feat: add function to get jsonlogic with solved vars (replaced by values)

[FlorianRuen]

Close #65

I added one function in vars.go (not exported)

func solveVarsBackToJsonLogic(rule, data interface{}) (json.RawMessage, error) {
	ruleMap := rule.(map[string]interface{})
	result := make(map[string]interface{})

	for operator, values := range ruleMap {
		result[operator] = solveVars(values, data)
	}

	resultJson, err := json.Marshal(result)

	if err != nil {
		return nil, err
	}

	// we need to use Unquote due to unicode characters (example \u003e= need to be >=)
	// used for prettier json.RawMessage
	resultEscaped, err := strconv.Unquote(strings.Replace(strconv.Quote(string(resultJson)), `\\u`, `\u`, -1))

	if err != nil {
		return nil, err
	}

	return []byte(resultEscaped), nil
}

And one exported function which uses the one above

func GetJsonLogicWithSolvedVars(rule, data json.RawMessage) ([]byte, error) {
	if data == nil {
		data = json.RawMessage("{}")
	}

	// parse rule and data from json.RawMessage to interface
	var _rule interface{}
	var _data interface{}

	err := json.Unmarshal(rule, &_rule)
	if err != nil {
		return nil, err
	}

	err = json.Unmarshal(data, &_data)
	if err != nil {
		return nil, err
	}

	return solveVarsBackToJsonLogic(_rule, _data)
}

The README.md has also been updated to add an example of this new function and a test has been added in jsonlogic_test.go

[codecov]

Codecov Report

Merging #66 (4d3c856) into master (1a4645b) will decrease coverage by 1.37%.
The diff coverage is 55.88%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
- Coverage   95.84%   94.47%   -1.37%     
==========================================
  Files           9        9              
  Lines         962      996      +34     
==========================================
+ Hits          922      941      +19     
- Misses         28       38      +10     
- Partials       12       17       +5