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-- A trivial reloadable class system

local _ENV = mkmodule('class')

-- Metatable template for a class

class_obj = class_obj or {}

-- Methods shared by all classes

common_methods = common_methods or {}

-- Forbidden names for class fields and methods.

reserved_names = { super = true, ATTRS = true }

-- Attribute table metatable

attrs_meta = attrs_meta or {}

-- Create or updates a class; a class has metamethods and thus own metatable.

function defclass(class,parent)

class = class or {}

local meta = getmetatable(class)

if not meta then

meta = {}

setmetatable(class, meta)

end

for k,v in pairs(class_obj) do meta[k] = v end

meta.__index = parent or common_methods

local attrs = rawget(class, 'ATTRS') or {}

setmetatable(attrs, attrs_meta)

rawset(class, 'super', parent)

rawset(class, 'ATTRS', attrs)

rawset(class, '__index', rawget(class, '__index') or class)

return class

end

-- An instance uses the class as metatable

function mkinstance(class,table)

table = table or {}

setmetatable(table, class)

return table

end

-- Patch the stubs in the global environment

dfhack.BASE_G.defclass = _ENV.defclass

dfhack.BASE_G.mkinstance = _ENV.mkinstance

-- Just verify the name, and then set.

function class_obj:__newindex(name,val)

if reserved_names[name] or common_methods[name] then

error('Method name '..name..' is reserved.')

end

rawset(self, name, val)

end

function attrs_meta:__call(attrs)

for k,v in pairs(attrs) do

self[k] = v

end

end

local function apply_attrs(obj, attrs, init_table)

for k,v in pairs(attrs) do

local init_v = init_table[k]

if init_v ~= nil then

obj[k] = init_v

elseif v == DEFAULT_NIL then

obj[k] = nil

else

obj[k] = v

end

end

end

local function invoke_before_rec(self, class, method, ...)

local meta = getmetatable(class)

if meta then

local fun = rawget(class, method)

if fun then

fun(self, ...)

end

invoke_before_rec(self, meta.__index, method, ...)

end

end

local function invoke_after_rec(self, class, method, ...)

local meta = getmetatable(class)

if meta then

invoke_after_rec(self, meta.__index, method, ...)

local fun = rawget(class, method)

if fun then

fun(self, ...)

end

end

end

local function init_attrs_rec(obj, class, init_table)

local meta = getmetatable(class)

if meta then

init_attrs_rec(obj, meta.__index, init_table)

apply_attrs(obj, rawget(class, 'ATTRS'), init_table)

end

end

-- Call metamethod constructs the object

function class_obj:__call(init_table)

-- The table is assumed to be a scratch temporary.

-- If it is not, copy it yourself before calling.

init_table = init_table or {}

local obj = mkinstance(self)

-- This initialization sequence is broadly based on how the

-- Common Lisp initialize-instance generic function works.

-- preinit screens input arguments in subclass to superclass order

invoke_before_rec(obj, self, 'preinit', init_table)

-- initialize the instance table from init table

init_attrs_rec(obj, self, init_table)

-- init in superclass -> subclass

invoke_after_rec(obj, self, 'init', init_table)

-- postinit in superclass -> subclass

invoke_after_rec(obj, self, 'postinit', init_table)

return obj

end

-- Common methods for all instances:

function common_methods:callback(method, ...)

return dfhack.curry(self[method], self, ...)

end

function common_methods:cb_getfield(field)

return function() return self[field] end

end

function common_methods:cb_setfield(field)

return function(val) self[field] = val end

end

function common_methods:assign(data)

for k,v in pairs(data) do

self[k] = v

end

end

function common_methods:invoke_before(method, ...)

return invoke_before_rec(self, getmetatable(self), method, ...)

end

function common_methods:invoke_after(method, ...)

return invoke_after_rec(self, getmetatable(self), method, ...)

end

return _ENV