const lodash = require('lodash');
const assert = require('assert');
const is = require('is-type-of');
const FileSync = require('./adapters/FileSync');

class JsonDBMain {

  constructor(options = {}) {
    this.opt = options;
  }

  create() {
    const adapter = new FileSync(this.opt);

    assert(typeof adapter === 'object', 'An adapter must be provided');

    // Create a fresh copy of lodash
    const _ = lodash.runInContext()
    const db = _.chain({})
  
    // Add write function to lodash
    // Calls save before returning result
    _.prototype.write = _.wrap(_.prototype.value, function(func) {
      const funcRes = func.apply(this)
      return db.write(funcRes)
    })
  
    function plant(state) {
      db.__wrapped__ = state
      return db
    }
  
    // Expose _ for mixins
    db._ = _
  
    db.read = () => {
      const r = adapter.read()
      return is.promise(r) ? r.then(plant) : plant(r)
    }
  
    db.write = returnValue => {
      const w = adapter.write(db.getState())
      return is.promise(w) ? w.then(() => returnValue) : returnValue
    }
  
    db.getState = () => db.__wrapped__
  
    db.setState = state => plant(state)
  
    return db.read()
  }

}

module.exports = JsonDBMain;