include and use plugins en2em and nobreaks

1 files changed, 38 insertions, 0 deletions

diff --git a/_extensions/js/en2em/en2em.lua b/_extensions/js/en2em/en2em.lua
new file mode 100644
index 0000000..520474d
--- /dev/null
+++ b/_extensions/js/en2em/en2em.lua
@@ -0,0 +1,38 @@
+--- en2em - replace space-enclosed en-dash with nospace em-dash
+---
+--- Some typographical styles, including danish,
+--- use en-dash with spaces around to indicate a short pause,
+--- whereas others, including some british and american styles,
+--- use an em-dash without spaces.
+---
+--- This plugin allows to always use en-dash at the source --
+--- which also eases writing with semantic line breaks, like here --
+--- and then convert while rendering as needed.
+---
+--- SPDX-FileCopyrightText: 2025  Jonas Smedegaard <dr@jones.dk>
+--- SPDX-License-Identifier: GPL-3.0-or-later
+
+local em_dash = pandoc.Str("\u{2014}")
+local nothing = pandoc.Str("")
+
+local TypeIsSpacy = {
+  Space = true,
+  SoftBreak = true
+}
+
+function Para(el)
+  for i = 1, #el.content - 1 do
+    if el.content[i].t == "Str" and el.content[i].text == "\u{2013}" then
+      local el_prev = el.content[i - 1]
+      local el_next = el.content[i + 1]
+      if el_prev and el_next
+        and TypeIsSpacy[el_prev.t] and TypeIsSpacy[el_next.t]
+      then
+        el.content[i] = em_dash
+        el.content[i - 1] = nothing
+        el.content[i + 1] = nothing
+      end
+    end
+  end
+  return el
+end