/**
 * @module RESTController
 */
import * as debugStuff from 'debug'
const debug = debugStuff.debug('dbApiRESTCtrl')
import { Router } from 'express'

const MAX_RESULTS = 100

/**
 * REST controller for MongoDB backend.
 */
class RESTController {
  /**
   * Generates a controller for a model type.
   *
   * @param  {mongoose.Model} mongoose model to use
   * @param  {key} Key to use as index. Default is '_id'
   * @return {null}
   */
  constructor (model, key = '_id', subDocuments = {}) {
    this.model = model
    this.modelName = model.modelName.toLowerCase()
    this.key = key
    this.findOptions = {}
    this.findCriteria = {}
    this.extendData = (data) => data
    this.updateExtendedData = (data) => data
    this.subDocuments = subDocuments
    debug('created RESTController', this.modelName)
  }

  /**
   * Creates a DB item.
   *
   * @param  {object} data object
   * @return {Promise}
   */
  create (data) {
    debug('create data item', data)
    const newData = this.extendData(data)
    const p = this.model
      .create(newData)
      .then(instance => {
        debug('created instance', instance)
        return instance
      })
    // debug('create return value', p)
    return p
  }

  /**
   * Read a DB item.
   *
   * @param  {String} id
   * @return {Promise}
   */
  read (id) {
    debug('reading data item', id)
    const filter = {}
    filter[this.key] = id

    const p = this.model
      .findOne(filter)
      .then(instance => {
        debug('read instance', instance)
        return instance
      })
    // debug('read return value', p)
    return p
  }

  /**
   * Get a list of all DB items.
   *
   * @return {Promise}
   */
  list () {
    debug('reading data list')
    const p = this.model
      .find({})
      .limit(MAX_RESULTS)
      .then(instance => {
        debug('read list instance', instance)
        return instance
      })
    // debug('read return value', p)
    return p
  }

  /**
   * Update a DB item.
   *
   * @param  {String} id
   * @param  {String} data
   * @return {Promise}
   */
  update (id, data) {
    debug('update data item', id, data)
    const filter = {}
    filter[this.key] = id

    const p = this.model
      .findOne(filter)
      .then(instance => {
        debug('found data instance', instance)
        for (let attribute in data) {
          if (data.hasOwnProperty(attribute) && attribute !== this.key && attribute !== '_id') {
            instance[attribute] = data[attribute]
          }
        }
        return instance.save()
      })
      .then(instance => {
        debug('updated data instance', instance)
        return instance
      })
    // debug('read return value', p)
    return p
  }

  /**
   * Delete a DB item.
   *
   * @param  {String} id
   * @return {Promise}
   */
  delete (id) {
    debug('delete data item')
    const filter = {}
    filter[this.key] = id

    const p = this.model
      .remove(filter)
      .then(() => {
        return {}
      })
    // debug('read return value', p)
    return p
  }

  route (parent = undefined) {
    const router = new Router({mergeParams: true})

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

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

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

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

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

    Object.keys(this.subDocuments).forEach(key => {
      router.use(`/:parentKey/${key}`, this.subDocuments[key].route())
    })

    return router
  }
}

export default RESTController