From 881b45209e8fd70079e409d05fa7402741501940 Mon Sep 17 00:00:00 2001
From: John MacFarlane <jgm@berkeley.edu>
Date: Sun, 7 Nov 2021 14:33:18 -0800
Subject: Replace old sample custom reader with a full-featured reader for
 creole.

This is better as an example.  And it is faster than pandoc's
regular creole parser, which shows that high-performance readers
can be developed this way.
---
 data/creole.lua | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)
 create mode 100644 data/creole.lua

(limited to 'data/creole.lua')

diff --git a/data/creole.lua b/data/creole.lua
new file mode 100644
index 000000000..ffde73638
--- /dev/null
+++ b/data/creole.lua
@@ -0,0 +1,197 @@
+-- A sample custom reader for Creole 1.0 (common wiki markup)
+-- http://www.wikicreole.org/wiki/CheatSheet
+
+-- For better performance we put these functions in local variables:
+local P, S, R, Cf, Cc, Ct, V, Cs, Cg, Cb, B, C, Cmt =
+  lpeg.P, lpeg.S, lpeg.R, lpeg.Cf, lpeg.Cc, lpeg.Ct, lpeg.V,
+  lpeg.Cs, lpeg.Cg, lpeg.Cb, lpeg.B, lpeg.C, lpeg.Cmt
+
+local whitespacechar = S(" \t\r\n")
+local specialchar = S("/*~[]\\{}|")
+local wordchar = (1 - (whitespacechar + specialchar))
+local spacechar = S(" \t")
+local newline = P"\r"^-1 * P"\n"
+local blankline = spacechar^0 * newline
+local endline = newline * #-blankline
+local endequals = spacechar^0 * P"="^0 * spacechar^0 * newline
+local cellsep = spacechar^0 * P"|"
+
+local function trim(s)
+   return (s:gsub("^%s*(.-)%s*$", "%1"))
+end
+
+local function ListItem(lev, ch)
+  local start
+  if ch == nil then
+    start = S"*#"
+  else
+    start = P(ch)
+  end
+  local subitem = function(c)
+    if lev < 6 then
+      return ListItem(lev + 1, c)
+    else
+      return (1 - 1) -- fails
+    end
+  end
+  local parser = spacechar^0
+               * start^lev
+               * #(- start)
+               * spacechar^0
+               * Ct((V"Inline" - (newline * spacechar^0 * S"*#"))^0)
+               * newline
+               * (Ct(subitem("*")^1) / pandoc.BulletList
+                  +
+                  Ct(subitem("#")^1) / pandoc.OrderedList
+                  +
+                  Cc(nil))
+               / function (ils, sublist)
+                   return { pandoc.Plain(ils), sublist }
+                 end
+  return parser
+end
+
+local re = require're'
+x = re.compile[[
+      listname <- {| {:tag: '' -> 'list':} (name s)* |}
+      name <- {| {:tag: '' -> 'id':} {[a-z][a-z]*} |}
+      s <- ' '*
+]]
+
+-- Grammar
+G = P{ "Doc",
+  Doc = Ct(V"Block"^0)
+      / pandoc.Pandoc ;
+  Block = blankline^0
+        * ( V"Header"
+          + V"HorizontalRule"
+          + V"CodeBlock"
+          + V"List"
+          + V"Table"
+          + V"Para") ;
+  Para = Ct(V"Inline"^1)
+       * newline
+       / pandoc.Para ;
+  HorizontalRule = spacechar^0
+                 * P"----"
+                 * spacechar^0
+                 * newline
+                 / pandoc.HorizontalRule;
+  Header = (P("=")^1 / string.len)
+         * spacechar^1
+         * Ct((V"Inline" - endequals)^1)
+         * endequals
+         / pandoc.Header;
+  CodeBlock = P"{{{"
+            * blankline
+            * C((1 - (newline * P"}}}"))^0)
+            * newline
+            * P"}}}"
