Adding new extensions for map and evaluate strings

[BuddhiWathsala]

Description:

Problem

Currently, Siddhi execution string does not support string manipulation for the following scenarios.

1. Let say I have a stringS=" {{prize}} > 100 " and the value of the prize coming from a different stream. Assume that, now the prize is 300. Then I need to get the string S'= "300 > 100"
2. The next scenario is get the string S' = "300 > 100" and evaluate it. The evaluation of that mathematical expression should return true.

Suggestion

1. Implement an extension called str: map(STRING, STRING...) and this will return a STRING.
2. Implement an extension called str: eval(STRING, STRING...) and this will return an Object.

Suggested Labels: Feature improvement

[BuddhiWathsala]

According to the discussion of this siddhi-dev mail thread, we are going to implement two functions to cater above requirements.

1. Update previous str:fillTemplate receive a string and a key-value map. Then replace all key entries with a corresponding value. For example it will receive,

   str:fillTemplate("{{prize}} > 100 && {{salary}} < 10000",  map:create('prize', 300, 'salary', 10000)))

   and return string 300 > 100 && 10000 < 10000

2. Then we will add another function js:eval( "56 > 76", 'bool') to evaluate expressions in https://github.com/siddhi-io/siddhi-script-js