From b2ab0ab20e2455ef112cf340e09e2f33cf641993 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg@phi-gamma.net>
Date: Sun, 2 Mar 2014 15:07:14 +0100
Subject: distinguish between overlined and underline-only sections with the
 same adonment

Closing #4

See http://docutils.sourceforge.net/docs/user/rst/quickstart.html#sections
for the legalese.
---
 src/rst_context.lua | 80 ++++++++++++++++++++++++++++++-----------------------
 src/rst_parser.lua  |  6 ++++
 2 files changed, 52 insertions(+), 34 deletions(-)

diff --git a/src/rst_context.lua b/src/rst_context.lua
index c7e21fe..1654832 100644
--- a/src/rst_context.lua
+++ b/src/rst_context.lua
@@ -15,19 +15,21 @@
 ---   good.
 
 
-local helpers        = helpers        or thirddata and thirddata.rst_helpers
-local rst_directives = rst_directives or thirddata and thirddata.rst_directives
-
-local utf         = unicode.utf8
-local utflen      = utf.len
-local utflower    = utf.lower
-local utfupper    = utf.upper
-local iowrite     = io.write
-local tableconcat = table.concat
-
-local stringmatch  = string.match
-local stringgmatch = string.gmatch
-local stringgsub   = string.gsub
+local helpers           = helpers        or thirddata and thirddata.rst_helpers
+local rst_directives    = rst_directives or thirddata and thirddata.rst_directives
+
+local utf               = unicode.utf8
+local utflen            = utf.len
+local utflower          = utf.lower
+local utfupper          = utf.upper
+local iowrite           = io.write
+local tableconcat       = table.concat
+
+local stringgmatch      = string.gmatch
+local stringgsub        = string.gsub
+local stringmatch       = string.match
+local stringsub         = string.sub
+local stringformat      = string.format
 
 local dbg_write = helpers.dbg_writef
 
@@ -50,7 +52,6 @@ do
     end
 end
 local stringstrip  = string.strip
-local stringformat = string.format
 
 local err = function(str)
     if str then
@@ -681,24 +682,34 @@ local function get_line_pattern (chr)
     return P(chr)^1 * (-P(1))
 end
 
-function rst_context.section (...)  -- TODO general cleanup; move validity
-    local tab = { ... }             -- checking to parser.
-    local section, str = true, ""
-    local adornchar 
-    local ulen = utflen
-    if #tab == 3 then -- TODO use unicode length with ConTeXt
-        adornchar = tab[1]:sub(1,1)
-        section = ulen(tab[1]) >= ulen(tab[2])
-        str = stringstrip(tab[2])
-    else -- no overline
-        adornchar = tab[2]:sub(1,1)
-        section = ulen(tab[1]) <= ulen(tab[2])
-        str = tab[1]
+--[[--
+        Quoth the spec:
+            An underline-only adornment is distinct from an
+            overline-and-underline adornment using the same character.
+
+    We store the depths by hashing the adorn character and distinguish
+    the overlined ones from only underlined ones by prefixing them with
+    “O” and “U”, respectively.
+--]]--
+
+function rst_context.section (first, second, third)
+    local section   = true
+    local str       = ""
+    local adornchar = nil
+    local ulen      = utflen
+    if third then --- overlined
+        adornchar   = "O" .. stringsub(first, 1,1)
+        section     = ulen(first) >= ulen(second)
+        str         = stringstrip(second)
+    else -- underline-only
+        adornchar   = "U" .. stringsub(second, 1,1)
+        section     = ulen(first) <= ulen(second)
+        str         = stringstrip(first)
     end
 
     if section then -- determine level
         local level = rst_context.last_section_level
-        local rca = rst_context.collected_adornments
+        local rca   = rst_context.collected_adornments
         if rca[adornchar] then
             level = rca[adornchar]
         else
@@ -707,14 +718,15 @@ function rst_context.section (...)  -- TODO general cleanup; move validity
             rst_context.last_section_level = level
         end
 
-        ref = get_context_reference (str)
+        local ref = get_context_reference (str)
 
-        str = stringformat("\n\\\\%s[%s]{%s}\n", sectionlevels[level], ref, str)
-    else
-        return [[{\\bf fix your sectioning!}\\endgraf}]]
+        str = stringformat("\n\\\\%s[%s]{%s}\n",
+                           sectionlevels[level],
+                           ref,
+                           str)
+        return str or ""
     end
-
-    return section and str or ""
+    return [[{\\bf fix your sectioning!}\\endgraf}]]
 end
 
 -- Prime time for the fancybreak module.
diff --git a/src/rst_parser.lua b/src/rst_parser.lua
index 93d8a11..3928161 100644
--- a/src/rst_parser.lua
+++ b/src/rst_parser.lua
@@ -127,6 +127,12 @@ state.addme                = {}
 
 local valid_adornment
 do
+    --[[--
+
+        valid_adornment -- This subpattern tests if the string consists
+        entirely of one repeated adornment char.
+
+    --]]--
     local first_adornment    = ""
     local adornment_char     = S[[!"#$%&'()*+,-./:;<=>?@[]^_`{|}~]] + P[[\\]]
     local check_first        = Cmt(adornment_char, function(_,_, first)
-- 
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