implement more markdown postprocessing

render.rkt

@@ -1,6 +1,6 @@
 #lang racket/base
 
-(require racket/list racket/match racket/port racket/set racket/string
+(require racket/list racket/match racket/port racket/pretty racket/set racket/string
          markdown markdown/display-xexpr markdown/toc
          "compiler.rkt" "defs.rkt"
          threading
@@ -10,7 +10,7 @@
          (prefix-in article: "templates/article.html.rkt"))
 
 (struct input-doc [metadata text] #:transparent)
-(struct ir-doc [metadata hashtags html] #:transparent)
+(struct ir-doc [metadata html] #:transparent)
 
 (define (read-input-doc [port (current-input-port)])
   (define metadata (read port))
@@ -19,9 +19,13 @@
   (define text (port->string port))
   (input-doc metadata text))
 
-;; transforms the xexpr into an xexpr that includes links to hashtags
-(define (extract-hashtags xexpr)
-  (define hashtags (mutable-set))
+(define *xref-char* "^")
+(define *user-char* "@")
+(define *hashtag-char* "#")
+
+;; transforms the xexpr into an xexpr that includes links to entities
+(define (extract-text-starting-with xexpr start-char tag-name)
+  (define re (pregexp (string-append start-char "(\\p{L}|\\p{N})+")))
   (define (process+ xexpr)
     (match xexpr
       ;; do not descend into code or math
@@ -31,57 +35,66 @@
        (list (cons tag (cons attrs
                        (apply append
                               (map (lambda (child) (process+ child)) children)))))]
-      ;; extract and transform hashtags
+      ;; extract and transform the prefixed text
       [(? string? str)
-       (define posns (regexp-match-positions* #px"#(\\p{L}|\\p{N})+" str))
+       (define posns (regexp-match-positions* re str))
        (define-values [items last-pos]
          (for/fold ([items '()] [last-pos 0]) ([pos (in-list posns)])
-           (define hashtag (substring str (car pos) (cdr pos)))
-           (set-add! hashtags hashtag)
-           (values (cons `(hashtag () ,hashtag)
+           (define value (substring str (car pos) (cdr pos)))
+           (values (cons `(,tag-name ([target ,(substring value 1)]) ,value)
                          (cons (substring str last-pos (car pos)) items))
                    (cdr pos))))
        (reverse (cons (substring str last-pos) items))]))
-  (values (first (process+ xexpr)) hashtags))
+  (first (process+ xexpr)))
+(define (extract-text-starting-with/many xexprs start-char tag-name)
+  (map (λ (xexpr) (extract-text-starting-with xexpr start-char tag-name)) xexprs))
 
-;; xref links start with ^
-(define (xref-link? x)
-  (and (string? x) (> (string-length x) 1) (char=? (string-ref x 0) #\^)))
-
-;; extracts xref-prefixed links and converts them into the <xref> pseudo-tag
-(define (extract-xrefs xexpr)
+;; extracts prefixed links and converts them into the <xref> pseudo-tag
+(define (extract-prefixed-links xexpr start-char tag-name)
+  (define (pred? s)
+    (and (string? s) (> (string-length s) 1) (string=? start-char (substring s 0 1))))
+  (define (extract-prefixed-links+ xexpr)
     (match xexpr
       [(list 'a attrs body ...)
        (match (assoc 'href attrs)
-       [(list _ (? xref-link? xref))
-        (define target (substring xref 1))
-        `(xref ([target ,target]) ,@(map extract-xrefs body))]
-       [_ (apply list 'a attrs (map extract-xrefs body))])]
+         [(list _ (? pred? value))
+          (define target (substring value 1))
+          `(,tag-name ([target ,target]) ,@(map extract-prefixed-links+ body))]
+         [_ (apply list 'a attrs (map extract-prefixed-links+ body))])]
       [(list tag attrs children ...)
-     (apply list tag attrs (map extract-xrefs children))]
+       (apply list tag attrs (map extract-prefixed-links+ children))]
       [(? string? str) str]))
+  (extract-prefixed-links+ xexpr))
+(define (extract-prefixed-links/many xexprs start-char tag-name)
+  (map (λ (xexpr) (extract-prefixed-links xexpr start-char tag-name)) xexprs))
 
 (define (input-doc->ir-doc doc)
   (match-define (input-doc md text) doc)
   (define output-raw (parse-markdown text))
-  (define output-cooked (mathml:transform-xexprs (syntax:transform-xexprs output-raw)))
-  (let-values ([(output-cooked hashtags) (extract-hashtags output-cooked)])
-    (let ([output-cooked (extract-xrefs output-cooked)])
-      (ir-doc md hashtags output-cooked))))
+  (define output-cooked
+    (~> output-raw syntax:transform-xexprs mathml:transform-xexprs
+        (extract-text-starting-with/many *hashtag-char* 'hashtag)
+        (extract-text-starting-with/many *user-char* 'user)
+        (extract-prefixed-links/many *xref-char* 'xref)
+        (extract-prefixed-links/many *user-char* 'user)))
+  (ir-doc md output-cooked))
 
 ;; lowers pseudo-tags into their final form
 (define (lower-specials xexpr base-url)
   (define (lower-specials* xexpr)
     (match xexpr
       ;; hashtags
-      [(list 'hashtag _ hashtag)
-       `(a ([class "hashtag"]
-            [href ,(string-append base-url "/tag/" (substring hashtag 1))])
-           ,hashtag)]
+      [(list 'hashtag (list (list 'target target)) body ...)
+       `(a ([class "hashtag"] [href ,(string-append base-url "/hashtag/" target)])
+           ,@(map lower-specials* body))]
       ;; xrefs
       [(list 'xref (list (list 'target target)) body ...)
        `(a ([class "xref"] [href ,(string-append base-url "/xref/" target)])
            ,@(map lower-specials* body))]
+      ;; users
+      [(list 'user (list (list 'target target)) body ...)
+       `(a ([class "user"] [href ,(string-append base-url "/user/" target)])
+           ,@(map lower-specials* body))]
       ;; everything else
       [(list tag attrs children ...)
        (apply list tag attrs (map lower-specials* children))]
@@ -89,7 +102,7 @@
   (lower-specials* xexpr))
 
 (define (ir-doc->page doc)
-  (match-define (ir-doc md hashtags content) doc)
+  (match-define (ir-doc md content) doc)
   (let ([content (lower-specials content "https://awoo.systems")])
     (define content-toc (toc content))