var BaseOverviewsDataview = require('./base');
var BaseDataview = require('../formula');

var dot = require('dot');
dot.templateSettings.strip = false;

var formulaQueryTpls = {
  'count': dot.template([
      'SELECT',
      'sum(_feature_count) AS result,',
      '(SELECT count(1) FROM ({{=it._query}}) _cdb_formula_nulls WHERE {{=it._column}} IS NULL) AS nulls_count',
      'FROM ({{=it._query}}) _cdb_formula'
  ].join('\n')),
  'sum': dot.template([
      'SELECT',
      'sum({{=it._column}}*_feature_count) AS result,',
      '(SELECT count(1) FROM ({{=it._query}}) _cdb_formula_nulls WHERE {{=it._column}} IS NULL) AS nulls_count',
      'FROM ({{=it._query}}) _cdb_formula'
  ].join('\n')),
  'avg': dot.template([
      'SELECT',
      'sum({{=it._column}}*_feature_count)/sum(_feature_count) AS result,',
      '(SELECT count(1) FROM ({{=it._query}}) _cdb_formula_nulls WHERE {{=it._column}} IS NULL) AS nulls_count',
      'FROM ({{=it._query}}) _cdb_formula'
  ].join('\n')),
};

function Formula(query, options, queryRewriter, queryRewriteData, params) {
    BaseOverviewsDataview.call(this, query, options, BaseDataview, queryRewriter, queryRewriteData, params);
    this.column = options.column || '1';
    this.operation = options.operation;
}

Formula.prototype = Object.create(BaseOverviewsDataview.prototype);
Formula.prototype.constructor = Formula;

module.exports = Formula;

Formula.prototype.sql = function(psql, filters, override, callback) {
    var formulaQueryTpl = formulaQueryTpls[this.operation];

    if ( formulaQueryTpl ) {
        // supported formula for use with overviews
        var formulaSql = formulaQueryTpl({
            _query:     this.rewrittenQuery(this.query),
            _operation: this.operation,
            _column:    this.column
        });
        callback = callback || override;

        return callback(null, formulaSql);
    }

    // default behaviour
    return this.defaultSql(psql, filters, override, callback);
};