module wizzi-mtree@${wzCtx.version}.loader.appender
    kind es6
    
	var util = require('util')
    var errors = require('../errors')
    var utilnode = require('../utils/node')

	#
		# Ittf commands
		#   $group
		#   $append
		#   $override
        #   $fragment (searched and removed only, processing is by includer and mixer)
    
	set module.exports
        function 
            { mixedMTreePiece
            callback
            
			var appends
                { 
            var groups
                [ 
            var overrides
                [ 
            var fragments
                [ 
            var ctx
                { 
                    @ id 1
            
			foreach node in mixedMTreePiece.nodes
                _ assignId
                    @ node
                    @ ctx
            
			var errors
                [ 
            
			foreach node in mixedMTreePiece.nodes
                _ searchAppend(node, node, appends, groups, overrides, fragments, errors, mixedMTreePiece)
                if errors.length > 0
					return
						_ callback
							@ errors[0]
            for var key in appends
				# loog 'wizzi-mtree.loader.appender.appends.key', key, appends[key]
                var appobj = appends[key]
                _ utilnode.replace
                    @ appobj.appto
                    @ appobj.items
            for var key in overrides
                var overobj = overrides[key]
                _ utilnode.replace
                    @ overobj.virt
                    @ overobj.items
            for var key in fragments
                var fragobj = fragments[key]
                _ utilnode.remove
                    @ fragobj.frag
            foreach item in groups
				if !item.parent 
					return
						_ callback
							_ local_error
								@ 'InvalidIttfError'
								@ 'appender'
								@ "The tag $group must have a parent and cannot be the root of a primary ittf document. Hint: check for ittf fragments not in a tfolder."
								@ item
                _ utilnode.replace
                    @ item
                    @ item.children
            var toremove
                [ 
            foreach node in mixedMTreePiece.nodes
                _ searchPendingNodes(node, toremove)
            foreach item in toremove
                _ utilnode.remove(item)
            _ callback(null, mixedMTreePiece)
    
	function searchAppend
        param item
        param root
        param appends
        param groups
        param overrides
        param fragments
        param errors
		param mixedMTreePiece
        
		if item.name === '$group'
            _ groups.push(item)
        
		elif item.name === '$append'
            if !item.value
                _ errors.push
					_ local_error
						@ 'InvalidIttfError'
						@ 'searchAppend'
						@ "The tag $append requires a node-value."
						@ item
                return 
            var appto
                _ utilnode.findHookExt
                    @ item
                    _ item.value.trim()
					@ 1
            if appto == null
				set appto
					_ utilnode.findHookExt
						@ item
						_ item.value.trim()
						@ 0
				if appto == null
					# loog 'mixedMTreePiece.dump\n', mixedMTreePiece.toText()
					_ errors.push
						_ local_error
							@ 'InvalidIttfError'
							@ 'searchAppend'
							@ 'Cannot find hook ' + (item.value || '') + ', root is ' + root.name 
								\b + ' ' + (root.value || '') + ', in ' + item.model.uri + ', brickKey ' + item.model.brickKey
								\b + ', remember that $hook/$append does not work between sibling nodes.' 
								\b + 'After mixup the $hook node must be a parent node or a descendant of a parent node of $append'
								\b + ', but not a sibling node.'
							@ item
					return 
            var appobj = appends[item.id]
            if appobj
                set appobj.items = appobj.items.concat(item.children)
            else 
                set appobj =
                    { 
                        @ appto appto
                        @ items item.children
                set appends[item.id] = appobj
        
		elif item.name === '$override'
            if !(item.value)
                _ errors.push
					_ local_error
						@ 'InvalidIttfError'
						@ 'searchAppend'
						@ "The tag $override requires a value."
						@ item
                return 
            var virt
                _ utilnode.findVirtual
                    @ item
                    _ item.value.trim()
            if virt == null
                _ errors.push
					_ local_error
						@ 'InvalidIttfError'
						@ 'searchAppend'
                        @ 'Cannot find virtual to override ' + (item.value || '') + ', root is ' + root.name + ' ' + root.value
						@ item
                return 
            var overobj = overrides[item.value]
            if overobj
                _ errors.push
					_ local_error
						@ 'InvalidIttfError'
						@ 'searchAppend'
						@ 'The virtual node ' + item.value + ' has already been overridden. Root is ' + root.name + ' ' + root.value
						@ item
                return 
            else 
                set overobj =
                    { 
                        @ virt virt
                        @ over item
                        @ items item.children
                set overrides[item.value] = overobj
		elif item.name === '$fragment'
            var fragobj
                { 
                    @ frag item
            set fragments[item.value] = fragobj

		foreach child in item.children
            _ searchAppend(child, root, appends, groups, overrides, fragments, errors, mixedMTreePiece)
    
	function searchPendingNodes
        param item
        param toremove
        if ['$hook', '$append', '$override'].indexOf(item.name) >= 0
            _ toremove.push(item)
        foreach child in item.children
            _ searchPendingNodes(child, toremove)
    
	function assignId
        param item
        param ctx
        set item._id = ctx.id++
        foreach child in item.children
			_ assignId(child, ctx)

    local_error( wizzi-mtree@${wzCtx.version}.loader.appender )