import mongoose from 'mongoose';

const {Schema, connect, model: _model} = mongoose;
const defaultOptions = {useNewUrlParser: true, useUnifiedTopology: true};

export class mongoDB {
  constructor(url, options = defaultOptions) {
    /**
     * @type {string}
     */
    this.url = url;
    /**
     * @type {mongoose.ConnectOptions}
     */
    this.options = options;
    this.data = this._data = {};
    /**
     * @type {mongoose.Schema}
     */
    this._schema = {};
    /**
     * @type {mongoose.Model}
     */
    this._model = {};
    /**
     * @type {Promise<typeof mongoose>}
     */
    this.db = connect(this.url, {...this.options}).catch(console.error);
  }
  async read() {
    this.conn = await this.db;
    const schema = this._schema = new Schema({
      data: {
        type: Object,
        required: true, // depends on whether the field is mandatory or not
        default: {},
      },
    });
    try {
      this._model = _model('data', schema);
    } catch {
      this._model = _model('data');
    }
    this._data = await this._model.findOne({});
    if (!this._data) {
      this.data = {};
      const [_, _data] = await Promise.all([
        this.write(this.data),
        this._model.findOne({}),
      ]);
      this._data = _data;
    } else this.data = this._data.data;
    return this.data;
  }

  write(data) {
    return new Promise(async (resolve, reject) => {
      if (!data) return reject(data);
      if (!this._data) return resolve((new this._model({data})).save());
      this._model.findById(this._data._id, (err, docs) => {
        if (err) return reject(err);
        if (!docs.data) docs.data = {};
        docs.data = data;
        this.data = {};
        return docs.save(resolve);
      });
    });
  }
}

export const mongoDBV2 = class MongoDBV2 {
  constructor(url, options = defaultOptions) {
    /**
     * @type {string}
     */
    this.url = url;
    /**
     * @type {mongoose.ConnectOptions}
     */
    this.options = options;
    /**
     * @type {{ name: string, model: mongoose.Model}[]}
     */
    this.models = [];
    /**
     * @type {{ [Key: string]: any }}
     */
    this.data = {};
    this.lists;
    /**
     * @type {mongoose.Model}
     */
    this.list;
    /**
     * @type {Promise<typeof mongoose>}
     */
    this.db = connect(this.url, {...this.options}).catch(console.error);
  }
  async read() {
    this.conn = await this.db;
    const schema = new Schema({
      data: [{
        name: String,
      }],
    });
    try {
      this.list = _model('lists', schema);
    } catch (e) {
      this.list = _model('lists');
    }
    this.lists = await this.list.findOne({});
    if (!lists?.data) {
      await this.list.create({data: []});
      // await (new this.list({ data: [] })).save()
      this.lists = await this.list.findOne({});
    }
    const garbage = [];
    for (const {name} of this.lists.data) { // get data from list
      /**
       * @type {mongoose.Model}
       */
      let collection;
      try {
        collection = _model(name, new Schema({data: Array}));
      } catch (e) {
        console.error(e);
        try {
          collection = _model(name);
        } catch (e) {
          garbage.push(name);
          console.error(e);
        }
      }
      if (collection) {
        this.models.push({name, model: collection});
        const collectionsData = await collection.find({});
        this.data[name] = Object.fromEntries(collectionsData.map((v) => v.data));
      }
    }
    try {
      // Delete list if not exist
      const del = await this.list.findById(this.lists._id);
      del.data = del.data.filter((v) => !garbage.includes(v.name));
      await del.save();
    } catch (e) {
      console.error(e);
    }

    return this.data;
  }
  write(data) {
    return new Promise(async (resolve, reject) => {
      if (!this.lists || !data) return reject(data || this.lists);
      const collections = Object.keys(data); const listDoc = []; let index = 0;
      for (const key of collections) {
        // Update if exist
        if ((index = this.models.findIndex((v) => v.name === key)) !== -1) {
          const doc = this.models[index].model;
          await doc.deleteMany().catch(console.error); // alwasy insert, no matter delete error
          await doc.insertMany(Object.entries(data[key]).map((v) => ({data: v})));
          if (doc && key) listDoc.push({name: key});
        } else { // if not exist, create new model
          const schema = new Schema({
            data: Array,
          });
          /**
           * @type {mongoose.Model}
           */
          let doc;
          try {
            doc = _model(key, schema);
          } catch (e) {
            console.error(e);
            doc = _model(key);
          }
          index = this.models.findIndex((v) => v.name === key);
          this.models[index === -1 ? this.models.length : index] = {name: key, model: doc};
          await doc.insertMany(Object.entries(data[key]).map((v) => ({data: v})));
          if (doc && key) listDoc.push({name: key});
        }
      }

      // save list
      this.list.findById(this.lists._id, function(err, doc) {
        if (err) return reject(err);
        doc.data = listDoc;
        this.data = {};
        return doc.save(resolve);
      });
      return resolve(true);
    });
  }
};