const _ = require('lodash')
const defaults = require('./defaults')
const { Op } = require('sequelize')
const { diffBy, sanitize } = require('../util')
const { sequelize } = require('../database')

const crudController = (opts) => {
  opts = defaults(opts)
  const { Type } = opts
  const options = Object.assign({}, opts.options)

  const subset = async (req) => {
    const subset = {}
    const params = _.toPairs(req.params)
      .map(([key, value])=>({key, value}))
      .filter(({value}) => value !== opts.paramAll)
    for (let { key, value } of params) {
      const assoc = Type.associations[key]
      if (assoc) {
        subset[assoc.foreignKey] = (await assoc.target.findOne({
          parameters: ['id'],
          where: { key: value }
        })).id
      }
    }
    return subset
  }

  const list = async (req, res) => {
    // TODO Pagination (http://docs.sequelizejs.com/manual/tutorial/querying.html#pagination-limiting)
    if (req.query && req.query.q) {
      const fields = [Type.tableAttributes.name, Type.tableAttributes.tag].filter(x => x)
      if (!fields) throw new Error('Table has no searchable fields')
      const or = fields.map(field => ({
        [field.fieldName]: { [Op.like]: `%${req.query.q}%` }
      }))
      const where = { ...subset, [Op.or]: or }
      const data = await sanitize(req, await Type.findAll({ ...options, where }))
      res.status(200).send(data)
    } else if (res.query && res.query.ids) {
      const ids = res.query.ids.split(',')
      const data = await sanitize(req, await Type.findAll({ ...options, where: { ...(await subset(req)), id: { [Op.in]: ids }}}))
      res.status(200).send(data)
    } else {
      const data = await sanitize(req, await Type.findAll({ ...options, where: { ...(await subset(req)) }}))
      res.status(200).send(data)
    }
  }

  const setAssociations = async (record, data, transaction) => {
    for (let [key, assoc] of _.toPairs(Type.associations)) {
      if (record[key] && assoc.associationType === 'BelongsToMany' && assoc.target.attributes.key) {
        await assoc.set(
          data,
          await assoc.target.findAll({
            attributes: ['id'],
            where: {
              key: {
                [Op.in]: record[key]
              }
            }
          }),
          {transaction}
        )
      }
    }
  }
  
  const getAssociations = async (data, json) => {
    for (let [key, assoc] of _.toPairs(Type.associations)) {
      if (assoc.associationType === 'BelongsToMany' && assoc.target.attributes.key) {
        json[key] = (await assoc.get(data, {
          attributes: ['id', 'key']
        })).map(x => x.key)
      }
    }
  }

  const create = async (req, res) => {
    const transaction = await sequelize.transaction()
    try {
      const record = { ...req.body, ...(await subset(req))}
      const data = (await Type.create(record, {transaction}))
      await setAssociations(record, data, transaction)
      await transaction.commit()
      res.status(200).send(await sanitize(req, data))
    } catch (err) {
      await transaction.rollback()
      throw err
    }
  }
  const read = async (req, res) => {
    const data = (await Type.findOne({where: {id: req.params[opts.routeParam]}}))
    const json = await sanitize(req, data)
    await getAssociations(data, json)
    res.status(200).send(json)
  }
  const update = async (req, res) => {
    const transaction = await sequelize.transaction()
    try {
      const record = _.omit(req.body, _.keys(await subset(req)))
      const updated = (await Type.update(record, { where: { id: req.params[opts.routeParam] }, transaction }))
      const data = (await Type.findOne({where: { id: req.params[opts.routeParam] }}))
      const json = await sanitize(req, data)

      await setAssociations(record, data, transaction)
      await transaction.commit()
      await getAssociations(data, json)
      res.status(200).send(json)
    } catch (err) {
      await transaction.rollback()
      throw err
    }
  }
  const $delete = async (req, res) => {
    const data = (await Type.destroy({ where: { id: req.params[opts.routeParam] } }))
    res.status(204).end()
  }
  const trash = async (req, res) => {
    const data = (await Type.findAll({
      model: Type,
      paranoid: false,
      where: {
        ...(await subset(req)),
        deletedAt: { [Op.ne]: null }
      }
    }))
    res.status(200).send(await sanitize(req, data))
  }
  const undelete = async (req, res) => {
    const data = (await Type.update({ deletedAt: null }, {
      paranoid: false,
      where: { id: req.params[opts.routeParam] }
    }))
    res.status(200).send(await sanitize(req, data))
  }
  // TODO: Create, Read, Update, Delete

  return {
    list,
    create,
    read,
    update,
    delete: $delete,
    trash,
    undelete
  }
}

module.exports = crudController