----------------------------------------------------------------
--
-- To add hotkeys to an object (such as a Brick Oven), you will
-- be adding a function 'lookhotkeys' to the appropriate class,
-- like this:
--
-- function brickoven.lookhotkeys(keys)
--    keys:add("X", "Light Oven", function () ... end)
--    keys:add("A", "Add Fuel", function () ... end)
-- end
--
-- This function will get called twice: once in a 'probe' when
-- Unreal wants to know what hotkeys exist, and a second time in
-- an 'invoke' to find the right closure.
--
-- When the probe happens, we construct a "hotkeylist" to hold
-- the complete list of hotkeys.  We populate this hotkeylist as
-- follows:
--
--    local keys = hotkeylist.create()
--    brickoven.lookhotkeys(keys)
-- 
-- At this point, if you were to pprint(keys), the output would
-- look like this:
--
--    { "hotkeys", "X", "Light Oven", "A", "Add Fuel" }
--
-- The first array element is always the word "hotkeys".  Notice
-- also that a hotkeylist doesn't store the closures, they are
-- silently ignored.  The resulting array is in a format that can
-- be returned directly to Unreal.
--
-- Later, when the user presses a key, such as the "Light Oven" key,
-- we will construct a "hotkeypress" object whose job is to record
-- the name of the hotkey that was pressed, and the closure that
-- goes with it.  We populate this object as follows:
--
--    local keys = hotkeypress.create("Light Oven")
--    brickoven.lookhotkeys(keys)
--
-- So as you can see, we're using the same 'brickoven.lookhotkeys'
-- function, but this time, we've passed in a parameter of class
-- hotkeypress instead of a parameter of class hotkeylist.  This
-- changes the behavior of the 'add' method: the add function of
-- a hotkeylist stores all the hotkeys into the list.  But the 'add'
-- function of a hotkeypress only stores the one closure that
-- we are interested in.  If you were to pprint(keys), the result
-- would look like this:
--
--    { pressed="Light Oven", closure=<function> }
--
-- So the only data stored by a 'hotkeypress' object is the name
-- of the pressed hotkey, and the closure that goes with it.
--
----------------------------------------------------------------

makeclass("hotkeylist")
makeclass("hotkeypress")

function hotkeylist.create()
    local result = { "hotkeys" }
    setmetatable(result, hotkeylist)
    return result
end

function hotkeylist.add(self, key, action, closure)
    table.insert(self, key)
    table.insert(self, action)
end

function hotkeypress.create(key)
    local result = { pressed=key }
    setmetatable(result, hotkeypress)
    return result
end

function hotkeypress.add(self, key, action, closure)
    if action == self.pressed then
        self.closure = closure
    end
end