--[[
Copyright 2017 YANG Huan (sy.yanghuan@gmail.com).

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
--]]

local System = System
local throw = System.throw
local Object = System.Object
local debugsetmetatable = System.debugsetmetatable
local ArgumentNullException = System.ArgumentNullException

local setmetatable = setmetatable
local assert = assert
local select = select
local type = type
local unpack = table.unpack
local tmove = table.move

local Delegate
local multicast

local function appendFn(t, count, f)
  if type(f) == "table" then
    for i = 1, #f do
      t[count] = f[i]
      count = count + 1
    end
  else
    t[count] = f
    count = count + 1
  end
  return count
end

local function combineImpl(fn1, fn2)
  local t = setmetatable({}, multicast)
  local count = 1
  count = appendFn(t, count, fn1)
  appendFn(t, count, fn2)
  return t
end

local function combine(fn1, fn2)
  if fn1 ~= nil then
    if fn2 ~= nil then
      return combineImpl(fn1, fn2)
    end
    return fn1
  end
  if fn2 ~= nil then return fn2 end
  return nil
end

local function equalsMulticast(fn1, fn2, start, count)
  for i = 1, count do
    if fn1[start + i] ~= fn2[i] then
      return false
    end
  end
  return true
end

local function delete(fn, count, deleteIndex, deleteCount)
  local t =  setmetatable({}, multicast)
  local len = 1
  for i = 1, deleteIndex - 1 do
    t[len] = fn[i]
    len = len + 1
  end
  for i = deleteIndex + deleteCount, count do
    t[len] = fn[i]
    len = len + 1
  end
  return t
end

local function removeImpl(fn1, fn2)
  if type(fn2) ~= "table" then
    if type(fn1) ~= "table" then
      if fn1 == fn2 then
        return nil
      end
    else
      local count = #fn1
      for i = count, 1, -1 do
        if fn1[i] == fn2 then
          if count == 2 then
            return fn1[3 - i]
          else
            return delete(fn1, count, i, 1)
          end
        end
      end
    end
  elseif type(fn1) == "table" then
    local count1, count2 = #fn1, # fn2
    local diff = count1 - count2
    for i = diff + 1, 1, -1 do
      if equalsMulticast(fn1, fn2, i - 1, count2) then
        if diff == 0 then
          return nil
        elseif diff == 1 then
          return fn1[i ~= 1 and 1 or count1]
        else
          return delete(fn1, count1, i, count2)
        end
      end
    end
  end
  return fn1
end

local function remove(fn1, fn2)
  if fn1 ~= nil then
    if fn2 ~= nil then
      return removeImpl(fn1, fn2)
    end
    return fn1
  end
  return nil
end

local multiKey = System.multiKey

local mt = {}
local function makeGenericTypes(...)
  local gt, gk = multiKey(mt, nil, ...)
  local t = gt[gk]
  if t == nil then
    t = setmetatable({ ... }, Delegate)
    gt[gk] = t
  end
  return t
end

Delegate = System.define("System.Delegate", {
  __add = combine,
  __sub = remove,
  EqualsObj = System.equals,
  Combine = combine,
  Remove = remove,
  RemoveAll = function (source, value)
    local newDelegate
    repeat
      newDelegate = source
      source = remove(source, value)
    until newDelegate == source
    return newDelegate
  end,
  DynamicInvoke = function (this, ...)
    return this(...)
  end,
  GetType = function ()
    return System.typeof(Delegate)
  end,
  GetInvocationList = function (this)
    local t
    if type(this) == "table" then
      t = {}
      tmove(this, 1, #this, 1, t)
    else
      t = { this }
    end
    return System.arrayFromTable(t, Delegate)
  end
})

local delegateMetaTable = setmetatable({ __index = Object, __call = makeGenericTypes }, Object)
setmetatable(Delegate, delegateMetaTable)
if debugsetmetatable then
  debugsetmetatable(System.emptyFn, Delegate)

  function System.event(name)
    local function a(this, v)
      this[name] = this[name] + v
    end
    local function r(this, v)
      this[name] = this[name] - v
    end
    return a, r
  end
else
  System.DelegateCombine = combine
  System.DelegateRemove = remove

  function System.event(name)
    local function a(this, v)
      this[name] = combine(this[name], v)
    end
    local function r(this, v)
      this[name] = remove(this[name], v)
    end
    return a, r
  end
end

multicast = setmetatable({
  __index = Delegate,
  __add = combine,
  __sub = remove,
  __call = function (t, ...)
    local result
    for i = 1, #t do
      result = t[i](...)
    end
    return result
  end,
  __eq = function (fn1, fn2)
    local len1, len2 = #fn1, #fn2
    if len1 ~= len2 then
      return false
    end
    for i = 1, len1 do
      if fn1[i] ~= fn2[i] then
        return false
      end
    end
    return true
  end
}, Delegate)

function System.fn(target, method)
  assert(method)
  if target == nil then throw(ArgumentNullException()) end
  local f = target[method]
  if f == nil then
    f = function (...)
      return method(target, ...)
    end
    target[method] = f
  end
  return f
end

local binds = setmetatable({}, { __mode = "k" })

function System.bind(f, n, ...)
  assert(f)
  local gt, gk = multiKey(binds, nil, f, ...)
  local fn = gt[gk]
  if fn == nil then
    local args = { ... }
    fn = function (...)
      local len = select("#", ...)
      if len == n then
        return f(..., unpack(args))
      else
        assert(len > n)
        local t = { ... }
        for i = 1, #args do
          local j = args[i]
          if type(j) == "number" then
            j = select(n + j, ...)
            assert(j)
          end
          t[n + i] = j
        end
        return f(unpack(t, 1, n + #args))
      end
    end
    gt[gk] = fn
  end
  return fn
end

local function bind(f, create, ...)
  assert(f)
  local gt, gk = multiKey(binds, nil, f, create)
  local fn = gt[gk]
  if fn == nil then
    fn = create(f, ...)
    gt[gk] = fn
  end
  return fn
end

local function create1(f, a)
  return function (...)
    return f(..., a)
  end
end

function System.bind1(f, a)
  return bind(f, create1, a)
end

local function create2(f, a, b)
  return function (...)
    return f(..., a, b)
  end
end

function System.bind2(f, a, b)
  return bind(f, create2, a, b)
end

local function create3(f, a, b, c)
  return function (...)
    return f(..., a, b, c)
  end
end

function System.bind3(f, a, b, c)
 return bind(f, create3, a, b, c)
end

local function create2_1(f)
  return function(x1, x2, T1, T2)
    return f(x1, x2, T2, T1)
  end
end

function System.bind2_1(f)
  return bind(f, create2_1)
end

local function create0_2(f)
  return function(x1, x2, T1, T2)
    return f(x1, x2, T2)
  end
end

function System.bind0_2(f)
  return bind(f, create0_2)
end

local EventArgs = System.define("System.EventArgs")
EventArgs.Empty = setmetatable({}, EventArgs)