From d45722a72e37c6b214877a81d53b22bfb422a900 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Paul=20H=C3=A4nsch?= <paul@plutz.net>
Date: Wed, 21 Jun 2023 19:49:10 +0200
Subject: [PATCH] Omit link IDs in nested headings, to prevent ambiguous IDs

---
 markdown.awk | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/markdown.awk b/markdown.awk
index fbfc455..29dc64d 100755
--- a/markdown.awk
+++ b/markdown.awk
@@ -38,6 +38,7 @@
 #
 # Extensions - Block elements:
 # ----------------------------
+# - [x] Automatic <section>-wrapping (custom)
 # -  ?  Heading identifiers (php md, pandoc)
 # - [x] Automatic heading identifiers (custom)
 # - [x] Fenced code blocks (php md, pandoc)
@@ -307,13 +308,18 @@ function inline( line, LOCAL, len, code, href, guard ) {
 }
 
 # Nested Block, resets heading counters
-function _nblock( block, LOCAL, st, len, hlvl, htxt, hlsav, sec, guard, code, indent, attrib ) {
+function _nblock( block, LOCAL, hlsav, sec ) {
+  # Keeping arrays in a local scope is awkward, so we serialize the HL array
+  # into the scalar hlsav
   hlsav = HL[1] " " HL[2] " " HL[3] " " HL[4] " " HL[5] " " HL[6];
   HL[1] = 0; HL[2] = 0; HL[3] = 0; HL[4] = 0; HL[5] = 0; HL[6] = 0;
 
+  # Block Level
+  blvl++;
+
   block = _block( block );
   sec = ""; for ( n = 1; n <= 6; n++ ) { sec = sec (HL[n]?"</section>":""); }
-  split(hlsav, HL);
+  split(hlsav, HL); blvl--;
   return block sec;
 }
 
@@ -568,35 +574,47 @@ function _block( block, LOCAL, st, len, hlvl, htxt, sec, guard, code, indent, at
   # First Order Heading H1
   } else if ( match( block, /^[^\n]+\n===+(\n|$)/ ) ) {
     len = RLENGTH; sec = "";
+
     for ( n = 1; n <= 6; n++ ) { sec = sec (HL[n]?"</section>":""); }
     HL[1]++; HL[2] = 0; HL[3] = 0; HL[4] = 0; HL[5] = 0; HL[6] = 0;
-    return sec "<section id=\"" HL[1] ":" URL(gensub( /\n.*$/, "", "g", block )) "\"><h1>" \
-           inline( gensub( /\n.*$/, "", "g", block ) ) \
-           "<a class=\"anchor\" href=\"#" HL[1] ":" \
-           URL(gensub( /\n.*$/, "", "g", block )) "\"></a></h1>\n\n" \
+    hid = HL[1] ":" URL(gensub( /\n.*$/, "", "g", block ));
+
+    return sec "<section class=\"h1\"" ((blvl > 1)?"":" id=\"" hid "\"") ">" \
+           "<h1>" inline( gensub( /\n.*$/, "", "g", block ) ) \
+           ((blvl > 1)?"":"<a class=\"anchor\" href=\"#" hid "\"></a>") \
+           "</h1>\n\n" \
            _block( substr( block, len + 1 ) );
 
   # Second Order Heading H2
   } else if ( match( block, /^[^\n]+\n---+(\n|$)/ ) ) {
     len = RLENGTH; sec = "";
+
     for ( n = 2; n <= 6; n++ ) { sec = sec (HL[n]?"</section>":""); }
     HL[2]++; HL[3] = 0; HL[4] = 0; HL[5] = 0; HL[6] = 0;
-    return sec "<section id=\"" HL[1] "." HL[2] ":" URL(gensub( /\n.*$/, "", "g", block )) "\">" \
+    hid= HL[1] "." HL[2] ":" URL(gensub( /\n.*$/, "", "g", block ));
+
+    return sec "<section class=\"h2\"" ((blvl > 1)?"":" id=\"" hid "\"") ">" \
            "<h2>" inline( gensub( /\n.*$/, "", "g", block ) ) \
-           "<a class=\"anchor\" href=\"#" HL[1] "." HL[2] ":" \
-           URL(gensub( /\n.*$/, "", "g", block )) "\"></a></h2>\n\n" \
+           ((blvl > 1)?"":"<a class=\"anchor\" href=\"#" hid "\"></a>") \
+           "</h2>\n\n" \
            _block( substr( block, len + 1) );
 
   # Nth Order Heading H1 H2 H3 H4 H5 H6
   } else if ( match( block, /^#{1,6}[ \t]*[^\n]+([ \t]*#*)(\n|$)/ ) ) {
     len = RLENGTH; sec = "";
+
     hlvl = length( gensub( /^(#{1,6}).*$/, "\\1", "g", block ) );
     htxt = gensub(/^#{1,6}[ \t]*(([^ \t\n]+|[ \t]+[^ \t\n#]|[ \t]+#+[^\n#])+)([ \t]*#*)(\n.*)?$/, "\\1", 1, block);
+
     for ( n = hlvl; n <= 6; n++ ) { sec = sec (HL[n]?"</section>":""); }
     HL[hlvl]++; for ( n = hlvl + 1; n <= 6; n++) { HL[n] = 0;}
     hid = HL[1]; for ( n = 2; n <= hlvl; n++) { hid = hid "." HL[n] ; }
-    return sec "<section id=\"" hid ":" URL(htxt) "\"><h" hlvl ">" inline( htxt ) \
-           "<a class=\"anchor\" href=\"#" hid "\"></a></h" hlvl ">\n\n" \
+    hid = hid ":" URL(htxt);
+
+    return sec "<section class=\"h" hlvl "\"" ((blvl > 1)?"":" id=\"" hid "\"") ">" \
+           "<h" hlvl ">" inline( htxt ) \
+           ((blvl > 1)?"":"<a class=\"anchor\" href=\"#" hid "\"></a>") \
+           "</h" hlvl ">\n\n" \
            _block( substr( block, len + 1) );
 
   # block images (wrapped in <figure>)
-- 
2.39.2