feat(lua): Replace Autocall with Target-object, Autocall_config -> Autocall

Deep-copy `__namestack` decouples all instances of Autocall, previously it
worked as singleton. This allows to store call-chains as variables, aliases.

Target-object allows to avoid duplication of the target-parameter as required
with Autocall by storing them as variables.

Autocall_config renamed to Autocall for brevity.

lua/rtorrent.lua

@@ -4,40 +4,51 @@ local args = {...}
 local rtorrent = args[1]
 
 -- Autocall
--- Allows syntax like `rtorrent.autocall.system.hostname()`
+-- Passes an empty first argument implicitly, as "".
+-- Allows syntax like:
+-- - `rtorrent.autocall.system.hostname()` or
+-- - `rtorrent.autocall.session.directory.set("/tmp/")`
+-- Has assignment operator, syntax sugar for `.set()` with single argument
+-- - `rtorrent.autocall.session.directory = "/tmp/"`
+-- Autocall-chains can be reused as aliases:
+-- ```lua
+-- a = rtorrent.autocall.system
+-- a.hostname() -- same as `rtorrent.autocall.system.hostname()`
+-- a.pid()      -- same as `rtorrent.autocall.system.pid()`
 local mt = {}
 function mt.__call (t, ...)
    name = table.concat(rawget(t, "__namestack"), ".")
-   success, ret = pcall(rtorrent.call, name, ...)
+   tg = rawget(t, "__target") or ""
+   success, ret = pcall(rtorrent.call, name, tg, ...)
    if not success then error(name..": "..ret, 2) end
    return ret
 end
 function mt.__index (t, key)
-   ns = rawget(t, "__namestack") or {}
+   ns = {table.unpack(rawget(t, "__namestack") or {})}
+   tg = rawget(t, "__target") or nil
    table.insert(ns, key)
-   return setmetatable({__namestack=ns}, mt)
-end
-rtorrent["autocall"] = setmetatable({}, mt)
-
--- Autocall-config
--- Same as autocall, but passes an empty first target implicitly, for syntax
--- like `rtorrent.autocall_config.session.directory.set("/tmp/")` or
--- like `rtorrent.autocall_config.session.directory = "/tmp/"`
-local mt = {}
-function mt.__call (t, ...)
-   name = table.concat(rawget(t, "__namestack"), ".")
-   success, ret = pcall(rtorrent.call, name, "", ...)
-   if not success then error(name..": "..ret, 2) end
-   return ret
-end
-function mt.__index (t, key)
-   ns = rawget(t, "__namestack") or {}
-   table.insert(ns, key)
-   return setmetatable({__namestack=ns}, mt)
+   return setmetatable({__namestack=ns, __target=tg}, mt)
 end
 function mt.__newindex (t, key, value)
    t[key].set(value)
 end
-rtorrent["autocall_config"] = setmetatable({}, mt)
+rtorrent["autocall"] = setmetatable({}, mt)
+
+-- Target-object
+-- Sets first argment for Autocall, for commands that require target.
+-- Allows syntax like:
+-- - `rtorrent.Target("some_infohash").d.name()` or
+-- - `rtorrent.Target:new("some_infohash").d.name()`
+-- Also can be stored as variable
+local Target = setmetatable({
+   new = function (self, target)
+      return self(target)
+   end;
+}, {
+   __call = function (self, target)
+      return setmetatable({__target=target}, mt)
+   end
+})
+rtorrent["Target"] = Target
 
 return rtorrent