var _ = require('underscore')
var argx = require('argx')

/**
 * Way of standardizing and naming a function.
 * @param {Function} [fn] - The function you want to assign / get a name of.
 * @param {String} [fnName] - The function name override.
 * @param {Object} [objFns] - The object that contains function property `fnName`.
 * @return {Object} {fnName: [function]}
 * @throws {Error} no name found or provided
 * @example
 * _.mixin(fnToMethod(require('join-camel-case')))
 * @example
 * var anon = {}
 * anon.ifHappy = function(str){
 *   if (str == 'happy') return true
 *   return false
 * }
 * fnToMethod('ifHappy', anon) // => {'ifHappy': [function]}
 * @example
 * var anon = {}
 * anon.ifHappy = function(str){
 *   if (str == 'happy') return true
 *   return false
 * }
 * fnToMethod(anon.ifHappy) // throws
 * @example
 * // returns {'ifHappy': [function]}
 * var known = {}
 * known.ifHappy = function ifHappy(str){
 *   if (str == 'happy') return true
 *   return false
 * }
 * fnToMethod(known.ifHappy) // => {'ifHappy': [function]}
 * @example
 * function ifHappy(str){
 *   if (str == 'happy') return true
 *   return false
 * }
 * fnToMethod(ifHappy) // => {'ifHappy': [function]}
 * @example
 * var ifHappy = function(str){
 *   if (str == 'happy') return true
 *   return false
 * }
 * fnToMethod('ifHappy', ifHappy) // => {'ifHappy': [function]}
 */
function fnToMethod (/* fn, fnName, objFns */) {
  var args = argx(arguments)
  var fn = args.shift(Function)
  var fnName = args.shift(String)
  var objFns = args.shift(Object)
  if (!fn && objFns && objFns[fnName]) fn = objFns[fnName]
  if (!fnName && fn._name) fnName = fn._name
  if (!fnName && fn.name) fnName = fn.name
  if (!fnName) throw new Error('no name found or provided')
  return _.object([[fnName, fn]])
}

module.exports = fnToMethod