+            / pandoc.CodeBlock;
+  Placeholder = P"<<<"
+              * C(P(1) - P">>>")^0
+              * P">>>"
+              / function() return pandoc.Div({}) end;
+  List = V"BulletList"
+       + V"OrderedList" ;
+  BulletList = Ct(ListItem(1,'*')^1)
+             / pandoc.BulletList ;
+  OrderedList = Ct(ListItem(1,'#')^1)
+             / pandoc.OrderedList ;
+  Table = (V"TableHeader" + Cc{})
+        * Ct(V"TableRow"^1)
+        / function(headrow, bodyrows)
+            local numcolumns = #(bodyrows[1])
+            local aligns = {}
+            local widths = {}
+            for i = 1,numcolumns do
+              aligns[i] = pandoc.AlignDefault
+              widths[i] = 0
+            end
+            return pandoc.utils.from_simple_table(
+              pandoc.SimpleTable({}, aligns, widths, headrow, bodyrows))
+          end ;
+  TableHeader = Ct(V"HeaderCell"^1)
+              * cellsep^-1
+              * spacechar^0
+              * newline ;
+  TableRow   = Ct(V"BodyCell"^1)
+             * cellsep^-1
+             * spacechar^0
+             * newline ;
+  HeaderCell = cellsep
+             * P"="
+             * spacechar^0
+             * Ct((V"Inline" - (newline + cellsep))^0)
+             / function(ils) return { pandoc.Plain(ils) } end ;
+  BodyCell   = cellsep
+             * spacechar^0
+             * Ct((V"Inline" - (newline + cellsep))^0)
+             / function(ils) return { pandoc.Plain(ils) } end ;
+  Inline = V"Emph"
+         + V"Strong"
+         + V"LineBreak"
+         + V"Link"
+         + V"URL"
+         + V"Image"
+         + V"Str"
+         + V"Space"
+         + V"SoftBreak"
+         + V"Escaped"
+         + V"Placeholder"
+         + V"Code"
+         + V"Special" ;
+  Str = wordchar^1
+      / pandoc.Str;
+  Escaped = P"~"
+          * C(P(1))
+          / pandoc.Str ;
+  Special = specialchar
+          / pandoc.Str;
+  Space = spacechar^1
+        / pandoc.Space ;
+  SoftBreak = endline
+            * # -(V"HorizontalRule" + V"CodeBlock")
+            / pandoc.SoftBreak ;
+  LineBreak = P"\\\\"
+            / pandoc.LineBreak ;
+  Code = P"{{{"
+       * C((1 - P"}}}")^0)
+       * P"}}}"
+       / trim / pandoc.Code ;
+  Link = P"[["
+       * C((1 - (P"]]" + P"|"))^0)
+       * (P"|" * Ct((V"Inline" - P"]]")^1))^-1 * P"]]"
+       / function(url, desc)
+           local txt = desc or {pandoc.Str(url)}
+           return pandoc.Link(txt, url)
+         end ;
+  Image = P"{{"
+        * #-P"{"
+        * C((1 - (S"}"))^0)
+        * (P"|" * Ct((V"Inline" - P"}}")^1))^-1
+        * P"}}"
+        / function(url, desc)
+            local txt = desc or ""
+            return pandoc.Image(txt, url)
+          end ;
+  URL = P"http"
+      * P"s"^-1
+      * P":"
+      * (1 - (whitespacechar + (S",.?!:;\"'" * #whitespacechar)))^1
+      / function(url)
+          return pandoc.Link(pandoc.Str(url), url)
+        end ;
+  Emph = P"//"
+       * Ct((V"Inline" - P"//")^1)
+       * P"//"
+       / pandoc.Emph ;
+  Strong = P"**"
+         * Ct((V"Inline" -P"**")^1)
+         * P"**"
+         / pandoc.Strong ;
+}
+
+function Reader(input, reader_options)
+  return lpeg.match(G, input)
+end
-- 
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