--[[
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.save(k, v) rawset(self, k, v) end
   function mt.get(k, create) return mt.load(k, create) end
   function mt.__index(t, k) return mt.get(k) end
   function mt.__newindex(t, k, v) mt.save(k, v) end

   function mt.has_permission(user, permission)
      local p = permission..mt.path
      if mt.txn:search('/auth/permissions')[p] then
	 return user:check_permission(p)
      end

      if ({create=true, delete=true})[permission] then
	 permission = 'modify'
      end
      return has_permission(mt.parent, user, permission)
   end

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

function TreeNode:search(path, create)
   if type(path) == 'string' then path = pth.split(path) end

   if #path == 0 then return self end

   local mt = getmetatable(self)
   local name = path[1]
   if not mt.has_field(name) then
      raise(mt.path, 'Field does not exist: '..name)
   end

   local next = mt.get(name, create)
   if next == nil and (not create or #path > 1) then
      raise(mt.path, 'Subordinate does not exist: '..name)
   end

   table.remove(path, 1)
   if #path > 0 and type(next) ~= 'table' then
      raise(pth.join(mt.path, name), 'Is a primitive value')
   end

   return TreeNode.search(next, path, create)
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.has_field(name) return true end
   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.load(k, create) return mt.field:load(k, create) end
   function mt.save(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')
has_permission = meta_func('has_permission')
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.load(member) end
   return rawpairs(res)
end