--[[
Copyright (c) 2010-2013 Matthias Richter

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

Except as contained in this notice, the name(s) of the above copyright holders
shall not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
]] --
local function include_helper(to, from, seen)
  if from == nil then
    return to
  elseif type(from) ~= 'table' then
    return from
  elseif seen[from] then
    return seen[from]
  end

  seen[from] = to
  for k, v in pairs(from) do
    k = include_helper({}, k, seen) -- keys might also be tables
    if to[k] == nil then
      to[k] = include_helper({}, v, seen)
    end
  end
  return to
end

-- deeply copies `other' into `class'. keys in `other' that are already
-- defined in `class' are omitted
local function include(class, other)
  return include_helper(class, other, {})
end

-- returns a deep copy of `other'
local function clone(other)
  return setmetatable(include({}, other), getmetatable(other))
end

local function new(class)
  -- mixins
  local inc = class.__includes or {}
  if getmetatable(inc) then
    inc = {
      inc
    }
  end

  for _, other in ipairs(inc) do
    if type(other) == "string" then
      other = _G[other]
    end
    include(class, other)
  end

  -- class implementation
  class.__index = class
  class.init = class.init or class[1] or function()
  end
  class.include = class.include or include
  class.clone = class.clone or clone

  -- constructor call
  return setmetatable(class, {
    __call = function(c, ...)
      local o = setmetatable({}, c)
      o:init(...)
      return o
    end
  })
end

-- the module
return setmetatable({
  new = new,
  include = include,
  clone = clone
}, {
  __call = function(_, ...)
    return new(...)
  end
})
