prosody, prosodyctl: Load loader directly from source directory This should ensure that loader.lua is loaded from the source directory and does the right thing when installed with `make install` There are currently three ways Prosody can be run: - Directly from the source directory, like `./prosody` - Installed with `make install` - Installed into Lua paths with e.g. dh-lua or luarocks In the first two cases, Lua search paths need to include the source directory and ensure that `require "prosody.util.json"` ends up loading `util/json.lua` relative to the installation (CFG_SOURCEDIR) or the source checkout. Finally, in the last case where Prosody resources are installed under the 'prosody.*' namespace in regular Lua search paths, then loader.lua should activate the compatibility mode that makes sure that both `require"util.json"` and `require"prosody.util.json"` both resolve to `(one path from of package.path)/prosody/util/json.lua`

local m_type = math.type;

local function unescape_token(escaped_token)
	local unescaped = escaped_token:gsub("~1", "/"):gsub("~0", "~")
	return unescaped
end

local function resolve_json_pointer(ref, path)
	local ptr_len = #path + 1
	for part, pos in path:gmatch("/([^/]*)()") do
		local token = unescape_token(part)
		if not (type(ref) == "table") then
			return nil
		end
		local idx = next(ref)
		local new_ref

		if type(idx) == "string" then
			new_ref = ref[token]
		elseif m_type(idx) == "integer" then
			local i = tonumber(token)
			if token == "-" then
				i = #ref + 1
			end
			new_ref = ref[i + 1]
		else
			return nil, "invalid-table"
		end

		if pos == ptr_len then
			return new_ref
		elseif type(new_ref) == "table" then
			ref = new_ref
		elseif not (type(ref) == "table") then
			return nil, "invalid-path"
		end

	end
	return ref
end

return { resolve = resolve_json_pointer }