/**
 * @module mongoRouter
 *
 * Backend module to store React-Redux components in MongoDB.
 */
import mongoose from 'mongoose'
import { Router } from 'express'
mongoose.Promise = Promise

const MAX_RESULTS = 100

class RESTController {
  constructor (model, key) {
    this.model = model
    this.modelName = model.modelName.toLowerCase()
    this.key = key
  }

  create (data) {
    return this.model
      .create(data)
      .then(instance => {
        const response = {}
        response[this.modelName] = instance
        return response
      })
  }

  read (id) {
    const filter = {}
    filter[this.key] = id
    return this.model
      .findOne(filter)
      .then(instance => {
        const response = {}
        response[this.modelName] = instance
        return response
      })
  }

  list () {
    return this.model
      .find({})
      .limit(MAX_RESULTS)
      .then(instance => {
        const response = {}
        response[this.modelName] = instance
        return response
      })
  }

  update (id, data) {
    const filter = {}
    filter[this.key] = id

    return this.model
      .findOne(filter)
      .then(instance => {
        for (let attribute in data) {
          if (data.hasOwnProperty(attribute) && attribute !== this.key && attribute !== '_id') {
            instance[attribute] = data[attribute]
          }
        }
        return instance.save()
      })
      .then(instance => {
        const response = {}
        response[this.modelName] = instance
        return response
      })
  }

  route () {
    const router = new Router()

    router.get('/', (req, res) => {
      this
        .list()
        .then(data => res.json(data))
        .then(null, error => res.status(404).send(error))
    })

    router.post('/', (req, res) => {
      this
        .create(req.body)
        .then(data => res.json(data))
        .then(null, error => res.status(404).send(error))
    })

    router.get('/:key', (req, res) => {
      this
        .read(req.params.key)
        .then(data => res.json(data))
        .then(null, error => res.status(404).send(error))
    })

    router.put('/:key', (req, res) => {
      this
        .update(req.params.key, req.body)
        .then(data => res.json(data))
        .then(null, error => res.status(404).send(error))
    })

    router.delete('/:key', (req, res) => {
      this
        .delete(req.params.key)
        .then(data => res.json(data))
        .then(null, error => res.status(404).send(error))
    })

    return router
  }
}

export default RESTController

/**
 * Generates GET, POST, UPDATE and DELETE handlers which interact with
 * MongoDB.
 *
 * For versioned objects, allow querying for tags or for IDs. When querying
 * tags, return the head version, when querying for IDs, just return the
 * element.
 *
 * @param  {object} Model - mongoose model to use
 * @param  {boolean} versioned - use a revision control mechanism
 * @return {[type]}
 */
function routeGen (Model, versioned = true) {
  /** GET handler (request one item or a list of items) */
  const get = (req, res) => {
    let { id } = req.params

    /** check whether an id was specified. */
    if (typeof id === 'string' && id.length > 1) {
      try {
        // try to convert the id string to a valid ObjectId
        const _id = mongoose.Types.ObjectId(id)
        // if yes, return the one item
        Model.findOne({ _id }, function (err, item) {
          console.log(item)
          if (err) {
            res.status(404)
            res.send(err)
            return
          }
          res.json(item)
        })
      } catch (err) {
        // If id couldn't be converted, assume it's a tag.
        const tag = id
        // if yes, return the one item
        Model.findOne({ tag, 'history.head': true }, function (err, item) {
          if (err) {
            res.status(404)
            res.send(err)
            return
          }
          res.json(item)
        })
      }
    } else {
      // if not, return a list of items
      // limit the number of returned items and use an offset
      const limit = req.query.limit ? Math.min(Math.max(parseInt(req.query.limit), 1), 100) : 20
      const offset = req.query.offset ? Math.max(parseInt(req.query.offset), 0) : 0
      Model.find({'history.head': true}, {limit: limit, skip: offset}, function (err, items) {
        console.log(err, items)
        if (err) {
          res.status(404)
          res.send(err)
          return
        }
        res.json(items)
      })
    }
  }

  /** POST handler (insert a new item into the database) */
  const post = (req, res) => {
    // create the new item
    console.log(req.body)
    const item = new Model(req.body)
    console.log(item)

    // Check, if the model supports revision control
    if (typeof Model.schema.obj.__history !== 'undefined') {
      console.log('creating new history')
      item.__history = {
        author: 'Tomi',
        created: new Date(),
        tag: 'myTag',
        reference: 'reference',
        head: true,
        comment: 'My Comment'
      }
    }
    console.log(item)

    // save the item
    console.log('before save')
    const p = item.save()
    console.log(p)
    p.then(savedItem => {
      console.log('in save', savedItem)
      res.status(200)
      res.send({ _id: savedItem._id })
    }).catch(err => {
      console.log('in save', err)
      res.status(422)
      res.send(err)
    })
    console.log('after save', p)
  }

  /** PUT handler (update existing project) */
  const put = (req, res) => {
    let id = req.params['0']
    /** check whether an id was specified. */
    if (typeof id === 'string' && id.length > 1) {
      // remove leading slash
      id = id.substring(1)
      try {
        // try to convert the id string to a valid ObjectId
        id = mongoose.Types.ObjectId(req.params['1'].substring(1))
      } catch (err) {
        // If id couldn't be converted, return an error message.
        res.status(422)
        res.send({error: err.message})
        return
      }
    }

    // Find the object in the database
    Model.findOne({ _id: id }, function (err, item) {
      if (err) {
        res.status(404)
        res.send(err)
      }

      // Check, if the model supports revision control
      if (typeof Model.schema.obj.__history !== 'undefined') {
        // If yes, don't update the item, but create a new one based on the original
        const newItem = Model(item)
        // replace the requested elements
        for (let prop in req.body) {
          newItem[prop] = req.body[prop]
        }
        // give it a new history with updated reference array. Set the head-indicator to true
        newItem.__history.create({
          author: '',
          created: Date(),
          tag: '',
          reference: [ ...item.__history.reference, item._id ],
          head: true
        })
        // set the original item's head indicator to false
        item.__history.head = false
        // save the documents
        newItem.save(function (err) {
          if (err) {
            res.status(422)
            res.send(err)
          }
          res.json({ message: `${Model.modelName} updated.` })
        })
      } else {
        for (let prop in req.body) {
          item[prop] = req.body[prop]
        }
      }

      item.save(function (err) {
        if (err) {
          res.status(422)
          res.send(err)
        }
        res.json({ message: `${Model.modelName} updated.` })
      })
    })
  }

  /** DELETE handler (delete project) */
  const del = (req, res) => {
    const id = mongoose.Types.ObjectId(req.params['0'])

    Model.remove({ _id: id }, function (err, project) {
      if (err) {
        res.send(err)
      }
      res.json({ message: 'Movie deleted.' })
    })
  }

  return {
    get,
    post,
    put,
    del
  }
}

export { routeGen }