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package toolbox
import (
"encoding/json"
"fmt"
"io"
"strings"
)
//MacroEvaluator represents a macro expression evaluator, macros has the following format macro prefix [macro parameter] macro postfix
type MacroEvaluator struct {
Prefix, Postfix string
ValueProviderRegistry ValueProviderRegistry
}
//HasMacro checks if candidate has a macro fragment
func (e *MacroEvaluator) HasMacro(candidate string) bool {
prefix, postfix := e.Prefix, e.Postfix
prefixPosition := strings.Index(candidate, prefix)
if prefixPosition == -1 {
return false
}
postfixPosition := strings.Index(string(candidate[prefixPosition:]), postfix)
return postfixPosition != -1
}
func (e *MacroEvaluator) expandArguments(context Context, arguments *[]interface{}) error {
//expanded macros within the macro
for i, argument := range *arguments {
if IsString(argument) {
if argumentAsText, ok := argument.(string); ok {
if e.HasMacro(argumentAsText) {
expanded, err := e.Expand(context, argumentAsText)
if err != nil {
return fmt.Errorf("failed to expand argument: " + argumentAsText + " due to:\n\t" + err.Error())
}
(*arguments)[i] = expanded
}
}
}
}
return nil
}
func (e *MacroEvaluator) decodeArguments(context Context, decodedArguments string, macro string) ([]interface{}, error) {
var arguments = make([]interface{}, 0)
if len(decodedArguments) > 0 {
decodedArguments = strings.Replace(decodedArguments, `\"`, `"`, len(decodedArguments))
decoder := json.NewDecoder(strings.NewReader(decodedArguments))
err := decoder.Decode(&arguments)
if err != nil && err != io.EOF {
return nil, fmt.Errorf("failed to process macro arguments: " + decodedArguments + " due to:\n\t" + err.Error())
}
err = e.expandArguments(context, &arguments)
if err != nil {
return nil, err
}
}
return arguments, nil
}
func (e *MacroEvaluator) extractMacro(input string) (success bool, macro, macroName, macroArguments string) {
prefix, postfix := e.Prefix, e.Postfix
var isInQuotes, argumentCount, previousChar, expectArguements, argumentStartPosition, argumentEndPosition = false, 0, "", false, 0, 0
prefixPosition := strings.Index(input, prefix)
if prefixPosition == -1 {
return false, "", "", ""
}
for i := prefixPosition + len(prefix); i < len(input); i++ {
aChar := input[i : i+1]
if i > 0 {
previousChar = input[i-1 : i]
}
if strings.ContainsAny(aChar, " \b\n[") {
expectArguements = true
}
if aChar == "\"" && previousChar != "\\" {
isInQuotes = !isInQuotes
}
if !isInQuotes && aChar == "[" && previousChar != "\\" {
if argumentCount == 0 {
argumentStartPosition = i
}
argumentCount++
}
if !isInQuotes && aChar == "]" && previousChar != "\\" {
argumentEndPosition = i
argumentCount--
}
macro = macro + aChar
if argumentCount == 0 {
if aChar == postfix {
break
}
if !expectArguements {
macroName = macroName + aChar
}
}
}
if argumentStartPosition > 0 && argumentStartPosition < argumentEndPosition {
macroArguments = input[argumentStartPosition : argumentEndPosition+1]
}
return true, prefix + macro, macroName, macroArguments
}
//Expand expands passed in input, it returns expanded value of any type or error
func (e *MacroEvaluator) Expand(context Context, input string) (interface{}, error) {
success, macro, macroName, macroArguments := e.extractMacro(input)
if !success {
return input, nil
}
valueProviderRegistry := e.ValueProviderRegistry
if !valueProviderRegistry.Contains(macroName) {
return nil, fmt.Errorf("failed to lookup macro: '%v' while processing: %v", macroName, input)
}
arguments, err := e.decodeArguments(context, macroArguments, macro)
if err != nil {
return nil, fmt.Errorf("failed expand macro: %v due to %v", macro, err.Error())
}
valueProvider := valueProviderRegistry.Get(macroName)
value, err := valueProvider.Get(context, arguments...)
if err != nil {
return nil, err
}
if len(macro) == len(input) {
return value, nil
}
expandedMacro := fmt.Sprintf("%v", value)
result := strings.Replace(input, macro, expandedMacro, 1)
if e.HasMacro(result) {
return e.Expand(context, result)
}
return result, nil
}
//NewMacroEvaluator returns a new macro evaluator
func NewMacroEvaluator(prefix, postfix string, registry ValueProviderRegistry) *MacroEvaluator {
return &MacroEvaluator{
Prefix: prefix,
Postfix: postfix,
ValueProviderRegistry: registry,
}
}
//ExpandParameters expands passed in parameters as strings
func ExpandParameters(macroEvaluator *MacroEvaluator, parameters map[string]string) error {
for key := range parameters {
value := parameters[key]
if macroEvaluator.HasMacro(value) {
textValue, err := macroEvaluator.Expand(nil, AsString(value))
if err != nil {
return err
}
parameters[key] = AsString(textValue)
}
}
return nil
}
//ExpandValue expands passed in value, it returns expanded string value or error
func ExpandValue(macroEvaluator *MacroEvaluator, value string) (string, error) {
if macroEvaluator.HasMacro(value) {
expanded, err := macroEvaluator.Expand(nil, value)
if err != nil {
return "", err
}
return AsString(expanded), nil
}
return value, nil
}
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