var mongoose = require('mongoose');

var EventSchema = new mongoose.Schema({
    name: {type:String},
    start_date: {type:Date},
    duration: {type:String},
    event_id:{type: mongoose.Schema.Types.ObjectId}
});
var Project = new mongoose.Schema({
    name: {
        type: String,
        required: '{PATH} is required!'
    },
    user_id:{
        type: mongoose.Schema.Types.ObjectId,
        required:'{PATH} is required!'
    },
    client: {type: Object},
    no_of_events: {type: String, required: '{PATH} is required!'},
    start_date:{type:Date, required: '{PATH} is required!'},
    end_date:{type:Date, required: '{PATH} is required!'},
    budget:{type: String},
    groom:{type:Object},
    bride:{type:Object},
    events:[EventSchema],
    status:{type:Number,Default:1}, //0=Inactive, 1=Active, 2=Completed
    created_at: { type: Date, default: Date.now },
    updated_at: { type: Date, default: Date.now }
});

module.exports = mongoose.model('Project', Project);

{
    "_id": {
        "$oid": "5b43582a716d9a4e96345f4a"
    },
    "bride": {
        "city": "Hyderabad",
        "phone": "09876543211",
        "dob": "1993-05-06T18:30:00.000Z",
        "name": "Shriya Bhupal"
    },
    "groom": {
        "city": "Hyderabad",
        "phone": "09876543211",
        "dob": "1993-08-09T18:30:00.000Z",
        "name": "Anindith Reddy"
    },
    "client": {
        "name": "Apoorva Pagar"
    },
    "end_date": {
        "$date": "2018-07-22T18:30:00.000Z"
    },
    "start_date": {
        "$date": "2018-07-10T18:30:00.000Z"
    },
    "no_of_events": "4",
    "user_id": {
        "$oid": "5b126966bcc8072e526346ad"
    },
    "name": "Big Fat Wedding",
    "updated_at": {
        "$date": "2018-07-09T12:42:18.263Z"
    },
    "created_at": {
        "$date": "2018-07-09T12:42:18.263Z"
    },
    "events": [
        {
            "name": "Engagement",
            "event_id": {
                "$oid": "5b3b232914cdec23c19c034c"
            },
            "start_date": {
                "$date": "2018-07-11T18:30:00.000Z"
            },
            "duration": "1 Day",
            "_id": {
                "$oid": "5b43582a716d9a4e96345f4b"
            }
        },
        {
            "name": "Mehndi",
            "event_id": {
                "$oid": "5b3b23b314cdec23c19c034d"
            },
            "start_date": {
                "$date": "2018-07-12T18:30:00.000Z"
            },
            "duration": "1 Day",
            "_id": {
                "$oid": "5b43582a716d9a4e96345f4c"
            }
        },
        {
            "name": "Sangeet",
            "event_id": {
                "$oid": "5b3b232914cdec23c19c034c"
            },
            "start_date": {
                "$date": "2018-07-17T18:30:00.000Z"
            },
            "duration": "2 Days",
            "_id": {
                "$oid": "5b43582a716d9a4e96345f4d"
            }
        }
    ],
    "__v": 0
}

{"events": [
            {
// it should include event_detail:{ details about event from defaultevents}
                "name": "Engagement",
                "event_id": {
                    "$oid": "5b3b232914cdec23c19c034c"
                },
                "start_date": {
                    "$date": "2018-07-11T18:30:00.000Z"
                },
                "duration": "1 Day",
                "_id": {
                    "$oid": "5b43582a716d9a4e96345f4b"
                }
            },
            {
// it should not include event_details as there is no event_id
                "name": "Mehndi",
                "start_date": {
                    "$date": "2018-07-12T18:30:00.000Z"
                },
                "duration": "1 Day",
                "_id": {
                    "$oid": "5b43582a716d9a4e96345f4c"
                }
            }
    ]
    }

{
    "_id": {
        "$oid": "5b3b232914cdec23c19c034c"
    },
    "image": "https://dostbucket.s3.us-east-2.amazonaws.com/events/1530601666360mehndi.svg",
    "description": "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
    "name": "Sangeet",
    "updated_at": {
        "$date": "2018-07-03T07:18:01.166Z"
    },
    "created_at": {
        "$date": "2018-07-03T07:18:01.166Z"
    },
    "__v": 0
}

var products = Product.find();

products.forEach(product => {
    product.events.forEach(event => {
        if ('event_id' in event) {
            var product = product.events[event];
            product.event.event_details = 'my details';
            product.save(product);
        }
    });
});

db.colletion.aggregate([
  { "$unwind": "$events" },
  { "$lookup": {
    "from": DefaultEventSchema.collection.name,
    "localField": "events.event_id",
    "foreignField": "_id",
    "as": "events.event_id"
  }},
  { "$group": {
    "_id": "$_id",
    "events": { "$push": "$events" }
    "otherFields": { "$first": "$otherFields" }
  }}
])