prevent deletion of objects referred to by other objects

4 files changed, 66 insertions, 12 deletions

diff --git a/acf/model/init.lua b/acf/model/init.lua
index a53cc0d..e1a4dd9 100644
--- a/acf/model/init.lua
+++ b/acf/model/init.lua
@@ -114,6 +114,14 @@ function Reference:_validate(context, value)
    return value
 end
 
+function Reference:deleted(context, addr)
+   local target = self:load(context)
+   if target and node.addr(target) == addr then
+      -- TODO raise error for the target object
+      raise(context.path, 'Refers to '..addr)
+   end
+end
+
 
 Model = fld.Model
 
diff --git a/acf/model/node.lua b/acf/model/node.lua
index 4c05d4d..0e22d63 100644
--- a/acf/model/node.lua
+++ b/acf/model/node.lua
@@ -6,8 +6,10 @@ 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 isinstance = object.isinstance
 local super = object.super
 
 local pth = require('acf.path')
@@ -103,6 +105,38 @@ function TreeNode:fetch(path, create)
    return TreeNode.fetch(next, path, create)
 end
 
+function TreeNode:search_refs(path)
+   if type(path) == 'string' then path = pth.split(path) end
+
+   if #path == 0 then return {} end
+
+   local mt = getmetatable(self)
+   local name = path[1]
+   table.remove(path, 1)
+
+   local function collect(name)
+      local next = mt.load(name)
+      if not next then return {} end
+      
+      local member = mt.member(name)
+      if member.deleted then return {member} end
+      
+      return isinstance(next, TreeNode) and TreeNode.search_refs(
+	 next, path
+      ) or {}
+   end
+
+   if name == pth.wildcard then
+      local res = {}
+      for _, member in ipairs(mt.members()) do
+	 util.extend(res, collect(member))
+      end
+      return res
+   end
+
+   return collect(name)
+end
+
 
 Collection = class(TreeNode)
 
@@ -111,6 +145,7 @@ function Collection:init(context, params)
 
    self.init = nil
    self.fetch = nil
+   self.search_refs = nil
 
    local mt = getmetatable(self)
    local field = BoundMember(self, pth.wildcard, params.field)
@@ -221,7 +256,7 @@ local rawpairs = pairs
 local rawipairs = ipairs
 
 function pairs(tbl)
-   if not object.isinstance(tbl, TreeNode) then return rawpairs(tbl) end
+   if not isinstance(tbl, TreeNode) then return rawpairs(tbl) end
    local mt = getmetatable(tbl)
    local res = {}
    for _, member in rawipairs(mt.members()) do res[member] = mt.load(member) end
@@ -235,6 +270,6 @@ local function _ipairs(mt, i)
    return i, v
 end
 function ipairs(tbl)
-   if not object.isinstance(tbl, TreeNode) then return rawipairs(tbl) end
+   if not isinstance(tbl, TreeNode) then return rawipairs(tbl) end
    return _ipairs, getmetatable(tbl), 0
 end
diff --git a/acf/model/root.lua b/acf/model/root.lua
index d17f8a9..2d3b2a0 100644
--- a/acf/model/root.lua
+++ b/acf/model/root.lua
@@ -40,7 +40,7 @@ function topology(addr, create)
    else addr = pth.split(addr) end
 
    local function defaults(top)
-      return util.setdefaults(top, {members={}, paths={}})
+      return util.setdefaults(top, {members={}, paths={}, referrers={}})
    end
 
    while #addr > 0 do
@@ -77,14 +77,11 @@ function register(name, field, params)
       table.insert(top.paths, record.path)
 
       if record.scope then
-	 set(
-	    'scope',
-	    node.addr(
-	       root:fetch(
-		  pth.to_absolute(record.scope, pth.parent(record.path))
-	       )
-	    )
+	 local scope = node.addr(
+	    root:fetch(pth.to_absolute(record.scope, pth.parent(record.path)))
 	 )
+	 set('scope', scope)
+	 table.insert(topology(scope, true).referrers, record.path)
       end
    end
 end
diff --git a/acf/transaction/init.lua b/acf/transaction/init.lua
index a76e7bf..76a8d47 100644
--- a/acf/transaction/init.lua
+++ b/acf/transaction/init.lua
@@ -6,7 +6,7 @@ See LICENSE file for license details
 module(..., package.seeall)
 
 local ErrorDict = require('acf.error').ErrorDict
-local RootModel = require('acf.model.root').RootModel
+local root = require('acf.model.root')
 local object = require('acf.object')
 local pth = require('acf.path')
 local be_mod = require('acf.transaction.backend')
@@ -46,7 +46,7 @@ function Transaction:init(backend, validate)
    self.validate = validate
    self.validable = {}
 
-   self.root = RootModel(self)
+   self.root = root.RootModel(self)
 end
 
 function Transaction:check()
@@ -94,6 +94,20 @@ function Transaction:_set_multiple(mods)
 
       local delete = value == nil
 
+      if delete then
+	 -- assume one-level refs for now
+	 local top = root.topology(ppath)
+	 if top then
+	    local errors = ErrorDict()
+	    for _, refs in ipairs(top.referrers) do
+	       for _, ref in ipairs(self.root:search_refs(refs)) do
+		  errors:collect(ref.deleted, ref, path)
+	       end
+	    end
+	    errors:raise()
+	 end
+      end
+
       if type(old) == 'table' then
 	 if delete then
 	    for _, child in ipairs(old) do self:set(pth.join(path, child)) end