-- see: https://github.com/davidm/lua-glob-pattern
local M = {_TYPE='module', _NAME='globtopattern', _VERSION='0.2.1.20120406'}

function M.globtopattern(g)
	-- Some useful references:
	-- - apr_fnmatch in Apache APR.  For example,
	--   http://apr.apache.org/docs/apr/1.3/group__apr__fnmatch.html
	--   which cites POSIX 1003.2-1992, section B.6.

	local p = "^"  -- pattern being built
	local i = 0    -- index in g
	local c        -- char at index i in g.

	-- unescape glob char
	local function unescape()
		if c == '\\' then
			i = i + 1; c = g:sub(i,i)
			if c == '' then
				p = '[^]'
				return false
			end
		end
		return true
	end

	-- escape pattern char
	local function escape(c)
		return c:match("^%w$") and c or '%' .. c
	end

	-- Convert tokens at end of charset.
	local function charset_end()
		while 1 do
			if c == '' then
				p = '[^]'
				return false
			elseif c == ']' then
				p = p .. ']'
				break
			else
				if not unescape() then break end
				local c1 = c
				i = i + 1; c = g:sub(i,i)
				if c == '' then
					p = '[^]'
					return false
				elseif c == '-' then
					i = i + 1; c = g:sub(i,i)
					if c == '' then
						p = '[^]'
						return false
					elseif c == ']' then
						p = p .. escape(c1) .. '%-]'
						break
					else
						if not unescape() then break end
						p = p .. escape(c1) .. '-' .. escape(c)
					end
				elseif c == ']' then
					p = p .. escape(c1) .. ']'
					break
				else
					p = p .. escape(c1)
					i = i - 1 -- put back
				end
			end
			i = i + 1; c = g:sub(i,i)
		end
		return true
	end

	-- Convert tokens in charset.
	local function charset()
		i = i + 1; c = g:sub(i,i)
		if c == '' or c == ']' then
			p = '[^]'
			return false
		elseif c == '^' or c == '!' then
			i = i + 1; c = g:sub(i,i)
			if c == ']' then
				-- ignored
			else
				p = p .. '[^'
				if not charset_end() then return false end
			end
		else
			p = p .. '['
			if not charset_end() then return false end
		end
		return true
	end

	-- Convert tokens.
	while 1 do
		i = i + 1; c = g:sub(i,i)
		if c == '' then
			p = p .. '$'
			break
		elseif c == '?' then
			p = p .. '.'
		elseif c == '*' then
			p = p .. '.*'
		elseif c == '[' then
			if not charset() then break end
		elseif c == '\\' then
			i = i + 1; c = g:sub(i,i)
			if c == '' then
				p = p .. '\\$'
				break
			end
			p = p .. escape(c)
		else
			p = p .. escape(c)
		end
	end
	return p
end

return M