'use strict';

const _ = require('lodash/fp');

const helpers = require('./helpers');

const createQueryBuilder = (uid, db) => {
  const meta = db.metadata.get(uid);
  const { tableName } = meta;

  const state = {
    type: 'select',
    select: [],
    count: null,
    first: false,
    data: null,
    where: [],
    joins: [],
    populate: null,
    limit: null,
    offset: null,
    orderBy: [],
    groupBy: [],
  };

  let counter = 0;
  const getAlias = () => `t${counter++}`;

  return {
    alias: getAlias(),
    getAlias,

    select(args) {
      state.type = 'select';
      state.select = _.uniq(_.castArray(args)).map(col => this.aliasColumn(col));

      return this;
    },

    addSelect(args) {
      _.uniq(_.castArray(args))
        .map(col => this.aliasColumn(col))
        .forEach(toSelect => {
          if (!state.select.includes(toSelect)) {
            state.select.push(toSelect);
          }
        });

      return this;
    },

    insert(data) {
      state.type = 'insert';
      state.data = data;

      return this;
    },

    delete() {
      state.type = 'delete';

      return this;
    },

    ref(name) {
      // TODO: name to column ?
      return db.connection.ref(name);
    },

    update(data) {
      state.type = 'update';
      state.data = data;

      return this;
    },

    count(count = '*') {
      state.type = 'count';
      state.count = count;

      return this;
    },

    where(where = {}) {
      const processedWhere = helpers.processWhere(where, { qb: this, uid, db });

      state.where.push(processedWhere);

      return this;
    },

    limit(limit) {
      state.limit = limit;
      return this;
    },

    offset(offset) {
      state.offset = offset;
      return this;
    },

    orderBy(orderBy) {
      state.orderBy = helpers.processOrderBy(orderBy, { qb: this, uid, db });
      return this;
    },

    groupBy(groupBy) {
      state.groupBy = groupBy;
      return this;
    },

    populate(populate) {
      state.populate = helpers.processPopulate(populate, { qb: this, uid, db });
      return this;
    },

    search(query) {
      state.search = query;
      return this;
    },

    init(params = {}) {
      const { _q, where, select, limit, offset, orderBy, groupBy, populate } = params;

      if (!_.isNil(where)) {
        this.where(where);
      }

      if (!_.isNil(_q)) {
        this.search(_q);
      }

      if (!_.isNil(select)) {
        this.select(select);
      } else {
        this.select('*');
      }

      if (!_.isNil(limit)) {
        this.limit(limit);
      }

      if (!_.isNil(offset)) {
        this.offset(offset);
      }

      if (!_.isNil(orderBy)) {
        this.orderBy(orderBy);
      }

      if (!_.isNil(groupBy)) {
        this.groupBy(groupBy);
      }

      if (!_.isNil(populate)) {
        this.populate(populate);
      }

      return this;
    },

    first() {
      state.first = true;
      return this;
    },

    join(join) {
      state.joins.push(join);
      return this;
    },

    aliasColumn(columnName) {
      if (typeof columnName !== 'string') {
        return columnName;
      }

      if (columnName.indexOf('.') >= 0) return columnName;
      return this.alias + '.' + columnName;
    },

    raw(...args) {
      return db.connection.raw(...args);
    },

    getKnexQuery() {
      const aliasedTableName = state.type === 'insert' ? tableName : { [this.alias]: tableName };

      const qb = db.connection(aliasedTableName);

      if (!state.type) {
        this.select('*');
      }

      switch (state.type) {
        case 'select': {
          if (state.select.length === 0) {
            state.select = [this.aliasColumn('*')];
          }

          if (state.joins.length > 0 && !state.groupBy) {
            // add a discting when making joins and if we don't have a groupBy
            // TODO: make sure we return the right data
            qb.distinct(`${this.alias}.id`);
            // TODO: add column if they aren't there already
            state.select.unshift(...state.orderBy.map(({ column }) => column));
          }

          qb.select(state.select);
          break;
        }
        case 'count': {
          qb.count({ count: state.count });
          break;
        }
        case 'insert': {
          qb.insert(state.data);

          if (db.dialect.useReturning() && _.has('id', meta.attributes)) {
            qb.returning('id');
          }

          break;
        }
        case 'update': {
          qb.update(state.data);

          break;
        }
        case 'delete': {
          qb.del();

          break;
        }
      }

      if (state.limit) {
        qb.limit(state.limit);
      }

      if (state.offset) {
        qb.offset(state.offset);
      }

      if (state.orderBy.length > 0) {
        qb.orderBy(state.orderBy);
      }

      if (state.first) {
        qb.first();
      }

      if (state.groupBy.length > 0) {
        qb.groupBy(state.groupBy);
      }

      // if there are joins and it is a delete or update use a sub query
      if (state.where) {
        helpers.applyWhere(qb, state.where);
      }

      // if there are joins and it is a delete or update use a sub query
      if (state.search) {
        qb.where(subQb => {
          helpers.applySearch(subQb, state.search, { alias: this.alias, db, uid });
        });
      }

      if (state.joins.length > 0) {
        helpers.applyJoins(qb, state.joins);
      }

      return qb;
    },

    async execute({ mapResults = true } = {}) {
      try {
        const qb = this.getKnexQuery();

        const rows = await qb;

        if (state.populate && !_.isNil(rows)) {
          await helpers.applyPopulate(_.castArray(rows), state.populate, { qb: this, uid, db });
        }

        let results = rows;
        if (mapResults && state.type === 'select') {
          results = helpers.fromRow(meta, rows);
        }

        return results;
      } catch (error) {
        db.dialect.transformErrors(error);
      }
    },
  };
};

module.exports = createQueryBuilder;