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-- Class.lua
-- Compatible with Lua 5.1 (not 5.0).
--
-- Modified to use a metatable to reference base objects instead
-- or performing shallow copies. This means smaller classes that
-- are a bit more dynamic at the expence of some performance.

-- NOTE, this class definition is ONLY defined for the current environment, NOT the _G environment so it is totally safe to use with other plugins, even those that depend on older Turbine samples
class = function( base )
        if ( base ~= nil ) then
                local baseType = type( base );

                if ( baseType ~= 'table' ) then
                        error( "Base class is not a table. Base class was a " .. baseType );
                end
        end

        -- The class definition table. Contains all of the actual class
        -- methods, constructor, and an IsA function automatically
        -- provided.
        local c  = { };

        c.base = base;
        c.IsA = function( self, klass )
                local m = getmetatable( self );
                
                while m do 
                        if m == klass then
                                return true;
                        end
                        
                        m = m.base;
                end
                
                return false;
        end

        -- The class definition metatable. This is used to hook up
        -- base classes and then to register a call handler that is
        -- used to construct new instances of the class.
        local mt = { };
        mt.__index = base;

        mt.__call = function( class_tbl, ... )
                if ( class_tbl.Abstract ) then
                        error "Abstract class cannot be constructed.";
                end

                -- Create the new class instance.
                local instance = { };
                setmetatable( instance, { __index = c } );
                
                -- Invoke the constructor if it exists.
                if ( ( instance.Constructor ~= nil ) and ( type( instance.Constructor ) == 'function' ) ) then
                        instance:Constructor( ... );
                end
                
                return instance;
        end

        setmetatable( c, mt );
        return c;
end