text Text -> Inline -> Inline
-link hm (Code attrs xs)
-  | Just sp <- HashMap.lookup xs hm = RawInline (Format "html") sp
+link :: HashMap Text Reference -> Inline -> Inline
+link hm inline@(Code (_, classes, kv) text)
+  | isToBeLinked =
+    case HashMap.lookup identifier hm of
+      Just ref -> RawInline "html" (renderReference ref text)
+      Nothing -> inline
+  where
+    classes' = map T.toLower classes
+
+    isToBeLinked = ("agda" `elem` classes')
+                && ("nolink" `notElem` classes')
+
+    identifier =
+      case lookup "ident" kv of
+        Just id -> id
+        _ -> text
 link _ x = x
 
-parseSymbolRefs :: [Block] -> HashMap Text Text
+renderReference :: Reference -> Text -> Text
+renderReference (Reference href cls) t =
+  renderTags [ TagOpen "pre" [("class", "Agda")]
+             , TagOpen "a" [("href", href), ("class", cls)]
+             , TagText t
+             , TagClose "a"
+             , TagClose "pre"
+             ]
+
+data Reference =
+  Reference { refHref  :: Text
+            , refClass :: Text
+            }
+  deriving (Eq, Show)
+
+parseSymbolRefs :: [Block] -> HashMap Text Reference
 parseSymbolRefs = go mempty . concat . mapMaybe getHTML where
+  getHTML :: Block -> Maybe ([Tag Text])
   getHTML (RawBlock (Format x) xs)
-    | x == "html" = Just (parseTags (T.unpack xs))
+    | x == "html" = Just (parseTags xs)
   getHTML _ = Nothing
 
-  go map (TagOpen "a" meta:TagText t:TagClose "a":xs)
-    | Just id <- lookup "id" meta, Just cls <- lookup "class" meta
-    = go (HashMap.insert (T.pack t) (T.pack (renderTags tags)) map) xs
+  go :: HashMap Text Reference -> [Tag Text] -> HashMap Text Reference
+  go map (TagOpen a meta:TagText t:TagClose a':xs)
+    | a == "a"
+    , a' == a
+    , Just id <- lookup "id" meta
+    , Just cls <- lookup "class" meta
+    , Just href <- lookup "href" meta
+    = go (addIfNotPresent t (Reference href cls) map) xs
+
     | otherwise = go map xs
     where
       tags = [ TagOpen "span" [("class", "Agda")], TagOpen "a" meta', TagText t, TagClose "a", TagClose "span" ]
       meta' = filter ((/= "id") . fst) meta
+
   go map (_:xs) = go map xs
   go map [] = map
+
+addIfNotPresent :: Text -> v -> HashMap Text v -> HashMap Text v
+addIfNotPresent = HashMap.insertWith (\_ old -> old)