'use strict';

var _ = require('lodash');

var sliced = require('sliced');

var FunctionCall = require(__dirname + '/node/functionCall');

// create a function that creates a function call of the specific name, using the specified sql instance

var getFunctionCallCreator = function(name) {

return function() {

// turn array-like arguments object into a true array

return new FunctionCall(name, sliced(arguments));

};

};

// creates a hash of functions for a sql instance

var getFunctions = function(functionNames) {

var functions = _.reduce(functionNames, function(reducer, name) {

reducer[name] = getFunctionCallCreator(name);

return reducer;

}, {});

return functions;

};

// aggregate functions available to all databases

var aggregateFunctions = [

'AVG',

'COUNT',

'DISTINCT',

'MAX',

'MIN',

'SUM'

];

// common scalar functions available to most databases

var scalarFunctions = [

'ABS',

'COALESCE',

'LEFT',

'LENGTH',

'LOWER',

'LTRIM',

'RANDOM',

'RIGHT',

'ROUND',

'RTRIM',

'SUBSTR',

'TRIM',

'UPPER'

];

// hstore function available to Postgres

var hstoreFunction = 'HSTORE';

//text search functions available to Postgres

var textsearchFunctions = ['TS_RANK','TS_RANK_CD', 'PLAINTO_TSQUERY', 'TO_TSQUERY', 'TO_TSVECTOR', 'SETWEIGHT'];

var standardFunctionNames = aggregateFunctions.concat(scalarFunctions).concat(hstoreFunction).concat(textsearchFunctions);

// creates a hash of standard functions for a sql instance

var getStandardFunctions = function() {

return getFunctions(standardFunctionNames);

};

module.exports.getStandardFunctions = getStandardFunctions;