_ = require 'underscore'
mongoose = require("mongoose")
mongooseHelper = require("mongoose-helper")
async    = require 'async'

populationPlugin = (schema, options) ->
    cached = null
    
    getPopulationFields = ()->
        
        return cached if cached?

        cached = _.chain(schema.tree)
            .map( (v, k)->
                v._fieldName = k
                return v
            )
            .filter( (v, k)->
                return _.isArray(v) or v.ref?
            )
            .pluck('_fieldName')
            .value()

        return cached

    schema.methods.getNestedJson = (_callback)->
        console.log 'start with', @_modelName
        popFields = getPopulationFields()
        return _callback @toJSON() unless popFields?.length 
        popQuery = _.map popFields, (fieldName)-> {path: fieldName}
        mongoose.models[@_modelName].findById(@_id)
            .populate(popQuery)
            .exec (err, doc)->
                async.eachSeries(popFields, (field, innerCallback)->
                    return innerCallback null unless doc[field].length
                    _.each doc[field], (model, index, array) ->
                        mongoose.models[model._modelName].findById model._id, (err, nestedModel) ->
                            nestedModel.getNestedJson (JSON) ->
                                doc[field][index] = JSON
                                if index is array.length - 1
                                    innerCallback null, {}
                , (err, res) ->
                    _callback doc
                )

module.exports = populationPlugin