INI: Switch to using LPEG for unpack

Issue: #99

Switching to LPEG should make it easier to properly support the file
format.  In particular, double quoted lists are now handled properly.
Additionally, fewer assumptions regarding values are made.

For unquoted values, everything until the EOL is now returned.  Within
the game files there are cases where trailing comments are not removed.
There are cases where they are.  How are we supposed to know?

For quoted values, both single and double, the quotes are no longer
removed.  There are cases where some values must be double quoted.
Others must be singled quoted.  Again, how are we supposed to know?

So we make less assumptions, and let the user decide.

CHANGELOG.md

@@ -4,6 +4,8 @@
 ### Fixed
 - Trigger Strings (`wts`):
   - Nested bracket support restored.
+- INI (`txt`):
+  - Properly handle quoted lists.
 
 ### Added
 - Trigger Strings (`wts`):
@@ -20,6 +22,9 @@
 
 - Objects (`w3a`, `w3b`, `w3d`, `w3h`, `w3q`, `w3u`, `w3t`):
   - Unpacked format has changed.
+- INI (`txt`):
+  - Quotes are no longer removed from values.
+  - Trailing comments are no longer removed from values.
 
 ## [0.10.1] - 2020-01-05
 ### Fixed

file/ini.lua

@@ -1,68 +1,60 @@
-local INI = {}
-
-function INI.unpack (input)
-	assert (type (input) == 'string')
+local LPeg = require ('lpeg')
+local Re = require ('re')
 
-	local output = {}
-	local current
+local INI = {}
 
-	if input:sub (1, 3) == '\239\187\191' then
-		input = input:sub (4)
-	end
+local grammar
+do
+	local P = LPeg.P
 
-	for line in input:gmatch ('[^\r\n]+') do
-		line = line:find ('^%s*//') and '' or line
-		local section = line:match ('^%[([^%]]+)%]$')
+	local definitions = {
+		eol = P ('\r\n') + P ('\n'),
+        bom = P ('\xEF\xBB\xBF'),
+		set = rawset
+	}
 
-		if section then
-			current = output [section] or {}
-			output [section] = current
+	grammar = Re.compile ([[
+		INI <- bom? ({||} contents*) ~> set eof {}
+		contents <- eol / comment / section / skip
 
-		elseif not current then -- luacheck: ignore 542
-			-- Do nothing.  All key/value pairs must be in a section.
+		section <- {: header ({||} body*) ~> set :}
+		header <- '[' name ']'
+		name <- { (!']' !eol .)+ }
+		body <- eol / comment / pair
 
-		else
-			local index = line:find ('=', 1, true)
+		pair <- {: key '=' value :}
+		key <- { (!'=' !eol .)+ }
+		value <- quoted / unquoted
 
-			if index then
-				local key = line:sub (1, index - 1)
-				local value = line:sub (index + 1)
+		quoted <- { singles / doubles } skip*
+		unquoted <- { (!eol .)* }
 
-				-- Double quotes only apply if the first character of the
-				-- value (i.e. that immediately after the equals sign) is
-				-- one.  If so, the value is considered to be that which
-				-- extends to the first closing double quote or the end of
-				-- the line, whichever comes first.
-				if value:sub (1, 1) == '"' then
-					value = value:match ('^"([^"]*)"?')
+		singles <- single (',' single)*
+		single <- "'" (!"'" !eol .)* "'"
 
-				-- Otherwise, we remove any trailing comments.
-				else
-					value = value:match ('^(.-)//') or value
-				end
+		doubles <- double (',' double)*
+		double <- '"' (!'"' !eol .)* '"'
 
-				current [key] = value
-			end
-		end
-	end
+		comment <- '//' (!eol . )*
+		skip <- !eol .
+		bom <- %bom
+		eol <- %eol
+		eof <- !.
+	]], definitions)
+end
 
-	return output
+function INI.unpack (input, position)
+	return grammar:match (input, position)
 end
 
 function INI.pack (input)
-	assert (type (input) == 'table')
-
 	local output = {}
 
 	for section, contents in pairs (input) do
 		output [#output + 1] = '[' .. section .. ']'
 
 		for key, value in pairs (contents) do
-			-- Remove trailing comments.  If the user wishes to include `//`
-			-- in their value, then they should use double quotes.
-			value = value:match ('^(.-)//') or value
-
-			output [#output + 1] = key .. '=' .. value .. ''
+			output [#output + 1] = key .. '=' .. value
 		end
 
 		output [#output + 1] = ''