/**
 * @module mongoRouter
 *
 * Backend module to store React-Redux components in MongoDB.
 */
import mongoose from 'mongoose'
import { History } from './core/basicSchema'

/**
 * Generates GET, POST, UPDATE and DELETE handlers which interact with
 * MongoDB.
 *
 * @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
        id = mongoose.Types.ObjectId(id)
      } catch (err) {
        // If id couldn't be converted, return an error message.
        res.status(422)
        res.send({error: err.message})
        return
      }
      // if yes, return the one item
      Model.findOne({ _id: id }, 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({}, {limit: limit, skip: offset}, function (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
    const item = new Model(req.body)

    // Check, if the model supports revision control
    if (typeof Model.schema.obj.__history !== 'undefined') {
      item.__history = new History({
        author: '',
        created: Date(),
        tag: '',
        reference: [],
        head: true
      })
    }

    // save the item
    item.save(function (err) {
      if (err) {
        res.status(422)
        res.send(err)
        return
      }
      res.send({ success: `${Model.modelName} added.` })
    })
  }

  /** 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 = new History({
          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 default routeGen