--[[
Copyright (c) 2012-2013 Kaarle Ritvanen
See LICENSE file for license details
--]]

module(..., package.seeall)

local raise = require('acf.error').raise
local object = require('acf.object')
local class = object.class
local super = object.super

local pth = require('acf.path')
local update = require('acf.util').update


BoundField = class()

function BoundField:init(parent, field)
   local pmt = getmetatable(parent)
   local mt = {}

   function mt.__index(t, k)
      local member = field[k]
      if type(member) ~= 'function' then return member end
      return function(self, ...)
		local name
		if field.name then name = field.name
		else
		   name = arg[1]
		   table.remove(arg, 1)
		end
		return member(
		   field,
		   {
		      txn=pmt.txn,
		      parent=parent,
		      path=pth.join(pmt.path, name),
		      addr=field.addr or pth.join(pmt.addr, name)
		   },
		   unpack(arg)
		)
	     end
   end

   setmetatable(self, mt)
end


TreeNode = class()

function TreeNode:init(context)
   local mt = getmetatable(self)
   update(mt, context)

   function mt.set(k, v) rawset(self, k, v) end
   function mt.__index(t, k) return mt.get(k) end
   function mt.__newindex(t, k, v) mt.set(k, v) end

   mt.txn.validable[mt.path] = mt.addr
end

function TreeNode:search(path)
   if #path == 0 then return self end
   local name = path[1]
   local next = self[name]
   if next == nil then
      raise(getmetatable(self).path, 'Subordinate does not exist: '..name)
   end
   table.remove(path, 1)
   return TreeNode.search(next, path)
end


Collection = class(TreeNode)

function Collection:init(context, params)
   super(self, Collection):init(context)

   self.init = nil
   self.search = nil

   local mt = getmetatable(self)

   mt.field = BoundField(self, params.field)
   mt.meta = {type='collection', members=mt.field:meta('$')}
   function mt.mmeta(name) return mt.meta.members end
   function mt.members() return mt.txn:get(mt.addr) or {} end

   function mt.validate()
      if params.required and #mt.txn:get(mt.addr) == 0 then
	 raise(mt.path, 'Collection cannot be empty')
      end
   end
   
   function mt.get(k) return mt.field:load(k) end
   function mt.set(k, v) mt.field:save(k, v) end
end


-- experimental
Mixed = class(Collection)

function Mixed:init(context, params)
   super(self, Mixed):init(context, params)
   -- TODO dynamic meta: list non-leaf children
   getmetatable(self).meta = {type='mixed'}
end


local function meta_func(attr)
   return function(node, ...)
	     local res = getmetatable(node)[attr]
	     if type(res) == 'function' then return res(unpack(arg)) end
	     return res
	  end
end

addr = meta_func('addr')
members = meta_func('members')
meta = meta_func('meta')
mmeta = meta_func('mmeta')
parent = meta_func('parent')
path = meta_func('path')
validate = meta_func('validate')


local rawpairs = pairs

function pairs(tbl)
   if not object.isinstance(tbl, TreeNode) then return rawpairs(tbl) end
   local mt = getmetatable(tbl)
   local res = {}
   for _, member in ipairs(mt.members()) do res[member] = mt.get(member) end
   return rawpairs(res)
end