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package funcs
import (
"fmt"
"strings"
)
// CallbackFunc is a function which can be executed by the mapreduce engine
type CallbackFunc func(text string) string
// Function embeddes the function name to the callback function
type Function struct {
// Name of the callback function
Name string
call CallbackFunc
}
// FunctionStack is a list of functions stacked each other
type FunctionStack []Function
// NewFunctionStack parses the input string, e.g. foo(bar("arg")) and returns a corresponding function stack.
func NewFunctionStack(in string) (FunctionStack, string, error) {
var fs FunctionStack
getCallback := func(name string) (CallbackFunc, error) {
var cb CallbackFunc
switch name {
case "md5sum":
return Md5Sum, nil
case "maskdigits":
return MaskDigits, nil
default:
return cb, fmt.Errorf("unknown function '%s'", name)
}
}
aux := in
for strings.HasSuffix(aux, ")") {
index := strings.Index(aux, "(")
if index <= 0 {
return fs, "", fmt.Errorf("unable to parse function '%s' at '%s'", in, aux)
}
name := aux[0:index]
call, err := getCallback(name)
if err != nil {
return fs, "", err
}
fs = append(fs, Function{name, call})
aux = aux[index+1 : len(aux)-1]
}
return fs, aux, nil
}
// Call the function stack.
func (fs FunctionStack) Call(str string) string {
for i := len(fs) - 1; i >= 0; i-- {
//logger.Debug("Call", fs[i].Name, str)
str = fs[i].call(str)
//logger.Debug("Call.result", fs[i].Name, str)
}
return str
}
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