@mangar2/decision

Abstract

Provides a JSON based term evaluator to calculate decisions based on configuration files The syntax of the JSON-terms is derived from Lisp .

Contents

• Meta
• Class Decision
  • Parameters
  • Methods
    • _ISOStringToDate
    • eval
    • on
• Class EvalResult
  • Parameters
  • Members

Meta

File	decision.js
Abstract	Provides a JSON based term evaluator to calculate decisions based on configuration files The syntax of the JSON-terms is derived from Lisp .
Author	Volker Böhm
Copyright	Copyright ( c ) 2020 Volker Böhm
License	This software is licensed under the GNU LESSER GENERAL PUBLIC LICENSE Version 3 . It is furnished "as is" , without any support , and with no warranty , express or implied , as to its usefulness for any purpose .

Class Decision

new Decision(variables)

Creates a value class providing the ability to evalutate a json based value . Additionally it explains the value in a juman readable string . Supported operations are

• [ "or" , t1 , t2 , . . . ]
• [ "and" , t1 , t2 , . . . ]
• [ operator , t1 , t2 ] with operators '>' , '<' , '> = ' , '< = ' , ' ! = ' , ' = '
• [ "+/-" , t1 , t2 ]
• [ "if" , t1 , then , else ]
• [ "switch" , t1 , { map } ] where map is an array of variable value maps . Example [ "switch" , 1 , { 1 : "a" , 2 : "b" } ] results in 'a'
• [ "function" , . . . parameter ] where function is registrated by a call to 'on'

Example

const variables = {
   'a/b': 1,
   'b/c': 2,
   'system/presence': 'awake'
}
const value = new Decision(variables)
const result = value.decide(
     [
          'and',
          ['or', ['<', 'a/b', 10], ['<', 'b/c', 2]],
          ['or', ['>=', 'a/b', 10], ['>=', 'b/c', 2]]
      ]
)
// returns result.value = true and result.reason = 'a/b (1) is < 10 and b/c (2) is >= 2'

Decision Parameters

Name	Type	Attribute	Default	Description
variables	Object	optional	{ }	list of known variables and values

Decision Methods

_ISOStringToDate

_ISOStringToDate (value) => {Date, any}

Converts any value from an ISO formatted date string to a date object If it is not an ISO formatted date string , the original value will be returned

_ISOStringToDate Parameters

Name	Type	Description
value	any	any value

_ISOStringToDate returns

Type	Description
Date, any	a Date object or the original value

eval

eval (jsonTree) => {EvalResult}

Calculates a value based on a json based json tree

eval Parameters

Name	Type	Description
jsonTree	Object	json structured boolean logic

eval throws

Type	Description
Error	on any error in the jsonTree

eval returns

Type	Description
EvalResult	result of the evaluation

on

on (event, callback)

Sets a callback .

on Parameters

Name	Type	Description
event	string	event name ( not case sensitive ) for the callback
callback	function	( parameter )

on throws

Type	Description
Error	if the callback is not 'function'

Class EvalResult

new EvalResult(value, reason)

Creates a result object with a "value" and a "reason" and a list of used variable : value pairs

EvalResult Parameters

Name	Type	Description
value	Date, string, number, boolean	evaluation value
reason	string	value reason in human readable form

EvalResult Members

Name	Type	description
reason	string	Reason explaining the result
value	Date, string, number, boolean	Value of the result
variables	Array.<string>	List of missing variables found